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The thermodynamic properties of copper-nickel mattes Matousek, Jan Werner 1961

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THE THERMODYNAMIC PROPERTIES OF COPPER-NICKEL MATTES by JAN WERNER MATOUSEK A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department of MINING AND METALLURGY We accept t h i s t h e s i s as conforming to the standard r e q u i r e d from candidates f o r the degree of Master of A p p l i e d Science. Members of the Department Mining and Metallurgy THE UNIVERSITY OF BRITISH COLUMBIA March 1961 In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n permission. Department of Mining and Metallurgy, The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8, Canada. Date March 1961 ABSTRACT The thermodynamic p r o p e r t i e s of the components i n the Cu-Ni-S t e r n a r y system have been measured by means of the E^s/h^ r a t i o i n a gas phase e q u i l i b r a t e d w i t h the molten matte at 1200°C. The measured sulphur p o t e n t i a l s were i n t e g r a t e d to e s t a b l i s h the a c t i v i t i e s i n the Cu 0S-Ni,S 0 d 3 2 pseudobinary and the i s o a c t i v i t y l i n e s over the t e r n a r y system,, The r e s u l t a n t a c t i v i t y p a t t e r n suggests the presence of a pseudocomponent at approximately the composition 0.02 N ^ , 0.63 ^ Q U » and 0.35 N . The i n f l u e n c e exerted by the pseudocomponent causes the a c t i v i t y of Cu^S to be n e a r l y constant i n the m i s c i b i l i t y gap. In t h i s same region the a c t i v i t y of Ni S i s r e s t r i c t e d to low v a l u e s . - i i -ACKNOWLEDGEMENT The author expresses h i s g r a t i t u d e f o r a s s i s t a n c e and h e l p f u l d i s c u s s i o n s to the members of the Department of Mining and Me t a l l u r g y of the U n i v e r s i t y of B r i t i s h Columbia, He i s e s p e c i a l l y g r a t e f u l to Dr. C.S. Samis f o r h i s d i r e c t o r s h i p of t h i s p r o j e c t and to Mrs. A.M. Armstrong f o r h e l p f u l d i s c u s s i o n s during the chemical a n a l y s i s of the mattes and the a n a l y s i s of the r e s u l t s . The author i s g r a t e f u l to the N a t i o n a l Research C o u n c i l of Canada f o r f i n a n c i a l a s s i s t a n c e which made t h i s work p o s s i b l e . — i i i -TABLE OF CONTENTS I I T T R O L ^ U C T I O N o o o D O O O o e » o o * o o o o o o » e * o o o o o o X Scope of the Present I n v e s t i g a t i o n , . . . . . . . . . . . . . . 2 Summary of Previous Work, . . . . . . . . . . . . . . . . . . o 2 P t l c l S 6 D i I*3.II1S « o » o o o o o o o o o o o o a o o o o o o 2 Phase E q u i l i b r i a Studies « » 0 0 « o o ' » - 0 . « . o 0 o o o 3 Indus t r i a l Studies© o o • o • o « « © o « a o o o o o 3 T he ore t i c a l S t u d i e s • o o © o o o © o © * o o o o o o 4 A ^ M A . ^ 2 ^ e o o o o o o o o o o o o o e e o o o o o 4 C U ^ C U ^ S © 0 0 « » O O O O 0 0 0 O O O 0 O O O 0 0 4 The Binary Systems Fe-S, Co-S, Ni-S, . , . . , . 6 C U ~ F e — S • © o o o o e o o o o o » o o o o o o o o 6 Sulphide Systems Con t a i n i n g Oxygen . . . . o . » 8 Thermodynamics and the St r u c t u r e s of Mattes . . <> . . © . ' . . , . 1 0 EXPERIMENTAL O O . O O O . O O . . 0 . O O . O O O . O C O O O O O o l O ApparatUS © O O O . . . O O O . . O * © . © © . © © . . © © O O 1 0 FUrnaCe . o © 0 . 0 0 . © O O O O O O O © O . O O O O O O O 1 0 Temperature Controlo © © © © o o . o o o . o o o o . o . o 1 2 G a s S y s t e m © o o • o o « • o * * © • . © © © © • o o o » o 1 2 Gas A n a l y s i s Equipment o o o » o o o o o . . o . o o . . o 1 3 Materials© © « • © o • © © o © o © o » o o o » o © • o o © o o 13 Experimental Procedure© © . o , o . o o . o o « . o « o o o o o l 5 P r e p a r a t i o n of Mattes. . . . . . . . . . . . . . . . . o . 1 5 E q u i l i b r a t i o n . . . . . . . . . . . . . . . . . . . . . . . 1 6 A n a l y s i s . o © . . . © o © © o © o © o o . o . o o o o o o o o . 1 8 - i v Matte A n a l y s i s . . . . . . . . . . . 18 Gs,s Aji£ilysxs o o o o o o « » « 0 o » » o » * * « « « o o . o X8 D i s s o c i a t i o n of H^S . . . . . . . . . . . . . . . . . . . . . . 19 SOUJTCGS o f E r r o r © © © © * • « o • o o * • o o • • o o o o o o o 20 T 6 HipG r£i t Ll 1*6 o o o o o o o o o o o o o o o a o o o o o o o o 20 Establishment of E q u i l i b r i u m . . . . . . . . . . . . . . o 20 XVi©rmsil Sc^rG^ett/iorio o o o © « © o o o © o o o o © © o o o 2X AnstXysis « © © © © © © © o o © © © o o o • © * o o o o o o 2X Presence of Other Gases. . . . . . . . . . . . . . . . o o 21 JRESUXlTS O O O O O * O O O O O O O O O O O O O O O O O O O O O O O O O 22 The Ternary Phase Diagram . . . . . . . . . . . . . . . . . . . 22 The Binary Systems. . . . . . . . . . . . . . . . . . . o o . . 22 N X ^ N X ^ S ^ . . . . O O O O O . . . . 0 O . . . O . . 0 0 . 0 24 CU~CU2S O . O 0 O . . . . . O O . 0 0 0 0 . 0 0 0 0 0 0 0 26 C U — N X . o . o o o o o o e o o o . . . o . e . . o o o o o o 2*7 C U ^ S — N l ^ S ^ . o o o o o o . o o o . « . . o o o o o o o . o 219 A c t i v i t y from Mol F r a c t i o n s . . . . . . . . . . . . . 29 A c t i v i t y from the Phase Diagram . . . . . . . . . . . 5 1 D i s c u s s i o n of A c t i v i t i e s i n the C^S-Ni^S,, Pseudobinary 33 Sulphur A c t i v i t i e s i n the Ternary System at 1200 °Co . . . . . . 34 The A c t i v i t i e s of Cu 0S and N i _ S 0 . 36 d: id Choice of Systems and Standard States 36 The A c t i v i t y of C i ^ S . , 37? The A c t i v i t y of Ni^S^. . . . . . . . . . . . . . . • • • • • « 38 D i s c u s s i o n of the A c t i v i t y P a t t e r n . . . . . . . . . . . . . . . 40 S e l f - C o n s i s t e n c y of the A c t i v i t y P a t t e r n . . . . . . . . . 40 _ v -The A c t i v i t y of CugS i n the M i s c i b i l i t y Gap, 40 o o o DISCUSSION Agreement with Previous Work* Phase Diagram* * « . • . The Cu-Cu2S Binary « • < The A c t i v i t y Pattern O o • • • o O O O O O o o o o o o o o o o o o o o o o The Entropy of Fusion of Cu2S A Pseudocomponent of the Ternary System o o o o O O O O O The Thermodynamic Analysis of a Commercial Matte at 1200 C O O O 42 42 43 43 43 44 46 46 CONCLUSIONS. . . . 0 0 0 * 0 0 0 O O O O O O O O APPENDICES . I. Summary of Thermodynamic Data l l o Correction for the Dissociation of H^S III. Summary of Data for Ni-Ni^S,, System . e e o o o o. o o o o o o o o o o o e o o o o o o o o o o o o o o o o o o IV. Calculation of ,Q. from the Phase Diagram of the Cu„S-Ni„S 0 Pseudobinary. O O O O O o o o . . . . o o o . o o o o o o V. Experimental Results VI. Integration Data for Cu,,S V I I o Integration Data for Ni^S^. . . . . . . « . . o . . VIII. Calculation o f & S f (Cu 2S) from aQu g and the C u ^ - N i ^ Phase Diagram 2. o e o o o o o o o o o o o o o o 47 48 48 49 52 52 53 54 58 59 - v i -LIST OF FIGURES No. Pag_e 1 Cu-CUgS Phase Diagram 5 2: N i - N i ^ S 2 Phase Diagram 7 3 Cu-Fe-S Phase Diagram, 1350°C 9 4 Experimental Furnace 11 5 Gas A n a l y s i s Apparatus 14 6 Approach to E q u i l i b r i u m 17 7 Cu-Ni-S Phase Diagram, 1200°C 23 8 A c t i v i t i e s of N i , S 0 and Ni i n the Bin a r y System at 1200°C; 25 9.: Cu-Ni Phase Diagram 28 10 Ni S -Cu S Phase Diagram 30 3 2 2 11 A c t i v i t y of Cu^S i n Cu^-Ni ^ S g Pseudobinary 32 12: Log H 2S/H 2 R a t i o s , Cu-Ni -S System 1200°C 35 13 Copper Sulphide I s o a c t i v i t y P a t t e r n , Cu-Ni-S System, 1200°C 39 14 N i c k e l Sulphide I s o a c t i v i t y P a t t e r n , Cu-Ni-S System, 1200°C 41 LIST OF TABLES No. Page I Phase Diagrams of Importance i n Smelting 3 II Composition of Laboratory Prepared Sulphides 16 THE THERMODYNAMIC PROPERTIES OF COPPER-NICKEL MATTES INTRODUCTION At the present time, n e a r l y a l l of the world's supply of n i c k e l i s obtained from c o p p e r - n i c k e l - i r o n sulphide deposits© These ores are commonly t r e a t e d by f l o t a t i o n to produce one or more sulphide c o n c e n t r a t e s . The copper-nickel concentrates are u s u a l l y roasted and then smelted i n reve r b e r a t o r y furnaces. The products obtained from the smelting furnaces are a s l a g and a matte of mixed sulphides which a l s o contains the pr e c i o u s metals 0 The processes used to r e f i n e r e v e r b e r a t o r y mattes are i n f l u e n c e d by s e v e r a l f a c t o r s . For mattes c o n t a i n i n g very s m a l l q u a n t i t i e s of pre c i o u s metals, h y d r o m e t a l l u r g i c a l r e f i n i n g processes can be economically employed.''" P y r o m e t a l l u r g i c a l r e f i n i n g c o n s i s t s of f i r s t c o n v e r t i n g the r e v e r b e r a t o r y matte to remove i r o n and a p o r t i o n of the sulphur. The treatment of c o p p e r - n i c k e l converter mattes has experienced c o n s i d e r a b l e change i n recent years. The processes i n use at the present and those which have been used f o r producing m e t a l l i c copper and n i c k e l 2 3 4 5 6 from converter mattes have been d e s c r i b e d i n the l i t e r a t u r e . 9 1 1 1 Although the commercial aspects of the treatment of copper-n i c k e l mattes have been dis c u s s e d , there i s l i t t l e i n f o r m a t i o n a v a i l a b l e concerning the thermodynamic p r o p e r t i e s of the mattes. _ 2 -Scope of the Present I n v e s t i g a t i o n In order to understand more f u l l y the p y r o m e t a l l u r g i c a l processes, both those p r e s e n t l y i n use and those which have been used, f o r the t r e a t -ment of c o p p e r — n i c k e l ores, t h i s i n v e s t i g a t i o n of the thermodynamic pro-p e r t i e s of c o p p e r - n i c k e l mattes has been undertaken. The o b j e c t i v e s of the present study were; ( l ) to measure expe r i m e n t a l l y the thermodynamic p r o p e r t i e s of the Cu-Ni-S system as 1200°C: by means of the E^S/E^ r a t i o s and (2) to e s t a b l i s h the i s o a c t i v i t y p atterns of Cu„S and Ni_S 0„ Summary of Previous Work Phase Diagrams Table I summarizes the sources of inf o r m a t i o n f o r the phase diagrams used i n t h i s study. The f i r s t f i v e l i s t e d are of primary import-ance. The other phase diagrams have been r e f e r r e d to during the present i n v e s t i g a t i o n , both as a guide to a n a l y s i n g the data and as a means of obt a i n i n g a more complete understanding of the smelting and r e f i n i n g process. TABLE I Phase Diagrams of Importance in Smelting System Reference Cu-Cu2S Ruddleg Ni-Ni S 2 Hanseng Cu-Ki Hansen Cu 2S-Ni 5S 2 Haywardy Stansfield and F a i t h ^ Koster and Mulfinger^^ Cu-Ni-S Koster_and Mulfinger Cu-Fe Ruddle' Fe-FeS Ruddle' Cu2S-FeS Ruddle Schlegen and Schuller Cu-Fe-S Ruddle 7 2 Schlegen and Schuller Krivsky and Schuhmanl5 Phase E q u i l i b r i a Studies  Industrial Studies An investigation of the role of nickel in copper-nickel-iron-sulphur mattes was completed in 1910 by the Canadian Copper Company, 14 Copper C l i f f , Ontario, Prior to this study, nickel was considered to be an element replacing iron in mattes and i t had been thought that nickel could be removed by converting. In this work, reverberatory mattes of approximately the composition, 11$ Cu, 22% Ni, 31% Fe, and 2&% S, were blown to b l i s t e r metal in Bessemer converters. The conclusions of this work as given in the o r i g i n a l report are l i s t e d below, 1, Nickel i s not an element replacing iron in matte, 2, Nickel-copper alloys act in the matte-blow l i k e one metal, 3 = Nickel-copper alloys follow, during the matte-blow, exactly the same laws that govern the behaviour of copper alone. The f l u i d i t y c h a r a c t e r i s t i c s of c o p p e r - n i c k e l mattes have been 15 i n v e s t i g a t e d by Guess and Lathe and the composition of i n d u s t r i a l mattes 16 has been reported by Drummond . A d d i t i o n a l i n f o r m a t i o n concerning i n d u s t r i a l s t u d i e s i s i n c l u d e d i n the r e f e r e n c e s p r e v i o u s l y c i t e d f o r d e s c r i p t i o n s of processes. T h e o r e t i c a l Studies ' Summaries of the knowledge of the t h e o r e t i c a l aspects of copper 7 17 smelting have been g i v e n i n the l i t e r a t u r e ' . Since these r e p o r t s were pub l i s h e d , s e v e r a l important phase e q u i l i b r i a s t u d i e s have been completed. Ag-Ag 2S 18 Rosenqvist has made a comprehensive study of the Ag-Ag 2S system by e q u i l i b r a t i n g a melt phase with an atmosphere of H^Cg) and E^S(g) i n order to measure the a c t i v i t y of sulphur i n the melt. A Gibbs-Duhem i n t e g r a t i o n has been used to c a l c u l a t e the a c t i v i t y of s i l v e r . The a c t i v i t y of Ag 2S was obtained from the e q u i l i b r i u m constant, the a c t i v i t y of sulphur, and the a c t i v i t y of s i l v e r . Cu-Cu 2S The Cu-Cu 2S phase diagram, c o n s t r u c t e d from the data g i v e n by 7 Ruddel , i s shown i n Fi g u r e 1. Thi s b i n a r y system i s c h a r a c t e r i z e d by a region of i m m i s c i b i l i t y which extends from a melt of low sulphur content to a melt of n e a r l y the composition Cu 2S. The r e g i o n of composition i n the neighbourhood of Cu,>S has been s t u d i e d by Schuhman and Moles 1^ at 1150°C.', 1250°C, and 1350°C u s i n g 1083 1000 Cu 10 20 Mol % Sulphur Cu2S F i g u r e l o Cu-Cu^S Phase Diagram the Hg-H^S e q u i l i b r a t i o n technique. The apparatus used i n the present i n v e s t i g a t i o n has been patterned a f t e r that of Schuhman and Moles, Using the Gibbs-Duhern equation the authors c a l c u l a t e d the a c t i v -i t i e s of copper and Cu^S from the change i n the a c t i v i t y of sulphur with composition. The standard s t a t e s f o r both copper and Cu^S were chosen as the melt of composition Cu^S, On t h i s b a s i s the a c t i v i t y of copper i n the i m m i s c i b i l i t y r e g i o n was found to be approximately two as compared with an a c t i v i t y of u n i t y i n the melt of composition Cu^S, The a c t i v i t y of C ^ S i s approximately 0,96 i n the m i s c i b i l i t y gap. The Cu-Cu^S system w i l l be r e f e r r e d to l a t e r i n the d i s c u s s i o n of the r e s u l t s of the present i n v e s t i g a t i o n . The Binary Systems Fe-S, Co-S, and Ni-S 20 These three b i n a r y systems have been s t u d i e d by Rosenqvist using the technique p r e v i o u s l y d e s c r i b e d . Of the three, the Ni-S binary i s of the most importance i n the present work. The phase diagram f o r the Ni-Ni^S^ system i s shown i n F i g u r e 2, The r e s u l t s of Rosenqvist f o r temperatures below 1000°C have been e x t r a p o l a t e d to 1200°C and combined with the r e s u l t s of the present study to analyze the b i n a r y . These data are t a b u l a t e d i n Appendix I I I , The a n a l y s i s of t h i s system i s d i s c u s s e d i n a l a t e r s e c t i o n , Cu-Fe-S The ternary system Cu-Fe-S has been i n v e s t i g a t e d by K r i v s k y and Schuhman 1^ at 1150°C, 1250°C, and 1350°C„ They have analyzed t h e i r o r e s u l t s at 1350 C„ 8 The Cu-Fe-S s e c t i o n at 1 3 5 0 C, F i g u r e 3 , i s composed of seven areas as given belows l o A r e g i o n on the high sulphur s i d e of the pseudobinary v/here the vapour pressure of sulphur exceeds one atmosphere, 2 0 A narrow l i q u i d matte r e g i o n along the pseudobinary, 3 o An i m m i s c i b i l i t y r e g i o n of l i q u i d m a t t e - l i q u i d metal which extends n e a r l y half-way a c r o s s the ternary diagram from the Cu-Cu 2S b i n a r y toward the Fe-FeS b i n a r y , 4 o Regions of s o l i d i r o n - l i q u i d matte, s o l i d i r o n - l i q u i d matte-l i q u i d metal, and s o l i d i r o n - l i q u i d metalo 5 , A narrow r e g i o n of l i q u i d metalo Most of the melts i n v e s t i g a t e d by K r i v s k y and Schuhman f e l l i n the two phase, l i q u i d m a t t e - l i q u i d metal, r e g i o n . They used modified forms of the Gibbs-Duhem equation to o b t a i n the a c t i v i t i e s of Cu^S and FeS i n t h i s area. From the edge of the m i s c i b i l i t y gap, corresponding to metal s a t u r a t e d matte, a m o d i f i c a t i o n of Schuhman's i n t e r c e p t method of i n t e g r a -2 1 t i o n has been employed to o b t a i n the a c t i v i t i e s of C^S and FeS i n the pseudobinary. The a c t i v i t i e s of Cu^S and FeS i n the pseudobinary show small negative departures from Raoult's law i n d i c a t i n g that the pseudobinary i s n e a r l y i d e a l . F u r t h e r mention w i l l be made of t h i s work i n l a t e r s e c t i o n s . Sulphide Systems C o n t a i n i n g Oxygen 1 7 Rosenqvist and co-workers have r e c e n t l y i n v e s t i g a t e d the systems F e - S - 0 and Fe-Cu-S - 0 , Oxygen has been excluded from the present F i g u r e 5 ° Cu-Fe-S Phase Diagram, 1 3 5 0°C , ( N o t drawn t o s c a l e ) i i i n v e s t i g a t i o n , but the work of Rosenqvist does i n d i c a t e that"the presence of oxygen increases the a c t i v i t y of sulphur. Below about three atomic per cent oxygen however, t h i s increase i s n e g l i g i b l e . Thermodynamics and the S t r u c t u r e s of Mattes A summary of thermodynamic data of importance i n the smelting of c o p p e r - n i c k e l sulphides i s presented i n Appendix I.' While i t appears that s l a g s are l a r g e l y composed of i o n s , experimental evidence i n d i c a t e s that t h i s i s not the case f o r mattes. C o n d u c t i v i t y s t u d i e s on molten mixtures of Cu^S and FeS show that con-22 d u c t i v i t y i s e l e c t r o n i c r a t h e r than i o n i c . More recent i n v e s t i g a t i o n s 23 24 conclude that both Cu^S and FeS are semi-conductors ' . The use of s t r u c t u r a l models has been used to a c o n s i d e r a b l e 25 extent to e x p l a i n the thermodynamic p r o p e r t i e s of fused s a l t s . S e v e r a l 17 of these models have been extended i n attempts to describe mattes. Three such models which have been a p p l i e d to the Cu^S-Ni^S^ pseudobinary i n the present i n v e s t i g a t i o n are presented i n a l a t e r s e c t i o n . EXPERIMENTAL Apparatus Furnace The experimental furnace used i n t h i s i n v e s t i g a t i o n i s shown i n F i g u r e 4. / - 11-To A n a l y s i s ~* C 1 To A n a l y s i s L~ or Waste H-3-"* Entrant Gas To C o n t r o l l e r . i i i i i • i < \ II i i i j I I . D: —*• s \ ,' / i • > ^ • & * i A ' \ ' » A / 1 A t> • > I I I >v -D i I A - Entrant Gas Tube B - Thermocouple and P r o t e c t i o n Tube C - Water Cooled Cap D - Globar E - R e f r a c t o r y F - Furnace Tube G - C r u c i b l e H - S i l i c o n Rubber Gasket I - E x i t Gas Tube 1 J - Sampling and Charging Tube Fig u r e 4o Experimental Furnace - 12 -Two types of furnace tubes (F) were used during the course of experimentation. The f i r s t used was of " Z i r c o " and the second of m u l l i t e . Both were s u p p l i e d by the McDaniel Corporation and were thz same s i z e , three inches I.D. by 15 inches l o n g 0 Neither tube showed s i g n s of chemical a t t a c k by H^S gas. The " Z i r c o " tube was s u p e r i o r with respect to r e s i s t a n c e to breaking on c o o l i n g due to thermal shock. For a l l work " Z i r c o " c r u c i b l e s were used. These c r u c i b l e s were two inches I 0 D 0 by s i x inches long. No evidence of chemical a t t a c k by e i t h e r the furnace gases or by the mattes was observed. The gas tubes (A) and ( i ) were l/4 i n c h O.D. " Z i r c o " tubes and the sampling tube ( j ) was a 3/8 i n c h O.D. " Z i r c o " tube. The thermocouple p r o t e c t i o n tube (B) was a close d end " Z i r c o " tube of 1/4 i n c h O.D. Power was s u p p l i e d to the furnace by a 3 KVA transformer. Heating was provided by s i x v e r t i c a l Globars ( D ) wired i n p a r a l l e l . Temperature C o n t r o l Temperature c o n t r o l was maintained us i n g a platinum-platinum (90%), rhodium (lO%) thermocouple and a Wheelco c o n t r o l l e r . The temperature was checked using a second thermocouple i n s e r t e d through the sampling tube ( j ) and a potentiometer. It was observed that the temperature d i d not deviate more than 5°C above or below 1200°C during the c o n t r o l l e r ' s on-off c y c l e . Gas System Hydrogen, s u p p l i e d by Canadian L i q u i d A i r Company L t d . , was passed through a "DEOXO" c a r t r i d g e and a drying column f o r p u r i f i c a t i o n . - 13 -Hydrogen sulphide s u p p l i e d by the Mat he son Company was used as received,, Gas flow was r e g u l a t e d by passing each gas through separate, c a p i l l a r y r e s i s t a n c e , manometer flow meters c a l i b r a t e d by displacement of water. The gases passed from the flow meters to a mixing chamber and then to the furnace or to a n a l y s i s . A t o t a l flow of approximately 200 ml/min was maintained f o r a l l experiments. T h i s r a t e of flow i s considered s u f f i c i e n t to prevent thermal s e g r e g a t i o n . I n c r e a s i n g the flow r a t e above t h i s value produced no change i n the e x i t gas composition, i n d i c a t i n g that thermal segregation does not take p l a c e . The gas system to and from the furnace was constructed of rubber and g l a s s . A l l rubber tubing was b o i l e d i n a potassium hydroxide s o l u t i o n and thoroughly e q u i l i b r a t e d with the gases before u s i n g 0 Gas A n a l y s i s Equipment The gas a n a l y s i s equipment i s shown i n Figure 5. The gas burette c o n s i s t e d of a g l a s s tube of approximately 70 ml volume with stopcocks at each end. The procedure f o r gas a n a l y s i s i s discussed i n a l a t e r s e c t i o n . M a t e r i a l s Cu^S and Ni^S^ were prepared from copper and n i c k e l powders s u p p l i e d by S h e r r i t t Gordon Mines, Ltd. A l l other m a t e r i a l s were standard chemical reagents. - 14 S t o p c o c k -Gas Burette-Rinse Water U L Furnace Gas KOH S o l u t i o n F i g u r e 5» Gas A n a l y s i s Apparatus, - 15 -Experimental Procedure When two phases are i n e q u i l i b r i u m , the chemical p o t e n t i a l of any component i n one phase i s equal to the chemical p o t e n t i a l of t h i s component i n the second phase. The experimental procedure of the present i n v e s t i g a t i o n i s based upon t h i s concept. The experimental technique c o n s i s t e d of e q u i l i b r a t i n g the sulphide matte with mixtures of H 2(g) and H 2 S ( g ) , The p a r t i a l pressure of S^Cg) i n the gas phase i s determined by equation ( l ) and the a c t i v i t y of sulphur i n the matte phase by equation (2), 2 H 2 S ( g ) = 2 H 2(g) + S 2 ( g ) ( l ) S g ( g ) = 2 S ( i n matte) (2) The thermodynamics of these r e a c t i o n s are w e l l known and from the above equations i t can be seen that the a c t i v i t y of sulphur i n the matte i s p r o p o r t i o n a l to the HgS/Hg* r a t i o . Knowing t h i s r a t i o then, the a c t i v i t y of sulphur i n the matte can be evaluated and by s u i t a b l e i n t e g r a t i o n s of the Gibbs-Duhem equation the a c t i v i t i e s of other components of the matte can be obtained. P r e p a r a t i o n of Mattes The mattes were prepared from mixtures of l a b o r a t o r y produced s u l p h i d e s . These sulphides were made by heating the metal powder with powdered sulphur i n a graphite c r u c i b l e u n t i l r e a c t i o n occurred. T y p i c a l analyses of the two sulphides prepared i n t h i s way are g i v e n i n Table I I , * Throughout t h i s paper "HgS/H,,"1 i s used to denote the r a t i o of the p a r t i a l pressures of the gases. 16 TABLE II Composition of Laboratory Prepared Sulphides Sulphide Wt % S S t o i c h i o m e t r i c wt t S N i 3 S 2 29c8 26,5 Cu 2S! 23.8 20.0 E q u i l i b r a t i o n The experimental program was s t a r t e d with a charge of 200 grams of the l a b o r a t o r y prepared N i ^ S 2 i n the furnace at 1200°C o Through t h i s was bubbled c o n t r o l l e d mixtures of H 2(g) and H 2 S ( g ) . The normal course of the gas flow was from the c y l i n d e r s , through the matte, and out the e x i t gas tube to waste. At periods of about one-half hour, samples of the e x i t and entrant gases were drawn f o r a n a l y s i s . F o l l o w i n g a n a l y s i s , the composition of! the entrant gas was changed i n the d i r e c t i o n to produce the e x i t gas composition and the procedure was repeated. E q u i l i b r i u m was considered to be e s t a b l i s h e d when the gas compositions became constant and remained so f o r s e v e r a l hours. In most cases the e q u i l i b r i u m composition was approached from both the r i c h and lean s i d e s with respect to H 2S composition. S e v e r a l of the experimental runs are shown in' F i g u r e 6. When e q u i l i b r i u m was considered to be e s t a b l i s h e d the bubbler tube was r a i s e d and the matte allowed to s e t t l e before sampling. Samples of the matte were drawn through the tube (j). using a s m a l l rubber bulb attached to a g l a s s tube which was c l o s e d to a p i n hole at one end. From f i v e to ten grams of matte were drawn at each sampling. - 17 -Time i n Hours Fi g u r e 6 0 Approach to E q u i l i b r i u m . 18 A charge a d d i t i o n was then made through the sampling tube and the procedure d e s c r i b e d above was repeated to a second po i n t of e q u i l i b r i u m , Ajialy_sis^ Matte A n a l y s i s The matte samples were analysed by standard techniques - copper 26 by the e l e c t r o l y t i c method , n i c k e l by p r e c i p i t a t i o n as n i c k e l - d i m e t h y l -26 27 glyoxime , and sulphur by p r e c i p i t a t i o n as barium sulphate 0 Gas A n a l y s i s A v a r i e t y of procedures f o r a n a l y s i n g the gases i n t h i s type of study have been suggested i n the l i t e r a t u r e c i t e d p r e v i o u s l y . These methods are c h a r a c t e r i z e d by complex apparatus and c a l i b r a t i o n s or time consuming procedures i n order to analyse f o r very low H^S c o n c e n t r a t i o n s . Since i t had been p r e v i o u s l y decided to r e s t r i c t t h i s study to the regions of the system where the R^S/R^, r a t i o s are reasonably high, i t was f e l t that a chemical method of a n a l y s i s would be the most simple. Of the chemical methods of a n a l y s i s given i n the l i t e r a t u r e the p r e c i p i t a t i o n of sulphur, from the hydrogen sulphide absorbed i n an a l k a l i n e s o l u t i o n , with arsenous a c i d according to equation (3) i s considered to be the . 28,29 ,30 most accurate, A s 2 0 3 + 3 H 2S = A s 2 S + 3 H 2 0 (3) R e f e r r i n g back to the diagram of the gas a n a l y s i s equipment. Fi g u r e 5, the a n a l y t i c procedure was as f o l l o w s . The gas burette was f i l l e d with a 5$ potassium hydroxide s o l u t i o n and both stopcocks were c l o s e d , A sample of e i t h e r entrant or e x i t gas could then be drawn - 19 -by connecting the gas tube to the top of .the burette and opening both stopcocks. The lower stopcock was c l o s e d with approximately ten ml of s o l u t i o n remaining i n the burette and the upper stopcock was c l o s e d immediately a f t e r the lower. The burette was then given a vigorous shaking to insure complete a b s o r p t i o n of the HgS. The lower end of the burette was next immersed i n the s o l u t i o n removed during the drawing of t,he gas sample and the lower stopcock opened. In t h i s way the hydrogen i n the sample was returned to atmospheric pressure and i t s volume determined by measuring the volume of d i s p l a c e d s o l u t i o n . The s o l u t i o n c o n t a i n i n g H^S was then placed i n a beaker together with water used to r i n s e the b u r e t t e . To t h i s s o l u t i o n was added ah excess of 0.1 N As^O^. Upon making the s o l u t i o n a c i d w i t h HC1, the sulphur was p r e c i p i t a t e d according to equation (3). The s u l p h i d e was removed from the sample by f i l t r a t i o n and the p r e c i p i t a t e thoroughly washed with water to insure that a l l the excess ASgO^vas obtained i n the f i l t r a t e . Sodium bicarbonate was added to n e u t r a l i z e the f i l t r a t e and the excess As_0„ was t i t r a t e d with 0.1 N i o d i n e using s t a r c h as an i n d i c a t o r . The volume of H^S i n the sample could be c a l c u l a t e d from the q u a n t i t y of A s o 0 , r e q u i r e d f o r p r e c i p i t a t i o n . T h i s volume was c o r r e c t e d d 3 to room temperature and pressure and the r a t i o H^s/H^ c a l c u l a t e d . D i s s o c i a t i o n of H^S It was observed i n t h i s study and i n others that no sulphur deposits form i n the c o l d p o r t i o n s of the e x i t gas tube. T h i s i n d i c a t e s that the sulphur present i n the hot zone r e a c t s with hydrogen to produce E^S as the temperature of the gas decreases. The observed values of H ^ . S / H ^ are t h e r e f o r e higher than those in. the hot zone. From a knowledge of the thermodynamics of equation ( l ) , the e f f e c t of the back r e a c t i o n on the observed H ^ S / H ^ r a t i o can be c a l c u l a t e d . The experimental r e s u l t s have been c o r r e c t e d i n the manner suggested by 18 Rosenqvist . A sample c a l c u l a t i o n and the c o r r e c t i o n curve are shown i n Appendix I I . Sources of E r r o r Temperature It has been s t a t e d p r e v i o u s l y that the temperature d i d not o o vary more than 5 C from 1200 C during the course of a run. Ko e r r o r s of any s i g n i f i c a n c e are to be expected from such a v a r i a t i o n . Establishment of E q u i l i b r i u m In s t u d i e s u s i n g the procedure as described above, i t appears that e q u i l i b r i u m between the matte and the gas bubbling through i t , i s 19 e s t a b l i s h e d very r a p i d l y . Schuhman and Moles concluded from t h e i r work that the long p e r i o d of time r e q u i r e d f o r e q u i l i b r i u m was not to e q u i l i b r a t e the matte but to b r i n g the furnace tube i t s e l f to e q u i l i b r i u m . The recent 32 work of G r i f f i n g and Healy , on the e f f e c t of chromium on the a c t i v i t y of sulphur i n iron., using a s i m i l a r technique, i n d i c a t e s that e q u i l i b r i u m i s e s t a b l i s h e d i n l e s s than three hours. It may be concluded then, that the d e v i a t i o n from e q u i l i b r i u m f o r any experiment i s s m a l l . - 21 Thermal Segregation The f a c t o r s i n v o l v e d i n thermal segregation have been discussed 31 by Dastur and Chipman „ By using a high flow rate of gas t h i s e f f e c t has been e l i m i n a t e d i n the present i n v e s t i g a t i o n , . A n a l y s i s The estimated a c c u r a c i e s f o r a n a l y s i s are as follows? Sulphur +_ 2%, copper _+ 2$, n i c k e l _+ 3%? hydrogen +_ 1%9 and hydrogen sulphide + 3%° In a l l cas-es reported i n t h i s work, the sum of copper plus n i c k e l plus sulphur f e l l between 98 o0 and 102$, Owing to the very r a p i d a b s o r p t i o n of H^S by the a l k a l i n e s o l u t i o n , i t was found d i f f i c u l t to prepare mixtures of known composition. R e p r o d u c i b i l i t y of analyses on i d e n t i c a l , unknown samples however, was very good. Presence of Other Gases The thermodynamics of the formation of such gases as S^, 17 Sg, Sg, and HS have been disc u s s e d by Rosenqvist, He concludes that 32 the formation of these gases i s not l i k e l y , G r i f f i n g and Healy , using a mass spectrometer to analyse f o r H^Sj found no other species present, - 22 -RESULTS The Ternary Phase Diagram The Cu-Ni-S phase diagram, based mainly on the work of Koster 11 and Mulfinger i s shown i n Figure 7. T h i s f i g u r e g i v e s an i s o t h e r m a l s e c t i o n at 1200°C. The s e c t i o n presented here d i f f e r s s l i g h t l y i n the C u ^ C u S d 19 b i n a r y from that of Schuhman and Moles i n that the m i s c i b i l i t y gap i n the work of Koster and Mulfinger extends to 30 atomic percent sulphur while'that of Schuhman and Moles extends to 32 c7 atomic percento It i s seen that the Cu-Ni-Ni_S 0-Cu_S p o r t i o n of the diagram t> d d i s made up of four s i g n i f i c a n t regions as o u t l i n e d below. l o A two phase region of s o l i d metal i n e q u i l i b r i u m w i t h l i q u i d matte. 2 0 A s i n g l e phase region of l i q u i d matte. 3. A two phase region of l i q u i d matte plus l i q u i d metal. 4. A region on the sulphur r i c h s i d e of the pseudobinary where the sulphur vapour pressure exceeds one atmosphere. The area of the ternary s e c t i o n d i s c u s s e d above i s bounded by three binary and one pseudobinary systems. The sources of the phase diagrams f o r these b i n a r i e s have been g i v e n p r e v i o u s l y . The phase e q u i l i b r i a s t u d i e s on the two sulphide systems have a l s o been mentioned. A f u r t h e r a n a l y s i s i s given below. Ni-Ni,S_ y- 2 The H 2S/H 2 ratios for the N i - N i ^ b i n a r y at 1200°C are tabulated in Appendix l i t . From the change in log H 2S/H 2 with composition, the a c t i v i t y of Ni^S,, has been calculated by a Gibbs-Duhem integration using equation ( 4 ) . l 0 g * " 3 S 2 = J W M 5 S 2 d l Q S H2 S/ H2 <*> The standard state f o r Ni^Sg i s chosen as the melt whose composition i s exactly that of Ni,S_. In evaluating the above i n t e g r a l , the composition i s computed on the basis that a l l the nickel i s in the form of Hi^S^ The composition i s then given as a mol fra c t i o n of Ni_S„ and a negative mol fr a c t i o n of sulphur. The int e g r a l in this form has been found to be very convenient. The results of the Gibbs-Duhem integration for 2„. _ are shown N l3 S2 i n Figure 8 and are tabulated i n Appendix I I I . Knov/ing the H 2S/H 2 r a t i o and the a c t i v i t y of N i ^ S ^ the a c t i v i t y of "nickel can be calculated using equation (5). 3/2 Ni(s) + H 2S(g) = l/2 N i 3 S 2 > ( l ) + H ?(g) (5) K = At Q.2 mol fra c t i o n of sulphur, the solution i s saturated with s o l i d F i g u r e 8 0 A c t i v i t i e s of N i _ S ? and Ni i n the B i n a r y System at 1200°(r - 26 -n i c k e l and hence the a c t i v i t y of n i c k e l i s u n i t y at t h i s p o i n t . I n s e r t i n g the known a c t i v i t y values i n the above equation then, K i s c a l c u l a t e d to be 107, Knowing K, g , and H 2S/H 2, the a c t i v i t y of n i c k e l may be 3 2 c a l c u l a t e d a cross the b i n a r y . These r e s u l t s are shown i n Fi g u r e 8, The standard s t a t e f o r n i c k e l i s s o l i d metal at 1200°C. Al s o shown i n Fi g u r e 8 i s a curve of N as a f u n c t i o n of N l 3 S 2 the mol percent of sulphur. T h i s has been c a l c u l a t e d on the b a s i s that a l l of the sulphur i s combined as N i , S 0 . I t can be observed from the 3 2 curves that the b i n a r y , Ni-Ni_S„, does not d e v i a t e a p p r e c i a b l y from 3 2 i d e a l i t y . Cu-Cu_S 2— The H ^ S / H ^ r a t i o s as a f u n c t i o n of composition, from the v/ork 19 o of Schuhman and Moles , are g i v e n i n Table I I I f o r 1200 C„ The a c t i v i t y of C u 2 S has been c a l c u l a t e d i n the manner d e s c r i b e d above f o r n i c k e l sulphide and the standard s t a t e has again been chosen as the melt of s t o i c h i o m e t r i c composition. The a c t i v i t y of copper i n the m i s c i b i l i t y gap has been estimated 13 o by K r i v s k y and Schuhman as 0.960 at 1350 C„ T h i s corresponds to 0.958 at 1200°C, assuming that RT In YCu i s constant over t h i s range 33 of temperature . - 27 From equation (6) a value of 244 f o r K i s obtained. 2 C u ( l ) + H 2S(g) = C u 2 S ( l ) + H 2(g) (6) K ( ^ C u ) 2 ( H 2 S / H 2 ) The standard s t a t e f o r copper i s pure, l i q u i d copper at 1200°C'„ The a c t i v i t y data f o r t h i s b i n a r y are t a b u l a t e d below. TABLE III A c t i v i t i e s i n Cu-Cu 2S System Atom %s l o g H 2 S / H 2 a C u ^ s aQu 2.0* -2,37 Oo962 0.958 32.7* -2.37 0,962 0,958 33.3 -1.75 1,000 0,480 * Composition l i m i t s of the m i s c i b i l i t y gap Cu-Ni The phase diagram f o r the Cu-Ni system i s given i n F i g u r e 9. The thermodynamics of b i n a r y m e t a l l i c systems of t h i s type have been 34 discussed by C o t t r e l l . For such a binary phase diagram i t i s necessary that the heat of mixing term, i n the equation f o r the free energy of mixing, be very s m a l l . That i s , the s o l u t i o n i s e s s e n t i a l l y i d e a l , 35 Recently, Alcock has given the excess f r e e energy of mixing f o r the Cu-Ni system. Although, as observed by the author, the values are probably too high they i n d i c a t e p o s i t i v e d e v i a t i o n from Raoult's Law. From the data of Alcock however, two conclusions can be made. F i r s t , that the a c t i v i t i e s of copper and n i c k e l are i d e a l above the - 28 -- 29 -r e s p e c t i v e mol f r a c t i o n s of 0«7. Secondly, that Henry's Law i s obeyed below mol f r a c t i o n s of about 0.4. In view of the d i s c u s s i o n of C o t t r e l l g i v e n above i t i s probable that the Cu-Ni system i s i d e a l . While the data of Alcock cannot be used to support t h i s view d i r e c t l y i t i s apparent that the observations of Alcock, concerning the regions where Henry's and Raoult's Laws apply, are most r e a d i l y e x p l a i n e d by an i d e a l s o l u t i o n . In such a s o l u t i o n e i t h e r law holds over the complete range of composition.-The phase diagram f o r the Cu^S-Ni^S^ pseudobinary i s g i v e n i n F i g u r e 10. L i t t l e work has been done i n t h i s system other than the phase diagram s t u d i e s . An accurate phase e q u i l i b r i a study of the pseudobinary i s d i f f i c u l t due to the r a p i d i n c r e a s e i n sulphur pressure, -4 6 x 10 atm. to over one atmosphere, over a range of three to f o u r atomic percent sulphur. T h i s can be observed i n the binary s u l p h i d e systems i n the neighbourhood of Cu„S and Ni,S„. 2 3 d A second method of d e s c r i b i n g the Cu 0S-Ni_S_ system i s by 2 3 I means of s t r u c t u r a l models as p r e v i o u s l y d i s c u s s e d . Three such models have been a p p l i e d i n the present i n v e s t i g a t i o n . A c t i v i t y From Mol F r a c t i o n s 17 Rosenqvist and co-workers have a p p l i e d two s t r u c t u r a l models to various pseudobinary systems. Both models assume that the heat of mixing i s zero. One of the models assumes that there i s complete i n t e r -change of a l l atoms and the second model assumes that the metal atoms are - 30 31 interchangeable i n a m e t a l l i c l a t t i c e and the sulphur atoms i n a sulphur l a t t i c e . The a c t i v i t y f o r Cu 2S using these models can then be c a l c u l a t e d from equations (7) and (8)0 Model I. Q. = K Ns (7) Cu^S Cu s ' 'Cu J \ l2u Vcu™mJ Model I I . a = MTTW-) N S (8) The constants K are chosen to make the a c t i v i t i e s u n i t y at the composition Cu S. S i m i l a r equations can be w r i t t e n f o r & „ . _. . 2 N l 3 S 2 The a c t i v i t y f o r Cu 2S u s i n g these models i s given i n F i g u r e 11 and i t i s observed that there i s l a r g e negative d e v i a t i o n from Raoult's law. E s s e n t i a l l y the same a c t i v i t y p a t t e r n i s obtained from e i t h e r model. A c t i v i t i e s From the Phase Diagram The technique of o b t a i n i n g a c t i v i t i e s from phase diagrams has been discussed by s e v e r a l authors ' » Using t h i s method, the a c t i v i t y of Cu 2S at p o i n t s on the l i q u i d u s can be c a l c u l a t e d from equation (9) n e g l e c t i n g the small amount of s o l i d s o l u b i l i t y of Ni^S,, i n Cu 2S. Tm i s the temperature of melting of Cu 2S, T i s the temperature of a p o i n t on the l i q u i d u s , a n dAS^ i s the entropy of f u s i o n of Cu 2S„ i o g a c u . . ( 9 ) C u 2 S 4 .575 I For accurate a c t i v i t y p atterns i t i s e s s e n t i a l to have an accurate phase diagram and accurate data on the heat of f u s i o n of Cu 2S. There i s good agreement between the phase diagrams p u b l i s h e d i n the l i t e r a t u r e . S e v e r a l values f o r the entropy of f u s i o n of Cu 2S have been g i v e n . These values are discussed i n d e t a i l i n a l a t e r s e c t i o n . - 32 -10 20 30 40 50 60 70 80 90 Mol fo Cu 2S A A c t i v i t y from phase diagram, 1200°C B I d e a l s o l u t i o n C S t r u c t u r a l models I and II Fig u r e 11. A c t i v i t y of Cu ?S i n Cu S-Ni S Pseudobinary. For the purpose of c a l c u l a t i o n of a c t i v i t i e s , an entropy of f u s i o n of 1.64 e.u.has been used i n the present case. Th i s value has been suggested 3 T 38 by two references ' . The a c t i v i t i e s of Cu 2S at 1200°C, c a l c u l a t e d using equation ( 9 ) , are shown i n F i g u r e 11 and tabulated i n Appendix IV„ From the a c t i v i t y of Cu 0S, CL- can be c a l c u l a t e d by a 39 Gibbs-Duhem i n t e g r a t i o n as suggested^by Darken and Gurry „ The a c t i v i t y curve f o r Ni^S^ a l s o shows large p o s i t i v e d e v i a t i o n . D i s c u s s i o n of A c t i v i t i e s i n the Cu^S-Ni^S^ Pseudobinary R e f e r r i n g to F i g u r e 11, i t i s seen that there i s no agreement of a c t i v i t y patterns from models based upon what appear to be e q u a l l y v a l i d assumptions. A number of points concerning these models can be made however. In the f i r s t place the mol f r a c t i o n models neglect the e f f e c t of temperature on a c t i v i t y . Considerable e r r o r i s to be expected t h e r e -f o r e at higher temperatures where the s o l u t i o n should approach i d e a l i t y 0 -Since the phase diagram f o r the Cu^S-Ni^S^ pseudobinary i s q u i t e w e l l e s t a b l i s h e d , any e r r o r s i n the a c t i v i t y p a t t e r n must be introduced i n the entropy of f u s i o n or i n the method of a c t i v i t y c a l c u l a t i o n i t s e l f . The subject of the c o r r e c t entropy of f u s i o n i s d i s c u s s e d l a t e r but i t should be mentioned at t h i s point that the use of the value of 1 064 e.u. i n these c a l c u l a t i o n s may be s e r i o u s l y questioned. The use of the phase diagram to c a l c u l a t e a c t i v i t i e s has been used e x t e n s i v e l y f o r m e t a l l i c s o l u t i o n s ^ and f o r s l a g s y s t e m s ^ * ^ , , - 34 -No previous attempts to c a l c u l a t e the a c t i v i t i e s of s u l p h i d e s from pseudo-bi n a r y phase diagrams have been r e p o r t e d . A f a c t o r which should be considered i n such c a l c u l a t i o n s i s that t h i s system i s not t r u l y a b i n a r y system but r a t h e r a s e c t i o n through the ternary,, In view of the u n c e r t a i n t i e s i n the use of the models suggested above, no accurate a c t i v i t y patterns can be obtained from t h e i r use. However, c e r t a i n comparisons can be made with the Cu^S-FeS pseudobinary 0 42 Butts s t a t e s that the heat of s o l u t i o n i n the Cu^S-FeS system i s small and may be assumed to be zero. The phase e q u i l i b r i a study on the Cu-Fe-S system d i s c u s s e d p r e v i o u s l y , i n d i c a t e d that the behavior of Cu^S and FeS i s n e a r l y i d e a l . C o n s i d e r i n g the previous d i s c u s s i o n s of the r e s u l t s of the converter s t u d i e s , the a c t i v i t y of N i , S 0 i n the N i - N i _ S 0 binary, and the i d e a l nature of the Cu-Ni b i n a r y , one would p r e d i c t even more i d e a l behaviour i n the Cu^S-Ni^S^ pseudobinary than i s observed i n the CUgS-FeS system. T h i s c o n c l u s i o n i s supported by the r e s u l t s . o f the i n t e g r a t i o n s discussed below. Sulphur A c t i v i t i e s i n the Ternary System at 1200°C The melts f o r which H^S/H^ r a t i o s were measured i n the present i n v e s t i g a t i o n are shown i n Figure 12, The experimental data f o r these p o i n t s are t a b u l a ted i n Appendix V. From the experimental r e s u l t s , the H^S/H^ r a t i o s can be found f o r any composition along a l i n e near the pseudobinary or along a l i n e from N i _ S n to the copper corner by 3 d e x t r a p o l a t i o n . F i g u r e 13, showing H^S/H^ r a t i o s as f u n c t i o n s of composition, has been drawn from the smoothed experimental data and the a v a i l a b l e Figure 12.. Log H S / H Ratios, Cu-Ni-S System, 1200°C information discussed previously for the Cu-Cu0S and Ni-Ni,S. binaries, d 3 2 1 By converting log I^s/H to the pressure of sulphur gas, i t -3 can be shown that P varies along the pseudobinary from 2.3 x 10 atm. at -5 2 Ni^S^ to 1.8 x 10 atm. at Cu^S. In the immiscibility region, at / -4 log H^S/H^ equals -1.35, the sulphur pressure i s 1.2 x 10 atm. and for mattes in equilibrium with s o l i d metal P 0 i s less than 10~ atm. The S2 sulphur pressure is approximately one atmosphere along a line from the point, 0.43 mol fraction sulphur in the Ni-S binary, to the point, 0.36 mol fraction sulphur in the Cu-S binary. A c t i v i t i e s of Cu^S and Ni„S„ _—, , . — ^ When the a c t i v i t y of one component of a ternary system is known as a function of composition, the a c t i v i t i e s of the other compon-ents can be calculated by integrations of the ternary Gibbs-Duhem equation. 21 43 This technique has been thoroughly discussed by Schuhman and Gokcen „ Choice of Systems and Standard States Due to the lack of data in the two phase, l i q u i d matte-solid metal, region of the ternary and the high degree of uncertainty in estimating sulphur a c t i v i t i e s in this region, i t is, not convenient to choose copper and nickel metal as components of the ternary for integra-tion purposes. Instead the Cu„S-Ni,S0-S ternary system i s selected. 2 ? 2 The fact that the data to be integrated f a l l outside this ternary does not limit the integration. As in the binary systems previously analysed, the standard states for Ni,S„ and CunS are chosen as the melts of 3 d d stoichiometric composition. The standard state for sulphur i s sulphur gas (.Sg) at one atmosphere pressure. - 37 -The A c t i v i t y of Cu S The a c t i v i t y of Cu 2S was c a l c u l a t e d over both the s i n g l e phase, l i q u i d region and the two p h a s e , l i q u i d region using equation (lO).. l o S acu S = l 0 g aru S " / T I T " 2 Cu2S. „u S A 3 Cu_S./ H 0S J \ 2 / l o g 2 ,n H, N i 3 S 2 nCu 2S < 1 0> K l 3 S 2 It i s necessary to i n t e g r a t e t h i s equation along paths of constant n C u S/^Ni S r a t i P s except i n the two phase, l i q u i d r e g i o n where the r e s t r i c t i o n i s not r e q u i r e d . It would be most convenient to i n t e g r a t e equation (lO) from the pseudobinary toward the Cu-Ni b i n a r y . In order to c a r r y out such i n t e g r a t i o n s however, the a c t i v i t y of Cu^S i n the pseudobinary must f i r s t be e s t a b l i s h e d . The second choice of i n t e g r a t i o n path i s i n the m i s c i b i l i t y gap where the i n t e g r a t i o n can be c a r r i e d out from a point of known a i n the Cu-Cu 2S bi n a r y to p o i n t s of unknown a c t i v i t y . Owing to an unusual f e a t u r e of the m i s c i b i l i t y gap however, t h i s i n t e g r a l proved to be d i f f i c u l t to e v a l u a t e . R e f e r r i n g to F i g u r e 12 i t can be seen that, proceeding across the m i s c i b i l i t y gap from the c r i t i c a l point to the Cu-Cu 2S b i n a r y , the i n t e r c e p t s of the extended t i e l i n e s on the Cu-S binary, ^ ng/^nQu s' change from e s s e n t i a l l y a common i n t e r c e p t to undefined v a l u e s . In the low n i c k e l regions of the m i s c i b i l i t y gap then, the i n t e g r a l i s d i f f i c u l t to e v a l u a t e . On the b a s i s of composition c o n s i d e r a t i o n s and e x t r a p o l a t i o n of the i n t e g r a l curve f o r the higher n i c k e l regions of the m i s c i b i l i t y - 38 -gap a p a t t e r n of r e l a t i v e a c t i v i t i e s can be obtained. The c o r r e c t a c t i v i t y of Ct^S iis known i n the Cu-Cu^S b i n a r y and can be used to determine the necessary c o r r e c t i o n s f o r the r e l a t i v e a c t i v i t i e s . Both the r e l a t i v e and c o r r e c t e d a c t i v i t i e s are tabulated i n Appendix VI, From the c r i t i c a l point the i n t e g r a t i o n may be c a r r i e d out to the pseudobinary. The a c t i v i t y of Cu^S at the pseudobinary i s found to be 0,84 along the l i n e , N C u / N W i = 0„75/o,25, The mol f r a c t i o n of Cu 2S at t h i s point i s 0,82, T h i s i n d i c a t e s a s l i g h t p o s i t i v e d e v i a t i o n from i d e a l i t y i n the pseudobinary. In view of the inherent u n c e r t a i n t i e s i n the i n t e g r a t i o n technique and c o n s i d e r i n g the d i s c u s s i o n of the Cu 2S-Ni^S 2 system given p r e v i o u s l y , i t has been assumed f o r subsequent c a l c u l a t i o n s that the pseudobinary i s an i d e a l s o l u t i o n of Cu nS and N i _ S n , d id Having e s t a b l i s h e d the a c t i v i t y of Cu^S i n the pseudobinary the i n t e g r a t i o n s i n the s i n g l e p h a s e ? l i q u i d r e g i o n are r e a d i l y c a r r i e d out. As i n the m i s c i b i l i t y gap a r e l a t i v e a c t i v i t y i s f i r s t c a l c u l a t e d by i n t e g r a t i o n and the c o r r e c t e d a c t i v i t y i s c a l c u l a t e d from a point of known a c t i v i t y . In t h i s case the poi n t of known a c t i v i t y i s the pseudobinary. The a c t i v i t y of Cu^S as a f u n c t i o n of composition at 1200°C: i s shown i n Figure 13» The i n t e g r a t i o n data i s tabulated i n Appendix VI, A sample i n t e g r a t i o n curve and the curves f o r r e l a t i v e and c o r r e c t e d a c t i v i t y are i n c l u d e d . The A c t i v i t y of Ni„S„ In the s i n g l e p h a s e , l i q u i d region of the ternary, equation ( l l ) was used to o b t a i n the a c t i v i t y of Ni S , Th i s equation was i n t e g r a t e d 90 80 70, • 60 50 40 30 20 10 Mol % Ni - 40 -along l i n e s of constant n c / n M - a r a t i o s proceeding from the pseudo-Cu 2S N i 3 S 2 b i n a r y to p o i n t s of unknown a c t i v i t y , , A -II ,. nI I (<lnS \ d log H 0S/H 0 (11) n C u 2 S N i 3 S 2 In the m i s c i b i l i t y gap the a c t i v i t y of N i _ S n was c a l c u l a t e d 3 2 with equation ( l 2 ) once the, a c t i v i t y of Cu 2S was known i n t h i s r e g i o n . i o g . log 4•-[(d^L) * ^  ^cu 2s ( i 2 ) 3 2 3 2J \aill3S2J log C. , n s 2 The a c t i v i t y p a t t e r n f o r N i ^ S 2 i s shown i n F i g u r e 14. The i n t e g r a t i o n data i s t a b u l a t e d i n Appendix V II. D i s c u s s i o n of the A c t i v i t y P a t t e r n S e l f - C o n s i s t e n c y of the A c t i v i t y Curves 21 In Schuhman's paper on te r n a r y i n t e g r a t i o n s a method i s presented f o r checking a c t i v i t y p a t t e r n s . T h i s check i s based on the f a c t that when the d i r e c t i o n s of the tangents to two a c t i v i t y curves are known at a given p o i n t , the d i r e c t i o n of the tangent to the t h i r d a c t i v i t y curve at that p o i n t can be determined. The curves of H2S/'H2, Q„ c , and <2T have been analysed u s i n g t h i s technique and the system i s observed to be s e l f - c o n s i s t e n t . The A c t i v i t y of Cu^S i n the M i s c i b i l i t y Gap R e f e r r i n g to F i g u r e 12, i t can be seen that the t i e l i n e s i n the m i s c i b i l i t y gap, i f extended, i n t e r s e c t i n a common point g i v e n N i c k e l Sulphide I s o a c t i v i t y P a t t e r n , Cu-Ni-S System, 1200 ° C o Mol % Ni 42' -by the approximate composition = 0o0'2, N ^ = 0.63, and N = 0.35 o Furthermore, i t i s ' observed that the a c t i v i t y of Cu^S i s n e a r l y constant i n the m i s c i b i l i t y gap (0.96 to 0.87). 13 K r i v s k y and Schuhman have g e n e r a l i z e d from observations i n the Cu-Fe-S system that when an extended t i e l i n e passes through a corner of the ternary corresponding to one of the components, the i s o a c t i v i t y l i n e of that component i s tangent to the m i s c i b i l i t y gap at the ends of the t i e l i n e . It may be f u r t h e r g e n e r a l i z e d from the present i n v e s t i g a t i o n that when a s e r i e s of t i e l i n e s pass through a corner corresponding to one of the components, the area enclosed between these t i e l i n e s i s an i s o a c t i v i t y area of that component. Theref o r e , i f the point of common t i e l i n e i n t e r s e c t i o n d i s c u s s e d above was chosen as one of the components of a pseudoternary system, i t s a c t i v i t y would be found to be constant throughout the two phase, l i q u i d r e g i o n . Since there i s l i t t l e composition d i f f e r e n c e between t h i s point and CUgSo i t i s to be expected that the a c t i v i t y of Cu^S w i l l be n e a r l y constant i n the m i s c i b i l i t y gap. T h i s c o n c l u s i o n i s v e r i f i e d by the i n t e g r a t i o n s . DISCUSSION Agreement with Previous Work Although there have been no previous phase e q u i l i b r i a s t u d i e s on the ternary system i t s e l f a number of points of comparison wi t h other work can be made. - 43 -Phase Diagram The conjugate l i n e obtained i n the two phase, l i q u i d r e g i o n i s i n good agreement with the phase diagram of Koster and MulfingerM. The t i e l i n e i n the present study i n d i c a t e s s l i g h t l y more c l o s u r e of the m i s c i b i l i t y gap than i s given i n the published phase diagram. In view of the d i f f e r e n c e s i n the Cu-Cu^S bi n a r y g i v e n by Schuhman and 19 Moles and by Koster and Mulfinger a d d i t i o n a l work i s r e q u i r e d to a c c u r a t e l y d e f i n e the l i m i t s of the ternary m i s c i b i l i t y gap. The Cu-Cu^S Bina r y One melt of approximately the composition Cu^S was. studied,. Although the HgS/H^ r a t i o f e l l w i t h i n the range of values observed by 19 Schuhman and Moles , the accuracy of the analyses i n the present study do not permit a more exact comparison. The H^S/H^ r a t i o s i n t h i s r e g i o n change by more than a f a c t o r of ten over a composition range of l e s s than one atomic percent sulphur. The A c t i v i t y P a t t e r n As there are no other ternary a c t i v i t y patterns f o r t h i s system with which to compare the present r e s u l t s , an i n d i r e c t check must be made. The i n t e g r a t i o n across the m i s c i b i l i t y gap to the Cu 0S-Ni_.S 0 d yd pseudobinary and the s e l f - c o n s i s t e n c y of the a c t i v i t y p a t t e r n i n d i c a t e that the pseudobinary i s an i d e a l s o l u t i o n . T h i s o b s e r v a t i o n agrees 13 17 with the n e a r l y i d e a l nature found i n the CugS-FeS and FeS-FeO systems. In the f o l l o w i n g a n a l y s i s of an i n d u s t r i a l matte i t i s observed that the sum of c2„ Q plus Cl... _ equals approximately u n i t y . Rosenqvist _ 44 -17 and' co-workers have found s i m i l a r behavior f o r copper-iron mattes. The Entropy of Fusio n of Cu^S I f the a c t i v i t i e s of a component of a b i n a r y system are known from experimental data, the procedure of c a l c u l a t i n g a c t i v i t i e s from the phase diagram can be reversed and the a c t i v i t i e s used to c a l c u l a t e 44 the entropy of f u s i o n , Richardson and Webb have a^/Med t h i s technique to c a l c u l a t e the entropy of f u s i o n c f PbO from a c t i v i t i e s i n PbO-SiO^ melts. "The value f o r the heat of f u s i o n from t h e i r work i s approximately 45 three times that g i v e n by K e l l e y Since the a c t i v i t y of Cu^S i s known along the pseudobinary from the r e s u l t s of the present i n v e s t i g a t i o n the entropy o f . f u s i o n may be c a l c u l a t e d from the phase diagram. T h i s has been done i n Appendix VIII and an average value of 6.5 e.u, i s obtained. The corresponding heat of f u s i o n of Cu^S i s 9100 cal/mole. 45 A / K e l l e y has g i v e n A H ^ ^ as 5.500 cal/mole c a l c u l a t e d from the change i n the f r e e z i n g point of Cu^S i n various b i n a r y systems. ^£>f(Cu gy equals 3.92 e.u. According to Richardson and Webb, A l l e y ' s values c a l c u l a t e d i n t h i s manner are too low. 37 Richardson and Ant i l l have obtained a value of 1.64". e.u. as the entropy of f u s i o n of Cu^S from a heat of f u s i o n of 2300 cal/mole observed i n t h e i r i n v e s t i g a t i o n of the heat of s o l u t i o n of s o l i d Cu^S i n l i q u i d Cu^S-Na^S melts. 38 Kubaschewski and C a t t e r a l l have a l s o c a l c u l a t e d a heat of f u s i o n f o r Cu^S of 2300 cal/mole from the d i f f e r e n c e i n the heats of formation at the meltin g point of s o l i d and l i q u i d Cu^S. _ 45 -7 It has been suggested by Ruddle that because of the s i m i l a r i t y i n s t r u c t u r e s of Cu^S and Ag^S the e n t r o p i e s of f u s i o n f o r the two 18 compounds should be approximately the same. Rosenqvist has c a l c u l a t e d the entropy of f u s i o n of Ag^S to be approximately 0.72 e 0 u 0 He concludes that because of the s t r u c t u r e of kg^S, e s s e n t i a l l y a random d i s t r i b u t i o n of s i l v e r i n the sulphur l a t t i c e , the entropy of f u s i o n should correspond to the breaking down of the sulphur l a t t i c e only. Using the data of 33 Kubaschewski and Evans the entropy of f u s i o n f o r monoclinic sulphur i s c a l c u l a t e d to be 0.765 e,u, From the data of K e l l e y ^ , As^(Ag^S.): i s found to be 3.0 e.u. Kubaschewski and Catterall have given the heat of f u s i o n of AggS as 2700 cal/mole corresponding to an entropy of f u s i o n of 2»42 e.u. 46 In a recent paper by F o s t e r and Frank , i t has been suggested that the c a l o r i m e t r i c heat of f u s i o n i s made up of two components, a heat of f u s i o n plus a heat of d i s s o c i a t i o n . I t i s b e l i e v e d that the 7 metal sulphides are l a r g e l y d i s s o c i a t e d . T h i s f a c t may account f o r the d i f f e r e n t values f o r A s ^ C U g S ) which have been observed. Owing to the l a r g e s o l i d s o l u b i l i t y which e x i s t s i n the Cu^S-FeS pseudobinary, i t i s not p o s s i b l e to c a l c u l a t e a c t i v i t i e s from t h i s phase diagram. Since there are no other accurate phase diagrams and a c t i v i t y p a t t e r n s f o r binary s u l p h i d e systems i t does not appear p o s s i b l e to check the entropy values without f u r t h e r experimental work. Neither does i t appear f r u i t f u l at t h i s point to compare the v a r i o u s entropy values of CUgS with each other or with those f o r Ag^S. - 46 -A Pseudo-component of the Ternary System The point of common t i e l i n e i n t e r s e c t i o n of the m i s c i b i l i t y gap has been mentioned p r e v i o u s l y i n connection with the a c t i v i t y p a t t e r n of C ^ S o - Although no compound has been r e p o r t e d i n t h i s r e g i o n of the ternary the point behaves as a component of the system and c o n t r o l s the a c t i v i t y p a t t e r n f o r a large p o r t i o n of the l i q u i d r e g i o n . I t should be pointed out that the copper to sulphur r a t i o at t h i s point i s very 8 n e a r l y that of the compound d i g e n i t e , Cu^S^ ° I t i s u n l i k e l y however, that d i g e n i t e i s s t a b l e at 1200°C. It has been shown that the a c t i v i t y , of a pseudocomponent of t h i s composition would have a constant a c t i v i t y i n the i m m i s c i b i l i t y r e g i o n . The presence of t h i s pseudocomponent causes the i n t e r c e p t s of the extended t i e l i n e s of the m i s c i b i l i t y gap to be approximately constant on the Cu„S-Ni_S n pseudobinary and on the Cu-S b i n a r y . The presence d t> d of these constant i n t e r c e p t s causes the a c t i v i t y of C^S to be n e a r l y constant i n t h i s r e g i o n and r e s t r i c t s the a c t i v i t y of Ni_.S„ to low y d values over an a p p r e c i a b l e composition range. The question of the form t h i s pseudocomponent takes or why i t e x i s t s cannot be answered from the data a v a i l a b l e at present. The Thermodynamic A n a l y s i s of a Commercial. Matte at 1200°C In recent l i t e r a t u r e a converter matte of the composition 6 46$ N i , 30$ Cu, and 21,5$ S has been g i v e n . T h i s corresponds to mol f r a c t i o n s of 0.42 N i , 0.25 Cu, and 0.33 S . From F i g u r e s 13 and 14 c^Cu g = 0.46 and (X^^ g = 0,53, Log H g S / H g i s observed to be —1,153 and the sulphur pressure i s c a l c u l a t e d to be approximately 3 x 10 atmospheres. _ 47 -From equation (6), (2^ i s c a l c u l a t e d to be 0.163 and from equation (5);, <Xa, equals 0.208. CONCLUSIONS Techniques have been devised f o r e q u i l i b r a t i n g l i q u i d copper-n i c k e l mattes at 1200°C with atmospheres of E^. and HgS. The e q u i l i b r i u m r a t i o s of H^S/H^,which are a measure of the a c t i v i t y of sulphur, have been obtained. From the H^S/H^ r a t i o s the a c t i v i t i e s of Cu^S and Ni^S^ have been c a l c u l a t e d by m o d i f i c a t i o n s of the Gibbs-Duhem equation. E q u i l i b r i u m constants have been obtained f o r the Cu-Cu-S and N i - N i , S 0 2 32 b i n a r i e s from which the a c t i v i t i e s of Cu and Ni can be c a l c u l a t e d f o r any point i n the l i q u i d r e g i o n . It has been found that the a c t i v i t i e s of Cu 0S and Ni_S,. obey 2 3 2 Raoult's Law i n the pseudobinary. The presence of a pseudocomponent of the composition 0.02 0.63 N Q ^ J A N D 0°35 Ng 9 has been observed. T h i s pseudocomponent has a constant a c t i v i t y i n the i m m i s c i b i l i t y r e g i o n and i t s presence dominates the a c t i v i t i e s of the other components i n t h i s a rea. The a c t i v i t y of Cu^S i s approximately a constant i n the m i s c i b i l i t y gap and the a c t i v i t y of N i , S 0 i s r e s t r i c t e d to low v a l u e s . 3 2 The entropy of f u s i o n f o r Cu^S has been c a l c u l a t e d from the phase diagram and a c t i v i t y p a t t e r n f o r the Cu_S-Ni,S 0 pseudobinary. 2 3 2 The va l u e obtained was 6.5 e.u. , An i n d u s t r i a l converter matte has been thermodynamically analysed. It i s observed that the sum of (2 plus £2 _ i s approximately u n i t y . Cu 2u - N i 3 S 2 - 48 -APPENDIX I Summary of Thermodynamic Data D i s c u s s i o n s of the thermodynamic data of importance to copper 48 T IT smelting have been g i v e n by Schuhman , Ruddle , and Rosenqvist The thermodynamics of r e a c t i o n s of i n t e r e s t to the present i n v e s t i g a t i o n are summarized below. H 2-S 2 l o 2 H 2 + S 2 = 2 H 2 S A F ° = - 4 3 , 1 6 0 + 2 3 . 6 1 T ( 4 8 ; ) * 2 „ S 2 = 2 S A F ° = + 7 7 , 2 5 0 - 2 9 o 7 0 T ( 4 8 ) Cu - S 3 o 2Cu(s); + l / 2 S 2 ( g ) = Cu2S(0(X A F ° ( 2 9 8 - 3 7 6 ° K ) ; = - 3 2 , 4 8 0 + 1 0 . 0 9 T ( 4 8 ) ; 4 . 2Cu(s) + l / 2 S 2 ( g ) = Cu 2 S ( | 3 ) A F ° ( 3 7 6 - 6 2 3 ° K ) = - 3 1 , 5 6 0 : + 7 o 6 4 T ( 4 8 ) 5 o 2Cu(s) + l / 2 S 2 ( g ) ; = C u 2 S (Y) A F ° = ( 6 2 3 - 1 3 5 6 ° K ) ; = - 3 1 , 3 6 0 + 7 o 3 2 T ( 4 8 ) 6 . 2Cu(l) = 2Gu(s) A F ° = - 6 2 0 0 + 4 o 5 6 T ( 3 3 ) 2Cu(l); + l / 2 S 2 ( g ) = cu 2 s (y) A F ° ( l 3 5 6 - 1 4 0 3 ° K ) = -37,560 + 11„88 T * Reference i n b i b l i o g r a p h y 8. Cu 2S(Y) = C u 2 S ( l ) ; A F ° = 2,300 - l c 6 4 T 9. 2Cu(l) + l/2'S 2(g) = Cu 2S(l); A F ° ( T > 1403°K); = -35,260 + 10..24 T combining equations 1 and 9s 10. 2Cu(l); + H 2S(g); = C u 2 S ( l ) + H 2(g) A F ° ( T > 1403°K); = ^13 9680 + 1.57 T Ni~S l l o - 3/2Ni(s) + l/2S 2(g) = l/2Ni 3S 2(p) A F ° ( 6 7 3 - 808°K): = -39,620 + 19.51 T 12. 3/2Ni(s) + l / 2 S 2 ( g ) = l/2 Ni S 2(YX A F ° ( 8 0 8 - 1063°K); = -34,750 + 13.5 T 13. l/2Ni 3S 2 ( Y ) . = 1/2 Hi 3S 2 ( l ) A F ° = 2900 - 2.7 T 14. 3/2Ni(s) + l/2S 2(g) = l / 2 N i 3 S 2 ( l ) A F ° ( l 0 6 3 - 1723°K) = -31,850 + 10.8 T 15. Combining equations 1 and 14s 3/2Ni(s) + H 2S(g) = l / 2 N i 3 S 2 ( l ) + H2(g) A F ° ( 1 0 6 3 - 1723°K) = -10,270 - 1.0 T APPENDIX I I C o r r e c t i o n f o r the D i s s o c i a t i o n of H^S From equation 1, Appendix- -I; ** C a l c u l a t e d from the data given by Rosenqvist 50 -2Hg + S 2 = 2H2S A F ° = -43,160 + 23.61 T (P H c/P H )' K = H 2 S V S 2 At 1200°C; P s = 0.0575 (P„ Jv ) S 2 H 2 S H2 Assuming that P„ „ = 0,2: atm. and PTT = 0.8 atm, i n t h e hot zone of the furnace, HgS/Hg equals 0,25 and Pg i s c a l c u l a t e d t o be 0,00359 atm In the cold zone of the furnace each S 2 molecule combines with t w o E^ molecules to produce t w o E^S molecules. The observed H 2 s / H 2 r a t i o can be c a l c u l a t e d as f o l l o w s . P + 2P H ? S/H (observed) = H 2 S S 2 = 0.26 P - 2P H 2 S 2 The change i n the H 2 S / H 2 r a t i o can be calculated from the differe n c e between H 2 S / H 2 (observed) and H 2 S / H 2 (corrected). A (H 2S/H 2) - H 2 S / H 2 (observed) - H 2 S / H 2 (corrected) = 0.26 - 0,25 = 0.01 For a series of assumed values of H 2 S / H 2 (corrected), the change i n the r a t i o s can be calcula t e d , and plo t t e d as a function of the observed r a t i o s as shown i n Figure I I - l . The observed experimental r a t i o s have been corrected using a curve such as t h i s . o F i g u r e I I - l . C o r r e c t i o n Curve f o r D i s s o c i a t i o n of H„S, 1 2 0 0 C. - 52 -APPENDIX I I I Summary of Data f o r Ni-Ni^S^ System Statement: l o g Q. log H 2 S / » 2 N i 3 S 2 ~ J N N i 3 S 2 V N N i 3 S 2 d l o g H 2S/H 2 l o g a N i 3 S 2 a 0,412 0,400 0,380 0,360 0,340 0,320 0,300 0,280 0,260 0,240 0,220 0,200 0.121* 0,70 + 05 35 60 80 95 ICT 20 2.257+ 2.35 + 2.40 + 0.000 -0.163 -0.318 -0,455 -0.573 -0.713 -0.834 -0.946 0.000 -0.024 -0.106 -0.184 -0,286 -0.383 -0,488 -0.578 1.000 0,945 0,784 0,655 0,517 0,415 0,325 0.264 0.288** 0.200** 0,184** -it-+ From the present i n v e s t i g a t i o n E x t r a p o l a t e d from the data of Rosenquist E x t r a p o l a t e d 20 APPENDIX IV C a l c u l a t i o n of Q „ „ from the Phase Diagram of the Cu^S-Ni^S^ Pseudobinary ( T -T'm ) A S f (C u 2 S ) Statement; l o g fl*.^ = 4,575 T AS f(Cu 2,S) = 1,64 e.u. N C u 2 S Liquidus Temperature T l o g a (°K) C U 2 S T Q C u 2 S ^1200°C. Cu 2S 1.00 1403 0.000 1.000 1.000 0.92 1373 -0.0078 0.984 0.976 0.73 1273 -0.0366 0.920 0.890 0.54 1173 -0.0704 0.850 0.760 0,36 1073' -0.110 0.777 0.630 0,245 993 -0.148 0.712 0.514 * Regular s o l u t i o n c o r r e c t e d f o r temperature APPENDIX V Experimental R e s u l t s Melt $ N i * $Cu* Ni N N s (H S/H ) obs. A(H S/H ) (H S/H ) logH S/H. Cu c o r r . 1 72,3 0 ' 27.7 0.588 0.000 0.4121 0.986 0.229 0.757 -0.121 2 68o5 4.5 27.0 0.560 0.035 0.405 0.486 0.044 0.442 -0.355 3 65.9 7.5 26.6: 0.5.41 0.059 0.400 0.285 0.013 0.272 -0.565 4 48.5 27.0 25 o 5 0.403 0.209 0.388 0.188 0.004 0.184 -0.735 5 46.2 28.9 24c9 0.390 0.226 0.384 0.189 0.004 0.185 -0.733 6 40.4 35 = 7 23 c9 0.346 0.282 0.372 0.175 0.0034 0.172 -0.764 7 27.5 49.9 22.6 0.239 0.401 0.360 0.110 0.0010 0.109 -0.963 8 71.4 3.2 25o4 0.590 0.027 0.383 0.122 0.0012 0.121 -0.917 9 68.4 6.7 24.9 0.572 0.052 0.376 0.090 0.0007 0.089 -1.051 10 63.6 12.7 23.8 0.535 0.098 0.367 0.075 0.0004 ' 0.075 -1.125 11 35.8 50..7 13.5 0.333 0.437 0.230 0.055 0.0002' 0.055 -1.260 12 26.4 6 2..8 10.8 0.254 0.556 0.190 0.050 0.050 -1.301 13-A 20.9 73.5 5.6 0.212 0.684 0.104 0.045 0.045 -1..347 13-B 6.2 76.1 17.-7 0.056 0.644 0.300 0.045 0.045 -1.347 14 0.0 20.2 79.8 0.000 0.665 0.335 0.039 0.039 -1.457 2 • C o r r e c t e d to 100$ t o t a l - 5 4 -APPENDIX VI I n t e g r a t i o n data f o r Cu^S Statement: Equation 10, page 37 A'-.. Two Phase L i q u i d Region lo g H 2S/H 2 n S / n C u 2 S 6 l 0 g a C u 2 S * ^Cu 2S 4u2S -1.28 0.145' 0.000 1.00 0.870 -1.30 0.163 0.0028 1.01 0.885 -1.33 0.175 0.0071 1.02 0.890 -1.35 0.226 0.0119 1.03 0.897 -1.40 0.289 0.017 1.04 0.906 -1.45 1.06 0.925 -1.65 1.08 0.940 -2.37 1.10 0.958 B. S i n g l e Phase L i q u i d Region Cu' Ni N S l o g H 2S/H 2 a n S ^ n C u 2 S d l 0 e * C u 2 S * a C u 2 S Cu 2S 0.75/0.25 0.250 -1.28 0.125 +0.011 1.030 0.844 0.320 -1.20 0.077 +0.003 1.010 0.826 0.368 -1.00 0.000 0.000 1.000 0.818 0.60/0.40 0.095 -1.65 -1.040 -0.345 0.452 0.313 0.120 -1.35 -1.020 -0.370 0.920 0.646 0.170 -1.30 -0.5.90 +0.003 1.010 0.699 0.294 -1.20 +0.058 +0.017 1.040 0.720 0.330 -1.15 +0.148 +0.013 1.030 0.714 0.360 -1.00 +0.030 0.000 loOOO 0.692 0„40/0„60 0.145 -2.00 -1.180 -0.949 0.113 0.057 0.190 -1.35 -1.240 -0.169 0.678^ 0.339 0.215 -1.30 -1.180 -0.108 0.780 0.390 0.257 -1.25 -0.750 -0.059 0.875 0.438 0.290 -1.20 -0.370 -0.031 0.932 0.466 0.320 -1.15 -0.183 -0.018 0.960 0.480 0.370 -1.00 -0.030 -0.003 0.994 0.495 55 Appendix VI Continued 0.20/b.80 0.160 -2.40" -1.050 -0.973' 0.107 0.229 0.217 -2.00 -1.450 -0..473 0.337 0.092: 0.273 -1.35 -1.540 -0.245 0.570 0.156 0o290 -1.30 -1.360 -0.175 0.670 0.183 0o309 -1.25 -1.080 -0.113 0.773 0.211 Oo330 -1.20 -0.872' -0.065 0.862 0.237 0„350 -1.15 -0.436 -0.034 0.925 0.253 * R e l a t i v e A c t i v i t y + Corrected A c t i v i t y C. Sample I n t e g r a t i o n To i l l u s t r a t e the i n t e g r a t i o n technique a sample i n t e g r a t i o n i s shown i n t h i s s e c t i o n . The i n t e g r a t i o n path of n C u / n N i equals 0.40/0.60 i s chosen. This corresponds to an n n 0 / n „ . 0 r a t i o of 0.50/o.50. The i n t e r c e p t s of the tangents to the i s o a c t i v i t y l i n e s of sulphur on the Cu-S b i n a r y are given i n column four of the t a b l e i n Appendix VI-B. These i n t e r c e p t s are p l o t t e d as a f u n c t i o n of l o g H^S/H^ as shown i n Figure V I-1. d log Q. i s obtained by grap h i c i n t e g r a t i o n Ou^o and i s tabulated i n the f i f t h column. From the change i n d log G Cu^S a r e l a t i v e a c t i v i t y f o r Cu^S can be c a l c u l a t e d . The r e l a t i v e a c t i v i t y curve i s shown i n Fig u r e VI-2. The r e l a t i v e a c t i v i t y curve can be e x t r a p o l a t e d to the pseudo-binary where the a c t i v i t y of Cu^S i s known. The c o r r e c t i o n f a c t o r i s thus obtained to adjust the r e l a t i v e a c t i v i t i e s and the c o r r e c t e d a c t i v i t i e s are c a l c u l a t e d . The c o r r e c t e d a c t i v i t i e s are shown i n F i g u r e VI-2 and are t a b u l a t e d i n the preceeding t a b l e . 56 --1.0 -2.0 l o g K 2S/H 2 F i g u r e VI-1. Graphic I n t e g r a t i o n Curve f o r l o g <2( - 57 -F i g u r e VI-2„ R e l a t i v e and Corrected A c t i v i t i e s f o r Cu0S<, 5 8 -APPENDIX VII I n t e g r a t i o n Data f o r ^ i ~ S 2 A o S i n g l e Phase L i q u i d Region Statement: Equation 1 1 , page 4 0 . ®n AM-Cu' Ni N s log H2S/H'2 dVHi s d 3 2 3 2 * a N i 3 S 2 O o 2 0 / 0 . 8 0 O0I6O - 2 . 4 0 - 1 . 2 5 - 0 . 8 7 1 0 . 1 3 5 0 . 1 0 2 O0I88 - 2 , 2 5 - 1 . 0 5 - 0 . 6 9 9 0 . 2 0 0 0 . . 1 5 2 0 „ 2 4 3 - 2 „ 0 0 - 0 . 6 4 0 - 0 . 2 3 4 0 . 5 8 4 0 . 4 4 3 0 . 2 7 3 - 1 . 6 5 - 0 . 5 8 5 - 0 . 0 8 4 0 . 8 2 5 b . 6 2 5 0 o 3 5 0 - 1 . 1 5 - 0 . 2 3 8 - 0 , 0 1 9 0 . 9 5 7 0 . 7 2 5 O o 4 0 / O o 6 0 0 o l 4 5 - 2 . 0 0 -0.935 - 0 . 6 7 3 0 o 2 1 2 0 . 1 1 6 O0I8O - 1 . 4 5 -0.685 - 0 . 2 0 6 0 o 6 2 2 0 . 3 4 1 O o 2 1 5 - 1 . 3 0 - 0 . 5 4 5 - 0 . 1 1 2 0 o 7 7 9 0 . 4 2 7 O o 3 2 0 - 1 . 1 5 - 0 . 3 8 0 - 0 . 0 4 0 0 . 9 1 2 0 . 5 0 0 0 o 6 0 / 0 o 4 0 0 , 1 2 0 - 1 . 3 5 - 0 . 8 3 5 - 0 . 3 0 6 0 . 4 9 5 0 . 1 5 3 0 o l 7 0 - 1 . 3 0 - 1 . 2 4 - 0 . 2 5 5 0 . 5 5 6 0 . 1 7 1 ' 0 o 2 9 4 - 1 . 2 0 - 1 . 1 8 - 0 . 1 2 3 0 . 7 5 5 0 . 2 3 2 O o 3 3 0 - 1 . 1 5 - 0 . 8 4 8 - 0 . 0 7 1 0 . 8 5 0 0 . 2 6 2 O o 3 6 0 - 1 . 0 0 - 0 . 0 7 9 0 . 0 0 0 1 . 0 0 0 0 . 3 0 8 0o75/0o25 0 o 2 5 0 - 1 . 2 8 - 2 . 7 8 - 0 . 3 6 0 0 . 4 3 7 0 . 0 9 6 0 o 2 8 0 - 1 . 2 5 - 2 . 2 2 - 0 . 2 3 3 0 . 5 8 5 0 . 1 2 8 0 » 3 2 0 - 1 . 2 0 - 1 . 5 5 - 0 . 1 4 0 0 . 7 2 5 0 . 1 5 9 O o 3 5 0 - 1 . 1 5 - 0 . 7 7 - 0 . 0 8 0 0 . 8 3 2 0 . 1 8 2 B. Two Phase L i q u i d Region Statement: Equation 1 2 , page 4 0 c a 0-u2S l o g a cu 2s d n C u 2 S / 9 n N i 3 S 2 d l o g a N i 3 S 2 a N i 3 S 2 a N i 3 S 2 0 . 8 7 0 0 . 8 8 0 0 . 8 9 0 0 . 8 9 7 0 . 9 0 6 0 . 9 2 5 0 . 9 4 0 0 . 9 5 8 •O0O6 - 0 . 0 5 6 - 0 . 0 5 1 - 0 . 0 4 7 - 0 o 0 4 2 - 0 . 0 3 4 - 0 . 0 2 7 - 0 . 0 1 8 23.4 4 6 . 0 . 0 . 0 0 0 - 0 . 0 9 7 - 0 . 2 3 6 - 0 . 3 2 7 - 0 . 5 2 8 - 0 . 8 3 2 - 0 . 1 1 3 6 1 . 0 0 0 0 . 8 0 0 0 . 5 8 0 0 . 4 7 0 0 . 2 9 6 0 . 1 4 7 0 . 0 7 3 0 . 0 0 0 0 . 1 0 0 . 0 8 0 . 0 5 8 0 . 0 4 7 0 . 0 3 0 0 , 0 1 5 0 , 0 0 7 0 , 0 0 0 „ 5 9 -APPENDIX VIII C a l c u l a t i o n o f A S . f C u ^ S J from an „ and the_Cu„S-Ni_S.Phase Diagram Statement: A S Cu S = 4 , 5 7 5 T L O G ^CUQS T-Tm T = temperature of l i q u i d u s Tm = f u s i o n temperature of Cu 0S T(°K) " C U 2 S a C u 2 S l 0 S a C u 2 S T-Tm A s f (e. 1403 1.00 1.00 0.000 0 1373 0.93 0.93 -0.320 30 6.70 1273 0.73 0.73 -0.137 130 6.14 1173 0.54 0.54 -0.268 230 6.25 1073 0.36 0.36 -0.444 330 6.60 993 0.245 0.245 -0.611 410 6.78 Average 6 .5 e.u. - 60 -BIBLIOGRAPHY lo R.F, Pearce, J„P„ Warner, and V.No Mackiw, J . 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