Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The simultaneous determination of vanadium and molybdenum Stuart, Frank Albert 1940

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1940_A8 S7 S5.pdf [ 1.53MB ]
Metadata
JSON: 831-1.0062261.json
JSON-LD: 831-1.0062261-ld.json
RDF/XML (Pretty): 831-1.0062261-rdf.xml
RDF/JSON: 831-1.0062261-rdf.json
Turtle: 831-1.0062261-turtle.txt
N-Triples: 831-1.0062261-rdf-ntriples.txt
Original Record: 831-1.0062261-source.json
Full Text
831-1.0062261-fulltext.txt
Citation
831-1.0062261.ris

Full Text

THE SIMULTANEOUS DETERMINATION.0? VANADIUM AND MOLYBDENUM by FRANK,ALBERT STUART A Thesis Presented to the Department of Chemistry as Part of the Requirements f o r the Degree of Master of A r t s * UNIVERSITY. QE BRITISH COLUMBIA APRIL 1940 ACKNOWLEDGMENT I wish to express to Dr. J . A l l e n H a r r i s my a p p r e c i a t i o n of h i s advice and assistance i n the supervision of t h i s research. CONTENTS PAGE INTRODUCTION •' 1 VANADIUM 2 Reduction with Sodium Sulphite 3 Reduction with Zinc 3 MOLYBDENUM 4 P r e c i p i t a t i o n of the Lead S a l t 4 Jones Reduetor Method 5 Reduction of Molybdate by a Metal 5 Reducing Agents other than Metals 6 Permolybdates 8 SUMMARY 8 COLQRIMETRIC RESEARCH 11 Molybdenum Blue 11 Reduction of Phospho Molybdic A c i d 12 Permolybdic A c i d 15 SUMMARY .16 BIBLIOGRAPHY 17 THE SIMULTANEOUS DETERMINATION OF VANADIUM AND MOLYBDENUM INTRODUCTION: The Increasing importance of s t e e l a l l o y s i n modern i n d u s t r y has g r e a t l y increased the demand f o r r a p i d and more accurate methods of determination f o r such metals, as manganese, chromium, n i c k e l , t i t a n i u m , vanadium and molybdenum. Inasmuch as seve r a l of these elements may be desired as a component of an a l l o y , the value'of methods which determine two or more metals i n the same procedure i s obvious. Considerable work has been done i n t h i s d i r e c t i o n by W i l l a r d and Young and a l s o by K o l t o f f and Sandell on the simultaneous determination of chromium, vanadium and 3 tungsten. Not since the work of S t e f f a n . however, i n 1902, has any reference, been found to an attempt to determine vanadium and molybdenum together. I f such a method were po s s i b l e i t would f i n d immediate a p p l i c a t i o n i n s t e e l and rock a n a l y s i s , as considerable amounts of both metals are found together i n these sources. To obtain such an a n a l y t i c method was the object of t h i s research. I t was hoped that t h i s could be obtained through the f o l l o w i n g general operations: 1. 764, 769, Indus and Eng. Chem. 1928. 2. 140 Indus and Eng. Chem. Anal. Sec. 1950. 3. S t e f f a n , Inaug. D i s s e r t a t i o n Zurich 1902. 1. Reduction of molybdate and vanadate to d e f i n i t e lower Valence s t a t e s . " 2. Quantitative o x i d a t i o n of both metals to t h e i r , o r i g i n a l s t a t e s . 3. Reduction of the vanadate alone. 4. Quantitative o x i d a t i o n of the reduced vanadium. 5. Vanadium and molybdenum concentrations obtained by simple c a l c u l a t i o n . Chief d i f f i c u l t i e s were expected to l i e i n o b t a i n -ing reducing agents of' proper strengths and i n removing t h e i r excess. To study these f a c t o r s p r e l i m i n a r y i n v e s t -i g a t i o n s were c a r r i e d out with vanadium and molybdenum separately. I*- VANADIUM; Vanadium i s reduced to various valence states by such common reducing agents as the metals, sodium t h i o -• s u l p h a t e > sulphur di o x i d e and hydrogen sulphide. Of these several lend themselves f a i r l y w e l l to the proposed plan of a n a l y s i s . Oxalic a c i d , c i t r i c a c i d or sulphur dioxide completely reduce vanadium without a t t a c k i n g molybdenum, and the problem of removal of excess i s not d i f f i c u l t . -Excess oxalate may be p r e c i p i t a t e d and excess sulphur dioxide may be removed by b o i l i n g and bubbling i n carbon d i o x i d e . In the course of t h i s i n v e s t i g a t i o n two o r i g i n a l methods of determining vanadium were devised. 1. REDUCTION WITH SODIUM SULPHITE: The a c i d vanadate s o l u t i o n i s heated to b o i l i n g and small amounts of s o l i d sodium s u l p h i t e are added. Reduction proceeds r a p i d l y to the c l e a r blue s o l u t i o n of the vanadyl s a l t and excess s u l p h i t e i s completely removed by b o i l i n g w i t h sulphuric a c i d f o r about ten minutes. The vanadyl s a l t may then be t i t r a t e d w ith standard potassium permanganate. This method i s e s s e n t i a l l y T r e a d w e l l - E a l l s 4 sulphur dioxide method, but i t avoids the n e c e s s i t y of gas apparatus and generators, and i s much more r a p i d . ' 2. REDUCTION WITH ZINC: The hot a c i d vanadate s o l u t i o n i s tr e a t e d with m e t a l l i c zinc u n t i l a deep green s o l u t i o n i s obtained. The excess z i n c i s removed and a few cc. of concentrated n i t r i c a c i d are added u n t i l a c l e a r blue c o l o r , i n d i c a t i n g the formation of vanadyl i o n , i s obtained. The vanadyl s a l t i s now t i t r a t e d i n the usual manner. I f , on th e - a d d i t i o n of n i t r i c a c i d , a green c o l o r persists., the o r i g i n a l r e d u c t i o n was incomplete. Zinc reduces a vanadate i n acid s o l u t i o n to the vanadyl and then to the vanadic s a l t . A green color i s obtained throughout the r e a c t i o n , but the f i r s t i s due to a combination of the blue vanadyl and yellow vanadate s a l t s . The vanadic i o n i s unstable and normally reacts with the vanadate, or i s o x i d i z -ed by a i r , to 'form the vanadyl s a l t . This a c t i o n , however, 4. P. 538 Treadwell-Halls A n a l y t i c Chemistry V o l . I I . i s extremely .slow, whereas the a d d i t i o n of n i t r i c aeid gives the blue vanadyl s a l t i n s t a n t l y . Both of the above methods of determination are rapi d and accurate and as they involve no s p e c i a l technique o f f e r considerable improvement over present methods. With these and other standard methods of vanadium a n a l y s i s , the l a t t e r part of the 1proposed method, i . e . reduction of vanadium with no a c t i o n on molybdenum, i s com-p a r a t i v e l y simple•and the problem reduces i t s e l f to an i n v e s t i g a t i o n of molybdenum reduction. I I . MOLYBDENUM: At the present time two methods are commonly employed i n lab o r a t o r y and i n d u s t r i a l work f o r the estimation 5 of molybdenum. 1* PRECIPITATION.OF THE LEAD SALT: Lead molybdate may be q u a n t i t a t i v e l y p r e c i p i t a t e d and weighed to give an exact determination of molybdenum over a wide range of c o n d i t i o n s . Very few substances i n t e r f e r e , a p r a c t i c a l l y pure p r e c i p i t a t e i s found, and a very accurate value i s obtained. The method, however, has the shortcomings of a l l gravametric determinations, i n that i t i s slow, and involves 5. Bureau of Mines Te c h n i c a l Paper No. 230. tedious f i l t r a t i o n and i g n i t i o n . 2. JONES RSDUCTOR .METHOD: This method in v o l v e s the passing of the a c i d molybdate s o l u t i o n through a Jones reduetor of amalgamated zin c i n t o a standard s o l u t i o n of ferrous ion.. The method i s reasonably accurate but rather slow, and as a i r must be excluded s p e c i a l technique i s r e q u i r e d . Other methods f o r estimating molybdenum have been proposed, but they are,.on the whole, u n s a t i s f a c t o r y due to • • • . • • f t ' - - -the i n t e r f e r e n c e of other elements. I t i s therefore appar-ent that even apart from the o r i g i n a l plan of t h i s research e x i s t i n g a n a l y t i c a l methods f o r molybdenum are by no means completely s a t i s f a c t o r y . On a p r e l i m i n a r y survey of the chemistry.- of molybdenum, s e v e r a l p r o p e r t i e s suggest themselves as l i k e l y means f o r estimating the element. I t e x i s t s i n seve r a l stages of oxidation.below the normal s i x , the lower forms being i n s o l u b l e i n a l k a l i n e s o l u t i o n , and also forms a permolybdate i n which molybdenum has the valence eight. .. We w i l l consider these valence states i n order, the methods a p p l i e d , and the r e s u l t s obtained. 1. REDUCTION OF MOLYBDATE BY A METAL: Acid molybdate solutions, are reduced by metals to 6. P. 221. B. S. Hopkins Chemistry of the Rarer Elements. 6. form a blue c o l l o i d a l complex oxide,; g e n e r a l l y recognized to be of the form MoOg-SMoOg. This complex i s b e l i e v e d to e x i s t i n seve r a l d i f f e r e n t combinations of the oxides but an e f f o r t was made to produce the same form c o n t i n u a l l y by maintaining the same conditions, with the idea of i n v e s t -i g a t i n g the p o s s i b i l i t y of o x i d i z i n g i t q u a n t i t a t i v e l y to the molybdate. . This attempt was not s u c c e s s f u l . I t was found that, i f the lower metals of the electromotive s e r i e s , e.g. lead or copper, were used, a black deposit forms on the surface of the metal, apparently removing some of the molybdenum from the s o l u t i o n and rendering any q u a n t i t a t i v e work im-p o s s i b l e . On the other hand, i f a c t i v e metals such as magnesium were used, reduction was not consistent and values obtained by t i t r a t i n g the complex with standard permangan-ate showed no d e f i n i t e r e l a t i o n to the concentration. 2. REDUCING AGENTS OTHER THAN METALS: Attempts at reduction w i t h other reducing agents i n n e a r l y a l l cases met with f a i l u r e . The reagents used include ferrous sulphate, sodium s u l p h i t e , arsenious a c i d , o x a l i c a c i d , and potassium i o d i d e . In a l l cases but the l a s t , no reduction could be obtained. This r e d u c t i o n has been e x t e n s i v e l y studied by S t e f f a n 7 and Gooch and F a i r b a n k s 8 . The l a t t e r workers 7. S t e f f a n , Inaug. D i s s e r t a t i o n , Z u r i c h 1902. 8. Z. Anorg. Chem. 13. 101 (1897) and 14, 317. attempted to use i t q u a n t i t a t i v e l y by d i s t i l l i n g the iodine vapors and t i t r a t i n g with sodium thio s u l p h a t e . They found the r e a c t i o n hard to c o n t r o l and could not obtain accurate r e s u l t s , as the degree of reduction v a r i e d with the time of-d i s t i l l a t i o n . Their r e s u l t s were confirmed by S t e f f a n . q Friedheim and Euler determined vanadic and moly-bd i c . a c i d s together i n s o l u t i o n by d i f f e r e n t i a l r e d u c t i o n with potassium bromide and potassium i o d i d e . I t has been proved, however, by Gooch and F a i r b a n k s 8 , that the r e a c t i o n i s not accurate, and may stop at any one of several stages. The r e a c t i o n was studied here, by electr o m e t r i e t i t r a t i o n of standard pota'ssoiula i o d i d e o s o l u t i o n i n t o a molybdate s o l u t i o n c o n t a i n i n g a large excess of hydr o c h l o r i c a c i d . No d e f i n i t e break i n the curve .vms observed and continuous f l u c t u a t i o n of the galvanometer needle during the course of the t i t r a t i o n i n d i c a t e d a complex r e a c t i o n . Error i s possible from two sources: (a) o x i d a t i o n of the reduced molybdenum by a i r , and (b.) oxi d a t i o n of potassium iodide by a i r . Inasmuch as the t i t r a t i o n , to be s u c c e s s f u l , would have to be c a r r i e d out e l e c t r o m e t r l c a l l y , e l i m i n a t i o n of t h i s e r r o r i s impossible. . I t i s evident then that to be p r a c t i c a l some method of c o n t r o l l i n g the r e a c t i o n i s necessary. This could best be accomplished by removing the pentavalent molybdenum s a l t from s o l u t i o n e i t h e r as a p r e c i p i t a t e or a complex i o n , or 9. Ber. 88, 2067 (1895). 8. Z. Anorg. Chem. 13. 101 (1897) and 14, 317. 8. by removal of free iodine by some method other than d i s t i l -l a t i o n , i n the absence of a i r . At t h i s time neither of these has been accomplished but i t would appear l i k e l y that with some such devieawihe r e a c t i o n would go to d e f i n i t e stages, depending on the temp-erature. The s o l u t i o n would seem to l i e i n an i n v e s t i g a t i o n of the pentavalent molybdenum compounds and.a study of t h e i r p r o p e r t i e s , with a view to separating the reduced molybdenum s a l t from the.molybdate. 3. PERMQ LYBDAT ES: > I f an a c i d s o l u t i o n of a molybdate i s treated with hydrogen peroxide, a compound i s formed whose composition corresponds to a perniolybdate^ The ' p o s s i b i l i t y of applying t h i s r e a c t i o n to a q u a n t i t a t i v e determination was considered but not attempted for s e v e r a l reasons. ; (a) The method would involve use of standard hydrogen peroxide, s o l u t i o n which i s h i g h l y u n s a t i s f a c t o r y . (b) The r e a c t i o n would require an excess of peroxide to o x i d i z e a l l of the molybdate to the permolybdate. (c) An i n d i c a t o r would have to be devised as the, c o l o r change i n the r e a c t i o n i s not great enough to be i t s own i n d i c a t o r . SUMMARY: (1) An i n v e s t i g a t i o n w i t h a view to determining molybdenum and vanadium simultaneously has been made. The e f f o r t was unsuccessful due to the f a c t that molybdenum can-not be q u a n t i t a t i v e l y reduced to i t s pentavalent state by any known procedure. I t may be w e l l to point out here that vanadium and molybdenum can, i n a l l p r o b a b i l i t y , be reduced together i n a Jones reduetor, both going down to the t e r -valent s t a t e . The reduced s o l u t i o n could be passed i n t o standard .ferrbus sulphate and the unoxidized ferrous Ion determined with permanganate. Vanadium could then be deter-mined by one of the methods e a r l i e r mentioned and by c a l c u l -a t i o n the concentration of both metals could be obtained. This method, however, would be.merely a combination of e x i s t -i n g methods, and o f f e r s no improvements. (2) Two o r i g i n a l methods for determining vanadium have been devised. (a) Reduction of a vanadate, i n a c i d s o l u t i o n , to the vanadyl s a l t by sodium s u l p h i t e , and subsequent t i t r a t i o n w i th permanganate a f t e r removing excess.sulphite by b o i l i n g with s u l p h u r i c a c i d . (b) Reduction of a vanadate to the vanadic s a l t by z i n c i n a c i d s o l u t i o n , followed by o x i d a t i o n to the vanadyl form with n i t r i c acid and t i t r a t i o n to the vanadate with potassium permanganate. Both of these methods o f f e r advantages over e x i s t -ing procedures, i n that they are r a p i d , accurate and e a s i l y c a r r i e d out. 10. (3) In the opinion of t h i s w r i t e r , the d i f f i c u l t y encountered i n working with molybdenum and vanadium, p a r t i c u l a r l y . t h e former, i s d i r e c t l y due to lack of informa-t i o n i n the l i t e r a t u r e on the reactions of these metals i n t h e i r various valence states i n s o l u t i o n . Workers i n the f i e l d have apparently been more concerned with the prepara-t i o n and i s o l a t i o n of compounds, i n many cases very complex and of doubtful composition, than i n a study of t h e i r chem-i c a l properties and the mechanism and products of t h e i r r e a c t i o n s . A great deal of research could be advantageously a p p l i e d to a systematic study of the pr o p e r t i e s of the vana-d y l and pentavalent molybdenum compounds. These two s e r i e s are only one step removed from the stable vanadates and molybdates and a good d e a l of l i g h t could be thrown on the chemistry of the metals by an i n v e s t i g a t i o n of the s t a b i l i t y , s o l u b i l i t y , and r e a c t i o n s of the sulphates, carbonates, hydroxides, oxalates, and other s a l t s considered of value. 11. .COLOR IMETRIC RESEARCH In the course of the foregoing research, several color r e a c t i o n s were observed and i n v e s t i g a t e d to determine t h e i r value as pos s i b l e methods f o r estimating molybdenum c o l o r l m e t r i c a l l y . Ten standard s o l u t i o n s of sodium molybdate were prepared with the f o l l o w i n g concentrations of molybdenum: 1. .0001 g Mo/cc. 6. .0032 { g Mo/cc 2. .0002 7. .0064 3.- .0004 8. .0128 4. .0008 9. .0256 5. . 0016 10. .0512 In the f o l l o w i n g procedures the reactions were, i n v e s t i g a t e d over t h i s range f o r a v a r i e t y of con d i t i o n s of temperature and concentrations of reagents. 1. MOLYBDENUM BLUE: The formation of the complex blue oxide commonly known as molybdenum blue was i n v e s t i g a t e d by reduction w i t h lead, z i n c and magnesium, over the range of the ten standard s o l u t i o n s . .With both lead and z i n c the excess metal must be removed mechanically and removal of molybdenum • i n some form as a dark coating on the. metals cannot be avoided. This can be prevented by using magnesium, as the metal r e a d i l y goes completely i n t o s o l u t i o n , but the r e a c t i o n •' ":• 12. i s not s u f f i c i e n t l y s e n s i t i v e . The blue oxide only forms . for concentrations above standard s o l u t i o n No.3, i n d i c a t i n g that the s e n s i t i v i t y would be of the order .0005 g per cc. of molybdenum, which i s f a r too large a quantity to be of any value In a q u a n t i t a t i v e determination. 2« REDUCTION OF PH0SPH0 MOLYBDIC ACID; The micro-estimation of phosphorus by reduction of phosphomolybdic a c i d i s a standard biochemical-procedure. The method and c o n d i t i o n s necessary f o r best r e s u l t s were devised by T. Kuttner and H. R. Coheh 1 0and were l a t e r Im-proved by T. Kuttner and L. L i e h t e n s t e i n . 1 1 In b r i e f the method i s as f o l l o w s : To the n e u t r a l phosphate s o l u t i o n i s added a d e f i n i t e amount of a mixture of 3 normal sulphuric a c i d and 7.5^ sodium molybdate s o l u t i o n . The phosphomolybdic a c i d forms as a yellow c o l o r a t i o n with no p r e c i p i t a t e at room temperature. The a d d i t i o n of 1 cc. of a very d i l u t e standard stannous c h l o r i d e s o l u t i o n gives a deep blue c o l o r of great s e n s i t i v i t y . The method i s extremely accurate, but the conditions must be c l o s e l y observed. For these, the o r i g i n a l a r t i c l e s should be consulted. This r e a c t i o n was here i n v e s t i g a t e d with a view to determining whether or not the conditions could be a l t e r e d 10. 517 - 75 Jo u r n a l of B i o l . Chem. 1927. 11. 671 - 86 J o u r n a l of B i o l . Chem. 1930. 13. so that the estimation of micro amounts of molybdenum could be made. To t e s t t h i s the f o l l o w i n g s o l u t i o n s were prepared. (1) 3 N. .'sulphuric a c i d . (2) .-10$ sodium a c i d phosphate. (3) 10 g. of stannous c h l o r i d e were d i s s o l v -ed i n 25 ec. concentrated h y d r o c h l o r i c a c i d . For immediate use one part was d i l u t e d to 200 ec. The best concentrations of the above s o l u t i o n s were obtained by holding two f i x e d , and vary i n g the t h i r d . I t was found that the amount of stannous c h l o r i d e must vary p r o p o r t i o n a t e l y to the amount of molybdenum present. Five ce, samples of the stock molybdate,solutions were treated i n a l l eases.' J With s o l u t i o n #1, concentration .0001 g Mo/cc, maximum c o l o r a t i o n was obtained with .4 cc. sulp h u r i c a c i d , .25 cc. sodium acid phosphate s o l u t i o n , and .25 cc. of the d i l u t e d stannous c h l o r i d e . With s o l u t i o n #10, concentration .0512 g Mo/cc. maximum c o l o r a t i o n was obtained with .4 cc. su l p h u r i c a c i d , .25 cc. of sodium a c i d molybdate s o l u t i o n and 1.5 ec. of d i l u t e d stannous c h l o r i d e . An excess:of stannous c h l o r i d e , i . e . more than .25 ce. at the lower molybdenum concentrations r e s u l t e d i n a green t u r b i d i d i t y which coagulated i n a short time. This renders the procedure va l u e l e s s as the depth of co l o r depends on the amount of stannous c h l o r i d e which must be ' .. ' • 14. adjusted to s u i t the unknown concentration of molybdenum. The a p p l i c a t i o n of a d e f i n i t e procedure which i s p a r t i c u l a r -l y necessary i n c o l o r i m e t r i c work i s hence impossible. Results with h y d r o c h l o r i c a c i d and n i t r i c acid were iden-t i c a l with those obtained with s u l p h u r i c . With a view to avoiding t h i s d i f f i c u l t y , reduction of the phosphomolybdateby m e t a l l i c magnesium was i n v e s t -igated. As before the concentrations of a c i d , phosphate, and reducing agent; were c a r e f u l l y checked over the range by a systematic treatment of s o l u t i o n s No's. 1, 3 and 6. B e t t e r r e s u l t s were obtained than with stannous c h l o r i d e but c o n s i s t e n t values could not be obtained. Maximum color was. found when 5 cc. of the stock s o l u t i o n were treated with 1.8 ec. of 3 N h y d r o c h l o r i c a c i d , .8 cc. of 10% sodium acid phosphate s o l u t i o n and 25 - 30 mg. of m e t a l l i c magnesium. The magnesium d i s s o l v e d completely i n about t h i r t y minutes, and a good gradation of color was obtained. The s o l u t i o n s were examined i n a colorimeter and the graph of concentra-t i o n of molybdenum against the r e c i p r o c a l depth of s o l u t i o n was very close to a s t r a i g h t l i n e f o r a s e r i e s of s o l u t i o n s . I f , however, four or f i v e samples of the same s o l u t i o n were tre a t e d i n the same manner, \a[ good deal of v a r i a t i o n i n color was noted. No. way of overcoming t h i s could be found and the method was abandoned. This v a r i a t i o n i n color may be explained i n two ways. In most cases'with the above concentrations the • . l b . magnesium stays at the bottom of the t e s t tube but occasion a l l y p a r t i c l e s are c a r r i e d to the surface where some hydro-gen i s l o s t d i r e c t l y to the a i r . This r e s u l t s i n ineomplet reduction of molybdenum, and hence, i n a paler color than should be obtained. V a r i a t i o n i n c o l o r may also r e s u l t from v a r i a t i o n of the p a r t i c l e s i z e of the c o l l o i d formed i n the r e a c t i o n . 3. PERMOLYBDIC ACID; I f an a c i d s o l u t i o n of an a l k a l i molybdate i s treated w i t h hydrogen peroxide, a yellow permolybdate i s formed. As t h i s c o l o r i s v i s i b l e i n s o l u t i o n s containing as l i t t l e as .0001 g Mo/ec. i t was considered l i k e l y that the r e a c t i o n could be employed i n c o l o r i m e t r i c .analysis. The r e a c t i o n was studied f o r a v a r i e t y of eond^, i t i o n s but i t was observed that the concentrations of a c i d and peroxide had n5 apparent e f f e c t , except f o r 'very small amounts of a c i d . The s e r i e s of stock s o l u t i o n s were examin ed using s u l p h u r i c " a c i d . A gradation i n c o l o r i n t e n s i t y was obtained but the s e n s i t i v i t y of the r e a c t i o n was not' 'great enough. When examined i n the v i s u a l type and even i n the p h o t o - e l e c t r i c colorimeter accurate comparisons could not be. made with 'this pale yellow c o l o r . Various solvents were tested i n an e f f o r t to f i n d a reagent which would extract the permolybdate i n a small volume, g i v i n g a more intense color which could better be 16. compared. A n i l i n e , acetone, carbon t e t r a c h l o r i d e , carbon d i s u l p h i d e , e t h y l and methyl alcohols were t r i e d w i t h no success. SUMMARY: Several c o l o r r e a c t i o n s were i n v e s t i g a t e d as pos s i b l e methods f o r determining molybdenum c o l o r i m e t r l c a l l y . (a) Reduction of molybdate by a metal to form molybdenum blue. (b) Reduction of phosphomolybdic acid by stannous c h l o r i d e and by m e t a l l i c magnesium. (c) Oxidation of a molybdate i n acid s o l u t i o n to a permolybdate by hydrogen peroxide. Results obtained i n a l l eases i n d i c a t e no improve-ments i n these methods over the potassium thiocyanate, stannous c h l o r i d e method now employed i n Bureau of Standards s t e e l a n a l y s i s . 17. BIBLIOGRAPHY 1. B. S. Hopkins Chemistry of the Rarer Elements. 2. Treadwell-Halls A n a l y t i c Chemistry V o l . I I . 3. M e l l o r V o l . XI. 4. Roscoe & Schorlemmer V o l , I I 5. Journal of B i o l o g i c a l Chemistry Vols. 75 and 86. 6. I n d u s t r i a l and Engineering Chemistry 1928, 1930 (Anal. Sec.) 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0062261/manifest

Comment

Related Items