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The system pyridine - hydrogen chloride as an acid medium Mitchner, Hyman 1953

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THE SYSTEM PYRIDINE-HYDROGEN CHLORIDE AS AN ACID MEDIUM BY HYMAN MITCHNER A THESIS.SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of CHEMISTRY We accept this thesis as conforming to the standard required from candidates for the degree of MASTER OF SCIENCE Members of the Department of Chemistry THE UNIVERSITY OF BRITISH COLUMBIA APRIL, 1953 ABSTRACT Pyridine s a l t s were investigated as acids i n the pyridine system. The mono and the dihydrochloride s a l t s were found to be the best d i s s o l v i n g reagents f o r the a metals and the sulphides used. Pyridine hydrochloride was most e f f e c t i v e i n the molten state, whereas pyridine dihydrochloride was found to be quite reactive at room temperature when dissolved i n a chloroform solution. Side reactions were investigated and were found to occur only with Mg, A l , and Zn with molten pyridinium chloride. The complex s a l t s , (C 5H eN.H) 8[MnCl B 3c 5H BN and (C 5H BN.H)HgCl 4 were i s o l a t e d and investigated. 1 I AKNOWLEDG-EMENT Sincere appreciation is expressed to Dr. K. Starke for his'encouragement and help in making this work possible. TABLE OF CONTENTS PAGE INTRODUCTION 1. Water as an unique solvent 1 2. H i s t o r i c a l approach to reactions i n nonaqueous systems a. . Confusion and misconcepts i n the acid-has e theory.............................. 1 b. Bronsted theory of acids and bases.. «,...© 4-3 . Disadvantages of water as a solvent........... 5 4 . Alms of inv e s t i g a t i o n ...... 5 EXPERIMENTAL 1. Purity of reagents 7 2. Preparation of pyridinium s a l t s a. Pyridinium n i t r a t e 7 b. Pyridinium t r l c h l o r o a c e t a t e 7 C o Pyridinium thiocyanate 8 d. Pyridinium oxalate 8 e. Pyridinium f l u o r i d e . . . . . . . . . . . . . . . . . . . . . . . 9 f . Pyridinium chloride 9 g. Pyridine dihydrochloride................. 11 h 0 Other s a l t s of pyridine......... 11 3 . Methods of using C5HBN.HC1 and CBHBN.2HC1 a. Molten C5H5N.HC1 and molten CBH6N.2HC1... 12 -11 b. Room temperature systems 1. C.6HBN.HCl i n pyridine,,.... ...... 14 l i e Saturated chloroform solutions of CBHBN.HC1 and CBHBN.2HC1............ 15 c. The reaction of metals i n molten C eH eN.HCl and the reaction of metals with a satur-ated chloroform solution of C6HBN.2HC1 at room temperature..... 16 S o l u b i l i t y of C5HBN.HC1 and CBHBN.2HC1 i n . - -chloroform at 23°C 17 Absorbency - wavelength, i n v e s t i g a t i o n of the. , chloroform solutions of G BH BN 0HC1 and CBH5N.2HC1 17 Side reactions a. Materials i . Preparation of 4-pyridyl-pyridinium d i c h l o r i d e 20 i i . P u r i f i c a t i o n of synthetic quinoline. 20 i i i . Preparation of quinoline hydrochlo-r i d e 21 b. Product of side reactions 1. Isolation............... 22 i i . Examination for b i p y r i d y l s . 23 i l l . Decomposition product of 4-pyridyl-pyridinium d i c h l o r i d e i n NaOH.......... 24 - i i i * i v . Further reactions of Zn + C 5H BN .HC1 reaction product..................•« 24 c. Reaction of quinoline hydrochloride with metals • . ,. i . Side reaction product ofquinoline, 'hydrochloride plus zinc 25 i i . Reaction of quinoline hydrochloride product with acetic. anhydride 25 7. Reactions with possible a n a l y t i c a l a p p l i c a t i o n a. Materials - preparation.of. Mn.(OAc ) 3 . . . . . . 26 b. Reaction of C BH BN .2HC1 i n CHC1 3 with MnS i . Nature of sample of, MnS 26 i i . Reaction of. manganese, s a l t s , . metal. •. and Mn08 with a saturated chloro-form solution of C BH BN . 2 H C 1 . . . . . 27 i i i . Heating of a fresh sample o f MnS..... 27 i v . E f f e c t of oxi d i z i n g agents ..... 27 v. C BH BN .2HC1 i n CHC1 S on Mh(OAc)8."..... 28 v i . I s o l a t i o n of the substance c o n f e r — ring.the green colour to the G 5 H 5 N . 2 H C I i n G H C I 3................. 28 v i i . Analysis p f the green c r y s t a l s . . . . . . 29 v i i i . Limit of v i s i b l e colour...,..,,......,. 29 i x . Colourometric analysis..,,.,....,... 29 x. Variation of colour with t i m e . 3 3 4 - i v -c. Reaction of C BH eN.2HCl i n CHC1 3 w i t h HgS. i . I s o l a t i o n of the•mercury s a l t . . . . . . . 33 i i . A n a l y s i s of the mercury s a l t . . . . . . . . 33 I I I DISCUSSION l o P y r i d i n e s a l t s as r e c t i o n media a. Type of r e a c t i o n most d e s i r a b l e . 37 b. Examination of the p y r i d i n e s a l t s pre-pared 37 2. Methods of usi n g CBHBN.HC1 and CBHBN.2HC1 a. Molten s t a t e 38 b. Room temperature systems 39 3. The nature of CBHBN.2HC1 i n CHC13 Al 4. Side r e a c t i o n s a. P o s s i b i l i t y of formation of b i p y r i d y l s . . . 42 b. Ring cleavage............................ 43 c. L i m i t a t i o n s due t o s i d e r e a c t i o n s 45 5. . Reactions w i t h p o s s i b l e a n a l y t i c a l a p p l i c a t i o n a. T r i v a l e n t manganese i . Formulation of the compound (C 5H BN.H) sCMnCl B3C BH 5N............... 46 i i . E x p l a n a t i o n of r e a c t i o n s of manganese sstXts© •»••••«*««»••«•««••»• • • • « o « • © • * i i i . Determination of t r i v a l e n t manganese by colourometric a n a l y s i s of the green complex... 48 - V -b. The mercury-pyridine complex .1. Formulation of the compound (C BH BN»H)gHgCl^••.••••.«•«..««*»•«.. 50 i i . Application of s o l u b i l i t y of HgS.... 51 6. Conclusions .. • ... 51 XV BIBLIOGRAPHY. «....-. . . . . . . . . . . . . . . . 0 . . . . . . . . 0 . . . . . . • « 52 TABLES . . .......... Table I Reactivity of sulphides i n molten C 5H eN.HCl and molten CBHBN.2HC1.......*.....*...••..... 13 Table II Reactivity of sulphides i n C BH BN.HCi i n pyridine. • 14-Table III Reaction of sulphides i n saturated chloroform solutions of CBHBN.HC1 and C5HBN.2HC1 15 Table IV The reaction of metals In molten C BH eN.HCl and the reaction of metals with a saturated chloroform solution of C5H6N.2HC1 at room temperature • 16 Table V Reaction of manganese s a l t s , metal and Mn08 with a saturated chloroform solu t i o n of C BHBN.2HC1................................... 27 0 - v i -FIGURES Figure I Absorbency-wavelength plo t for a saturated chloroform solution of C 6H BN .2HC1 and a di l u t e d chloroform sol u t i o n of C BH BN . H C 1 . . . f'lQ i Figure II Absorbency Twavelength.plot for a d i l u t e d • chloroform solution of C 5H BN .2HC1 . . 19 Figure III Spectral-Transmittance curve of green t r i -valent manganese complex l a a saturated chloroform solution of C BH BN . 2 H C 1 . . 31 Figure IV Concentration-Transmittance curve of green t r i v a l e n t manganese complex i n 10 cc. of a saturated chloroform solution of C 5 H 5 N . 2 H C I . Trivalent manganese obtained by reduction Figure V Concentration-Transmittance curve of green t r i v a l e n t manganese complex i n 10 cc. of a saturated chloroform solution of C BH 5N .2HC1. Trivalent manganese obtained by oxidation of divalent > manganese, o s»».»»•«.»..... •«... 34 Figure VI Vari a t i o n of colour of green t r i v a l e n t man-ganese complex with time. .35 -1-I - INTRODUCTION 1. Water as aaunique solvent. Of a l l our known solvents, the one most used i s water. As a solvent, water i s considered to be unique. Its physical properties, such as i t s capacity as a gen-eral solvent for salts and i t s power of electrolytic dissociation, i t s low molecular elevation constant, i t s high boiling point, and i t s heat of fusion, heat of volatilization, c r i t i c a l , temperature, specific heat, association constant, and dielectric constant with values so much higher than the corresponding values for other substances, a l l tend to remove i t far from other sol-vents and to place i t i n a class by i t s e l f . Furthermore, because of i t s abundance, i t i s one of the most studied substances known. ... . • 2. .Historical approach to reactions i n nonaqueous systems. a. Confusion and misconcepts i n the acid-base  theory. Following the discovery of the voltaic c e l l by Volta early i n the 19th century, considerable work was done to differentiate between those substances which conduct an electric current i n aqueous solutions and those which do not. Electrochemists of the middle 19th century such as Hittorf and Kohlrausch studied the -2-behavlour of the so-called electrolytes such as hydrogen chloride and ammonia in their liquid states. When these latter two substances were found to be nonconductors, i t was promptly assumed that they did not break up into ions and that only i n water did they possess character-i s t i c chemical and electrochemical properties, and hence only i n water was i t possible to effect ionic reactions. The criterion for the pure substance to be able to.act as an acid per se was thus related to i t s a b i l i t y to conduct el e c t r i c i t y . The role of water as an ionizing medium In electro-l y t i c dissociation intrigued many investigators. Arrhenius (1884) attempted to completely explain electro-l y t i c dissociation by placing the emphasis on the role 3 7 of water. Werner , the originator of the complex compound theory, also tried to explain what happened when a nonelectrolyte dissolved i n water to give a conducting solution. He introduced the terms "anhydro base" and "aquo base", as well as "anhydro acid" and "aquo acid". "Anhydro bases (such as ammonia) are compounds which combine with the hydrogen ions of water i n aqueous solu-tion, and thereby cause a shift i n dissociation e q u i l i -brium of water until their corresponding characteristic hydroxyl ion concentration has been reached." "Aquo bases (such as potassium hydroxide) are addition compounds of water, which i n turn dissociate i n aqueous solu t i o n to give hydroxy! ions." Anhydro acids (such as HCl) are "compounds which i n aqueous solution so combine with hydroxyl ions of water as to cause a s h i f t i n d i s s o c i a -t i o n equilibrium of the solvent water u n t i l the corres-ponding c h a r a c t e r i s t i c hydrogen ion concentration has been reached." I t was not long, however, before the l i m i t a t i o n s of the Arrhenius concept were recognized. Work on non-36 aqueeus solutions by Walden i n Europe and contemporary is a c t i v i t y i n the United States by Cady, Frankl i n , and Kraus made a r e v i s i o n of acid and base theory necessary. I t was shown that numerous solvents yielded conducting solutions and that a l l substances exhibit^solvent prop-erty to a greater or les s e r degree. Some compounds regarded as s a l t s i n the aquo system were found to behave as acids or bases i n nonaqueous systems and therefore, c e r t a i n changes with respect to the d e f i n i t i o n s of classes of compounds i n terms of the solvent employed, were obviously necessary. Ammonium sa l t s behave as ammono-acids i n l i q u i d ammonia as the solvent , whereas acetates behave as 9 aceto-bases i n g l a c i a l acetic acid . In general, "onium" s a l t s exhibit acid c h a r a c t e r i s t i c s i f the corresponding anhydro base i s the solvent. b. Br^nsted theory of acids and bases. One of the most useful theories proposed to coordinate these more advanced investigations was one proposed by Brpnsted . The phenomenon of a c i d i t y was simply considered as a matter of competition between the solvent and the acid anion as bases f o r the proton: A ^ = ± B + H + Thus an acid would be any molecule or ion which acted as a proton donor, a base, any molecule or ion which acted as a proton acceptor. A c i d i t y i n basic solvents would be due to the formation of the corresponding "onlum" ion . In ammonia there i s formed the ammoniated hydrogen io n or ammonium ion as the bearer of a c i d i t y : NH3. + H + NH 4 + S i m i l a r l y i n a n i l i n e there i s formed the anllinium ion (C 6H 6NH S«H +} and i n pyridine the pyridinium ion (C BH 5N.H +).* The natural experimental extension was to i n v e s t i -gate the s o l i d and fused states of the "onium" s a l t s i n which the "onium" ion must exist, to see i f the s a l t s of the solvent exhibited therein the properties of acids. Investigations carried out with fused pyridinium chlorfede * The Brc^nsted theory, of course, i s l i m i t e d because i t takes into consideration only protonic subs-tances, but where applicable i t i s extremely u s e f u l . As the solvents considered i n the i n v e s t i g a t i o n herein are protonic, the Brj^nsted theory i s used. i demonstrates conclusively that an extension to the molten state of the "onium" reactionsu&s p e r f e c t l y j u s t i -f i e d . Furthermore, a l l other "onium" s a l t s Investigated, have been found to behave i n a si m i l a r manner . Disadvantages of water as a solvent. The high d i s s o c i a t i n g power of water can prevent the formation of neutral molecules or complex ions which might form i n nonaqueous reactions, but dissociate i n the presence of water. Undesirable d i s s o c i a t i o n may even be followed by a reaction with the solvent as a r e s u l t of water i t s e l f being always dissociated. Thus, i n order to obtain an o v e r a l l picture of reactions i n nonaqueous solvents a series of reactions i n which water was not formed was carried out. Alms of i n v e s t i g a t i o n . a. I t was proposed to investigate the acid s a l t s of pyridine as reaction media f o r metals and common sulphides. b. I t was proposed to investigate further those s a l t s which showed, i n the molten state, good r e a c t i v i t y f o r the metals and sulphides used, with the aim of obtain-ing a solvent system which could be used at room temper-ature. c. I t was proposed to investigate any side reactions which might l i m i t the a p p l i c a b i l i t y of the reaction media used. d. I t was proposed to investigate any reactions that might suggest possible a n a l y t i c a l applications. II - EXPERIMENTAL 1. Purity of reagenta. The reagents used In a l l preparations were of "Reagent Grade" quality* The pyridine was further pur-i f i e d by r e f l u x l n g for two hours over sodium hydroxide p e l l e t s to remove any water that might have been absorbed from the a i r . The pyridine was then d i s t i l l e d and the f r a c t i o n coming over between 115-ll6°C. c o l l e c t e d . 2. Preparation of pyridinium s a l t s . 1 * 3 3 a. Pyridinium n i t r a t e (C 5H BN.HN0 3) S l i g h t l y more than an equivalent amount of concen-trated n i t r i c acid was added to 100 gm. of pyridine and ' the resultant mixture evaporated on a steam bath t i l l viscous. Upon cooling, a c r y s t a l l i n e product was obtained which was treated with ether, f i l t e r e d by suction and washed again with ether. The pyridinium n i t r a t e was then r e c r y s t a l l l z e d from absolute alcohol and white needles of large size were obtained, m.p. 115-116°C. The y i e l d was quantitative. No melting point has been previously reported. b. Pyridinium trichloroacetate (C 6H eN.GCl aC00H) To prepare pyridinium trichloroacetate, equivalent amounts of pyridine and t r i c h l o r o a c e t i c acid were used. P a r t i c u l a r care was taken to keep the t r i c h l o r o a c e t i c —8** acid free from moisture. The reaction was carried out in an ice bath. The pyridine was added slowly with s t i r -ring to the cooled trichloroacetic acid. A vigorous reaction ensued with the production of a yellow-brown semi-solid. After the reaction was complete, the product was heated on a steam bath t i l l l i q u i d and cooled again in the ice bath, where i t formed a yellow slush. The cold residue was treated with absolute ether, f i l t e r e d and washed twice with additional amounts of absolute ether. The buff coloured residue was recrystallized from-absolute alcohol and gave white, planar (mica-like) crystals which decomposed on heating at 111-112 C. Reitzenstein report-ed a melting point at 112°C. 1 3 c. Pyridinium thiocyanate (CeH6N.HSCN) Pyridinium thiocyanate was prepared by the add-i t i o n of alcoholic solutions of equivalent amounts of pyridine hydrochloride and ammonium thiocyanate. On addition of the two alcoholic solutions, NE^Cl precip-itated out. This was fi l t e r e d and the product recovered by evaporating the f i l t r a t e - t o a small volume. The crystals thus obtained were f i l t e r e d and washed with ether. They were easily recrystallized from ethanol to yield white planar crystals of melting point 98°C. No melting point has been previously reported. 3 8 > 3 X d. Pyridinium oxalate ((C 5H 5N) sC 2H s0 4) Pyridinium oxalate was prepared by the addition of pyridine to an acetone solution of axalic acid. A bulky white p r e c i p i t a t e was obtained which was f i l t e r e d , washed with acetone and r e c r y s t a l l i z e d from absolute alcohol to 3 i give white cr y s t a l s of m.p. 152-153°C. P f e i f f e r reported a. melting point at 153'vC. e. Pyridinium f l u o r i d e Pyridinium f l u o r i d e was not prepared. An- attempt to prepare i t along the l i n e of pyridinium n i t r a t e was not successful. Equivalent amounts of pyridine and hydrogen f l u o r i d e ( i n the form of 48$ HF) were mixed i n a stainless steel beaker and the r e s u l t i n g s o l u t i o n evaporated. No product was obtained. A second attempt to prepare the hydrofluoride was made by adding pyridine to aqueous HF, but t h i s time acetic anhydride was added to reacg with the water. The entire mixture was extracted with ether to remove the acetic acid and to leave behind the pyridinium f l u o r i d e , which, i f i t behaved as other pyridine s a l t s , would be insoluble i n ether. No product was obtained. The f i n a l method t r i e d Included the above two procedures, but an excess of hydrofluoric acid was used to the extent of six moles of HF to one mole of pyridine. No pyridinium f l u o r i d e could be i s o l a t e d . S 3 $ 3 mm f . Pyridinium chloride (C BH eN.HCl) Pyridinium chloride i s hygroscopic and i t was found best to prepare i t Just before use. Three methods were found to work quite r e a d i l y ! -10-i . Using a Kipp generator, HCl gas .was evolved by reacting concentrated sulphuric a c i d with ammonium chloride. The gas was dried by passing i t through two gas washing bottles containing concentrated sulphuric a c i d and was then introduced into ,a solution of pyridine i n dry ether. Pyridinium chloride p r e c i p i t a t e d almost immediately as a white s a l t * . I t was f i l t e r e d i n a Buchner funnel and stored i n a vacuum deslcaator over anhydrous magnesium .perchlorate. I i . Concentrated hydrochloric acid was added to a s l i g h t excess of pyridine and the r e s u l t i n g aqueous sol u t i o n of pyridinium chloride was d i s t i l l e d . The d i s -t i l l a t e coming over i n the range 218-218.5°C was c o l l e c t -ed as CBH6N.HC1. The s o l i d i f i e d s a l t was then dissolved i n absolute.alcohol and c r y s t a l l i z e d by cooling. The s a l t remaining i n the mother l i q u o r could be p r e c i p i t -ated with dry ether. i i i . Anhydrous ether was saturated with dry HCl and placed i n a separatory funnel. The solution was slowly added to freshly d i s t i l l e d pyridine u n t i l the pre-c i p i t a t i o n of the pyridinium chloride was almost complete, whereupon t h i s solution was treated as i n ( i i ) . The * Pyridine should be present i n excess to prevent the possible formation of C6H5N.2HC1. -11-melting point of pyridinium chloride prepared by any of these three methods was found to be l 4 3 - l 4 4°C. This value was i d e n t i c a l to that reported by Audrieth and a Long o 16 g. Pyridine dlhvdrochloride (CBHBN..2HC1) Dried HCI gas from a Kipp generator was passed through freshly d i s t i l l e d pyridine contained i n a three-neck f l a s k f i t t e d with both a s t i r r e r and a r e f l u x condenser. The pyridine hydrochloride formed f i r s t and the solution, was then kefit at a temperature s u f f i c i e n t to maintain a homogeneous solution. HCI was passed through continuously and, af t e r the formation.of the CBHBN.HC1 was completed, the temperature,of the f l a s k was lowered.so that i t was maintained Just above that point at which c r y s t a l s started to form. This was cont-inued t i l l the temperature of the solution i n the f l a s k f e l l to about 4 8 ° C . On cooling a c r y s t a l l i n e mass s o l i d -i f i e d , m.p. 46 -47°C. and decomposition point 55°C. These 16 values agreed closely to those of Kaufler and Kunz m.p, 46.7°C. and decomposition point 55°C. By d i r e c t weighing i t was observed that the pyridine had taken on two moles of HCI per mole of pyridine. The c r y s t a l s can be reprecipitated from anhydrous ether and alcohol as an o i l and white needle-like c r y s t a l s . h. Other "Se4-d- s a l t s of pyridine i . H sFe(CN) 6 and H4Fe(CN)6;8* 9 , 3 6 -12-13 i i . C 4H40 e (furoic acid) i i i . G 8H 60 4 + 2C eH BN (phthalic a c i d ) 3 9 3 3 i v . H 3P0 4 S3 v. HsMo04 16 >35*3 9 v i . HCr0 6 1»S3 v i i . H sS0 4 3 0 v i i i . HI 3 1 i x . HBr Methods of using C6HSN..HC1 and CBH6N.2HC1. a. Molten CBHBM.HCl and molten CBH5N.2HC1 A series of test tube reactions we>$^  c a r r i e d out using the reagents mentioned. The r e a c t i v i t y of these reagents on metal sulphides wf|®$. investigated with the evolution of HSS as the c r i t e r i o n of reaction. Lead acetate paper was used to check the evolution of the H aS gas. TABLE I Reactivity of sulphides in molten CKHKN.HC1 and molten CBHeN.02HCl Sulphide CBHeN.HCl at 175°C CBHBNi.2HCl at 53°C. Colour of Reactivity Colour of Reactivity solution solution MnS ZnS PeS CdS CoS NiS SnS SnS8 PbS Sb sS3 Bi sS a As 8S 3 CuS Ag8S HgS orange blue-green blue It. yellow 1 1 1 1 1 1 1 4 1 1 2 3 1 2 1 yellow blue-green blue It. yellow 2 1 1 1 1 1 i 4 3 1 3 4 2 2 1 1 - quite reactive: 2 - reactive: 3 * slightly reactive: 4 - unreactive. b. Room temperature systems i . C K H K I . H C X In pyridine (6N i n G B H 5 N . H C 1 ) TABLE II Reactivity of sulphides i n C B H B N . H C 1 i n pyridine Sulphide Colour of Re a c t i v i t y s o l u t i o n MnS 3 ZnS 3 FeS yellow 2 CdS . 3 GoS blue-green 2 N1S ... 4 SnS 3 SnS 8 4 PbS 3 Sb 8S a 4 B i a S 3 3 A s 3 S 3 4 CuS 3 Ag sS 4 HgS 4 1 - quite reactive: 2 - reactive: 3 - s l i g h t l y r eactive: 4 ~ unreactive* - 1 5 -11o Saturated chloroform solutions of C8HSN.HC1 and CBHBN.2HC1 TABLE III Reaction of sulrjhides in saturated chloroform solutions of C5HBN..HC1 and C5HBN.2HC1 Sulphide CBH6N.HC1 in CHC1S CBHBN.2HC1 in CHCla, MnS ZnS • FeS CdS CoS NiS SnS SnSa PbS SbaSa BigSg As sS 3 CuS AgsS HgS Colour of Reactivity Colour of Reactivity solution yellow blue-green blue It. yellow 3 1 2 1 2 2 3 4 3 2 4 4 3 3 2 solution dark green* yellow blue-green blue It. yellow 1 1 1 1 2 1 1 4 1 1 3 3 2 3 1 1 «• quite reactive:: 2 - reactive: 3 - slightly reactive: 4 - unreactive. * A freshly prepared sample of MnS gave a colour-less solution. An old sample gave a dark green solution. c. TABLE IV 3 > 3 » 36. The reaction of metals in molten 0 k H K N . . H C 1 and the reaction of metals with a saturated chloroform solution of CBH/BN.2HC1 at room temperature Metal Molten CH«N«HC1 Colour of Reactivity  solution CKHBN,2HC1 In CHCla (25°C;) Colour of Reactivity  solution Al brown 1 2 Bi 4 3 Mn 1 • 1 Qd yellow 1 yellow 1 Co blue-green 2 blue-green 2 Cr pink 2 pink 2 Cu yellow 1 yellow 1 Mg brown 1 1 Hg 4 4 Ni blue 2 blue 3 Pb 2 3 Sb 3 3 Sn 2 2 Zn brown 1 1 1 - quite reactive: 2 - reactive: 3 - slightly reactive: 4 - unreactive. - 1 T - . After driving off the chloroform, the only changes obs-erved i n the reactions carried out with the CBHBN.2HC1 in CHG13 on metals, were that the solutions of Al, Zn, and Mg turned brown. This was the same colour as was observed with the molten C5HBN.HC1 on the same metals. Solubility of C^HBN.HC1 and CfiHEN.2HCl In chloroform at  23° C. The solubilities of pyridinium chloride and pyridine dihydrochloride were measured by saturating a chloroform solution of known volume with these reagents and pre-cipitating the pyridine content as 2C5HBN.CuCls, using excess CuCl 8 in a water solution. The chloroform was driven off by heating on a steam bath. The values determined were: CBHBN.HC1 - 123 gm. per 100 cc. of chloroform CBHBN.2HC1 - 108 gm. per 100 cc. of chloroform Abserbencv - wavelength investigation of the chloroform  solutions of C5HEM.HC1 and CBH5M.2HC1. o The wavelength region \ = 3300 - 5300 A was inves-tigated on a Beckmann Spectrophotometer. The absorbency was taken as the dependent variable. A pure chloroform solution was used as the standard. Figure I represents a saturated solution of CBHeN.2HCl i n CHC13 and a diluted chloroform solution of CBHBN.HCl, Figure II represents a dilution of the saturated chloroform solution of CBHBN.2HC1. I L—-„ i ,_J C_. i _J i L.. I Ll. L I j i L_ 1 ! 1 3 * 0 0 HObO' .. HS0O • j'oOO WAVELENGTH X °^ V FIG.UR€ Io ' ABSORBENCY-WAVELENGTH PLOT FOR A SATURATED CHLOROFORM SOLUTION OF Cc;H^N«2HCl • AND A DILUTED CHLOFORM SOLUTION OF C5H5N0HCI0 • • FIS.URE II, ABSORBSNCY-WAVELENGEH "PLOT FOR A DILUTED CHLOROFORM SOLUTION OF C^H^N02HClo S i d e r e a c t i o n s . a. M a t e r i a l s i . P r e p a r a t i o n of 4 - p y r l d y l - p y r l d i n l u m 17/ d i c h l o r i d e One hudred and f i f t y grams of t h i o n y l c h l o r i d e were slow l y added t o 50 gm. of pure p y r i d i n e . The mixture was kept c o o l i n an i c e bath. The r e s u l t a n t y e l l o w s o l u t i o n was r e f l u x e d f o r f i v e hours, whereupon i t grad-u a l l y assumed a dark brown c o l o u r . The brown s o l u t i o n was d i s t i l l e d under vacuum; the temperature was s l o w l y r a i s e d t o 100°C. and was maintained t h e r e f o r one hour. The dark brown r e s i d u e i n the d i s t i l l i n g f l a s k was s t i r -r e d up w i t h 50 c c . of a b s o l u t e a l c o h o l and f i l t e r e d by s u c t i o n . There remained a b u f f c o l o u r e d g r a n u l a r r e s i d u e which was d i s s o l v e d i n d i l u t e h y d r o c h l o r i c a c i d , b o i l e d and f i l t e r e d . The f i l t r a t e was evaporated t i l l c r y s t a l -l i z a t i o n j u s t commenced. At t h i s p o i n t a l c o h o l was added to the cooled mixture. There r e s u l t e d a f a i n t l y y e l l o w i s h mass of c r y s t a l s of 4 - p y r i d y l * p y r i d i n i u m d i c h l o r i d e which were f i l t e r e d and washed w i t h a l c o h o l . 38 i i . P u r i f i c a t i o n o f s y n t h e t i c q u i n o l i n e One hundred c c . of q u i n o l i n e were d i s s o l v e d i n 1200 ml. of d i l u t e h y d r o c h l o r i c a c i d and heated t o 6 0 ° C , whereupon a s o l u t i o n of 140 gm. of Z n C l 8 i n 24o ml. of d i l u t e h y d r o c h l o r i c a c i d was added. -21-2C 9H 7N + Z n C l 8 + 2HC1 — —* C(0 9H 7N) 8ZnCu3H a A white p r e c i p i t a t e of the q u i n o l i n e c h l o r o z i n c a t e soon began to form and the w e l l s t i r r e d mixture was co o l e d i n an i c e bath. The c r y s t a l s were separated by f i l t e r i n g w i t h s u c t i o n and washing w i t h d i l u t e h y d r o c h l o r i c a c i d . The white c r y s t a l l i n e p r e c i p i t a t e was t r a n s f e r r e d to a beaker and 10% NaOH s o l u t i o n added t i l l the p r e c i p i t a t e of Zn(OH) 8 d i s s o l v e d . The s o l u t i o n was then e x t r a c t e d , w i t h s i x 100 ml. p o r t i o n s of ether and the combined ether e x t r a c t s were d r i e d w i t h 20 gm. of anhydrous magnesium s u l p h a t e . The ether was d i s t i l l e d o f f . The water con-denser was r e p l a c e d by an a i r condenser and the f r a c t i o n b o i l i n g between 237-238°C. was c o l l e c t e d . R e d i s t i l l a t i o n i n vacuo gave a c l e a r c o l o u r l e s s d i s t i l l a t e of q u i n o l i n e . i i i . P r e p a r a t i o n of q u i n o l i n e h y d r o c h l o r i d e  (0.9H7N,HC1) F i f t y c c . of the p u r i f i e d q u i n o l i n e were d i s s o l v e d i n 100 c c . of ether and dry HCI passed through the s o l u -t i o n t o p r e c i p i t a t e the q u i n o l i n e h y d r o c h l o r i d e which i s d i f f i c u l t l y s o l u b l e i n warm ether and s o l u b l e i n hot 1 0 ether . The p r e c i p i t a t e i n ether was c o o l e d i n an i c e b a t h and f i l t e r e d , u s i n g s u c t i o n . The p r e c i p i t a t e was washed twice w i t h c o l d ether and d r i e d In a vacuum des- ; , l o c a t o r , m.p. 134°C. The same v a l u e f o r the m e l t i n g 1 0 p o i n t was obtained by E r k s t e i n . -22-b. Product of side reactions i . I s o l a t i o n The reactions of Zn, Mg, and A l with molten pyridinium chloride r e s u l t i n a brown solution. The reaction with Zn has been studied as t y p i f y i n g those r e s u l t i n g i n side reactions. Pyridine plus ZnCl 8, pyridine dihydrochloride plus Zn, pyridine hydrochloride plus ZnCl 8 did not r e s u l t i n a solution of brown colour. The brown colour was t y p i c a l only of the reaction of the metal with pyridine hydrochloride. T h l r t y ^ f i v e grams of C BH eN.HCl were reacted with an excess of zinc dust at 175°C 8 As zinc dust was added, the solution turned light-yellow, but r a p i d l y turned brown on the addition of more Zn. On cooling, the mix-ture was treated with 600 ml. of 6N. NaOH. A brown o i l separated on the surface of the s o l u t i o n 0 The o i l had a very strong odour of pyridine. I t was separated from the a l k a l i n e solution by a separatory funnel. The brown o i l was washed with f i v e 50 ml. portions of 6N NaOH by shaking i n the separatory funnel and drawing o f f the NaOH. The pyridine i n the brown o i l was removed by evaporating the solution on a steam bath t i l l a tar r y brown sbstance remained. This product did not c r y s t a l l i z e from any of the common organic solvents. I t was found that the presence of pyridine with the residue Interferred with the i s o l a t i o n of the reaction - 2 3 -product and i t was necessary t o remove i t completely b e f o r e f u r t h e r p u r i f i c a t i o n c o u l d be made, R e p r e c l p i t a t i o n i n an amorphous form c o u l d be accomplished i f the the t a r r y r e s i d u e from which the p y r i d i n e had been completely evap-o r a t e d was t r e a t e d as f o l l o w s : 1, The r e s i d u e was d i s s o l v e d i n c h l o r o f o r m and the s o l u t i o n evaporated on a steam ba t h t i l l i t became a s t i c k y mass, 2 , The r e s i d u e was taken up w i t h about s i x times i t s volume of carbon t e t r a c h l o r i d e , a t which p o i n t some buff?-coloured p r e c i p i t a t e appeared. 3 , Low b o i l i n g petroleum ether ( 3 0 - 6 0 ° C , ) was added to complete the p r e c i p i t a t i o n . The maximum amount of b u f f . c o l o u r e d r e s i d u e o b t a i n -ed was about 6% of the s t a r t i n g weight of the p y r i d i n i u m c h l o r i d e . The powder obtained by the d e s c r i b e d method d i d not melt up t o 3 5 0 ° C , I t was found t o be s o l u b l e i n aqueous a c i d s , e t h a n o l , and c h l o r o f o r m g i v i n g a r e d c o l o u r e d s o l u t i o n i n each, but i n s o l u b l e i n benzene, water and et h e r , i i a Examination f o r b i p y r i d y l s The sodium hydroxide s o l u t i o n , the brown o i l , and the b u f f c o l o u r e d r e s i d u e were e x t r a c t e d w i t h ether f o r b i p y r i d y l s ( a l l o f which a r e s o l u b l e i n e t h e r ) . On ev a p o r a t i o n of the ether, no b i p y r i d y l s were o b t a i n e d . -24-: I i i . Decomposition product of 4-pyrldyl- pyrldinlum d l c h l o r i d e i n NaOH 4-Pyridyl-pyridinlum d l c h l o r i d e was added to a 6N s o l u t i o n of sodium hydroxide. An intense yellow colour appeared and, on the addition of more 4-pyridyl-pyridinium d l c h l o r i d e , a red-brown p r e c i p i t a t e formed,, An aldehydic cinnamon odour was noticeable. The p r e c i p i t a t e dissolved i n acetic acid to gfeve a red-brown colour, very much l i k e y t h a t of-the buff coloured reaction product from pyridine hydrochloride and zinc. However, t h i s new product formed a derivative with 2-4-dinitrophenylhydrazine, whereas the pyridinium chloride reaction product with zinc did not form any p r e c i p i t a t e with t h i s l a t t e r reagent. i v . Further reactions of Zn + CBH6N.HC1 reaction product A solution of the reaction product i n 6N acetic a c i d gave the following reactions: 1. Decolourized a 2% KMn04 solution. 2. Became colourless when allowed to stand a f t e r t r e a t i n g with 30$ H 80 8. 3 . Gave a yellow-brown p r e c i p i t a t e with 20% B r 8 i n aqueous KBr. 4 0 Gave a dark brown p r e c i p i t a t e with 20$ I 3 i n aqueous KI. On i s o l a t i o n of the bromine deri v a t i v e as a brown powder, no melting point could be determined. Analysis showed 5 .29$ n i t r o g e n . c. R e a c t i o n of quinoline h y d r o c h l o r i d e w i t h metals i . S i d e r e a c t i o n product of q u i n o l i n e  h y d r o c h l o r i d e p l u s z i n c Q u i n o l i n e h y d r o c h l o r i d e was found t o r e a c t w i t h a l l metals.above hydrogen i n t h e E l e c t r o m o t i v e S e r i e s t o g i v e a dark orange to r e d s o l u t i o n . The r e a c t i o n of q u i n o l i n e h y d r o c h l o r i d e and z i n c r e s u l t e d i n a dark r e d s o l u t i o n which, when poured i n t o water, formed a dark r e d r e s i d u e . T h i s r e s i d u e was powdered I n a morgar and p e s t l e and washed w i t h c o l d water. I t was d i s s o l v e d i n co n c e n t r a t e d h y d r o c h l o r i c a c i d s o l u t i o n and r e p r e c i p -i t a t e d w i t h c h l o r o f o r m . The r e s i d u e was a g a i n washed w i t h c o l d water and allowed t o dry i n a vacuum d e s i c -c a t o r . On standing, some of the substance appeared t o t u r n t a r r y , but on powdering the r e s i d u e , an a p p a r e n t l y u n i f o r m dark' r e d substance was ob t a i n e d , m.p. 126°C. The y i e l d was 60% of the weight of t h e q u i n o l i n e hydro-c h l o r i d e r e a c t e d . i i . R e a c t i o n of q u i n o l i n e h y d r o c h l o r i d e product w i t h a c e t i c anhydride The r e d product obtained from the r e a c t i o n of q u i n o l i n e h y d r o c h l o r i d e and z i n c was t r e a t e d w i t h an excess of a c e t i c anhydride and r e f l u x e d f o r two hours. Water was added t o decompose the excess a c e t i c anhydride and the s o l u t i o n was n e u t r a l i z e d w i t h d i l u t e ammonium -26-hydroxide. A yellow-brown colloidal precipitate resulted which was centrifuged, washed with very dilute ammonia, fi l t e r e d and dried. This substance did not melt up to 350°C. At this point research into these side reaction products had to be abandoned because of the lack of time. Reactions with possible analytical application. a. Materials - preparation of Mn(OAc)3 One hundred cc. of acetic acid were heated to b o i l -ing in an evaporating dish and 6.9 gm. of anhydrous Mn(0Ac)8 added. After the acetate had been dissolved, 1.6 gm. of KMn04 was added slowly with st i r r i n g . The solution turned dark brown and after heating for a few minutes was allowed to cool. The solution was concen-trated and on cooling a crop of manganiacetate crystals was obtained. The f i r s t crop was washed with dilute acetic acid and recrystallized twice from glacial acetic acid. The crystals were dried in a vacuum desiccator over KOH, KMn04 + 4Mn(0Ac)s + 8H0Ac — <+ 5Mn(0Ac)3 + KOAc + 4H30 .. b. Reaction of C6HBN,2HG1 in CHC13 with MnS i . Mature of sample of MnS Freshly prepared MnS reacted with the reagent used, but did not colour the solution. A sample of MnS pre-pared at least one year previously, reacted to give an intense green solution. . i i . TABLE V R e a c t i o n of manganese s a l t s , metal and MnOa with' a s a t -u r a t e d c h l o r o f o r m s o l u t i o n of C BH BN .2HC1 Substance R e a c t i o n C o l o u r of s o l u t i o n MnC03 Very r e a c t i v e Dark green MnS04 No v i s i b l e r e a c t i o n Mn ( N 0 3) a Some r e a c t i o n Dark green M nCl 3 No v i s i b l e r e a c t i o n Mn03 Very r e a c t i v e w i t h Dark green e v o l u t i o n of C l s Mn(OAc) a Some r e a c t i o n Mn Very r e a c t i v e The s a l t s , manganese metal, and MnOs were a l s o t e s t e d w i t h C BH BN .HC1 i n CHC13 but d i d not g i v e the green c o l o u r . \ i i i . Heating of a f r e s h sample of MnS A f r e s h sample of MnS which d i d not g i v e a green c o l o u r when t r e a t e d w i t h the d i h y d r o c h l o r i d e reagent was heated w i t h a bunsen burner f o r 10 minutes. On t r e a t -i n g t h i s sample w i t h the C eH BN . 2 H C l i n CHC13 reagent, the s o l u t i o n turned l i g h t green. The sample a f t e r heat-i n g f o r a lon g e r time turned t h e reagent s o l u t i o n a darker green. i v . E f f e c t o f o x i d i z i n g agents The C BH 5N .2HC1 i n CHC13 reagent was allowed t o -28-r e a c t w i t h manganese metal. Samples of the r e s u l t i n g s o l u t i o n were t r e a t e d w i t h C eH 5N.HN0 3, HN0 3 ( c o n e ) , K s C r s 0 7 , NaOCl, and H S 0 S . The a d d i t i o n of any of these o x i d i z i n g agents caused the f o r m a t i o n of the f a m i l i a r green c o l o u r . They a l s o caused the c o l o u r t o appear i n s o l u t i o n s o f the reagent and MnCl s or MnS0 4. Heating the s o l u t i o n of manganese metal i n the reagent d i d not have any apparent e f f e c t . v. C BH BN.2HC1 i n CHC1 3 on Mn(0Ac) 3 The Mn(0Ac) 3 c r y s t a l s prepared as d e s c r i b e d i n (4.a. ) r e a c t e d w i t h the reagent t o g i v e a dark green c o l o u r . v i . I s o l a t i o n o f the substance c o n f e r r i n g  t h e green c o l o u r t o t h e C BH BN.2HC1 i n CHC1 3 C BH BN.2HC1 i n CHCl^ s o l u t i o n was r e a c t e d w i t h an excess of Mn0 2. The dark green s o l u t i o n which r e s u l t e d was poured i n t o an excess of a l c o h o l i c HCl solution 3' 1 and on the a d d i t i o n of dry ether a dark green c r y s t a l l i n e p r e c i p i t a t e r e s u l t e d which was f i l t e r e d and d r i e d i n a vacuum d e s i c c a t o r . The m e l t i n g p o i n t was 100-101°C. I t was found t h a t the s o l u t i o n s used f o r i s o l a t i n g t he c r y s t a l s had to c o n t a i n an excess of HCl or l i g h t green t o w h i t i s h c r y s t a l s r e s u l t e d . The c r y s t a l s appeared t o * The a l c o h o l i c HCl s o l u t i o n was prepared by bub-b l i n g d r i e d HCl gas from a Kipp generator through abs-o l u t e a l c o h o l . -29-be q u i t e hygroscopic and d i s s o l v e d i n moist a i r w i t h a l o s s of c o l o u r . I t was found t h a t the o r i g i n a l s o l -u t i o n s of the green substance i n C BH SN.2HC1 i n CHC1 3 a l s o l o s t t h e i r c o l o u r on s t a n d i n g . The green c r y s t -a l s were ve r y s o l u b l e i n water, and on f i r s t d i s s o l v i n g a p i n k c o l o u r appeared momentarily. v i i . A n a l y s i s of the green c r y s t a l s The s o l u b l e c h l o r i n e content was analyzed by F a j a n s Method and the manganese content was determ-3 3 i n e d g r a v i m e t r i c a l l y as MnNH4P0 4.H s0 . The remainder was assumed t o be p y r i d i n e . % * Atomic Weight R a t i o Mn 11.5 55 = .21 1 CI 37.6 35.5 = 1.06 5 C 5H 5K 50 .9 79 = .64 3 v i l i . L i m i t of v i s i b l e c o l o u r S o l i d KMn04 (.0.2 gm. ) was d i s s o l v e d i n 10 c c . of p y r i d i n e . T h i s s o l u t i o n was added dropwlse t o 2 c c . o f th e reagent o f C BH BN.2HC1 i n CHC1 8. The green c o l o u r was j u s t v i s i b l e a f t e r the a d d i t i o n o f 0.02 c c . of the 5 KMn0 4 s o l u t i o n or 5 X 10" gm. of manganese, i x . Colourometric a n a l y s i s A Coleman Spectrophotometer was used f o r t h e c o l o u r o m e t r i c work. As a r e f e r e n c e standard, 10 c c . o f a s a t u r a t e d s o l u t i o n of p y r i d i n e d i h y d r o c h l o r i d e i n -30 chloroform was used 0 The spectrophotometer was adjusted so that for this,reference solution concentration C = 0 , and transmittance T = 0 . KMn0 4 dissolved in pyridine was added to a similar solution of reagent u n t i l a medium green colour was obtained. A Specttfal-Transmittance curve was made (Wavelength in millimicrons vs % Trans-mittance) to determine the portion where T was essent-i a l l y constant (Figure III). This region, at 665 m i l l i -microns was used i n a l l subseuent work. A solution of KMn0 4 in pyridine was added drop-wise to a saturated chloroform solution of pyridine dihydrochloride and the percent transmlttanee was record-ed as was, the volume of solution containing K M n 0 4 . The concentration of KMn0 4 was determined, accurately by t i t r a t i o n against a standard solution of A s s 0 3 . The volume of an average drop was measured, and hence the concentration of manganese in grams per dribp was known. A l l the manganese was assumed to exist as the green complex and KMn0 4 solution was added t i l l the percent transmittance dropped to a small value (Figure IV). Another run of the percent transmittance and conc-entration in grams of manganese was obtained by adding a known amount of manganese metal dissolved in a known volume of saturated solution of C 5H BN.2HC1 i n chloroform to 10 cc. of a saturated chloroform solution of C BH 6N.2HC1 in which excess C 5H BN .HN0 3 was dissolved. -33-This reagent produced the green colour on the addition of the manganese metal (Figure V). x. Variation of colour with time KMn0 4 i n pyridine was added to the pyridine dihydrochloride reagent i n chloroform to conform to 6 55 X 10"* gm. of manganese i n 10 cc. of reference s o l -u t i o n and the v a r i a t i o n of percent transmittance was studied with respect to time (Figure VI). c. Reaction of C BH BN.2HC1 i n CHCl a with HgS i . I s o l a t i o n of mercury s a l t A solution of C BH BN.2HC1 i n CHC1 3 was allowed to react with excess HgS. A vigorous reaction ensued, and the r e s u l t i n g solution was boiled to remove H3S, which i f present, was found to r e p r e c i p i t a t e the HgS on attempting to Isolate the mercuric s a l t . The boiled solution was poured into excess ethanol from which a white c r y s t a l l i n e p r e c i p i t a t e was obtained, which, a f t e r f i l t r a t i o n and after drying i n a vacuum desiccator had a melting point of 123°C. i i . Analysis of the mercury s a l t The c r y s t a l l i n e mercuric compound was soluble i n water. The chlorine content was determined by Fajan 1s 88 Method . Mercury, i f l e f t i n solution, l e d to erroneous r e s u l t s due to the formation of the soluble but non-ionized HgCl 8. I t was removed by pr e p i t a t i o n with Na s C 0 3 and f i l t r a t i o n of the solution. The amount of FIGURE VI. VARIATION OF COLOUR OF GREEN TRIVALENT MANGANESE COMPLEX WITH TIME. - 3 6 - . mercury was determined gravimetrically as LCuCNHsCHaCHgNHg ) s H H g I 4 i and the remainder was assumed to be pyridine. io * Atomic Weight Ratio Hg 39.6 201 = 0 197 1 CI 28.0 35 .5 = .788 4 CgHgN.H 32 e4 80 = e40§ 2 i i i . A compound was made by di s s o l v i n g HgCl 8 i n C eH B N o H C l . Aprecipitate was also obtained fuom ethanol which had a melting point of 123°C. A mixed melting point with the f i r s t mercuric s a l t also was 123°C. - 3 7 I I I •* DISCUSSION P y r i d i n e s a l t s as r e c t l o n media. a. Type of r e a c t i o n most d e s i r a b l e I t was decided t h a t the most s u i t a b l e r e a c t i o n s t o i n v e s t i g a t e would be those of metals and s u l p h i d e s . S u l p h i d e s were chosen because a c i d r e a c t i o n s w i t h them would produce H 2S which i s g i v e n o f f as a gas and would thus serve, not only to a i d the r e a c t i o n i n going to completion, but a l s o t o a c t as an e a s i l y observed c r i t e r i o n f o r a r e a c t i o n o c c u r r i n g . Furthermore, i t was deci d e to a v o i d those r e a c t i o n s i n which water might be formed as the presence of water might make i t d i f -2 f i c u l t to study the r e a c t i o n products . b. Examination of the p y r i d i n e s a l t s prepared P y r i d i n i u m t r i c h l o r o a c e t a t e c o u l d not be used as i t decomposed on m e l t i n g . P y r i d i n i u m o x a l a t e and p y r -i d i n i u m n i t r a t e o f t e n produce water as one of t h e i r r e a c t i o n products and were t h e r e f o r e d i s c a r d e d . Many of the other s a l t s used as a c i d s , such as p y r i d i n i u m t h i o c y a n a t e were too weak to d i s s o l v e many of the metals and t h e i r s a l t s . I t was not p o s s i b l e to prepare p y r -i d i n i u m f l u o r i d e w i t h the equipment a v a i l a b l e . P y r i d i n -ium f l u o r i d e might be a good medium, but would have the disadvatage o f be i n g h a r d to handle. I t should be pos-- 3 8 -s i b l e to prepare pyridinium f l u o r i d e by reacting pyr-i d i n e with l i q u i d HF i n a s t a i n l e s s s t e e l container.in the r a t i o of one mole of pyridine to about six of HF, f o l -lowed by evaporation of any excess of the low b o i l i n g HF, This excess of HF i s necessary as amines form com-pounds of the type B.4HF, where B i s a primary, second-6 ary, or t e r t i a r y amine, Berliner and Hann propose the structure: ii: B H-.F-H-.F: ii It was found that the pyridine s a l t s most s u i t -able for i n v e s t i g a t i o n as solvent systems for metals and sulphides were pyridinium chloride and pyridine dihydrochloride. These two s a l t s reacted with many metals and sulphides, were reasonably easy to obtain i n a pure state, and had the advantages of pyridine s a l t s i n general, that i s , the s t a b i l i t y of the pyridine nucleus and the existence of many r e a d i l y i s o l a t e d c r y s t a l l i n e derivatives. Furthermore, there was no p o s s i b i l i t y of the formation of water as a side prod-uct and the reaction should be r e l a t i v e l y simple. Methods of using C BH KM .HC1 and C KH KN . 2 H C 1 . a. Molten state Reactions with molten pyridinium chloride have been ca r r i e d out with a number of metals, metal oxides, and - 3 9 -S 9 8 6 ' 2 8 m e t a l c h l o r i d e s . Ho*ever, a l t h o u g h p y r i d i n i u m c h l o r i d e m e l t s a t t h e r e l a t i v e l y low t e m p e r a t u r e o f l44°C., r e a c t i o n s w i t h m e t a l s may r e s u l t i n s i d e p r o d u c t s as were e v i d e n c e d w i t h A l , Mg, and Zn. W i t h t h e e x c e p t -i o n o f t h e s e t h r e e m e t a l s i t was an e x c e l l e n t s o l v e n t medium f o r many m e t a l s and sulphides,, P y r i d i n e d i h y d r o c h l o r i d e was a l s o a f a i r l y good medium f o r t h e s u b s t a n c e s u s e d . However, b o t h p y r i d i n e s a l t s had c e r t a i n d i s a d v a n t a g e s . They were b o t h q t i i t e h y g r o s c o p i c and, s i n c e t h e p r e s e n c e o f w a t e r was t o be a v o i d e d , t h i s was a d e c i d e d d i s a d v a n t a g e . F u r t h e r m o r e , a l t h o u g h t h e te m p e r a t u r e s a t w h i c h t h e two h y d r o c h l o r -i d e s a l t s m e l t e d were low, i t would be more c o n v e n i e n t t o f i n d some system where h e a t was not n e c e s s a r y t o produce a medium w h i c h would r e a c t w i t h t h e m e t a l s and s u l p h i d e s u s e d . b. Room t e m p e r a t u r e systems The d i s a d v a n t a g e s mentioned i n t h e p r e v i o u s s e c t i o n a c o u l d be overcome by t h e u s e o f c h l o r o f o r m s o l u t i o n s o f pyridinfeum c h l o r i d e and p y r i d i n e d i h y d r o c h l o r i d e . B o t h s a l t s were r e l a t i v e l y s o l u b l e i n c h l o r o f o r m and b o t h s t i l l d i s s o l v e d many m e t a l s and s u l p h i d e s . The second-a r y r e a c t i o n s o f Mg, A l , and Zn n o t e d w i t h m o l t e n p y r -i d i n i u m c h l o r i d e were not e v i n c e d w i t h e i t h e r s o l v e n t . The r e a c t i o n s w i t h t h e d i h y d r o c h l o r i d e s o l u t i o n were more v i g o r o u s t h a n t h e c h l o r o f o r m s o l u t i o n o f t h e mono-- 4 0 -h y d r o c h l o r i d e and appeared t o be o n l y s l i g h t l y l e s s r e a c t i v e t h a n m o l t e n p y r i d i n i u m c h l o r i d e . The p r e s e n c e o f t h e a d d i t i o n a l mole of HCl t h u s i n f l u e n c e d t h e r e a c t -i v i t y o f t h e s o l v e n t and r e s u l t e d I n r e a c t i o n s w i t h some s a l t s o f manganese t h a t d i d n o t o c c u r w i t h any o f t h e o t h e r r e a c t i o n m i x t u r e s . The r e a c t i o n s i n g e n e r a l may be e x p r e s s e d i n two s t e p s : 2 C 6 H 6 N . H C 1 + MeS - 2 C e H 6 N + M e C l 8 + H 8S and, i f t h e f o r m a t i o n o f a d o u b l e s a l t i s p o s s i b l e 2 C 5 H 5 N . H C 1 + M e C l 8 - — * ( C e H B N . H ) 8 M e C l 4 where Me I s an^ example o f any d i v a l e n t element whose s u l p h i d e r e a c t s . I t might be e x p e c t e d t h a t o n l y t h o s e s u l p h i d e s r e a c t i n g w i t h aqueous h y d r o c h l o r i c a c i d would d i s s o l v e i n t h e systems s t u d i e d . However, t h e s t a b i l i t y o f t h e p y r i d i n e complexes must be c o n s i d e r e d as w e l l as t h e d i f f e r e n c e i n i o n i z i n g and d i s s o c i a t i n g powers o f t h e nonaqueous systems. M e r c u r i c c h l o r i d e was f o u n d t o d i s -s o l v e q u i t e r e a d i l y i n t h e c h l o r o f o r m s o l u t i o n o f p y r -i d i n i u m c h l o r i d e . I n t h e water - hydrogen c h l o r i d e system t h e s u l p h i d e i o n c o n c e n t r a t i o n cannot be r e d u c e d below t h a t w h i c h w i l l a l l o w t h e m e r c u r i c s a l t s t o s t a y i n s o l u t i o n . However, i n t h e c h l o r o f o r m s o l u t i o n , t h e s t a b i l i t y o f t h e mercury complex, and t h e i n h i b i t i o n o f t h e i o n i z a t i o n o f t h e H 8S, a l l o w HgS t o be d i s s o l v e d by C B H B N . H C 1 6 The nature of C BH eN.2HCl In CHC13. There i s very l i t t l e reported i n the l i t e r a t u r e concerning the nature of the compound CBHBN.3HC1. is; Kaufler and Kunz , who f i r s t prepared the substance, stated that HCl polymerized i n the same manner as the hydrofluorides (H 3F 8, H 3 F 3 ) . In t h e i r subseuent work, they found that the s t a b i l i t y of the dihydrochloride was e s s e n t i a l l y l i m i t e d by the degree of a l k y l a t i o n and.that only t e r t i a r y and quaternery bases formeithe dihydro-chlorides. No trihydrochlorides Mgre reported. The dihydrochlorides were simply postulated as: x C y NH][C18H] z Since t h i s compound was prepared, there has been no further suggestions as to why t e r t i a r y bases such as pyridine should take on a second molecule of HCl. In order to determine i f there existed any type of bonding of the second HCl molecule to the C BH eN.HCl molecule i n chloroform solution, the wavelength region X = 3300-5300 A was investigated on a Beckmann Spectro-photometer, The saturated chloroform solution of pyr-i d i n e dihydrochloride on d i l u t i o n showed that the p l a t -eau A i n Figure I was the same peak (Figure II) as was given by the monohydrochlorlde solution. On the basis of the s i m i l a r i t y of the plots, such possible structures as p i bond formation are ruled out, and i n the chloroform -4 ab-s o l u t i o n , t he CBHBN..2HC1 can be co n s i d e r e d as C BH BN.HC1 + HCI (the presence of HCI does not e f f e c t the absorb-ency). T h i s seemed q u i t e reasonable as the e v o l u t i o n of HCI fumes from such c h l o r o f o r m s o l u t i o n s was very n o t i c e a b l e . S i d e r e a c t i o n s . a. P o s s i b i l i t y o f fo r m a t i o n of b l o v r i d v l s P y r i d i n e has a s t r u c t u r e analogous to t h a t of benzene. The i n t r o d u c t i o n of the n i t r o g e n atom into, the r i n g in\place o f a carbon atom r e s u l t s i n a compound w i t h i t s own p a r t i c u l a r r e a c t i o n s , y e t m a i n t a i n i n g a c e r t a i n s t r u c t u r a l r e l a t i o n s h i p to the "parent" benzene. The resonance s t r u c t u r e s c o n t r i b u t i n g most t o the s t a b i l i t y o f the p y r i d i n e r i n g can be r e p r e s e n t e d as: Hydrogenation, i f i t d i d occur, would be v e r y d i f f i c u l t due to the i n e r t n e s s o f the p y r i d i n i u m i o n . T h i s i s e x p l a i n e d by assuming t h a t the n a t u r a l e l e c t r o n a t t r a c t -i o n of the n i t r o g e n atom i n the p y r i d i n e r i n g i s enorm-o u s l y enhanced i n an a c i d s o l u t i o n where the p y r i d i n e e x i s t s as the p o s i t i v e charged p y r i d i n i u m i o n VI. The e f f e c t o f the p o s i t i v e i o n c o u l d be r e p r e s e n t e d a c c o r d -i n g to the d e s i g n a t i o n of the E n g l i s h s c h o o l as VII, - 4 3 * w h i c h i n d i c a t e s t h a t t h e e l e c t r o n a t t r a c t i o n o f t h e p o s i t i v e l y charged n i r o g e n atom would r e d u c e t h e e l e c t r o n d e n s i t y i n t h e 2 and 4 p o s i t i o n s and t h e r e f o r e would enhance t h e p o l a r i z a t i o n I n d i c a t e d by t h e I I I , IV, and V r e s o n a n c e s t a t e s . M TEL S i n c e h y d r o g e n a t i o n c o u l d be r e p r e s e n t e d as a t t a c k by H 3 + , i t i s o b v i o u s t h a t h y d r o g e n a t i o n o f an a l r e a d y : p o s i t i v e charged p y r i d i n i u m i o n would be d i f f i c u l t and t h a t , when i t d i d o c c u r , i t would a t t a c k , n o t t h e 2 and 4 p o s i t i o n s o f low e l e c t r o n d e n s i t y , b u t would a t t a c k t h e p o s i t i o n w h i c h i s r e l a t i v e l y u n a f f e c t e d by t h e quat-e r n a r y n i t r o g e n atom, t h e 3 p o s i t i o n . I n p r a c t i c e , no b i p y r i d y l s were found and t h e s i d e r e a c t i o n s must be a c c r e d i t e d t o some o t h e r t y p e o f r e a c t i o n . b. R i n g Cleavage R i n g c l e a v a g e r e a c t i o n s w i t h p y r i d i n e a r e p o s s i b l e as t h e p y r i d i n e r i n g o f f e r s a n i t r o g e n atom w i t h an un-sha r e d p a i r o f e l e c t r o n s as a p o i n t o f a t t a c k . T h i s v@.s not t h e case w i t h p y r i d i n i u m compounds. However, w i t h c e r t a i n s p e c i a l d e r i v a t i v e s t h e normal p y r i d i n i u m -44-r e s i s t a n c e i s l o s t . I t i s suspected t h a t the s i d e r e a c t -i o n s which occur w i t h p y r i d i n i u m c h l o r i d e and Zn, Mg, and A l may be of t h i s type. One sueh s p e c i a l compound i s 4 - p y r i d y l - p y r i d i n i u m d i c h l o r i d e : R i n g opening i n t h i s compound should f o l l o w the proposed r e a c t i o n f o r 2 , 4 - d l n i t r o p h e n y l p y r i d i n i u m c h l o r i d e i n 4 0 ) 4 1 ) 4 3 a l k a l i n e s o l u t i o n . 4 - p y r i d y l - p y r i d i n i u m d i -c h l o r i d e undergoes a s i m i l a r r e a c t i o n w i t h the p r o d u c t i o n of a red-brown product q u i t e s i m i l a r t o t h a t o b t a i n e d i n the r e a c t i o n of p y r i d i n i u m c h l o r i d e p l u s Zn. The main evidence i n favour of an open c h a i n s t r u c t u r e w i t h the 4 - p y r i d y l - p y r i d i n i u m d i c h l o r i d e and 2 , 4 - d l n i t r o p h e n y l -p y r i d i n i u m c h l o r i d e I s t h e i r c o l o u r . S i n c e the o r i g -i n a l s t r u c t u r e s were c o l o u r l e s s , the c o l o u r e d compounds suggested a form w i t h an i n c r e a s e i n the conjugated s y s -tems to account f o r an i n c r e a s e d a b s o r p t i o n of v i s i b l e l i g h t . I f r i n g cleavage occurs i n the p y r i d i n i u m c h l o r i d e p l u s Zn r e a c t i o n , i t does so i n the fefsence of any oxy-genated substance,, T h i s e l i m i n a t e s the enol type s t r u c t -u r e as i s found w i t h the two examples of r i n g opening d i s c u s s e d . Because of the c o l o u r e d r e a c t i o n product t h e r e should e x i s t some i n c r e a s e d conjugation.- F u r t h e r -more, the d e c o l o u r a t i o n of a d i l u t e KMn04 s o l u t i o n sug-gested an open c h a i n w i t h at l e a s t one double bond. T h i s seemed s u b s t a n t i a t e d by the l o s s o f c o l o u r o f a s o l u t -i o n of the unknown product when t r e a t e d w i t h 30$ H 3 0 s and allowed t o stand. I f the s i d e ohain p o s t u l a t e d was o x i d i z e d , t h i s would account f o r the l o s s of c o l o u r . I t had been hoped t h a t a study of the r e a c t i o n products of q u i n o l i n e h y d r o c h l o r i d e and metals would o f f e r some c l u e as to the nature o f the r e a c t i o n . F u r t h e r -more, the l a r g e i n c r e a s e i n y i e l d of the q u i n o l i n e hydro-c h l o r i d e s i d e product was an a d d i t i o n a l advantage. At t h i s p o i n t however, r e s e a r c h was stopped. c. L i m i t a t i o n s due to s i d e r e a c t i o n s The o n l y s i d e r e a c t i o n s observed were those which o c c u r r e d at h i g h temperatures w\ifchpyridinium c h l o r i d e and only w i t h the e l e c t r o p o s i t i v e metals Zn, Mg, and A l . These r e a c t i o n s produced only a very s m a l l q u a n t i t y o f r e a c t i o n products and were assumed to occur to onl y a s l i g h t extent. In the other media no s i d e r e a c t i o n s were observed w i t h e i t h e r metals or s a l t s . S i n c e ^matty metals -46-and s u l p h i d e s a r e s o l u b l e i n some o f t h e s o l v e n t s y s -tems s t u d i e d , t h e y o f f e r e x c e l l e n t media f o r s o l u t i o n . The s o l v e n t system o f s p e c i a l n o t e because o f i t s h i g h r e a c t i v i t y and use a t room t e m p e r a t u r e was p y r i d i n e d i h y d r o c h l o r i d e i n chloroform,, R e a c t i o n s w i t h p o s s i b l e a n a l y t i c a l - a p p l i c a t i o n , a. T r i v a l e n t manganese i . F o r m u l a t i o n o f t h e compound  ( 0 5 H s N . H ) a E M n C l B i C e H 6 N I t was n o t i c e d t h a t C 5H 5N.2HC1 i n CHC1 3 gave d i s - . s i m i l a r r e a c t i o n s w i t h d i f f e r e n t samples o f MnS. A f r e s h l y p r e p a r e d sample d i s s o l v e d t o g i v e a c o l o u r l e s s s o l u t i o n , whereas an o l d sample r e s u l t e d i n a dark g r e e n c o l o u r . F r e s h l y p r e p a r e d MnS, when h e a t e d on exposure t o a i r , and a g a i n t r e a t e d w i t h t h e c h l o r o f o r m s o l u t i o n a l s o gave t h e gr e e n c o l o u r . Manganous s a l t s s uch as M n C l s and MnS04 d i d n o t g i v e t h e great c o l o u r i n t h e c h l o r o f o r m r e a g e n t , b u t i t appeared on t r e a t i n g t h e res'* u l t a n t s o l u t i o n s o f t h e s e s a l t s w i t h an o x i d i z i n g a g e n t . A l l t h e f o r e g o i n g e v i d e n c e seemed t o i n d i c a t e t h a t t h e g r e e n c o l o u r was due t o t h e e x i s t e n c e o f an o x i d a t i o n s t a t e e# g r e a t e r t h a n +2, MnO a r e a c t e d v e r y v i g o r o u s l y w i t h t h e r e a g e n t and th e e v o l u t i o n o f c h l o r i n e was n o t i c e a b l e , s u g g e s t i n g t h a t t h e o x i d a t i o n s t a t e o f t h e r e s u l t i n g manganese compound was l e s s t h a n +4. The p r e s e n c e o f manganese i n t h e t r i v a l e n t s t a t e seemed <#ite e v i d e n t . C o n f i r m -a t i o n was o b t a i n e d when a c o l o u r l e s s s o l u t i o n r e s u l t e d on r e a c t i n g M n ( 0 A c ) 3 w i t h t h e p y r i d i n e d i h y d r o c h l o r i d e i n c h l o r o f o r m whereas Mn(0Ac) 3, r e s u l t e d i n a g r e e n s o l -u t i o n on i d e n t i c a l t r e a t m e n t . A n a l y s i s o f t h e i s o l a t e d compound suggested t h e f o r m u l a t i o n o f t h e complex (C 6H eN.H) 8CMnCl 6 3 c 6H 6N. C a l c u l a t e d T h e o r e t i c a l CI 3 7 . 6 $ 3 7 . 6 $ Mn 11 . 5$ 11 . 6$ T h i s p a r t i c u l a r s t r u c t u r e was su g g e s t e d as t h e complexes o f t r i v a l e n t ' m a n g a n e s e a r e c o n f i n e d t o t h e u n u s u a l t y p e M a C M n i B l , o f t e n w i t h a m o l e c u l e o f wa t e r w h i c h presumably completes t h e c o o r d i n a t i o n number o f 6 ; t h e t y p e M 3[MnX 6 3 8 7 i s not known t o o c c u r . The compound i s o l a t e d i n t h i s c a s e had a m o l e c u l e o f p y r i d i n e t o complete t h e c o o r d i n -a t i o n number o f 6 i n s t e a d o f a m o l e c u l e o f w a t e r . i i . E x p l a n a t i o n o f r e a c t i o n s o f manganese  s a l t s 1. I t has been shown t h a t when MnS was h e a t e d o x i d a t i o n t a k e s p l a c e I n such a manner t h a t mang-a n e s e ^ i n an o x i d a t i o n s t a t e o f g r e a t e r t h a n +2 as t h e h e a t e d MnS r e a c t e d w i t h t h e CBHBN.2HC1 i n CHC13 t o g i v e t h e g r e e n c o l o u r e d t r i v a l e n t manganese complex. -48-2. Pure c r y s t a l l i n e MnC03, i s pi n k . - I t slo w l y darkens i n a i r through o x i d a t i o n . I t evolves C0S l e a v i n g MnO which i s r e a d i l y o x i d i z e d i n a i r t o h i g h e r S 0 o x i d a t i o n s t a t e s , e.g, Mn sO a and Mn s0 4 , S i n c e the sample used was not a f r e s h one, the presence o f Mn 30 3 and Mn 30 4 account f o r the green c o l o u r a t i o n . 3. The c o l o u r w i t h manganous n i t r a t e i s t o be expected due to the presence o f the n i t r a t e i o n . I t has been shown t h a t o x i d i z i n g agents such as HN03 cause the f o r m a t i o n o f the green complex from s t a b l e d i v a l e n t manganese s a l t s . 4. MnOl 3, MnS04, Mn(0Ac)8 d i d not g i v e a green c o l o u r as an o x i d a t i o n s t a t e of manganese g r e a t e r than +2 was not formed. i i i . D etermination o f t r i v a l e n t manganese. by c o l o u r o m e t r i c a n a l y s i s of the green complex The Lambert-Beer Law ( 1 ^ = IQ I O " * ^ 0 1 ) i s the only -r a t i o n a l means f o r t r a n s l a t i n g photometer r e a d i n g s t o expr e s s i o n s of the corresp o n d i n g c o n c e n t r a t i o n of the sample. A simple form f o r t h i s e x p r e s s i o n i s : . C = -K l o g T where C i s the c o n c e n t r a t i o n , K i s a p r o p o r t i o n a l i t y constant and T i s the t r a n s m i t t a n c e (T = It/lo)-» ^ the Lambert-BeBr Law i s obeyed, the C o n c e n t r a t i o n -Transmittance graph o f t h i s r e l a t i o n s h i p p l o t t e d on semi-l o g paper, i s a s t r a i g h t l i n e i n t e r s e c t i n g the p o i n t - 4 9 -0 = 0 , T = 100$. I t was necessary to show t h a t s o l u t i o n s o f the green t r i v a l e n t manganese complex obeyed t h i s law i n order to determine the T of one s o l u t i o n of known c o n c e n t r a t i o n and then draw a s t r a i g h t l i n e i n t e r s e c t -i n g t h i s p o i n t and the p o i n t C = 0 , T = 100$. Such a s t r a i g h t l i n e then r e p r e s e n t s a v a l i d C o n c e n t r a t i o n -Transmlttance graph and w i l l a l l o w the c o n t r a t i o n of any o t h e r s o l u t i o n to be determined by measuring only the p e r c e n t t r a n s m i t t a n c e . The Lambert-Beer Law r e q u i r e d t h a t the T measure-ment be made w i t h monochromatic l i g h t and at a wave-l e n g t h corresponding t o a r e g i o n of the constituent's S p e c t r a l - T r a n s m l t t a n c e curve where T was e s s e n t i a l l y c o n s t a n t . The r e f e r e n c e s e l e c t e d must be such t h a t C = 0 when T = 100$ and the nature of the sample s o l -u t i o n must be such t h a t i t s T responds o n l y to changes i n C. With these l i m i t a t i o n s the f l a t p o r t i o n b e s t chosen was 665 m i l l i m i c r o n s ( F i g u r e I I I ) . F i g u r e IV, o b t a i n e d by the r e d u c t i o n of KMnO*, showed t h a t the Lambert-Beer Law was obeyed i n the r e g i o n o f 8 X 10* gm. of manganese per 10 c c . of s o l u t i o n down _ e t o 3 X 10 gm. of t r i v a l e n t manganese i n the same volume of s o l u t i o n . F i g u r e V i s a s i m i l a r p l o t , but o b t a i n e d by forming the t r i v a l e n t complex by o x i d a t i o n o f a manganous s o l u t i o n . C o n c e n t r a t i o n s of t r i v a l e n t - 4 manganese g r e a t e r than 8 X 10 gm. i n 10 c c . of s o l u t i o n - 5 0 -can be determined by s u i t a b l e d i l u t i o n . I t must be noted, however, t h a t the c o l o u r r e p r e s e n t s not onl y any manganese o r i g i n a l l y present i n the t r i v a l e n t s t a t e , but any manganese of hi g h e r v a l e n c e which may be reduced t o the t r i v a l e n t s t a t e , and d i v a l e n t manganese which may become o x i d i z e d . F i g u r e VI r e p r e s e n t s the v a r i a t i o n o f c o l o u r o f a 6 55 X 10" gm. t r i v a l e n t manganese complex per 10 c c . of reagent s o l u t i o n w i t h time. The p l o t shows t h a t t h e time may be a very important f a c t o r and t h a t any c o l o u r -ometric a n a l y s i s based on the use of the green t r i v a l e n t manganese complex w i l l have t o take i n t o c o n s i d e r a t i o n the f a d i n g o f the c o l o u r w i t h time. b. The me r c u r v - p y r l d i n e complex i . F o r m u l ation of the compound (C BH 5N.H) aHgCl4 A n a l y s i s of the i s o l a t e d mercuric compound sug-gested t h a t the formula of the compound was (C BH BN.H) aHgCl4. C a l c u l a t e d T h e o r e t i c a l Hg 39.6$ 3 9 . 9 $ C l 28.0$ 28.2$ The mixed m e l t i n g p o i n t of t h i s compound prepared from p y r i d i n i u m c h l o r i d e i n c h l o r o f o r m w i t h HgS and the compound i s o l a t e d i n a s i m i l a r manner from H g C l a p l u s C 5H BN.HC1 was 123°C. This v a l u e agreed w i t h t h a t of 1 3 Grossmann and Hunseler f o r the above compound. - 5 1 -iio A p p l i c a t i o n of s o l u b i l i t y o f HgS The one a p p l i c a t i o n of the s o l u b i l i t y of HgS i n the reagent s o l u t i o n CBHBN.HC1 i n CHC13 t h a t suggested i t s e l f immediately was i n r a d i o c h e m i c a l s e p a r a t i o n s . HgS i s an e x c e l l e n t e a r r l e r f o r many r a d i o a c t i v e i s o t o p e s , and the ready s o l u b i l i t y o f HgS i n the reagent s o l u t i o n used here, may s i m p l i f y s e p a r a t i o n t e c h n i q u e s . 6„ C o n c l u s i o n s . I t i s evident t h a t r e a c t i o n s i n media such as molten p y r i d i n i u m c h l o r i d e or p y r i d i n e d i h d r o c h l o r i d e i n c h l o r o f o r m are d i f f e r e n t i n many r e s p e c t s t o s i m i l a r r e a c t i o n s c a r r i e d out i n water. The s t r o n g bonding o f the hydrogen atom t o the n i t r o g e n atom of the p y r i d i n e r i n g allows many s a l t s t o be heated t o h i g h temperatures without decomposing. The h y d r o c h l o r i d e s of p y r i d i n e have been shown -to be s t r o n g enough as a c i d s t o a c t as good d i s s o l v i n g r e a g e n t s . They have the f u r t h e r advantage of forming complexes which are s t a b l e . A l s o many of these complexes can be i s o l a t e d as c r y s t a l l i n e d e r i v a t i v e s at room temp-e r a t u r e . Thus, these h y d r o c h l o r i d e s of p y r i d i n e o f f e r media i n which the sometimes disadvantageous i o n i z a t i o n of water may be circumvented. The fo r m a t i o n — o f Many complexes which would d i s s o c i a t e i n water can occur and oaa be i s o l a t e d . -52-IV - BIBLIOGRAPHY 1. Anderson, T. Ann. 105: 337, 1858. 2. Audrieth, L.F., and Long, A. Trans. Illinois State Acad. Sci. 28 - 2: 121, 1935. 3. Audrieth, L.F., Long, A., and Edwards, R.E. J. Am. Chem. Soc. 58: 428, 1936. 4. Audrieth, L.F.., and Schmidt, M.T. Proc. Natl. Acad. Sci. 20: 221, 1934. 5. Berliner, J.F.T., and Hann, D.A. J. Phys. Chem. 32: 1142, 1928. 6. Brttnsted, J.N. Ber. 6 1 : 2049, 1928. 7. Christensen, O.T. Z. a. Ch. 27: 325, 1901. 8. Cumming, W.M. J. Chem. Soc. 121: 1287, 1922. 1 2 3 : 2457, 1923°. 125: 1106, 1924. 125: 244l, 1924. 9. Davidson, A.W. J. Am. Chem. Soc. 50: 1890, 1928. 10. Erkstein, 0. Ber. 39: 2136, 1906. 11. Franklin, E.C. J. Am. Chem. Soc. 27: 820, 1905. 12. Franklin, E.C. J. Am. Chem. Soc. 46: 2137, 1924. 13. Grossmann, H., and Hunseler, F. Z. a. Ch. 46: 372, 1920. 14. Hall, N. P . , Chem. Rev. 8: 191, 1931. 15. Hofmann, K.A., and Heinlmaler, H., Ber. 38: 3066, 1905. 16. Kaufler, F., and Kunz, E.C. Ber. 42: 385, 1909. -53-17. Koenigs, E., and Greiner, H. Ber. 64: 104a, 1931. 18. Lutz, E. Ber. 43: 2673, 1910. ' 19. Mohler, J. Ber. 21: 1015, 1888. 20. Partington,•J. R. Textbook of Inorganic Chemistry, MacMillan and Co., Ltd., New York. 1950. 21. Pfeiffer, P. Ber. 47: 1582, 19l4.-22. Pierce, W.C., - and Haenisch, E.L. Quantitative Analysi John Wiley and Sons, Inc., New York. 1944. 23. Pincussohn, 1. Z. a. Cu. l4: 385, 1897. 24. Reitzenstein, F. Ann. 326: 312, 1903. 25. Riesenfeld, E.H. Ber.' 38: 3381, 1905. . 26. Scott, A.F., and Coe, C.S. J. Am. Chem. Soc. 59: 1576, 1937. 27. Sidg^wick, N.V. Chemical Elements and their Compounds Oxford Press, London. 1951. 28. Starke, K. Can. J. Res. B, 28: 225, 1950. 29. Tingle, J.B., and Brenton, B.F.P. J. Am. Chem*. Soc. 31: 1162, 1910. * 30. Trowbridge, D.H. J. Am. Chem. Soc. 19s 327, I898. 31. Trowbridge, D.H., and Diehl, P.F. J. Am. Chem. Soc. 19: 562, 1898. 32. Vogel, A.I. Practical Organic Chemistry, Longmans, Green, and Co., London. 1948. 33. Vogel, A.I. Quantitative Inorganic Analysis, Longmans, Green, and Co.", London. 1948. p.534. 340 Vogel, A.I. Quantitative Inorganic Analysis, Longmans, Green, and Co., London. 1948. p.503. 35. Wagener, F.,' and Tollens, B. Ber. 39: 420, 1906. 36. Walden, P. Salts, Acids, and Bases., MeGraw-Hill Book Company, New York. 1929. - 5 4 -37. Werner, T.H. Neuere Auschauengen auf dem Gebiete der anorganischen Chemie, 1st ed. 1905. p. 8 8 . , 4 t h ed. 1920. p. 279. 3 8 . Whitford, E.L. J . Am. Chem. Soc. 47:. 2934, 1925 39 . Wiede, O.F. Ber. 3 0 : 2183, 1897. 4.0. Zincke, T6 Ann. 330: 367, 1904. 4 1 . Zincke, T., Heuser, G., and Moller, W. Ann. 333: 296, 1904. 42. Zincke, TI, and Wurker, W. Ann. 338: 107, 1905 0 

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