154 THE SIMPLER NATURAL BASES 



The acid chromate, C 5 H 14 ON . HCrO 4 , is on the other hand much 

 more soluble than the neurine salt (Cramer [1904]). 



Th&picrate, C 5 H 14 ON . C 6 H 2 O 7 N 3 , is fairly soluble in water and more 

 so in alcohol (Brieger [1885, 2, p. 56 ; Ch. I]). 



The ptcrolonate, C 5 H U ON . C 10 H 7 O 5 N 4 . H 2 O, loses water of crystal- 

 lisation at 130, melts at 158 and decomposes at 241-245 (Otori 

 [1904, 3]). 



^.}\^ platinichloride y (C 5 H 14 ON) 2 PtCl 6 , is dimorphous. It crystallises 

 from a mixture of equal volumes of absolute alcohol and water in the 

 regular system (octahedra, cubes) and from water in rhomb-shaped six- 

 sided or pyramidal crystals of the monoclinic system ; on slow eva- 

 poration the latter kind may attain considerable size (Kauffmann and 

 Vorlander [1910] ; Gulewitsch [1891, i] gives crystallographic details). 

 Both forms of the salt are anhydrous arid orange red in colour ; 

 they are stable in the dry state, but readily interconvertible by recry- 

 stallisation from the proper solvent. Since one form is isotropic and 

 the other anisotropic, the dimorphism of choline platinichloride is 

 readily detected in polarised light and affords according to Kauffmann 

 the surest qualitative means of identification. The platinichlorides of 

 potassium, ammonium, trimethylamine and neurine all crystallise from 

 dilute alcohol in the regular system only ; if, after adding water and 

 evaporating, crystals become anisotropic, choline is probably present. 



At 21 one part of choline platinichloride dissolves in 5-82 parts 

 of water (Gulewitsch). The melting point is not characteristic ; both 

 forms melt at 209-211 on slow heating and at 240-241 when heated 

 rapidly. 



The aurichloride, C 5 H 14 ON AuCl 4 , crystallises in deep yellow needles 

 and also (from very dilute alcohol) in octahedra and cubes ; it dis- 

 solves in 7 5 -2 parts of water at 21 and in hot alcohol (Gulewitsch). 

 The melting point has been variously given as 238-239, 249, 244- 

 264, etc. 



The mercurichloride, C 5 H 14 ONC1 . 6HgCl 2 . H 2 O, forms crossed 

 hexagonal prisms, loses water above 1 00 and melts at 249-251; it is 

 soluble in 56^6 parts of water at 24-5 (Gulewitsch). According to 

 M6rner[i896; Ch. I] the melting point is 242-243 and it dissolves 

 in 67 parts of water at I9'5. Schulze [1909] found that one part 

 of the mercury salt dissolves in about fifty parts of water at room 

 temperature ; the solubility determinations were not concordant, pro- 

 bably owing to hydrolytic dissociation. 



The slight solubility of choline mercurichloride in cold water was 

 used by Brieger for its isolation ; after complete - precipitation by 



