302 CHEMISTRY OF THE PTOMAINS. 



presents an interesting case of trimorphism. It crystallizes in mono- 

 clinic plates (Rinne) which are easily soluble in water (1 to 5.82 

 parts at 21°, G.) insoluble in alcohol, ether, chloroform, benzol ; also 

 in characteristic superposed plates, sometimes in the form of orange- 

 red flat prisms (Brieger). From a warm saturated solution contain- 

 ing 15 per cent, alcohol it crystallizes in yellow regular octahedra 

 containing one molecule of water of crystallization, from aqueous 

 solutions in six-sided plates (Jahns) ; from aqueous solution on slow 

 evaporation it forms plates, clinorhombic plates, or needles (Hoppe- 

 Seyler) which are anhydrous. When rapidly crystallized it forms 

 prisms (Hundeshagen, Jahns, Schulze) ; and if the solution is con- 

 centrated the prisms are very thin, almost needles. According to 

 Schulze, it sometimes forms beautiful orange-red, chiefly six-sided 

 plates. It is easily soluble, forming splendid, very large, red, super- 

 posed monoclinic plates ; may crystallize from cold saturated aqueous 

 solution in large, prismatic, or needle-shaped crystals (Schmidt). 

 Jahns maintained that the plates and prisms belong to the same 

 system ; while Hundeshagen held that they are distinct. Instead 

 of the salt presenting an instance of trimorphism as first stated by 

 Hundeshagen, it would seem that but two forms occur — anhydrous 

 monoclinic and octahedra with one molecule of water of crystalliza- 

 tion. It contains always more or less water of crystallization, which 

 it does not give up completely over sulphuric acid, but only at 110° 

 (Brieger). The natural platinochlorid becomes strongly electric on 

 rubbing, whereas the synthetic cholin double salt does not become 

 electric. It melts at 225° with effervescence (Jahns) ; at about 238° 

 (Partheil); at 233°- 234° (Bode) ; at 232°- 233°, and more often 

 at 240°— 241° (Schmidt), with marked effervescence. The synthetic 

 salt melts at 213°- 216° (Gulewitsch). The solubility, crystalline 

 form and melting-point render it wholly different from neurin. 

 The properties of this and other salts of cholin have been carefully 

 reexamined by Gulewitsch (1898). 



The aurochlorid, CjHi^NO.Cl.AuCl, (Au = 44.48 per cent.), is 

 crystalline and is difiicultly soluble in cold water, but can be recrys- 

 tallized from hot water or from boiling alcohol. It forms prisms, 

 or gold-yellow long needles which are very easily soluble in hot 

 water and alcohol (Lippmann). It may form cubes and at 23.5° it 

 dissolves in 67.2 parts of water (G.). It can be separated from 

 neuridin aurochlorid by its solubility in water (Brieger). On heat- 

 ing the gold salt melts to a brown liquid (Schulze), and decomposes 

 at 264°. It melts at 244°- 245° (Siebert, Jahns); at 245°- 246° 

 (Schmidt) ; at 241°-243° (G.). 



The picrate, C5Hj^NO.OC5Hj(NOj)3, forms long, broad needles 

 which are more easily soluble than neuridin picrate, and hence can 

 be separated by recrystallization. It is more easily soluble in alco- 

 hol than in water. 



