APPENDIX TO CHAPTER II w-AMINO-ACIDS 137 



The normal aurichloride, C 5 H n O 2 N . HAuCl 4 . H 2 O, crystallises in 

 monoclinic orange coloured crystals ; m.p. 86-87 ; an abnormal auri- 

 chloride, C 5 H U O 2 N . AuCl 3 , is also known; it forms pale yellow crystals 

 decomposing at 130 and is transformed to the more deeply coloured 

 normal salt by recrystallisation from dilute hydrochloric acid. 



Benzoyl--amino-valeric acid is formed by the oxidation of benzoyl 

 piperidine with potassium permanganate and by the benzoylation of 

 S-amino-valeric acid. It melts at 94 and at 105. 



S-Amino-valeric acid does not yield a blue copper salt on boiling 

 with cupric oxide or on adding cupric acetate. 



/3-Iminazolyl-propionic Acid. 



This substance was isolated by Ackermann from the filtrate of 

 the /9-iminazolyl-ethylamine picrate [1910, i] obtained in the putrefac- 

 tion of histidine. The picric acid was removed from this filtrate, the 

 solution was evaporated, the residue was extracted with alcohol and 

 to the alcoholic solution platinic chloride was added. A slight pre- 

 cipitate was filtered off and the alcoholic solution was evaporated to 

 dryness. The residue, dissolved in a minimum quantity of boiling 

 water, deposited the crystals of the platinichloride of /3-iminazolyl- 

 propionic acid. 



/3-Iminazolyl-propionic acid is readily soluble in water, less so in 

 alcohol and crystallises from dilute acetone ; m.p. 208-209. 



The nitrate, C 6 H 8 C>2N2 . HNO 3 , readily soluble in methyl alcohol, 

 forms elongated six-sided leaflets; m.p. 143-148. 



The platinichloride, (C 6 H 8 O 2 N 2 ) 2 . H 2 PtCl 6 , melts at 209. 



The phosphotungstate crystallises from hot water in characteristic 

 rectangular leaflets, decomposing above 300. 



The copper salt forms blue needles. 



Carnosine (Ignotine). 



Carnosine is obtained from the regenerated phosphotungstic acid 

 precipitate (after neutralisation with nitric acid) by means of silver 

 nitrate and excess of baryta. After decomposing the silver precipitate 

 with hydrogen sulphide and removing the baryta by carbon dioxide, 

 the solution is neutralised with nitric acid and concentrated ; carnosine 

 nitrate crystallises out after the addition of alcohol. 



Krimberg, by Gulewitsch's method, obtained 15-3 grm. of the free 

 base from I Ib. of Liebig's extract, or 3-4 per cent.; by Kutscher's 

 process he only obtained 3 grm. of carnosine from the same quantity 



