192 CONJUGATED ACIDS. 



hydrated hippuric acid) ; if Strecker had not ascertained that the 

 silver-salt was accurately represented by AgO.C 18 H 7 O 7 , we might 

 have regarded its composition as expressed by the formula 

 C 9 H 3 O 3 .HO, and therefore have considered hippuric acid as ana- 

 logous to oxamic, lactamic, tartramic, and aspartic acids, and as a 

 compound of this acid with its amide (H 2 N.C 9 H 3 O 2 + C 9 H 3 O 3 .HO 

 C 18 H 8 NO 5 .HO). The view, in accordance with which benzoic acid 

 exists preformed, is, however, still the most probable. 



Combinations. With alkalies and alkaline earths hippuric acid 

 forms crystallisable salts soluble in water and having a bitter taste; 

 its combinations with metallic oxides are difficult of solution in cold 

 water, but dissolve somewhat more freely in hot water. All the 

 crystallised salts contain water of crystallisation. Schwartz* has 

 analysed the following salts : 



Neutral hippurate of potash, KO.Hi + 2HO, occurs in micro- 

 scopic, oblique rhombic prisms, which part with their water at 100. 



The acid salt KO.Hi + HO.Hi + 2HO, crystallises in broad, satiny 

 plates. 



Hippurate of soda, 2NaO.Hi + HO, is crystalline, and dissolves 

 readily in water and alcohol. 



Acid hippurate of ammonia, H 4 NO.Hi + HOHi + 2HO, occurs 

 in very minute, four-sided, square prisms ; it behaves, when thrown 

 upon water, like butyrate of baryta. 



Hippurate of baryta, BaO.Hi + HO, is obtained in microscopic, 

 square prisms, and loses its water at 100. 



Hippurate of strontia, SrO.Hi+5HO, occurs in broad plates, 

 difficult of solution in cold water, or in microscopic, four-sided 

 prisms, with large terminal planes. 



Hippurate of lime, CaO.Hi + 3HO, occurs in oblique rhombic 

 prisms ; it parts with all its water at 100. 



Hippurate of magnesia, MgO.Hi + 5 HO, crystallises in wart-like 

 masses, is readily soluble, and at 100 loses only 4 atoms of water. 



Hippurate of cobalt, CoO.Hi + 5HO, occurs in rose-coloured 

 wart-like masses, consisting of microscopical, flat, four-sided prisms ; 

 at 100 it loses all its water, and it is perfectly insoluble in alcohol. 



Hippurate of nickel, NiO.Hi + 5HO, forms apple-green crusts, 

 dissolves in warm spirit, and at 100 loses all its water. 



* Ann. d. Ch. u. Pharm. Bd.54, S. 29-51. [Schwartz has published another 

 memoir on this acid during the last few months (in Ann. d. Ch. u. Pharm. Bd. 75, 

 S. 190.) o. E. D.] 



