856 BENZOYL. 



portion of uric acid in the urine suffers at the same time a great 

 diminution or is reduced to nothing.* 



The hippurates of the alkalies and alkaline earths are soluble 

 and crystallizable. Those of the metals proper with the ex- 

 ception of iron are very sparingly soluble in cold, but more 

 soluble in hot water and crystallize on cooling. The stronger 

 acids separate hippuric acid from all the hippurates ; distilled 

 with lime or hydrate of potash they give ammonia with an oily- 

 liquid supposed to be benzin. 



PRODUCTS OF THE DECOMPOSITION OF BENZOYL COMPOUNDS, 



Hyposulphobenzoic acid, 2HO-f-C 14 H 4 O 3 ,S 2 O 5 ; a bibasic 

 acid discovered by Mitscherlich. It is prepared by conducting 

 the vapour of anhydrous sulphuric acid into a dry receiver con- 

 taining benzoic acid and surrounded by cold water ; a viscid 

 mass is formed like turpentine, which is taken up by water, and 

 after the uncornbined benzoic acid has subsided from the liquid, 

 the latter is neutralised with carbonate of barytes, and after 

 evaporating the mixture, some hydrochloric acid is added to it f 

 the acid hyposulphobenzoate of barytes crystallizes upon cooling. 

 The free acid is obtained by precipitating the barytes of the last 

 salt by sulphuric acid, filtering, evaporating the solution by the 

 naked fire and finally in vacuo over sulphuric acid ; in this way 

 the acid is obtained in a crystalline state. The crystals may 

 be heated to 302 without alteration, but at a higher tempera- 

 ture they are decomposed. 



This acid forms both an acid and neutral class of salts, the 

 first containing one atom of water and one atom of metallic 

 oxide as base, the other two atoms of metallic oxide. All these 

 salts when distilled with an excess of hydrate of potash leave a 

 residue composed of sulphate and sulphite with carbonate of 

 potash, indicating the presence of hyposulphuric acid in the 

 original compound. Acid hyposulphobenzoate of barytes crys- 

 tallizes in oblique rhomboidal prisms, soluble in 20 parts of cold 

 water, and containing 9.6 per cent of water of crystallization or 

 3 atoms, which it loses at 212. 



Neutral hyposulphobenzoate of barytes, 2BaO -f C 14 H 4 O 3 , S 2 O & ; 

 is obtained by boiling the acid salt with carbonate of barytes ; 



* Proceedings of the Pharmaceutical Meetings at Mr. Bell's, Part 1, vol. 1. 1841. 



