238 CHEMISTRY OF THE PROTEIDS CHAP. 



but not the xantho-proteic test nor the tests of Adamkiewicz, Millon, 

 or Liebermann. 



Maly l then showed that Briicke's acid, which he called oxy-prot- 

 sulphonic acid or oxyproteic acid, was obtained from egg-white by 

 oxidising the latter at room -temperature with half its weight of 

 KMnO 4 ; precipitating the filtrate with acid, and drying the precipitate 

 at a low temperature. 



This oxy-prot-sulphonic acid had the percentage composition 



C H N S 



51-21 6-89 14-59 1'77 25'54 



In the pure condition it is a loose, white, non-hygroscopic powder 

 with strongly acid properties, insoluble in water and salt solutions, 

 but very soluble in alkalies, and precipitated from its solutions by 

 acids. The property last mentioned is used for purifying this acid, 

 but excess of strong acid must be avoided as otherwise the precipitate 

 re-dissolves. In faintly alkaline solutions the precipitation-limits for 

 oxyprot-sulphonic acid, prepared from crystalline serum-albumin, lie 

 between 2*8 and 4 '2 per cent saturated ammonium sulphate, and 

 there seems to be another substance, present in small amounts, having 

 precipitation limits between 4 - 8 and 6*4 per cent. 



Further oxidation of oxyprot-sulphonic acid with KMn0 4 resulted 

 in the formation of a pluri-basic acid rich in oxygen, which was called 

 peroxyproteic acid, with the percentage composition 



C H N S 



46-22 6-43 12-30 (V96 34*09 



Maly believed this compound to be formed by albumin taking up 

 oxygen without undergoing any other change. Calculation showed 

 each sulphur-atom to be associated with 71 0-atoms and 20-22 

 CO-groups. 



Peroxyproteic acid gives a strong biuret reaction, and is not pre- 

 cipitated by alkaloidal reagents such as phospho-tungstic acid, mercury, 

 potassium-iodide, or tannic acid. When treated with baryta water at 

 a gentle heat, it gives rise to large quantities of barium oxalate, and 

 traces of barium sulphate. On being boiled for several days with 

 baryta water there were obtained ammonia, glutaminic acid, leucin, 

 formic- acetic- and benzoic-acids, and a compound which Maly believed 

 to be isoglyceric acid. This last compound was not obtained from 

 gelatine, on oxidising the latter with double its weight of KMn0 4 , 

 while all the other oxidation-products were got. 



1 R. Maly, Untersuchungen uber die Oxydation des Eiweiss mittels Kalium- 

 permanganat, Monatsh.f. Cfiem. Q. 107 (1885), 9. 258 (1888), 10. 26 (1889). 



