30 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 



compounds of this substance, but, as Liebig 1 was the first to show, 

 this work was full of fallacies, and the only remnant of it is the survival 

 of the word proteid. 



Pavy 2 has used caustic potash in his researches on proteids, and 

 shown that the action of the alkali is to split off a substance of an amylose 

 nature which, on further treatment with mineral acids, yields a reducing 

 but non-fermentable sugar, C 6 H 12 6 , which gives a crystalline osazone 

 with phenylhydrazine. Pavy, however, himself points out that he is 

 not the first to obtain this result. Schiitzenberger 3 many years ago 

 obtained from proteid a dextrin-like substance by the prolonged use 

 of baryta water, which, after treatment with sulphuric acid, reduces 

 Fehling's solution, and " appears to be glucose, or an analogous substance." 

 From his own and Schiitzenberger 's work, he draws the conclusion that 

 proteid matter has the constitution of a glucoside. These experiments 

 will be again referred to under the gluco-proteids. 



0. Nasse 4 discovered that by boiling proteids with a strong solution 

 of barium hydrate some of their nitrogen was disengaged as ammonia, 

 but this only accounted for a small percentage of the total nitrogen. 

 He concluded that the nitrogen which is readily liberated is in the form 

 of an amide, that some is combined similarly to that of creatine, but that 

 the major part which is unaffected by this treatment is in the form of 

 an amido-acid. 



Schiitzenberger 5 has elaborated the baryta method. He obtained dif- 

 ferent results by varying the conditions of temperature and pressure, of 

 the time of treatment, and of the amount of barium hydrate employed. In 

 his earlier researches he employed coagulated egg-white, which had been 

 thoroughly washed with water, alcohol, and ether ; weighed amounts of 

 it were treated with from two to six times their weight of crystallised 

 barium hydrate and with water, the whole being heated in a closed iron 

 vessel to temperatures ranging from 100 to 250 C., and for periods of 

 time varying from 8 to 120 hours. He found that nitrogen to the extent 

 of about one per cent, of the total weight of albumin is given off as 

 ammonia at atmospheric pressure, by boiling for half an hour ; a second 

 one per cent, comes off slowly by continued boiling for 120 hours (this 

 result is, however, more easily obtained by treating with three parts of 

 barium hydrate at 120 C. for six to eight hours) ; a third one per cent, is 

 given off by treating with two parts of barium hydrate at 150 C., and a 

 fourth one per cent, by heating with excess of barium hydrate at 260 C. 



He next found that accompanying these four stages there were 

 different cleavage products obtained. First, some insoluble barium salts, 

 namely, oxalate, carbonate, phosphate, and sulphate. On calculating 

 the quantities of oxalate and carbonate formed, he arrived at the 

 interesting result that they were present in proportions to support the 

 hypothesis that, with the ammonia set free, they had existed in the pro- 

 teid molecule as a urea and oxamide radicle. The barium carbonate 

 and oxalate, moreover, were formed at different stages of ammonia 



1 Ann. d. Chem., Leipzig, Bd. Ixii. S. 132. 



2 "Physiology of the Carbohydrates," London, 1894, p. 28; Proc. Roy. Soc. 

 London, 1893, vol. liv. p. 53 ; Eep. Brit. Ass. Adv. Sc., London, 1896. 



3 Bull. Soc. chim., Paris, 1875, Se*r. 5, tome xxiii. p. 161. 



4 Chem. Centr.-BL Leipzig, 1873, S. 137; Arch. f. d. ges. Physiol., Bonn, Bde. vi. S. 

 589 ; vii. S. 139 ; viii. s. 381. 



5 Ann. dechim., Paris, Se"r. 5, tome xvi. p. 289 ; Compt. rend. Acad. d. sc., Paris, tomeci. 

 p. 1267 ; cii. p. 289 ; cvi. p. 1407 ; cxii. p. 189 ; Bull. Soc. chim., Paris, Ser. 5, tome xxiv. 



