50 PKOTEIDS. 



by the fact that the final products of any given decomposition do 

 not at all necessarily represent the primary mode of breaking 

 down of the proteid molecule ; many of them may be the out- 

 come of some secondary decomposition of the first-formed pro- 

 ducts. It may hence suffice to give a short account of the more 

 generally important researches on the decompositions of proteids 

 and to refer the reader for details to some larger work. 1 



The products of the decomposition of proteids by acids (HC1) 

 have been elaborately studied by Hlasiwetz and Habermann. 2 

 These observers subjected proteids (casein) to the action of boil- 

 ing concentrated hydrochloric acid in presence of stannous chlo- 

 ride for three days. From the fluid thus obtained they were able 

 ~to separate out by repeated crystallisations leucin, tyrosin, glu- 

 tamic and aspartic acids and ammonia; the mother liquor from 

 the above yielded no further well-defined substances. Schutzen- 

 berger, 3 treating proteids in presence of a little water with an 

 excess of baryta in sealed tubes at 200 250, observed a more 

 profound breaking down of these substances as judged by the 

 products of their decomposition. In addition to the products 

 described by Hlasiwetz and Habermann he obtained small quan- 

 tities of carbonic, oxalic, and acetic acids, together with other 

 amido-acids homologous with leucin, amido-acids of other series, 

 leuceins, 4 gly co-protein, tyroleucin, 5 &c. The chief difference in 

 the results obtained by the two sets of observers turns upon the 

 non-occurrence of carbonic, oxalic, and acetic acids among the 

 products of the action of hydrochloric acid. Drechsel 6 has how- 

 ever shown that if the noii-crystallisable residue from Hlasiwetz 

 and Habermann's experiments be appropriately treated with 

 baryta in sealed tubes it readily yields carbonic acid, so that the 

 difference may turn out after all to be more apparent than real. 

 Interesting as are the above researches they do not as yet enable 

 us to form any clear idea of the probable molecular composition 

 of proteids. According to Schiitzenberger the relative amounts of 

 carbonic acid and ammonia which make their appearance are the 

 same as would have arisen from a similar treatment of urea with 

 caustic baryta, and from this and the fact of the preponderating 

 appearance of amido-acids by the action of the alkaline oxide, 



1 Ladenburg's Handirorterbuch d. Chem. Bd. in. S. 541. Beilstein's Hdbch. d. 

 Chem. Bd. HI. S. 1258. 



2 Anzeig. d. Wie.n. Akad. 1872, S. 114; 1873, Nr. 15. Ann. d. Chem. u. Pharm. 

 Bd. 159 (1871), S. 304, Bd. 169 (1873), S. 150. Jn. f. prakt. Chem. (2) Bd. VH. 

 S. 397. See also E. Schulze, Zt.f. phi/swl. Chem. Bd.'ix. (1885), Sn. 63, 253. 



3 Ann. de Chim. et. de Ph>/s. (5 Scr.) T. xvi. (1879), p. 289. Bull, de la Soc. Chim. 

 xxin. 161, 193, 216, 242, 385, 433; xxiv. 2, 145 ; xxv. 147. Also in Chem. Centralb. 

 1875, Sn. 614, 631, 648, 681, 696; 1876, S. 280; 1877, S. 181. Compt. Rend. T. 101, 

 (1886), p. 1267. See also Nasse, Pfliiger's Arch. Bde. vi. (1872), 589; vn. 139; 

 viii. 381. 



4 Compt. Rend. T. 84 (1877), p. 124. 



5 Ibid. T. 106 (1888), S. 1407. 



6 Jn.f prakt. Chem. (N. F.) Bd. xxxix. (1889), S. 425. 



