34 CHEMICAL CONSTITUENTS OF BOD Y AND FOOD. 



to be a constant decomposition product of proteids and albuminoids. It 

 yields urea on treatment of its silver salt with barium hydrate. 



Other recently published work on the decomposition of proteids by 

 hydrochloric acid is by K. Cohn. 1 He used concentrated acid, and no 

 stannous chloride. From 1000 parts of casein he recovered 916'75 of 

 products ; these consisted of fatty acids, 34*25 tyrosine, 35 ; leucine, 321 ; an 

 oily product containing an acid, C 7 H 18 N 3 8 , 180; pyridine derivatives, 3'65 ; 

 other substances, including cystin, cystein, thiolactic acid, and Drechsel's bases, 

 the remainder. 



3. Treatment with oxidising agents. Treatment of proteids with 

 nitric acid yields, first, an insoluble yellow substance of uncertain 

 composition, called xanthoproteic acid ; this dissolves gradually, and 

 finally paraoxybenzoic acid (probabiy from the oxidation of tyrosine), 2 

 oxalic, fumaric, and saccharic acids are formed. 



Oxidation by manganese dioxide or potassium bichromate, with 

 sulphuric acid, has yielded (1) Fatty acids, from formic up to caprylic 

 (C 8 H 1C 2 ), and their aldehydes ; (2) nitrates of acetic, propionic, valeric, 

 butyric, and hydrocyanic acids ; (3) benzoic acid and benzoic aldehyde. 

 Oxidation with chlorine water has yielded, among other products, fumaric 

 acid, oxalic acid, and chlorazol. Oxidation with bromine water at high 

 temperatures in a sealed tube has yielded carbonic anhydride, oxalic 

 acid, ammonia, bromanil (C 6 Br 4 2 ), bromoform (CHBr 3 ), monobrom- 

 benzoic acid, mono- and dibromacetic acids, tribromamidobenzoic acid 

 (C G HBr 3 (NH)COOH), asparaginic and malaminic acids, leucine and 

 leucimide (C c H n NO). No tyrosine was obtained. 3 



4. Treatment % action of heat. Dry distillation leads to the forma- 

 tion of a complex oily material, called "Dippel's oil," which contains 

 a large number of substances; among these are hydrocarbons of the 

 fatty series, ammonium salts of fatty acids, nitrates and ketones of the 

 same series, carbonic anhydride, ammonia, amines of fatty acid radicles, 

 hydrocarbons and amines of the benzene series, aniline and its 

 homologues, phenol and its homologues, members of the pyridine 

 group of bases, namely, pyridine (C 6 H f) N 5 ), picoline (C C H 7 N), lutidine 

 (C 7 H 9 N), and collidine (C 8 H U N), and lastly, pyrrol. 



Some of the substances last mentioned will also be found in our list of the 

 animal alkaloids (p. 59) ; here we have direct proof that proteid substances 

 have within them, or are capable of forming by intramolecular rearrangement, 

 basic bodies of this nature. The pyridine bases have, moreover, been shown 

 to take a part in the formation of the vegetable alkaloids, piperidine, 

 cinchonine, etc. 



It is extremely probable that proteids contain within their molecule 

 a radicle of the closed ring series, but even if they do not, there still 

 remains the possibility that by the action of heat, substances with 

 open carbon chains may be transformed into those with closed rings. 

 The following example is selected by Brodie 4 : 



1 Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxii. S. 153. 



2 Baumann, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xii. S. 1453. 



3 Hlasiwetz and Habermann, Ann. d. Chem., Leipzig, 1871, Bd. clix. S. 304. Blennard, 

 Compt. rend. Acad. d. sc., Paris, tome xc. p. 612; xcii. p. 458. This latter observer also 

 obtained glnco-proteins. 



4 Loc. cit. 



