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 E. Colin. 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 ; H ls N 3 O s , 180; pyridine derivatives, 3*65; 
other substances, including eystin, 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 (probably from the oxidation of tyrosine), 2 
oxalic, fumarie, and saccharic acids are formed. 
Oxidation by manganese dioxide or potassium bichromate, with 
sulphuric acid, has yielded — (1) Fatty acids, from formic up to capiylic 
(C 8 H 10 O._,), and their aldehydes ; (2) nitrates of acetic, propionic, valeric, 
butyric, and hydrocyanic acids: (3) benzoic acid and benzoic aldehyde. 
Oxidation with chlorine water lias yielded, among other products, fumarie 
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 Br,O 2 ), bromoform (CHBr 3 ), monobrom- 
benzoic acid, mono- and dibromacetic acids, tribromamidobenzoic acid 
(C 6 HP>r. ; (XH)('OOH), asparaginic and malaminic acids, leucine and 
leucimide (C G H u XO). X T o tyrosine was obtained. 3 
4. Treatment by erf ion 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 liases, namely, pyridine (C 5 H-X 5 ), picoline (C H V N), lutidine 
(C 7 H y X), and collidine (C S H U X), 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 he transformed into those with closed rings. 
The following example is selected by Brodie 4 : — 
1 Ztschr.f. physiol. Chcm., Strassburg, 1896, Bd. xxii. S. 153. 
2 Baumann, Bcr.d. deutsch. chem. Gesellsch., Berlin, Bd. xii. S. 1453. 
3 Hlasiwetz and Habermaim, Ann. d. Cliem., Leipzig, 1871, Bd. elix. S. 304. Blennard, 
Compt. rend. Acad. d. sc, Paris, tome xe. p. 612 ; xcii. p. 4oS. This latter observer also 
obtained glueo-proteins. 
4 Loe. cit. 
