160 THE PROTEIN SUBSTANCES. 



ABDERHALDEN found 10.96 per cent. It also occurs in germinating plants 



(E. SCHULZE ! ). 



Histidine has been prepared synthetically by PvMAN. 2 4 (5) chlormethyl 

 glyoxalin yields with sodium chlormalonic ester the glyoxalinmethylchlormalonic 

 ester. 



CH.NHv 



|| ^CH , which on 



C N' 



CH 2 .CC1(C0 2 .C 2 H 5 ) 2 



hydrolysis gives cW-a-chlor-/3-glyoxalin-4 (5) propionic acid, 



CH NHv 



JOS 



C N 



CH 2 CHC1.COOH 



This latter treated with NH 3 yields d-Miistidine, which is changed into the active 

 forms by means of tartaric acid. 



In the anaerobic putrefaction of histidine, /3-imidazolylethylamine 

 and imidazolylpropionic acid are formed (ACKERMANN 3 ). 



Histidine crystallizes in colorless needles and plates and is readily 

 soluble in water, but less soluble in alcohol, and has an alkaline reaction. 

 It is precipitated by phosphotungstic acid, but this precipitate is soluble 

 in an excess of the precipitant (FRANKEL). With silver nitrate alone 

 the aqueous solution is not precipitated; on the careful addition of 

 ammonia or baryta-water an amorphous precipitate, which is readily 

 soluble in an excess of ammonia, is obtained. Histidine can be pre- 

 cipitated by mercuric chloride, or, still better, by the sulphate acidified 

 with sulphuric acid, and can in this way be separated from the other 

 diamino-acids (KossEL and PATTEN). The hydrochloride crystallizes in 

 beautiful plates (BAUER), dissolves rather readily in water, but is insolu- 

 ble in alcohol and ether. With hydrochloric acid and methyl alcohol 

 it gives the dihydrochloride of histidine methyl ester, which melts at 

 196. Histidine is laevorotatory, (a) D = 39.74, while its solution in 

 hydrochloric acid is dextrorotatory. On warming it gives the biuret test 

 (HERZOG), and it also gives WEIDEL'S reaction if performed as sug- 

 gested by FISCHER (see Xanthine, Chapter V) (FRANKEL 4 ). On adding 



1 Kossel, Zeitschr. f. physiol. Chem., 22; Hedin, ibid., Kutscher, ibid., 25; Wetzel, 

 ibid., 26; Lawrow, ibid., 28, and Ber. d. d. chem. Gesellsch., 34; Kossel and Kutscher, 

 Zeitschr. f. physiol. Chem., 31; Hart, ibid., 33; Abderhalden, ibid., 37; Schulze, ibid., 

 24 and 28. 



2 Cited from Chem. Centralbl., 1911, 2, p. 760. 



3 Zeitschr. f. physiol. Chem., 65. 



4 Kossel and Patten, Zeitschr. f. physiol. Chem., 38; Bauer, ibid., 22; Herzog, ibid., 

 37; Frankel, Sitz.-Ber. d. Wien. Akad., 112, II. B., 1903, and Hofmeister's Beitrage, 8. 



