80 THE PROTEINS OF THE WHEAT KERNEL. 



CYSTINE. 



300 grams of gliadin were digested for 2 to 3 hours at 85 with 900 cc. of 

 hydrochloric acid, sp. gr. 1.19, and the solution boiled for 3 hours. This 

 was then concentrated to a sirup under diminished pressure, diluted to 900 

 cc. with cold water, and neutralized with 50 per cent sodium-hydroxide solu- 

 tion. After boiling with a large amount of bone-black and concentrating to 

 800 cc, much substance separated, which was recr y stall ized from about 300 

 cc. of water. The recrystallized product was dissolved in 5 per cent sul- 

 phuric acid and precipitated by mercuric sulphate solution. 1 



The mercury precipitate was decomposed by hydrogen sulphide, the solu- 

 tion freed from hydrogen sulphide, neutralized with sodium hydroxide, and 

 acidified with acetic acid. On standing, cystine separated from the solution 

 in hexagonal plates, and by adding alcohol to the filtrate more was obtained. 

 When no more cystine could be thus obtained, the precipitation with mercu- 

 ric sulphate was repeated. By several repetitions of this process 1. 18 grams 

 of cystine were finally isolated, which, when recrystallized by dissolving in 

 dilute ammonia and acidifying with acetic acid, gave the following analysis : 



Carbon and hydrogen : 0.3063 gram substance, dried at no , gave 0.3379 gram C0. 2 and 



0.1444 gram H 2 0. 

 Calculated for C 6 Hi 2 4 N 2 S 2 , C 29.96, H 5.04 p. ct. ; found, C 30.08, H5.23 p. ct. 



TYROSINE. 



219 grams of gliadin, equal to 200 grams dried at no, were treated with 

 600 cc. of concentrated hydrochloric acid, digested for some time on a water- 

 bath, and the solution boiled for 12 hours on an oil-bath. The solution was 

 freed from most of the glutaminic acid by saturating with hydrochloric acid, 

 and the filtrate from the glutaminic acid was diluted, boiled with bone-black, 

 and then concentrated strongly to remove as much hydrochloric acid as 

 possible. The rest of the acid was neutralized with 50 per cent sodium- 

 hydroxide solution. On standing, a considerable precipitate separated, 

 which was filtered out and dissolved in ammonia. The resulting solution 

 was boiled until most of the ammonia had been removed and the tyrosine 

 that separated was filtered out. When dried, this weighed 2.4 grams, equal 

 to 1.2 per cent of the gliadin. Recrystallized from boiling water, this gave 

 the following results on analysis : 



Carbon and hydrogen: 0.3661 gram substance, dried at no,gave 0.7981 gram C0 2 and 



0.2160 gram H 2 0. 

 Calculated for C 9 H n 3 N, C 59.62, H 6.13 p. ct. ; found, C 59-45. H 6.56 p. ct. 



Tyrosine separated from our hydrolysis solutions of gliadin with very 

 great difficulty. Two other attempts to determine its proportion, which 

 were made by hydrolyzing with sulphuric acid, gave lower results, and the 



1 Cf. Hopkins & Cole, Journal of Physiology, 1901, xxvn, p. 418. 



