THE CLEAVAGE OF PROTEINS WITH ALKALI 105 



proteins and their simpler non-protein disruption products, 

 and, so long as a disrupted protein continues to give the 

 biuret test it must still be classed among the proteins. It 

 will certainly be understood that the pure poison may 

 not be a protein, but until it is purified sufficiently to fail 

 to give the biuret test it must be regarded as a protein. 



The poison responds nicely to the Adamkiewicz or gly- 

 oxylic acid test. Hopkins and Cole have shown quite 

 convincingly that this color test depends upon the presence 

 of tryptophan or indol-amino-propionic acid; therefore, while 

 we have made no direct search for tryptophan in our poison, 

 we assume its presence on account of the unequivocal 

 response to this test. 



When the poison is boiled with concentrated hydrochloric 

 acid to which a drop of concentrated sulphuric acid has 

 been added, the powder passes into solution and a violet 

 color results, thus giving Liebermann's test. At one time 

 Hofmeister believed this to be a carbohydrate reaction in 

 which furfurol and the aromatic oxyphenyl radicals take 

 part, but Cole has shown that this, like the Adamkiewicz 

 test, also once regarded as a carbohydrate test, is due to 

 the tryptophan group. We are quite convinced that our 

 soluble poison contains no carbohydrate, and we regard 

 the fact that it does respond to the Liebermann test as a 

 strong confirmation of the error of Hofmeister's explanation 

 of this test, and in favor of the explanation given by Cole. 



When heated with strong nitric acid the powdered poison 

 goes into solution, more or less yellow according to the 

 amount used, and this becomes orange on the addition of 

 ammonia, thus giving the xanthroproteic test and indicating 

 the existence of aromatic radicals. 



The ordinary test for sulphur in proteins, that of heating 

 with excess of sodium hydrate in the presence of a small 

 amount of acetate of lead, is not given by the portion of 

 the protein split off "by alkali in absolute alcohol. If, 

 however, a portion of the substance in a test-tube is fused 

 with metallic sodium and the cooled mass treated with 

 water, a few drops of a freshly prepared solution of sodium 



