I9I2] Charles Weisman 539 



If a moderate excess of iodine is used in the test, and protein is 

 present, a black precipitate of iodo-nitro products is usually formed 

 after the addition of ammonium hydroxide, upon which, after its 

 Sedimentation, yellow crystals are deposited. If just the proper 

 amount of iodine is present the liquid soon becomes yellowish and 

 any black precipitate that may have been formed upon the addition 

 of ammonium hydroxide is gradually trans formed more or less 

 completely into the yellow needles. In the presence of too great an 

 excess of iodine the reaction may be obscured or even prevented. 

 Insufficient iodine or too much protein may also prevent the reaction. 

 When excesses of both protein and iodine are present, a grayish- 

 green precipitate may form on adding ammonium hydroxide. 

 Under such conditions, if the proportions are favorable and the mix- 

 ture is stirred for a few moments, the precipitate is gradually trans- 

 formed into the yellow needles. 



In this extension of the work of Seaman and Gies, we determined 

 the behavior of the following substances in aqueous Solutions :^ 

 alanine, asparagine, aspartic acid, neutral arginine nitrate, glycocoll, 

 glycyl-tryptophan, guanidine carbonate, hippuric acid, histidine 

 dichloride, leucine, meta-phenylene diamine, toluene diamine hydro- 

 chloride, i, 2, 4. Needles were formed with arginine nitrate, glycyl- 

 tryptophan, and meta-phenylene diamine. Leucine yielded needles 

 together with rosettes, the latter form predominating, while toluene 

 diamine hydrochloride, i, 2, 4, gave hairs, mainly in tufts. 



Mixed products of protein hydrolysis were also studied. Tendo- 

 collagen, elastin, commercial dry egg-albumen and ovo-mucoid were 

 hydrolyzed with strong hydrochloric acid until the liquids no longer 

 gave a biuret reaction. On then applying the Bardach test to the 

 Solutions of mixed hydrolytic products, negative results were ob- 

 tained in each case except for ovo-mucoid. Characteristic needles 

 appeared in the tests on the hydrolytic products of the latter sub- 

 stance. It is possible that arginin and leucin in the other Solutions 

 failed to yield needles either because of interference by associated 

 products or insufficient concentration. 



From the fact, as shown by the foregoing results, that simple 

 amino substances yield a positive Bardach reaction, it is evident that 

 this test, like a number of other " protein " tests, is not a specific one. 



* These products were free from biuret-reacting material. 



