A FURTHER STUDY OF THE BARDACH TEST 



FOR PROTEIN 



CHARLES WEISMAN 



'{Lahoratory of Biological Chemistry of Columbia University, at the College 

 of Physicians and Surgeons, New York) 



Bardach's protein test,^ shortly after its publicatlon, was sub- 

 jected to a general examination in this laboratory. It was found 

 that every protein, of many that were selected for trial, promptly 

 yielded the reaction,^ thus strengthening the general conclusfon 

 which Bardach drew from a few observations. 



Dr. Gies recently concluded that Bardach's test might be given 

 "by various simple cleavage products of proteins and that possibly 

 the responsiveness of proteins in the test is due to radicals that also 

 appear in amino acids, hexone bases, or related substances, At his 

 Suggestion I have made an inquiry into this matter, with the results 

 'described below. 



Bardach's test depends upon the fact that (in the presence of 

 protein) acetone and iodo-potassium iodid and alkali react to yield 

 canary yellow needles of an tmidentified nitro material, instead of 

 the usual hexagonal crystals of iodoform. The test may be con- 

 ducted as follows : To 5 c.c. of the Solution under examination (con- 

 centration of protein should not exceed 5 per cent.), add 2-3 drops 

 of 0.5 per cent. Solution of acetone, then sufficient Lugol Solution^ 

 to supply a moderate excess of iodine and to produce a reddish- 

 "brown color; and finally an excess of ammonium hydroxide (about 

 3 c.c. of concentrated Solution). The required amount of Lugol 

 Solution depends on the quantities of protein, sugar and other iodine- 

 reacting substances that may be present, and may vary from one 

 drop to several cubic centimeters. The precipitate forms within a 

 Short time, usually within an hour, and if it consists of canary 

 yellow needles, protein is indicated. The crystals tend to form 

 rosettes, bundles, or knobbed and branching variations. 



^ Bardach : Zeitschrift für physiologische Chemie, 1908, liv, p. 355. 



^ Seaman and Gies : Proceedings of the Society for Experimental Biology 

 and Medicine, 1908, v, p. 125. 



' Containing 4 grams of iodine and 6 grams of potassium iodid per 100 c.c. 

 of water. 



538 



