Examination of Bardach's new Protein Test. 125 



79 (335) 



An examination of Bardach's new protein test. 



By EMILY 0. SEAMAN and WILLIAM J. GlES. 



\From the Laboratory of Biological Chemistry of Columbia Univer- 

 sity, at the College of Physicians and Surgcons.~\ 



In a recent paper, Bardach 1 drew attention to the fact that the 

 formation of typical iodoform crystals from iodopotassium iodide 

 and acetone in an alkaline solution may be prevented by albumin. 

 In the presence of a sufficient proportion of albumin in such solu- 

 tions, the production of characteristic hexagonal platelets or stellar 

 masses of iodoform does not occur, but, instead, fine yelloza needles, 

 apparently of some other substance, gradually appear. Bardach 

 found that the power of bringing about this interesting crystalline 

 reaction is also exhibited in a general way by acidalbumin, protoal- 

 bumoses, peptones, phytovitellin, casein, yeast nuclein, hemoglo- 

 bin, tendomucoid, gelatin, and by the following protein-containing 

 materials : pancreatin, sperm, blood, sputum, normal urine and 

 albuminous urine. He did not name any proteins that fail to give 

 the reaction. 



The best conditions and procedure for the test are stated by 

 Bardach to be as follows : To 5 c.c. of the moderately concen- 

 trated albuminous liquid, 2 add at first 2 or 3 drops of a dilute 

 aqueous acetone solution (0.5 per cent.), then sufficient Lugol re- 

 agent 3 to supply a moderate excess of iodine, 4 and lastly consid- 

 erable ammonium hydroxid (usually about 3 c.c. of concentrated 

 solution). 



If iodine is employed in moderate excess, the ammonium hy- 

 droxid usually produces at once a black precipitate of iodonitro- 

 compounds, upon which the yellow needles are gradually deposited. 

 If just the right amount of iodine is present, the liquid soon be- 

 comes yellowish and the black precipitate formed at once by the 



1 Bardach : Zeitschrift fitr physiologische C/iemie, I908, liv, p. 355. 



2 The proportion of protein should not exceed 5 per cent. 



3 Iodine (4 grams) and potassium iodide (6 grains) in water (100 c.c). 



4 Sufficient to impart a permanent reddish brown color to the shaken solution. 

 The required amount of Lugol reagent varies from I drop to several c.c. according to 

 the proportion of protein, sugar or other iodine-reacting materials present. 



