of the University of Pennsylvania. 31 



A PRELIMINARY NOTE ON A REACTION COM- 

 MON TO PEPTONE AND BILE-SALTS. 



IF the acid nitrate of mercury (Millon's reagent) 

 be added to a cold aqueous solution of potassium 

 iodide, a red precipitate of mercuric iodide always 

 appears. When, however, either peptone or biliary 

 salts are present in noteworthy amount, the precipi- 

 tate of nascent mercuric iodide assumes the yellow 

 phase. As practically applied, the red may vary 

 from salmon to scarlet, the yellow from pale lemon 

 to orange. 



In order to render the test sensitive to the 

 presence of minute quantities of the substances 

 in question, it is necessary to limit the amount 

 of potassium iodide employed. Thus to each five 

 cubic centimetres of the suspected fluid which 

 must be cold and either neutral or faintly acid are 

 added two drops of a saturated solution of potas- 

 sium iodide, the two liquids being well mixed. 



