368 Prof. J. A. Mac William. [Mar. 1J, 



II. " A New Test for Albumin and other Proteids." By JOHN 

 A. MAC WILLIAM, M.D., Professor of the Institutes of 

 Medicine in the University of Aberdeen. Communicated by 

 Sir WM. ROBERTS, F.R.S. Received March 5, 1801. 



Salicyl-sulphonic acid is a remarkably powerful precipitant of pro- 

 teid substances ; it is an extremely delicate reagent for the detection 

 of proteids' in solution ; it acts upon all the classes of proteid bodies. 



I shall state the results I have obtained with this reagent under 

 two heads : 



I. Its action on the various classes of proteids. 

 II. Its use as a test for the presence of proteids in urine. 



I. The Action of Salicyl-sulphonic Acid on the various Classes of 



Proteids. 



In order to obtain the full effect of this reagent, it should be 

 in saturated watery solution, and a drop or two of this solution sho 

 bo added to a small amount (e.g., 1 or 2 c.c.) of the fluid to betes 

 and the test-tube should be shaken so as to mix its contents well. 

 When any considerable amount of proteid is present, a copious white 

 precipitate at once results ; with only minute amounts of proteid a 

 cloudiness or opalescence of the fluid is what occurs. This cloudi-i 

 ness or opalescence is uniformly diffused over the fluid. Wlfli 

 dealing with traces of proteids it is well to use a control tube con- 

 taining some of the fluid to be tested, and if dilution has been per- 

 formed, another control tube with some of the water (or other liquid) 

 used for dilution along with one or two drops of the salicyl-sulphonic 

 acid. The observer then holds the three tubes between him and the 

 light, and looks through them at a dark ground. It is only, however, 

 when dealing with very slight traces of proteids that these precautions 

 are at all necessary. 



A. Native Albumins. 



(a.) Egg Albumin. Upon this proteid salicyl-sulphonic acid acts 

 with much precision. When a solution is obtained by diluting wliiu 

 of egg with water in the proportion of 1 part white of egg in 20 part 

 of the mixture, the addition of the reagent causes a dense white pre 

 cipitate to be at once formed. On boiling, the precipitate become* 

 markedly flocculent. (The solution of white of egg of course contain* 

 globulin, but when this is removed by saturation with magnesiuc 

 sulphate the albuminous filtrate gives the same reaction with salicyl 

 sulphonic acid as the original fluid.) 



