374 Prof. J. A. MacWilliam. [Mar. 



In the case of albuminous urine, on the other hand, it constitutes 

 an extremely delicate and precise test for the presence of pr 

 Hy its use, coupled with heat, one can, with great facility, recognise 

 very minute amounts of proteid substance, and can discriminat 

 between the so-called "albumin" (albumin and globulin), most com 

 monly found, and the albumoses or peptones, if such are preseni 

 This is easy, since the application of heat in the latter case causes th 

 precipitate to disappear to reappear on cooling ; while, in the case 

 ordinary albuminous urine, the precipitate does not clear up on heatinjj 



The method of performing the test in the case of urine is the same 

 as with other solutions. 



A very small amount of urine should be taken in the bottom of 

 ordinary test-tube (e.g., half an inch, or so), or a very small, narrow 

 test-tube may be used. The acid must be in a thoroughly saturate 

 aqueous solution. A drop of this solution is then added to the urine 

 and the tube is shaken. When any considerable amount of proteid is 

 present, a copious precipitation immediately occurs ; when there 

 only a minute proportion of proteid, the fluid becomes unifo: 

 opalescent. 



The delicacy of the test if. shown by the following results, ob 

 with one of the samples of albuminous urine examined : 



The urine was diluted to 10, 20, 30, 40, 50 times. AVith 



weakest of these fluids (1 in 50), salicyl-sulphonic acid quie 



gave a marked opalescence. 

 Heller's test gave no reaction for a considerable length of time 



then it gave a doubtful haziness at the junction of the nitric aci 



and the urine. 



Picric acid (saturated watery solution) = no reaction. 

 Cupric sulphate and potassic hydrate = 



The urine was then diluted twice as much, to 100 times, and still 

 gave, after standing a little, a distinct cloudiness with salicyl-snlph- 

 onic acid, specially noticeable when the tube was compared (in a 

 suitable light) with two control tubes, containing respectively (a) 

 some of the dilute urine, and (b) water with a drop or two of salicyl- 

 sulphonic acid. 



Even with much greater degrees of dilution, appreciable r< 

 were got by means of this test. Without going to the extreme limits 

 of its application, however, I find that in the case of the urine diluted 

 100 times, the amount of albumin contained must have been exceed- 

 ingly small. A quantitative determination showed that the amount 

 of urine present in the undiluted urinW was about O'l per cent. 

 Hence the amount present in the urine diluted 100 times must have 

 been about 1 in 100,000. 



The opalescence caused by the addition of salicyl-sulphonic acid to 



