PHYSIOLOGICAL CHEMISTRY 



445 



the urine should be diluted with two or three times its bulk of water, 

 and the test reapplied, when very little doubt will remain as to the 

 reaction. 



3. Salicyl-Sulphonic Acid Test. This is perhaps the most delicate 

 of all the tests. 



EXPERIMENT III. Add to about 10 c.c. of urine a drop or two of a 

 saturated solution of pure salicyl-sulphonic acid. A white precipitate 

 results, which on boiling changes into a number of coagula. 



This reaction occurs in a dilution of 1-230,000 albumin. The only 

 other body with which this reagent produces a precipitate is proteose, 

 in which case, however, the precipitate disappears on warming. 



The reagent, if pure, keeps indefinitely. If impure, however, it turns 

 red on keeping. It has the great advantage over nitric acid in being 

 non-corrosive, and therefore easily carried about (MacWilliam). 



There are numerous other tests, but their application is superfluous 

 if the above be properly applied. 



Proteoses are detected by the precipitates produced by nitric and 

 salicyl-sulphonic acids clearing up on heating the urine, and returning 



when it is cooled. The so-called " proteose " in Bence 



Jones' proteosuria is coagulated by moderate heat, 

 but redissolves on boiling the urine. Proteose can 

 best be separated from albumin by adding salicyl- 

 sulphonic acid, boiling and filtering. The coagulated 

 albumin remains on the filter paper, and the pro- 

 teose is gradually precipitated in the filtrate as it 

 cools. 



Quantitative Estimation of Albumin. For clinical 

 purposes this is done by means of Esbach's albumino- 

 meter (Fig. 255). The determination is made by mea- 

 suring the depth of the coagulum produced by adding 

 to the urine Esbach's reagent (a mixture of 10 grms. 

 picric acid and 20 grms. citric acid in 1000 c.c. dis- 

 tilled water). 



EXPERIMENT IV. Place clear urine, filtered if 

 necessary, in an Esbach's tube up to the mark U. 

 If the reaction be alkaline, render slightly acid by 

 the addition of acetic acid ; and if the specific gravity 

 be above 1008 dilute it with water till this density, or something below 

 it, is obtained. 1 Now add the reagent up to the mark R. Close the 

 tube with a tightly-fitting cork and invert several times, so as to mix 



1 These corrections should be made before the urine is measured into the 

 Esbach's tube. 



5 



FIG. 255. Esbach's 

 albuminometer. 



