ELEMENTARY CHEMICAL PHYSIOLOGY 271 



forms a layer underneath the urine. Where the two meet, a sharp 

 white ring (of coagulated acid albumin) is formed. The test may 

 also be done by placing the nitric acid first in the test tube, and 

 covering this with the urine slowly delivered from a pipette. The 

 ring does not disappear on warming. A similar ring may be obtained 

 when proteoses are present, but in this case the ring clears up on 

 gently warming the test tube, and reappears on cooling. In warm- 

 ing, very great care must be taken that no mixing of the two layers 

 occurs. When mucin is present in excess a diffuse haze may be 

 produced in the portion of urine next the acid. Certain resin acids 

 which may appear in the urine after the administration of such drugs 

 as copaiba also give a haze by Heller's test. Also when the urine 

 is very concentrated, acid urates or urea nitrate crystals may develop 

 and simulate the reaction. In these cases, 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. 



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. 



There are numerous other tests, but their application is super- 

 fluous 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 proteose is gradually 

 precipitated in the filtrate as it cools. 



Quantitative Estimation of Albumin. For clinical purposes this 

 is done by means of Esbach's albuminometer (Fig. 193). The 

 determination is made by measuring the depth of the coagulum 

 produced by adding to the urine Esbach's reagent (a mixture of 

 10 gms. picric acid and 20 gms. citric acid in 1,000 c.c. distilled 

 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 1,008 dilute it with water till this density, or something 



