PROTEIDS. 747 



ordinary cases HELLER'S test is sufficiently delicate. If no reaction is 

 obtained with this test within 2^ to 3 minutes, the urine tested contains 

 less than 0.003 per cent of proteid, and is to be considered free from pro- 

 teid in the ordinary sense. 



The use of precipitating reagents presumes that the urine to be investi- 

 gated is perfectly clear, especially in the presence of only very little 

 proteid. The urine must first be filtered. This is not easily done with 

 urine containing bacteria, but a clear urine may be obtained, as suggested 

 by A. JOLLES, by shaking the urine with infusorial earth. Although 

 a little proteid is retained in this procedure and lost, it does not seem to 

 be of any importance (GRUTZNER, SCHWEISSINGER *). 



The different color reactions cannot be directly used, especially in deep-colored 

 urines which contain only .little proteid. The common salt of the urine has a 

 disturbing action on MILLON'S reagent. To prove more positively the presence 

 of proteid, the precipitate obtained in the boiling test may be filtered, washed, 

 and then tested with MILLON'S reagent. The precipitate may also be dissolved in 

 dilute alkali and the biuret test applied to the solution. The presence of proteoses 

 or peptones in the urine is directly tested for by this last-mentioned test. 



In testing the urine for proteid one should never be satisfied with one 

 reaction alone, but must apply the heat test and HELLER'S or the potas- 

 sium-ferrocyanide test. In using the heat test alone the proteoses may 

 be easily overlooked, but these are detected, on the contrary, by HELLER'S 

 or the potassium-ferrocyanide test. If only one of these tests is employed, 

 no sufficient intimation of the kind of proteid present can be obtained, 

 whether it consists of proteoses or coagulable proteid. 



For practical purposes several dry reagents for proteid have been recommended. 

 Besides the metaphosphoric acid may be mentioned STUTZ'S or FURBRINGER'S 

 gelatin capsules, which contain mercuric chloride, sodium chloride, and citric 

 acid; and GEISSLER'S albumin-test papers, which consist of strips of filter-paper 

 some of which have been dipped in a solution of citric acid, and some into a 

 .solution of mercuric-chloride and potassium-iodide solution, and then dried. 



If the presence of proteid has been positively proven in the urine by 

 the above tests, it then remains necessary to determine its character. 



The Detection of Globulin and Albumin. In detecting serglobulin 

 the urine is exactly neutralized, filtered, and treated with magnesium 

 sulphate in substance until it is completely saturated at the ordinary 

 temperature, or with an equal volume of a saturated neutral solution of 

 ammonium sulphate. In both cases a white, flocculent precipitate is 

 formed in the presence of globulin. In using ammonium sulphate with 

 a urine rich in urates a precipitate consisting of ammonium urate may 

 separate. This precipitate does riot appear immediately, but only after 

 a certain time, and it must not be mistaken for the globulin precipitate. 

 In detecting seralbumiii heat the filtrate from the globulin precipitate 

 to boiling-point, or add about 1 per cent acetic acid to it at the ordinary 

 temperature. 



1 Jolles, Zeitschr. f. anal. Chem., 29; Gnitzner, Chem. Centralbl., 1901, 1; Schweis- 

 singer, ibid. 



