1880.] 



On the Urine in Disease. 



439 



nitrogen might not be excreted in some other form. With the view 

 of determining this point, the following experiments were undertaken. 



The cases npon which the observations were made fall into two 

 groups — the first, a series taken at random from the hospital, the 

 patients suffering from various diseases, and being under various con- 

 ditions as regarded diet, muscular exertion, &c. In the second series, 

 the patients were healthy, and placed under conditions as far as 

 possible constant, the amount of diet being fixed, and the patients at 

 absolute rest. 



The quantitative estimations were made in the following way. The 

 nitrogen in the urea was determined by the process which we have 

 previously described,* in which the urea is decomposed by sodic hypo- 

 bromite, and the volume of nitrogen evolved is measured. At first, 

 the total nitrogen was determined by the soda-lime process, but find- 

 ing that in some cases this method was untrustworthy, we abandoned 

 it, and in all the following experiments the total nitrogen was esti- 

 mated by burning the residue with oxide of copper, and measuring 

 over water the volume of nitrogen obtained. This volume was of 

 course afterwards corrected for temperature and pressure. 



In most cases, 5 cub. centims. of the urine was used. This was 

 very slightly acidulated by adding a small crystal of pure oxalic acid, 

 and evaporated as rapidly as possible in a small basin on a water-bath, 

 nearly to dryness. The residue was thoroughly incorporated with 

 oxide of copper, introduced into a combustion tube, and the basin 

 thoroughly cleaned with fresh portions of oxide. 



In order to ascertain whether any loss of ammonia occurred during 

 the evaporation, control experiments were made by adding, without 

 previous evaporation, a second sample of 5 cub. centims. of the urine 

 to oxide of copper already in a combustion tube, and proceeding 

 with the combustion slowly, but in the ordinary way. The same 

 amount of nitrogen was obtained by both processes. 



Although the determination of the nitrogen was the special object of 

 our research, we thought it well in each case to complete the analysis 

 by determining the amount of solid matter in solution, and from it 

 approximately the amount of organic and inorganic matter, as well as 

 the amount of chlorine, and the specific gravity. 



To determine the solid matter in solution, 5 cub. centims. of the 

 filtered urine was evaporated to dryness in a small light platinum dish, 

 and heated to 110 — 120°, till the weight remained constant. The 

 residue varied very much in appearance, sometimes it was hard and 

 granular, at others remaining in a sticky condition. 



The residue was heated to dull redness over a lamp, and what 

 remained we have called inorganic residue. It was found in some 

 cases impossible to completely burn away all carbonaceous matter 

 * " Journal of Chemical Society," 1874. 



2 i 2 



