166 INFLUENCE OF FOOD PBESEBVATIVES ON HEALTH. 

 TABLE XXVII. General summary of reaction of urine in Series II, III, IV, and V. 



VOLUME, SPECIFIC GRAVITY, AND TOTAL SOLIDS. 



In Tables XXX-XL are given the volume of urine, the specific 

 gravity, and the grams of total solids for each day, for each individual 

 belonging to the table, with totals and averages for each period of the 

 series. Averages of these data by periods are also given, including 

 those men who completed the series. A glance at the individual data 

 shows a very limited variation from normal conditons in respect of 

 specific gravity and solids eliminated. 



The specific gravity of all the samples of urine was taken at 25 0., 

 compared with water at 25 C. , as this is about the average laboratory 

 temperature for the year. At first the determinations were made with 

 the static balance and corrected to 25 C., but later the Westphal bal- 

 ance was found more convenient, the results agreeing, within one or two 

 units in the third place, with those secured by means of a piknometer. 



The factor of Neubauer, a 0.233, which is designed for specific gravity 

 at 15 referred to water at 0, and that of Long, 0.260, & for specific 

 gravity at 25 referred to water at 4, would therefore not answer for 

 calculation of the solids from the specific gravity of urine at 25 com- 

 pared with water at 25, as determined above. 



The method of determining the factor was based on the same prin- 

 ciple as that of Neubauer and Long, which consists of evaporating a 

 measured quantity of urine, the specific gravity being obtained exactly 

 by means of a piknometer, in a closed tube. The products are aspi- 

 rated through decinormal sulphuric acid, the excess of acid titrated with 

 approximately twentieth normal sodium hydroxid (cochineal being 

 used as indicator), the ammonia so obtained calculated to urea, and 

 this amount added to the solids obtained by direct weighing. The 

 factor is obtained by dividing the total solids by the last three figures 

 of the specific gravity. 



The error in this method, due to the amount of ammonia from the 

 ammonium salts present, is about offset by the ammonia obtained from 

 the breaking down of organic compounds, so that the results, while not 

 strictly correct, are about as close as can be obtained. 



aZeit. anal. Chem. 1: 166. 



&,T. Chem. Soc. 25: 257. 



