382 PHYSIOLOGICAL CHEMISTRY. 



transferred to the urine of persons using these drugs internally. 

 A sweetish smell sometimes attends the presence of large quan- 

 tities of sugar in urine. 



Reaction. This is generally acid in healthy urine which has 

 been recently passed, but may become neutral or alkaline within 

 a short period, by decomposition of urea and formation of am- 

 monium carbonate. 



Specific gravity. The normal specific gravity of an average 

 amount of 1500 c.c. of urine passed in twenty-four hours is 

 about 1020, but it varies, even in health, from 1012 to 1025 or 

 more. A specific gravity above 1028 generally indicates the 

 presence of sugar, larger quantities of which may cause the 

 specific gravity to rise to 1050, 



The determination of the specific gravity of urine is generally 

 accomplished by the urinometer, which is a small hydrometer 

 indicating specific gravities from zero (or 1000) to 60 (or 1060). 

 As the temperature influences the density of liquids, a urinometer 

 can only give correct results at a certain degree of temperature, 

 which is generally marked upon the instrument. Many of the 

 urinometers manufactured and sold, even at the normal (or 

 stated) temperature, show incorrect gravities, and for this reason 

 a urinometer should always be thoroughly tested before placing 

 full confidence in the results obtained by it. 



Determination of total solids. An approximate determination 

 of total solids may be deducted from the specific gravity of the 

 urine, as it has been found that the last two figures of the 

 specific gravity of urine, multiplied by 2.2, correspond to the 

 number of grams in 1000 c.c. of urine. If, for instance, 1750 

 c.c. of urine, of a specific gravity of 1018. have been discharged 

 in twenty-four hours, then the quantity of total solids in 1000 1 

 c.c. will be 18 X 2.2, or 39.6 grams; and in 1750 c.c., 69.3 

 grams. 



. A more exact method of determining the total solids in urine 

 is the evaporation of about 50 c.c. in a weighed platinum dish 

 over a water-bath (or, better, under the receiver of an air-pump 



