URINE 281 



ratus it is necessary to correct for temperature. The accuracy of 

 an areometer may be checked by trying it out on distilled water, 

 not forgetting the correction for temperature. 



d. Chemical Reaction. Test the chemical reaction of the urine 

 with litmus paper. A 24 hour sample is usually acid, due to the 

 presence of acid phosphates and both inorganic and organic 

 acids. If the urine is alkaline, allow the litmus paper to dry on 

 the water bath. If the blue color disappears, the alkaline reac- 

 tion is due to ammonia. If it persists, to fixed alkalies. 



e. For purposes of diagnosis of kidney disorders, it is some- 

 times advisable to determine both the freezing point and the 

 electrical conductivity of the urine. The technique of these proc- 

 esses, is, however, beyond the scope of this course. 



3. Quantitative Analysis (Make all Determinations in 

 Duplicate) 



1. Total Solids. In order to make an accurate determination 

 of total solids, it is necessary to evaporate a measured quantity 

 of urine in a vacuum at room temperature, as the temperature of 

 the boiling water bath causes decomposition of urea and loss of 

 ammonia and C0 2 . By acidifying slightly with acetic acid it is 

 possible partially to avoid this source of error. The residue is 

 weighed quantitatively, and the total solids calculated from the 

 result. 



An approximate but usually adequate estimation of total solids 

 per liter may be calculated by using Long's coefficent, 2.6. Multi- 

 plying the last two figures (second and third decimal) of the 

 specific gravity at 25 C. by 2.6 gives a rough idea of the amount 

 of total solids per liter. 



2. Acidity. For the determination of the acidity of the 

 urine, and for various others of the methods in this section, acid 

 or alkali of standard strength is required. The strength most 

 frequently used is tenth normal (N/10). A normal solution of 

 an acid is of such strength that one liter of the acid will contain 

 one gram equivalent of ionizable hydrogen (1.008 g.). A liter 

 of normal hydrochloric acid thus will contain a weight of hydro- 



