EXAMINATION OF NORMAL AND ABNORMAL URINE. 463 



Determination of total solids. An approximate determination 

 of total solids may be deduced 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 2.33, correspond to the number of grammes in 

 1000 c.c. of urine. If, for instance, 1450 c.c. of urine, of a specific 

 gravity of 1.018, have been discharged in twenty-four hours, then 

 the quantity of total solids in 1000 c.c. will be 18 X 2.33, or 41.94 

 grammes ; and in 1450 c.c. 60.81 grammes. 



A more exact method of determining the total solids in urine is the evapora- 

 tion of about 10 c.c. in a weighed platinum dish over a water-bath (or, better^ 

 under the receiver of an air-pump over sulphuric acid), until it is found that 

 no more loss in weight ensues on continued exposure of the dish in the drying 

 apparatus. By now reweighing the dish, plus contents, and deducting from the 

 weight that of the empty dish, the weight of total solids is found. 



Determination of inorganic constituents. The platinum dish 

 containing the known quantity of total solids is exposed to the action 

 of a non-luminous flame, and the heat continued until all organic 

 matter has been destroyed and expelled. By reweighing now, and 

 deducting the weight of the platinum dish, plus ash, from the weight 

 of the dish, plus total solids, the quantity of total organic matter is 

 determined ; and by deducting weight of dish from weight of dish 

 plus ash, the total quantity of inorganic matter is found. 



Experiment 72. Determine total solids, water, total organic and inorganic 

 matters in a specimen of urine by following the directions given above. Use 

 10 or 20 c.c. of urine for the analysis. 



The analysis of the ash is effected by the methods given in con- 

 nection with the consideration of the various acid and basic constitu- 

 ents themselves. Chlorine is determined by precipitating the solution 

 of the ash in nitric acid with silver nitrate, sulphuric acid by barium 

 chloride, phosphoric acid by ammonium molybdate, calcium by ammo- 

 nium oxalate, potassium by platinic chloride, iron by potassium ferro- 

 cyanide, etc. 



For the determination of many of the inorganic constituents, it is 

 not necessary to destroy the organic matter as described above, but 

 this determination can be effected directly. Thus, chlorine may be 

 precipitated directly from urine (slightly acidulated with nitric acid) 

 by silver nitrate ; the precipitated silver chloride is collected upon a 

 small filter, well washed, dried, and weighed in a porcelain crucible, 

 after the filter (to which particles of silver chloride adhere) has been 



