URINE. 87 



Free mineral acids are never present. By a proper relationship 

 between the dihydrogen and monohydrogen phosphates, a 

 neutral or amphoteric reaction may prevail (litmus). Under 

 normal conditions the 24-hour urine is never alkaline; but 

 portions of urine drawn a few hours after digestion may 

 react alkaline, due to the withdrawal of acidic radicals 

 (acid ions) from the blood in the formation of the acid gastric 

 juice. Alkaline urine may be caused by free or fixed alkalies 

 and when this is the case the urine is always cloudy or turbid. 

 Care should be taken that the observed alkalinity is not a 

 result of bacterial contamination. Volatile alkalies such 

 as ammonia react blue to litmus, but upon warming the 

 paper the red color returns ; this will not occur if the reaction 

 is caused by a fixed alkali. Organic acids are burnt in 

 the body to carbonates and the latter decrease the acidity, 

 sometimes, in fact, causing an alkaline reaction to appear. 



Volume and Specific Gravity. Under normal conditions 

 these two factors vary inversely with each other; a large 

 volume of urine is usually accompanied by a low specific 

 gravity and vice versa. The volume depends upon the 

 amount of water ingested and that excreted by the bowels, 

 skin, and lungs; it varies between 800 and 1500 c.c. (aver- 

 age 1250 c.c.). The specific gravity may fall between 1.010 

 and 1.030 (average 1.017-1.020). 



The volume should be measured in a graduated cylinder 

 capable of holding two liters. Should it be required to 

 retain the urine for some time, thymol must be added and 

 the fluid placed in a stoppered vessel. 



Determination of the specific gravity is made by means 

 of the urmometer (hydrometer). If there is a sediment the 

 urine must be warmed, filtered, and allowed to cool. 



Place the cylinder upon the table and fill it to within an 

 inch of the top with urine; then immerse the urinometer. 



