EXCRETIONS 485 



concentration a simplified logarithmic notation is generally employed. 

 Pure water, our standard of neutrality, contains : - - ~~ of a gram of 



JL\S m \J\J\J + * 



IP to a liter, and is therefore a ' X solution of H. For con- 



venience the logarithmic notation is employed, thus: 



= 10 "- Since the base is alwas 10 and 



10,000,000 N 



the logarithm always negative the expression is further simplified by 

 dropping both the figure 10 and the minus sign. The hydrogen ion con- 

 centration of pure water, then, is expressed in terms of its exponent, 

 pH = 7. Since the sum of the logarithmic expressions H and (OH) ion 

 concentrations is always 14, it will be readily seen that the concentration 

 of either ion may be estimated when one is known. In practice the 

 determination of the hydrogen ion has been found simpler. 



formally the urine appears to vary from an acid solution, of 

 pH = 4.82 to an alkaline solution of pH = 7.45, the average being close 

 to a solution of pH 6.0. By the administration of sodium bicarbonate 

 and sodium citrate (which is oxidized to the carbonate), Henderson and 

 Palmer(a) were able to lower the pH to 8.70, a condition of alkalinity. As 

 pointed out by Blatherwick(d) foods yielding basic ashes may likewise re- 

 duce the urinary acidity to that of neutrality (pH = 7), or even beyond 

 this to alkalinity. Among 30 vegetarians the pH varied from 5.30 to 7.48, 

 averaging 6.64. Palmer and Henderson (6) have shown that in cases with- 

 cardiorenal diseases, the acidity of the urine is usually increased. The 

 average pH of 57 cases was 5.33, representing a five-fold increase in 

 urinary acidity over the normal average of 6.0. 



Transparency. When voided the urine of a normal individual is 

 usually perfectly clear. On standing a few hours a cloud or "nubecula" 

 forms, even in normal urine. This cloud consists of mucus threads, 

 epithelial cells, etc., from the urinary passages. Under pathological con- 

 ditions, the latter may be greatly increased and accompanied by casts or 

 blood. If the acidity of the urine is somewhat diminished (as after a 

 meal) a turbidity due to phosphates will form. This will disappear on 

 adding a little acetic acid. On standing in the cold, urates may settle 

 out but will again go into solution on warming, 



Organic Constituents 



By far the greater number of organic compounds present in normal 

 urine contain nitrogen, and those that do not contain nitrogen constitute 

 an extremely small part of the total solids. Fifty grams may be given 

 as a rough figure for the solid content of urine and of this amount about 



