57^ 
THE CHEMISTR Y OF THE URIKE. 
If two salts contain an electrical ion in common (or without great inac- 
curacy we may say, a base or acid in common), each decreases the solubility 
of the other, whereas salts which contain no base or acid in common 
may mutually increase each the other's solubility. Thus the presence of 
sodium chloride in solution will diminish the solubility of sodium urate, 1 
and ammonium chloride that of ammonium urate : but the presence of 
either of these chlorides will increase the solubility of (say) calcium 
phosphate. These laws will be found to have important application in 
the explanation of certain urinary phenomena. 
In addition to products which arise from metabolism in the tissues, 
the urine contains substances which are derived more directly from the 
ingesta. These comprise a large proportion of the normal inorganic 
constituents, which are always found in the diet in excess of the needs 
of the organism ; and they may consist also of substances accidental or 
accessory to the diet, or again of drugs, or of substances experimentally 
introduced into the body. 
Some of these, while taking no share in metabolism proper, may 
form "conjugated" or synthetic compounds w T ith certain intermediate 
products of metabolism, and so modify excretion. Thus glycin and 
glycuronic acid are substances capable of easy oxidation in the body, 
and are therefore not properly terminal products of metabolism ; but 
they are protected from oxidation and are eliminated as synthetic 
compounds with certain aromatic substances, whenever the latter are 
absorbed in sufficient quantity from the bowel. 
Quantitative Composition of the Urine. 
The figures which follow are from the well-known table given by 
Parkes, representing the normal twenty-four hours' excretion of the chief 
urinary constituents : — 
Percentage 
Composition 
of Solids. 
Absolute Weight 
of Solids in Grins. 
Weight per 
1000 of 
Body-Weight. 
Urea, CH,N,0 .... 
4a'75 
33-18 
0-5000 
Creatinine, C 4 H 7 N 3 
1-25 
0-91 
0-0140 
Uric acid, C a H 4 N 4 s 
075 
0-55 
0-0084 
Hippuric acid, C 3 H N0 3 . 
0-55 
0-40 
0-0060 
Pigment and other organic substances 
13-79 
10-00 
0-1510 
Sulphuric acid, S0 3 .... 
:2-77 
2-01 
0-0305 
Phosphoric acid, P 2 5 
4-36 
3-16 
0-0480 
Calcium ...... 
0-35 
0-26 
0-0004 
Magnesium ..... 
0-28 
0-21 
0-0003 
Potassium ..... 
3-45 
2-50 
0-0420 
Sodium . . . . . 
15-29 
11-09 
0-1661 
Chlorine ...... 
10-35 
7 -50 
0-1260 
Ammonia . 
1-06 
0-77 
0-0130 
100-00 
72-54 
1-1057 
In the following analyses, derived from Bunge, all the figures were 
obtained from the same individual. They represent the twenty-four 
hours' excretion of a young man : in the one case, upon a diet con- 
sisting entirely of beef with a little salt and spring water; in the 
1 As was shown experimentally by Sir William Roberts, before the general principle 
enunciated above had been developed by Nernst. 
