6o6 THE CHEMISTRY OF THE URINE 
excreted as conjugated sulphate* (see p. 631), but the carboxyacids are 
only in part so excreted. Inosit, which belongs to this group chemically, 
has somewhat different physiological relationships to the other aro- 
matics of urine. 
Phenol (C ( H 5 .OH) and kresol (CH 3 .C 6 H 4 . OH).— Traces of carbolic 
acid are present in urine physiologically, but the " phenol " of the normal 
fluid consists, as a matter of fact, mainly of the homologous kresol ; and, 
of the isomeric forms of the latter, parakresol is the commonest. The 
properties of this substance, however, closely resemble those of phenol 
itself. The amount of phenol and kresol taken together may be upon a 
mixed diet no more than some 30 nigrms. per diem. If the urine 
lie acidified and distilled, the distillate made alkaline, concentrated, and, 
after concentration, neutralised, on the addition of bromine a whitish pre- 
cipitate will appear, due mainly to the formation of the tribromphenols. 
Pyrocatechin (orthodihydroxybenzene) and hydrochinon (para- 
dihydroxybenzene) C 6 H 4 (OH)o. — Of these two isomeric substances 
the former is a constant constituent of human urine in small 
quantity; the latter is found probably only under exceptional cir- 
cumstances. The former is easily removed from the acidified urine 
by shaking with ether; but its subsequent purification involves a 
lengthy procedure. 1 It is a white crystalline volatile solid, easily 
soluble in water. It mxes a dark <» - reen coloration with ferric chloride, 
which, on the addition of ammonia, becomes violet and afterwards 
cherry-red. 
Inosit. — This substance, from its sweet taste, was originally classed 
with the sugars, and was known as " muscle sugar." It strictly belongs, 
however, to the group of substances we are considering, as it is by com- 
position hexahydroxybenzene (CH.OH) 6 . It appears in normal urine 
with considerable frequency when polyuria is induced by diuretics or by 
copious drinking. On the other hand, its appearance is not entirely 
dependent upon the flushing of the tissues which such polyuria might 
denote, as extreme polyuria is at other times not associated with 
inosituria. It may occur in diabetes. Galloise found it in five out of 
thirty cases. 
It may be separated from the urine by precipitation with acetate of 
lead. The precipitate is decomposed with hydrogen sulphide, the fluid 
concentrated, and finally precipitated by admixture with a large bulk of 
alcohol. The alcohol precipitate is dissolved in water, the solution 
mixed with an ecpial bulk of spirit and poured into ether, which pre- 
cipitates the inosit almost pure. 
The substance forms crystals not unlike those of cholesterin. It is 
optically inactive and does not ferment. It is said to yield sarcolactic 
acid by the action of bacteria. 
Of the aromatic carboxyacids the following have been identified 
in human urine: — Parahyclroxyphenyl-acetic acid OH.C G H 4 — CTL.COOH; 
parahydroxyplu myl -propionic acid OH.C H 4 — C 2 H 4 .COOH ; clihydroxy- 
phenyl-acetic acid (OH) 2 — CH 2 .COOH (the homogentisic acid of 
Wolkow and Bauniann) : 2 and trihydroxyplienyl-propionic acid 
(OH) 3 C 6 H 2 .C 2 H 4 .COOH (the uroleucic acid of Kirk). 
In the urine of herbivora other analogous compounds have been 
1 Cf. Halliburton, "Chemical Physiology and Pathology," 1891, p. 745. 
2 Loc. cit., 1891, Bd. xv. S. 241. This is that isomeric acid which is related to hydro- 
chinon. 
