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•722 URINE.
given support to this assumption; Epstein and Bookman 1
found never-
theless in experiments with rabbits after feeding with benzoyl-leucine
that a great elimination of hippuric acid occurred which they consider
as a formation of glycocoll from this leucine. Free leucine on the con-
trary does not increase the hippuric acid elimination.
The kidneys may be considered in dogs as special organs for the syn-
thesis of hippuric acid (Schmiedeberg and Bunge 2
). In other animals
as in rabbits, the formation of hippuric acid seems to take place in other
organs, such as the liver and muscles. The synthesis of hippuric acid is
therefore not exclusively limited to any special organ, though perhaps
in some species of animals it may be more abundant in one organ than in
another.
Properties and Reactions of Hippuric Acid. This acid crystallizes in
semi-transparent, long, four-sided, milk-white, rhombic prisms or columns,
or in needles by rapid crystallization. They dissolve in 600 parts cold
water, but more easily in hot water. They are easily soluble in alcohol,
but with difficulty in ether. The acid dissolves more easily (about 12
; times) in acetic ether than in. ethyl ether. Petroleum-ether does not
dissolve hippuric acid.
On heating hippuric acid it first melts at 187.5° C. to an oily liquid
which crystallizes on cooling. On continued heating it decomposes,
producing a red mass and a sublimate of benzoic acid, with the genera-
tion, first, of a peculiar pleasant odor of hay and then an odor of hydro-
cyanic acid. Hippuric acid is easily differentiated from benzoic acid
by this behavior, also by its crystalline form and its insolubility in
petroleum ether. Hippuric acid and benzoic acid both give Lucre’s
reaction, namely, they generate an intense odor of nitrobenzene when
evaporated to dryness with nitric acid and when the residue is heated
with sand in a glass tube. Hippuric acid in most cases forms crystal-
lizable salts, with bases. The combinations with alkalies and alkaline
earths are soluble in water and alcohol. The silver, copper, and lead
salts are soluble with difficulty in water; the ferric salt is insoluble.
Hippuric acid is best prepared from the fresh urine of a horse or cow.
The urine is boiled a few minutes with an excess of milk of lime. The
liquid is filtered while hot, concentrated and then cooled, and the hippuric
acid precipitated by the addition of an excess of hydrochloric acid. The
crystals are pressed, dissolved in milk of lime by boiling, and treated as
above; the hippuric acid is precipitated again from the concentrated
1
Abderhalden, Gigon and Strauss, Zeitschr. f. physiol. Chem., 51; Abderhalden
and Hirseh, ibid., 78; Mangus-Levy, Bioch. Zeitschr., 6; Epstein and Bookman,
Journ. of biol. Chem., 13.
2
Arch. f. exp. Path. u. Pharm., 6; alpo A. Hoffmann, ibid., 7, and Kochs, Pfluger’s:
Arch., 20; Bashford and Cramer, Zeitschr. f. physiol. Chem., 35.
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