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LACTIC ACIDS. 585
The phosphocarnic acid (Siegfried) and the inosite are also considered
as possible mother-substances for sarcolactic acid. Further research
will show whether also other mother-substances for this acid occur. The
autolytic experiments of Tuhkel x
with livers and the formation of lactic
acid in the muscles, not from carbohydrates, inosite or alanine, as observed
by Embden 2
and his collaborators seem to indicate this.
The lactic acids are amorphous. They have the appearance of
colorless or faintly yellowish, acid-reacting syrups, which mix in all pro-
portions with water, alcohol, or ether. The salts are soluble in water,
and most of them also in alcohol. The two acids are differentiated from
each other by theit different optical properties—paralactic acid being
dextrogyrate, while fermentation lactic acid is optically inactive—also
by their different solubilities and the different amounts of water of crys-
tallization cf the calcium and zinc salts. The zinc salt of fermentation
lactic acid dissolves in 58-63 parts of water at 14-15° C, and contains
18.18 per cent water of crystallization, corresponding to the formula,
Zn(C3Hs03)2+3H20. The zinc salt of paralactic acid dissolves in 17.5
parts of water at the above temperature and contains ordinarily 12.9
per cent water, corresponding to the formula, Zn(C3H503)o+2H20.
The calcium salt of fermentation lactic acid dissolves in 9.5 parts water
and contains 29.22 per cent (=5 molecules) water of crystallization,
while calcium paralactate dissolves in 12.4 parts water and contains 24.83
or 26.21 per cent ( = 4 or 4^ molecules) water of crystallization. Both
calcium salts crystallize, not unlike tyrosine, in spears or tufts of very
fine microscopic needles. Hoppe-Seyler and Araki, who have closely
studied the optical properties of the lactic acids and lactates, consider
the lithium salt as best suited for the preparation and quantitative estima-
tion of the lactic acids. The lithium salt contains 7.29 per cent Li. For
further information as to the salts and specific rotation of the lactic acids
see Hoppe-Seyler-Thierfelder’s Handbuch. 8. Aufl., 1909.3
Lactic acids may be detected in organs and tissues in the following
manner: After complete extraction with water, the protein is removed
by coagulation at boiling temperature and the addition of a small quan-
tity of sulphuric acid. The liquid is then exactly neutralized, while
boiling, with caustic baryta, and then evaporated to a syrup after filtra-
tion. The residue is precipitated with absolute alcohol, and the pre-
cipitate completely extracted with alcohol. The alcohol is entirely
distilled from the united alcoholic extracts, and the neutral residue is
1
Tiirkel, Bioch. Zeitsehr., 20. The statements on the formation of lactic acid
in the muscle autolysis are rather conflicting; see Fletcher, Journ. of Physiol., 43.
2
Embden, Kalberlah and Engel, Bioch. Zeitsehr. 45; Kondo, Und., 45.
3
See also E. Jungfleisch, Compt. Rend., 139, 140, and 142; Herzog and Slansky,
Zeitsehr. f. physiol. Chem., 73.
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