LACTIC ACID in its pure state is a transparent, colorless, or slightly yellow uncrystallizable, syrupy liquid, of specific gravity 1,215. It is devoid of odor, has a sharp, acid taste, and is soluble•in all proportions in water, alcohol, and ether.
The hest method of obtaining this acid is by dissolving 8 parts of cane-sugar in about 50 parts of water, and then adding 1 part of decaying cheese and 3 parts of chalk. If this mixture be set aside for two or three weeks at a temperature of about SO', it becomes filled with a mass of crystals of lactate of lime. which must be purified by recrystallize don. and treated with about one-third of their weight of sulphuric acid. The residue must be digested in alcohol, which leaves the sulphate of lime, and dissolves the la•tic acid, which may be obtained pure on evaporating the solution. The mode in which the acid is produced in this process is described in the article LACTIC FERMENTATION.
Lactic acid is also formed in many other ways; thus, it is a frequent product of the acidification of vegetable substances, and in this way is formed in sa aer-kraut, in malt vinegar, and in the acid fermentation that takes place during the manufacture of wheat starch. It occurs ready formed in certain plants, and is very largely produced in the animal body. It is found either free or combined, or both, in the gastric juice (although not constantly), in the contents of the small and large intestine, in the chyle (after the use of Innylaceous food), in the muscular juice (both of the voluntary and involuntary muscles). in the parenchymatous juices of the spleen, liver, thymus, pancreas, lungs,
and brain, and is found as lactate of lime in the urine of the horse. It has been found in certain morbid conditions of the system in the milk, where it is formed front the sugar by the fermenting action of the easeine; in the blood in leucocythretnia, pytemia, and puerperal fever; in purulent and other transudations; in the urine when there is dis turbance of the digestive and respiratory organs, and in rickets and softening of the bones (and almost always after exposure to the air for some time); in the saliva in dia betes; in the sweat in puerperal fever; and in the scales thatform upon the skin in lepra.
The lactic acid occur:lug in the system may be traced to two distinct sources: that which is found in the intestinal canal is merely the product of the decomposition of the starchy matters of the food; but that which exists in the gastric juice (even when only animal food has been taken), in the muscular juice, and in the juices of the various glands. can only be regarded as a product of the regressive metamorphosis or disintegra tion of the tissues, and how it is formed is not accurately known.
There is no ready test for lactic acid. The best course to pursue is to obtain it, if it is present, as a lactate of lime, which crystallizes in beautiful tufts of acicular prisms, or as a lactate of zinc, which crystallizes in a very characteristic form in crusts consisting of delicate four-sided prisms.