gas was passed through the fluid, it assumed an orange colour, and deposited a brown resinous precipitate. The solution on the addition of nitric acid became reddishbrown; sulphuric acid produced a pink, rosy colour at the bottom stratum of the fluid, the supernatant fluid becoming turbid like milk. Under the influence of chromic acid, the solution became black. These tests are characteristic of carbolic acid.

After repeated rectification of the original distillate, a pale, yellowish, oily liquid, of the odour of creosote, was obtained, which, on the addition of caustic potash, transformed into a magma of white crystals, which had the smell of mint (krausemünze). This potash salt dissolved in water, had a very agreeable odour, and therefore must have contained eupione, besides carbolic acid. It yielded a pale, yellowish distillate, which after removal of the water by means of chloride of calcium, became clear and colourless, of an oily consistence, and scarcely emitted any odour. It burned with a sooty flame, had a corrosive taste, blistered the skin, began to bubble at a temperature of 203° C. (397 °F.), boiled between 215° and 220° C. (419° and 428° F.), and, with the exception of the first part of the distillate, remained fluid even at a temperature of-25°C. (-13° F.) The elementary analysis of this fluid yielded the following results:

12

H

= 6.79 0 = 23.31

100.00

From these figures results the formula C12H6O2 + HO, which corresponds to carbolic acid plus one equivalent of water. This latter, however, was undoubtedly merely an admixture of water, from which the substance could not be freed entirely before the combustion.

When the urine was neutralized with lime, it yielded an ammoniacal distillate, which, after removal of the ammonia by neutralization with sulphuric acid, left a residue from which alcohol extracted a substance having the smell of tar, and depositing in brown flakes on evaporation of the alcohol. The nature of this substance could not be ascertained any closer, as its quantity was too small. A similar substance could be extracted from the fresh urine by means of alcohol. When shaken with ether, the latter extracted from the urine a purple matter, which after evaporation became dark red, and was fusible.

Carbolic acid could only be obtained from the urine after the addition of sulphuric acid. It must therefore have been in combination with a base not ascertained.

Carbolic acid could not precipitate uric acid from its solution, as it is a weaker acid than even carbonic acid, and is driven out of its compounds by the latter. Another acid was therefore present in the urine, and precipitated uric acid.

Dr. Petters is of opinion that most of the constituents of tar may enter the organism, and pass out by the urine. The residue from which the volatile substances had been distilled off, yielded an alcoholic extract, which on evaporation gave a black, tough, tar-like deposit. This, after crystallization of the salts and resolution in alcohol, deposited a substance on the admixture of water, which had the odour of tar, was resinous, and underwent no further changes.

Physiology of Phenylic acid.

Phenylic acid when introduced into the animal economy is, at least in part, excreted unchanged. In case the food of man should contain this acid, its occurrence in human urine would be accounted for. Smoked and dried meat certainly contains a small amount of this acid, together with other substances, the products of dry distillation. There is, however, nothing improbable in the opinion, that phenylic acid may be a collateral product of the oxydation of aliments. For as it is found in the urine of animals feeding on matters which have not been proved, and à priori could not be supposed, to contain phenylic acid ready formed, we are driven to the conclusion that it is formed in the body.

Frerichs and Wöhler proved phenylic acid to be a poison. A few drops of it killed rabbits and dogs in a quarter of an hour. Most probably the creosote and tar treatment is only tolerated by patients because these substances are being constantly eliminated by the kidneys. In some of Petters's cases the inunction with tar caused symptoms of poisoning. These substances are the last refuge of despairing empirical therapeutics. Creosote is useful in septic conditions, but the healing effects of tar are mostly of an imaginary nature.

CHAPTER XLI.

DAMALURIC ACID.

Formula: CHO3 + HO.

History.

DISCOVERED by Städeler in the urine of man, the horse, and the cow.

Physical and Chemical properties.

Damaluric acid is an oily liquid, of an odour resembling valerianic acid, heavier than water, but somewhat soluble in it. It differs from phenylic acid, in the property of reddening litmus, which phenylic acid has not.

Compounds.

With baryta this acid forms a salt, crystallizing in groups of needles. The salt with silver is a white powder, which does not decompose on exposure to the air. The former is soluble in water, strongly alkaline, does not fuse on heating, and leaves carbonate of baryta on combustion, which retains the original form of the salt. Damaluric acid produces a precipitate in a solution of basic acetate of lead, which under the microscope appears crystalline.

Mode of obtaining it pure.

Städeler distilled the urine of the cow with sulphuric acid, and thereby obtained an acid distillate, which was decomposed by means of carbonate of soda. The solution of the soda salts thus obtained was freed from phenylic and taurylic acid by means of ether, evaporated, and, after addition of

sulphuric acid, again subjected to distillation. From the distillate the baryta salt was obtained, which contained 39 18 per cent. of baryta. The silver salt contains 49.36 per cent. of oxyde of silver.

Städeler distinguishes further damolic and taurylic acids as ingredients of human or animal urine. Without doubting in the least the correctness of his observations, it is just to say, that the existence of these acids is not, as yet, sufficiently established for me to describe them at full length in this treatise.

THE sal acetosellæ had been known and used for a long time, when, in 1784, Scheele described a proceeding of separating oxalic acid from it by acetate of lead, and also discovered the identity of this oxalic acid with the acid found by Bergmann to be the principal product of the oxydation of sugar by means of nitric acid.

Oxalic acid is one of the most frequent products of the oxydation of organic matter by artificial processes. Its compounds are very frequent in plants, where the acid represents most probably the first stage of the reduction of carbonic acid. Thus, binoxalate of potash was formerly manufactured from certain species of oxalis, in which, as in certain species of rumex, it is found in considerable quantities. The parallel soda salt is found in certain plants familiar at the seashore, or in the neighbourhood of salt-works, salicornia and salsola; the latter, like "lucus a non lucendo," termed salsola kali. Oxalate of lime enters largely into the construction of many

Opusc.,' vol. ii, p. 187.

2 Ibid., vol. i, p. 251; vol. iii, pp. 364, 370.