This, however, is not the case, only half the sodium carbolate being converted into salicylate. The reaction proceeds according to the following equation:—
2NaC6H5O + CO2 = Na2C7H4O3 + HC6H5O.
The disodic salicylate is dissolved in water and decomposed by hydrochloric acid. Salicylic acid then separates in crystalline films and may be purified by recrystallisation out of its solution in hot water.
Props.—Salicylic acid is a white solid which forms acicular crystals; it melts at from 155°-156° C.; it dissolves in about 1800 parts of cold water, but is more soluble in boiling water as well as in alcohol and in ether. An aqueous solution of salicylic acid mixed with one of a ferric salt produces a deep violet colour.
Professor Kolbe surmised that from the constitution of salicylic acid, as revealed by his synthetical process, that it would split up with heat into carbonic anhydrate and carbolic acid, and hence that it might be employed as an antiseptic and antiputrefactive agent. He quotes the following experiments as confirmatory of his views on this point:—Mustard meal, which, in a few minutes after being mixed with warm water, gave off a strong smell of mustard oil, formed with water a scentless mixture, when a little salicylic acid had been previously added. No fermentation was set up by yeast in a fermentation of grape sugar, to which salicylic
acid had been added; whilst in a sugar solution already in fermentation the action stopped after the addition of some salicylic acid. The preservation influence of this acid upon fresh meat is also recorded.
The following, among other experiments, in their results, illustrate the physiological action of salicylic acid:—
Solution of amygdalin mixed with emulsion of sweet almonds developed no smell of bitter almonds if some salicylic acid were added. Beer, to which salicylic acid, in the proportion of 1 to 1000, was added, was thereby prevented from being spoiled by fungoid growth.
Fresh pure cow’s milk, mixed with 0·04 per cent. of salicylic acid, and allowed to stand in an open vessel at a temperature of 18° C., curdled thirty-six hours later than a similar quantity of milk standing by the side of it, but containing no salicylic acid. The milk remained of a good flavour, the small quantity of salicylic acid present not being perceptible to the palate.
Some fresh urine was divided into two portions, and placed in separate vessels, after some salicylic acid had been added to one portion.