Mr Rother, an American chemist, contends that the antiseptic powers of salicylic acid have been much overrated. He states that he had tried it for the preservation of the syrups of marshmallow, raspberry juice, and milk, and that it was a failure. Professor Salkowsky regards it as of less value as an antiseptic than benzoic acid.
Dr Muter gives the following method for estimating the value of commercial samples of salicylic acid, and of detecting it in milk and similar organic solutions:—A standard solution of pure salicylic acid (1 grain of acid dissolved in 1 litre of water, so that 1 c.c. represents 1 mgm. of acid) is prepared; the indicator solution consists of a solution of pure neutral ferric chloride, of such a strength that 1 c.c. added, drop by drop, to 50 c.c. of standard acid, just ceases to give any increase in intensity of colour; 1 gram of the commercial sample is then dissolved in 1 litre of water, and 50 c.c. is put into a Nessler tube; to this 1 c.c. of ferric solution is added, and the colour observed after standing for five minutes, some of the standard acid is also poured into another tube, and made up to 50 c.c. with water, and the 1 c.c. of ferric chloride added. When the colours are alike the amount of pure acid present in the sample is equal to the amount of pure acid added. All mineral acids should be absent, even acetic acid affects the reaction. To detect the presence of salicylic acid added to beer or milk, four ounces of these liquids are dialysed for twelve hours in a pint of distilled water; if after that time salicylic acid is still found to be present, the dialysis must be continued for forty-eight hours. The amount present is determined in the manner above stated.
SALICYL′OUS ACID. C7H6O2. Syn. Salicylol, Hydrosalicylic acid†, Hydride of salicyl, Artificial oil of meadow-sweet. A nearly colourless, oily, inflammable liquid, discovered by Pagenstecher in the volatile oil of Spiræa ulmaria (meadow-sweet), which, when pure, entirely consists of it; and by Piria, as a product of the decomposition of salicin.
Prep. The oil of meadow-sweet is mixed with a strong solution of caustic potassa, and the yellow crystalline mass which separates on agitation is purified by pressure between folds of bibulous paper and recrystallisation from alcohol; the resulting crystals (salicylite of potassium) are then decomposed by the addition of dilute sulphuric acid, the floating oil separated from the water, and freed from
moisture by careful distillation from chloride of calcium.
Prop., &c. Salicylous acid is soluble in ether and alcohol, and slightly so in water, to which it imparts its peculiar fragrance and the characteristic property of striking a deep violet colour with the sesquisalts of iron. It is distinguished from salicylic acid, which also exhibits this reaction, by its liquid form and odour.
SALI′VA. See Mastication.
SALM′ON. Syn. Salmo, L. The Salmo Salar (Linn.), a well-known, soft-finned abdominal fish. Its normal locality is at the mouth or estuary of the larger rivers of the northern seas, which, during the breeding season, it ascends, sooner or later, in the summer months, against all obstacles, for the purpose of depositing its spawn.
The salmon is an excellent and highly esteemed fish; but it is rich, oily, and difficult of digestion, and, therefore, ill adapted to the delicate or dyspeptic. When pickled, salted, or smoked it is only fitted for persons of very strong stomachs, although in this state it is regarded as a great delicacy by epicures.
Salmon has the following composition:—