SALICYLIC GROUP. A cluster of chemical substances, compounds or derivatives of the electronegative radical talky! The members of this group—itself a subdivision of the benzoic series in Gerhardt's arrangement—are numerous ; including the odoriferous oil of meadow-sweet and of winter-green, and the bitter principle of willow-bark.
Sulicyl (C,,11,0,) itself ha not yet been isolated. As it contains the elements of phenyl (C„II,) and carbonic acid (C,0,), and as, more over, its compounds are not uufrequcntly converted into bodies identical with derivatives of phenyl, the salicylic group has sometimes been termed the plien yl-carbonic group.
Salieylide of benzoyl C„H,0,), parasalleyl, or spirine, is obtained by acting upon chloride of benzoyl with hydride of salicyl, or from the destructive distillation of salicylide of copper. It is insoluble in water, soluble in alcohol or ether, crystallises in prisms, melts at 260°, and sublimes at Fehr., and is converted into picric acid on being boiled with nitric acid.
Hydride of *alkyl (C,,H,0,, If); salicylous acid ; spirous acid, or essential oil of spirera ulmaria. Besides the method of obtaining this body from the flowers of mcadow-aweet, as described under ESSENTIAL OILS, it may be produced by decomposing salicin under the influence of oxidising agents. According to Buchner, auch an operation is simply an imitation of what occurs naturally in the spirtra flowers; the buds of this plant contain aalicin, and have scarcely any smell ; but, on expanding, freely expose their parts to the air, when oxidation of the saliciu goes on, and hydride of Balky' results, giving odour to the flowers The artificial oxidation of salicin is conveniently effected by bichromate of potash. To two parts of salicin, two of bichromate of potash, and sixteen of water, in a retort, are added three of oil of vitriol, previously diluted with eight peseta of water. After a abort time a gentle heat may be applied, when the oil passes over ; twenty five parts of aalicin yielding six of the essence. The salicin for this
process need not be pure ; indeed, aqueous extract of willow-bark serves very well.
'hen quite pure, hydride of salicyl is a colourless oil, but from contact of air soon acquires a red hue. It has an agreeable aromatic odour, acrid taste, boiling point 360' Fehr., specific gravity vapour density 4.276, and burns with a bright smoky flame. It is somewhat soluble in water, the solution giving a deep violet colour with persalta of iron. Hydride of salicyl is an acid body : it decomposes the alkaline carbonates with effervescence, and combines with bases generally to form neutral and acid salicylides. The potasaium salts contain respectively K,C,,H,0,+ 2 Aq. and K,C„11,0,+ H,C,,11,0,.
adorosalicylous acid (C„(11,C1)0„11), bromosalicylous acid (C Br10„ II), iodosalicylous acid, and hydride of nitrosalieyl (C„(H,N0.) 0 „II), are respectively produced by the action of chlorine, bromine, iodine, and nitric acid upon hydride of salicyl. They are crystalline compounds, and form crystalline salts with bases.
Salhydramide, salicylimide, or hydride of avisalicyl is the product of the action of ammonia upon hydride of salicyl 2;01,0. + 21:11, re + 6110 Itycirido of Ammonia. Salliydramide. water.
It crystallises in prisms, is insoluble in water, slightly soluble in cold alcohol, and more so in hot alcohol.
Chlorosamiele or the hydride of chlorazosalicyl, and bromosarnide (C„H„BrN,0„) or the hydride of bromazosalicyl, are formed on acting with ammonia upon the chlorine and bromine derivatives of hydride of salicyl.
Thiesalico/ (C„11.0,S,), or hydride of nulphosalicyl, is a pulverulent substance, formed on treating se Ihydrainide with sulphuretted hydrogen.
Sulphurous deriratires of hydride of salicyl, and of the preceding compounds of galley', result from the action of sulphurous acid upon their alkaline salts, or of the alkaline bisulphitea upon the compounds themselves.