Pilocarpinae Salicylas, Pilocarpine Salicylate.
Pilocarpine salicylate, C11H16N2O2C7H6O3, a salt of the alkaloid pilocarpine, may be prepared by neutralising 10 parts of pilocarpine in dilute alcoholic solution with about 6.7 parts of salicylic acid, evaporating the solution to dryness, taking up the residue with hot alcohol, and allowing to crystallise. It contains 60.12 per cent. of pilocarpine. Pilocarpine salicylate occurs in small, colourless, crystalline leaves, or as a white, crystalline powder, having a slightly bitter taste. Melting-point, 120°. It leaves no residue on ignition. It dissolves in concentrated sulphuric acid without colour. With fuming nitric acid, it dissolves with a yellowish-brown colouration. The aqueous solution produces with ferric chloride a deep violet colouration. It is not precipitated by solution of ammonia or potassium bichromate. Solution of sodium hydroxide produces (only in the concentrated aqueous solution) a separation of the base in the form of oily drops, which, however, dissolve on adding excess . of the alkali.
Easily soluble in water, less so in alcohol, the solutions having a slightly acid reaction.
Action and Uses.—Pilocarpine salicylate has properties closely resembling those of pilocarpine nitrate, and is used for similar purposes.
Dose.—3 to 30 milligrams (1/20 to ½ grain).