Prep. From the juice of lemons, limes, and other allied species, by first fermenting the juice with yeast, in order to get rid of the sugar, and then neutralizing the acid with chalk, to form a citrate of lime, purifying this and liberating the citric acid by means of sulphuric acid.

Prop). & Comp. Large transparent colourless crystals, right rhombic prisms, of an agreeable acid taste, decomposed by heat, soluble in water and spirit: the precipitate formed with acetate of lead is soluble in nitric acid. Citric acid does not render lime-water turbid (citrate of lime is, however, a sparingly soluble salt), and causes no precipitate with any salts of potash except the tartrate, from which it throws down the acid or bitartrate. Composition of the crystallized salt (3 HO, C12 H5 O11+HO) or (3 HO, Ci+ HO). Citric acid being regarded as tribasic, 3 equivalents of the water act the part of base. 67 grains of the crystals dissolved in water are neutralized by 100 measures of the volumetric solution of soda. It leaves no ash when burned with free access of air. The aqueous solution is not darkened by sulphuretted hydrogen, nor precipitated by chloride of barium, showing the absence of metallic impurities and sulphates.

Therapeutics. Citric acid given internally appears to act as a refrigerant, that is, in some way or other to diminish the preternatural temperature of the body in febrile states of the system; it also allays thirst and irritation of the skin.

Dose. 10 gr. to 30 gr. or more, dissolved in water and sweetened.

Adulteration. Traces of sulphuric acid may be present, also tartaric, both detected by the tests and characters given above.