The U. S. Pharmacopoeia directs this salt to be made by evaporating the officinal Solution of Citrate of Iron (Liquor Ferri Citratis, U. S.) to the consistence of syrup, and then spreading it on plates of glass to dry. The solution is prepared by gradually adding to a heated solution of citric acid, freshly precipitated hydrated sesquioxide of iron (see page 443) until it ceases to be dissolved, and the acid is saturated. A direct union takes place between the acid and oxide, resulting in the formation of a salt consisting of one equivalent of citric acid, and one of sesquioxide of iron.

Citrate of iron is an uncrystallizable salt, and, as above prepared, is in translucent laminae of a fine garnet-red colour, of a mild ferruginous taste, slowly soluble in cold, but readily in boiling water.

It is a mild chalybeate, and may be employed to obtain the general effects of iron on the system, either in pill or solution, in doses of from three to ten grains, three times a day. It has been considerably used in this country.

The officinal solution is a convenient form for administration, and may be given in the medium dose of ten minims, equivalent to five grains of the salt.

Citrates of the Protoxide and of the Black or Magnetic Oxide of Iron have been prepared, but have no special advantage to recommend them.

Citrate of Iron and Quinia (Ferri et Quiniae Citras, U. S.) is the name given to a preparation made by heating together recently precipitated quinia and officinal solution of citrate of iron, until a solution is effected, then evaporating, and drying upon glass plates. It is in thin, garnet-red scales, of a bitter, slightly chalybeate taste, and soluble in water. It is a double citrate of iron and quinia; but, as usually found in the shops, contains a large excess of the salt of iron. It may be used as a tonic, and would be especially adapted to that anemic condition of system which so frequently follows our autumnal fevers; but I can see no advantage it possesses over a mixture of the citrate of iron with sulphate of quinia, while it has this disadvantage, that the relative quantity of the two salts cannot be adjusted to the particular indications of the case. The dose is about five grains.