Related entry: Lemon
Preparation: This acid is obtained freely from lemon juice, cranberries, and currants; also in small quantities from elderberries, red raspberries, and some other fruits. It is mostly manufactured from lemons, the juice of which is put into a vat and allowed to ferment a little. The clear liquid is drawn off, and the precipitate washed, and afterward the lime neutralized by careful additions of diluted sulphuric acid. The sulphate of lime now falls; and the clear liquid holds the citric acid in solution. This being drawn off and slowly evaporated, yields the crystals of citric acid on cooling. These crystals are then dissolved in a very little water, treated with animal charcoal, filtered, and again evaporated.
Crystals of citric acid are large, white, and with a specific gravity of 1.6. They dissolve in water readily. Being obtained from lemons, it is supposed to be the same in properties as the juice of this fruit; but this is quite a mistake, as the citric acid can not be procured till the lemon juice has undergone a fermentation that changes the relations of the organic substances. (§32.) It should not be employed as a substitute for lemon juice, and I think should not be used at all; but it forms with carbonate alkalies a series of neutral salts that are comparatively inert. Twenty grains of citric acid will neutralize twenty-nine grains bicarbonate of potassa; fourteen grains carbonate of magnesia; and twenty-four grains bicarbonate of soda. Its combination with the potassa alkali forms the best effervescing draught; and the citrate of magnesia is just now a popular cathartic, but acting too much like epsom salts to be a very good one.
Properties and Uses: This is a sharp acid in its pure state; and a concentrated solution will provoke inflammation and diarrhea. One ounce diluted with twenty ounces of water, forms a. solution of about the common acidity of lemon-juice; and this is sometimes used as a refrigerant drink in fevers. A scruple of the acid to a pint of sweetened water, is strong enough for ordinary purposes; and this should be used only in moderate quantities. It is useful in scurvy, as are all vegetable acids if harmless. It has recently been commended in rheumatism, though apparently without any good cause. Its continued use impoverishes and thins the blood; and those practitioners who are perpetually afraid that the blood will become too rich and nourishing, consider this an argument for its use in inflammation and fever. Let it be borne in mind that, while the system must have vegetable acids, a chemical product of any fruit is a miserable substitute for the original article.
Pharmaceutical Preparations: I. Sirup. "Take of citric acid, in powder, two drachms; oil of lemons, four drops; sirup, two pints. Rub the citric acid and oil of lemons with a fluid ounce of the sirup, then add the mixture to the remainder of the sirup, and dissolve with a gentle heat." ( U. S. P. ) This is added to water and used as a drink. It is a poor substitute for the true lemon sirup. (See Citrus Limonum.)
II. Effervescing Draught. "Take of citric acid, half an ounce; oil of lemons, two minims; water, half a pint; bicarbonate of potassa, a sufficient quantity. Rub the citric acid with the oil of lemons, and afterward with the water till it is dissolved; then add the bicarbonate of potassa gradually till the acid is perfectly saturated." ( U. S. D. ) This preparation is also called neutral mixture and solution of citrate of potassa. A tablespoonful is given in sweetened water every third or second hour, and provokes sweating in intermitting and bilious fevers. It is usually very irritating to the bowels; and the drink of flaxseed and lemon-juice (see Lemons) is a far preferable diaphoretic and refrigerant.
The Physiomedical Dispensatory, 1869, was written by William Cook, M.D.
It was scanned by Paul Bergner at http://medherb.com