An aqueous solution in the cold is not precipitated by oxalate of ammonium. The
precipitate given by carbonate of sodium from a solution of 100 gr. should, after well washing and heating to redness, weigh 16·26 gr. (B. P.)
Digested in alcohol, the filtered liquid does not yield a precipitate with nitrate of silver nor burn with a yellow flame, and evaporates without residue. “Not deliquescent in the air.” (Ph. L.) 100 gr. of the pure crystallised sulphate yields 161⁄4 gr. of calcined magnesium oxide. (Pereira.) 10 gr., dissolved in 1 fl. oz. of water, and treated with a solution of carbonate of ammonium, are not entirely precipitated by 280 minims of solution of phosphate of sodium. (Ph. E.)
Uses, &c. Sulphate of magnesium is an excellent cooling purgative, and sometimes proves diuretic and diaphoretic.—Dose, 1 dr. to 1 oz., as a purgative, or an antidote in poisoning by lead. Large doses should be avoided. Instances are on record of their having proved fatal. Dr Christison mentions the case of a boy 10 years old who swallowed 2 oz. of salts, and died within 10 minutes. The best antidote is an emetic. A small quantity of Epsom salts, largely diluted with water (as a drachm to 1⁄2 pint or 3⁄4 pint), will usually purge as much as the common dose. This increase of power has been shown by Liebig to result rather from the quantity of water than the salt. Pure water is greedily taken up by the absorbents; but water holding in solution saline matter is rejected by those vessels, and consequently passes off by the intestines.
Obs. Oxalic acid has occasionally been mistaken for Epsom salt, with fatal results. They may be readily distinguished from each other by the following characteristics:—
| EPSOM SALT. | OXALIC ACID. |
| Tastes extremely bitter and nauseous. | Tastes extremely sour. |
| Does not volatilise when heated on platinum foil. | Volatilises when heated on platinum foil. |
| Does not produce milkiness when dissolved in hard water. | Produces milkiness when dissolved in hard water. |
Magnesium, Tar′trate of. Syn. Magnesiæ tartras, Magnesia tartarica, L. Prep. By saturating a solution of tartaric acid with carbonate of magnesium, and gently evaporating to dryness. It is only very slightly soluble in water.—Dose, 20 to 60 gr., or more; in painful chronic maladies of the spleen. (Pereira, ex Radmacher.) The effervescing tartrate of magnesium, commonly sold under the name citrate, has already been noticed.
Magnesium and Potas′sium, Tartrate of. Syn. Potassio-tartrate of magnesia; Magnesiæ potassio-tartras, M. et potassæ tartras, L. Prep. From acid tartrate of potassium (in powder), 7 parts; carbonate of magnesium, 2 parts; water, 165 parts; boiled until the
solution is complete, and then evaporated and crystallised. A mild aperient.—Dose, 1 to 5 dr.; in scurvy, &c.
MAG′NET. Syn. Magnes, L. Besides its application to the loadstone, this name was formerly given to several compounds used in medicine.—Arsenical magnet (MAGNES ARSENICALIS), a substance once used as a caustic, consisted of common antimony, sulphur, and arsenious acid, fused together until they formed a sort of glass. Magnes epilepsiæ was native cinnabar.