Bitter purging Salt. Epsom Salt.
Qualities. Form, small needle-like crystals. Taste, bitter and nauseous; when pure, it effloresces. Chemical Composition. In its crystallized state, it may be considered as composed of 1 proportional of dry sulphate (Magnesia 18·5, and sulphuric acid 37·5) and 7 proportionals of water. Solubility. f℥j of water dissolves ℥j, and the solution measures fʒxj¼; it is insoluble in alcohol. Incompatible Substances. Muriates of ammonia, baryta, and lime; nitrate of silver; sub-acetate, and acetate of lead. The fixed alkalies and their carbonates, precipitate from it magnesia and its carbonate. Phosphate of soda occasions no immediate precipitate, unless ammonia be present, in which case the triple ammoniaco-magnesian phosphate will be produced. The addition of ammonia, which in the form of Spiritus ammoniæ aromat. is not unfrequently prescribed in conjunction with a solution of this sulphate, forms also a triple salt, and a portion of magnesia is precipitated: whenever therefore this ammoniacal stimulant is ordered with a purgative salt, the scientific physician will prefer a solution of the sulphate of soda. Forms of Exhibition. Dissolved in the Infusum Rosæ, or in a suitable quantity of beef tea, gruel, or any aqueous vehicle, its cathartic powers are increased by dilution, as well as by the addition of a little common salt; magnesia renders the taste of its solution less nauseous; and tartarized antimony quickens its operation. Dose, ℥ss to ℥ij, taken either at once, or in divided doses. Form. 37, 69, 72, 76. Officinal Prep. Enema Catharticum. Enema Fœtid. D. Adulterations. Sulphate of Soda is often substituted for this salt, which it may be made to resemble by stirring it briskly at the moment when it is about to crystallize; the fraud may be detected by a precipitation not ensuing on adding carbonate of potass; if only a part of the salt be sulphate of soda, the degree of sophistication can be learnt by the quantity of the precipitate formed; 100 parts of sulphate of magnesia, if pure, will yield between 30 and 40 of the dry carbonate. Epsom salt, as it commonly occurs, contains muriate of magnesia, which disposes it to deliquesce, but lately this salt has appeared in the market in a state of great purity and beauty; the mode of purification is founded upon the well known chemical law, that a saturated solution of one salt is still capable of dissolving another; in the present instance, therefore, the impure crystals are washed in a saturated solution of the same sulphate, which, although unable to act upon its kindred salt, can dissolve with facility the muriate, and any other saline contamination. I confess, however, that I am induced to regard this process as rather chemically ingenious than as medicinally useful, for the usual saline impurities of Epsom salt are not only harmless, but capable of increasing its purgative powers; the double refined sulphate is certainly less efficient as a cathartic. The presence of the muriate may be at once detected by dropping upon the suspected sample some sulphuric acid, by which the disengagement of muriatic acid vapour will be produced. Since the publication of the fourth edition of the present work, I have received samples of the sulphate of Magnesia, prepared by Mr. West of Lymington, and I can confidently recommend the article to the profession; he contrives to obtain them in large and beautiful crystals, which cannot be so easily mistaken for those of oxalic acid, a circumstance of no small importance to the drug vender; the form of these crystals is that of a square prism, having its edges replaced, and commonly terminated by a pyramid of four planes; the only cleavage is parallel to one of the diagonals of the prism. The numerous accidents which so frequently occur from mistaking Oxalic acid for Epsom Salts have given rise to many suggestions for obtaining an easy and popular test which may at once distinguish these bodies; it is evident that no test can be so simple as that afforded by the taste; but if such accidents are in future to be prevented, it must be done by imparting to the acid some external character by which it may be at once recognised; if a test were even discovered a hundred times more sensible than any which we possess, what would it avail?
MANNA.[[561]] L.E.D.
(Fraxinus Ornus. Succus Concretus.)
Manna.
Qualities. Form, flakes of a granular texture; Colour, whitish, or pale yellow; Odour, slight but peculiar; Taste, nauseous sweet, with some degree of bitterness. Chemical Composition. This concrete vegetable juice, besides sugar, appears to contain mucilage and extractive, to which its taste and other peculiar properties are owing. Solubility. It is entirely soluble in water and alcohol. Med. Uses. It is now merely regarded as a laxative for children, or for weak persons. It generally requires some laxative adjunct, as castor oil, with which it may be combined by the medium of mucilage. Dose, for children, from ʒj to ʒiij, in warm milk. Officinal Prep. Confectio Cassiæ. L.E.D. Enema Cathart. D. Enema Fœtid. D. Syrup. Sennæ. D. Adulterations. There are several varieties in the market, the best of which is flake manna, manna canulata, in a stalactitic form. An article, entirely factitious, consisting of honey or sugar, mixed with scammony, is sometimes sold for genuine manna, but its colour, weight, transparency, and taste, must instantly lead to its detection.
MASTICHE. L.
(Pistachia Lentiscus. Resina.)
Mastich.
The use of this resinous substance is to fill the cavities of carious teeth; a solution of it in oil of turpentine is sold as an odontalgic. The Turkish and Armenian women use it as a masticatory for cleaning the teeth, emulging the salivary glands, and imparting an agreeable odour to the breath. It forms a constituent of the Dinner Pills. See Aloes. Sonnini tells us that, in Egypt, the smoke of Mastich is supposed to kill any sick person that inhales it.