MECON′IC ACID. H3C7HO7. Syn. Acidum meconicum, L. A peculiar acid, first obtained by Sertuerner from opium, in 1804.
Prep. Meconate of lime is suspended in warm water, and treated with hydrochloric acid. Impure meconic acid crystallises on cooling, and may be purified by repeated treatment in the same way with hydrochloric acid. Its purity is ascertained by its leaving no residue when heated in a platinum or glass capsule.
Prop. Meconic acid forms beautiful pearly scales; possesses a sour astringent taste; is
soluble in boiling water, and to a less extent in cold; it is also soluble in alcohol. With the acids it forms salts called ‘meconates,’ most of which are crystallisable. Meconate of lime is obtained by heating a solution of chloride of calcium with an infusion of opium made with cold water, and neutralised by powdered marble, and collecting the precipitate. Meconate of potassa is prepared by direct solution of the base in the impure acid obtained from meconate of lime till the liquor turns green, heat being applied, when the salt crystallises out as the liquid cools; it may be purified by pressure and recrystallisation.
Tests. Meconic acid is characterised by—1. Turning ferric salts red, and the red colour not being destroyed by the action of corrosive sublimate.—2. Precipitating a weak solution of ammonio-sulphate of copper green.—3. With acetate of lead, nitrate of silver, and chloride of barium, it gives white precipitates, which are soluble in nitric acid.—4. It is not reddened by chloride of gold.
MEC′ONIN. C10H10O4. A white, crystalline, odourless, neutral substance, discovered by Couerbe in opium.
MECO′NIUM. See Opium.
MED′ICINES. However skilful the medical practitioner may be, and however judicious his treatment, both are interfered with, and their value more or less neutralised, if the remedies he orders are not administered precisely according to his instructions. It is the duty of the attendant on the sick to follow implicitly the directions of the physician, as well in exactly complying with his orders as in doing nothing that she has not been ordered to do. At the same time there are exceptions to this rule, in which a suspension of the remedy, or a deviation from the order of the physician, is not only allowable, but is absolutely required. Thus, from idiosyncrasy or some other cause, the remedy in the doses ordered may have no effect, or may produce one widely different from that intended or expected. In such cases it is evident that a strict adherence to the direction of the physician would be productive of evil; but he should be immediately apprised of the circumstance. The common practice of neglecting to administer the doses of medicine at the prescribed time, or after prescribed intervals, and then, to compensate for the omission, giving the medicine more frequently or in larger doses, cannot be too severely censured, as destructive to the welfare of the patient and injurious to the credit of the physician.
For the purpose of disguising the taste of medicine, or lessening their nauseating properties, Dr Pollio has recommended a means founded on the physiological fact that a strong impression on the nerves (whether of vision, hearing, or taste) renders that which follows less perceptible than under the usual circumstances. Instead, therefore, of applying to
the mouth agreeable substances after swallowing nauseous medicines, we should prepare it beforehand, in order that the taste of the medicine may not be perceived. Aromatic substances, as orange or lemon peel, &c., chewed just before taking medicine, effectually prevent castor oil, &c., being tasted. In preparing the mouth for bitters, liquorice is the only sweet that should be used, the others creating a peculiarly disagreeable compound taste. We have noticed already the effect of oil of orange peel in correcting the nauseating qualities of copaiba. See Dose and Prescribing.