Incompatibility in prescriptions and how to avoid it : to which is added a dictionary of incompatibilities / by Thomas Stephenson.

  • Stephenson, Thomas, 1864-1938.
Date:
1929
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Licence: In copyright

Credit: Incompatibility in prescriptions and how to avoid it : to which is added a dictionary of incompatibilities / by Thomas Stephenson. Source: Wellcome Collection.

    19/76 (page 15)
    which breaks down into iodine and water. A yellow colour develops in the mixture, but this will not take place if the mixture is alkaline. Another instance in which iodine is set free, though not immediately, is when potassium chlorate is prescribed with syrup of ferrous iodide. In this case the chlorate is gradually reduced to chloride, and iodine is liberated from the ferrous iodide. In a case quoted by W. G. Smith the iodine liberated in such a mixture caused the death of a child. Glucosides are hydrolysed in presence of mineral acids or alkalis. Thus salicin is slowly changed into saligenin and glucose, and strophanthin is similarly decomposed. Reference has already been made under the heading of explosives (see p. 11) to the decomposition of substances rich in oxygen. Chloral hydrate is another substance that is readily decom- posed. With carbonates or hydroxides of the alkalis or alkaline earths (potassium, sodium, ammonium, or magnesium) chloroform is set free, and a formate of the base is produced. With certain soluble salts, such as bromides and iodides, in presence of alcohol, an oily layer of chloral alcoholate is formed. It is therefore unwise to prescribe chloral hydrate and potassium bromide along with a tincture. (e) Precipitation of Alkaloids.—As a general rule, alkaloids are insoluble in water, and can be held in solution only by addi- tion of an acid, which forms a soluble salt. The addition of an alkali to such solution will neutralize the acid and throw out the alkaloid in an insoluble form. Ammonia, such as aromatic spirit of ammonia or ammoniacal tinctures, alkaline carbonates, etc., ought not therefore to be prescribed with alkaloidal solu- tions.1 Strychnine is very slightly soluble in water (about 1 in 7000), and if sufficient water be used to dissolve the precipitated strychnine an alkali may be added with safety. But at least one ounce of water should be added for every 6 minims of liquor strychninae hydrochlor.—z>., 3i of liq. strych. hydrochlor. requires a 10 ounce or 12 ounce mixture to keep the liberated strychnine in solution if alkali is present. In the following prescription the strychnine was thrown out and taken with the last dose, causing severe symptoms of strychnine poisoning :— R Potass, bicarb. - Liq. strychninae Infus. gent. co. - 1 Quinine, though precipitated by ammonia, is soluble in excess of that substance ; this fact is utilized in the preparation of ammoniated tincture of quinine. The alcohol in this tincture assists in holding the quinine in solution, and addition of water pre- cipitates the alkaloid, as is well known. But there is no precipitation with aerated water, the C02 forming a soluble carbonate. The solution with aerated water is more palatable,