Medical Men are but rarely good chemists, for this would necessitate longer devotion to chemistry than the average medical student can afford. Hence the importance of dispensers being thoroughly well up in the general principles of chemical incompatibility. These are to be learnt in the ordinary course of pharmaceutical studies, especially in chemistry. Chemical incompatibility is not violation of chemical laws, but the prescribing of two or more substances together which produce new compounds the therapeutic action of which may differ from that of the original substances, while the therapeutic action of the latter is partly or wholly changed. Doubtless many such changes are intentional: that is a point which will be discussed later. For convenience of reference we group together the most important of the substances which are apt to be prescribed with others, and which, on compounding, produce chemical reaction. It is to be understood that in nearly every case solution is a condition preliminary to the change.

Dictionary Of Incompatibles

Acacia gum, with alcohol, borax, ferric chloride, lead subacetate, and sulphuric acid.

Acid, acetyl-salicylic, with potassium iodide and other substances decomposed by weak acids. Splits up with water into acetic and salicylic acids.

Acid, arsenious, with lime-water, magnesia, iron oxide, and vegetable astringents.

Acid, benzoic, with ferric salts, lead acetate, and mercuric chloride.

Acid, carbolic, with chloral hydrate, ferrous sulphate, and lime.

Acid, chromic, with alcohol, arsenious acid, ether, glycerin, and organic solvents and substances. (Dangerously explosive.)

Acid, citric, with acetates, potassium tartrate, and sulphides.

Acid, gallic, with iron salts, spt. aether, nit., and metallic salts generally.

Acid, hydrobromic, same as hydrochloric.

Acid, hydrochloric, with lead and silver salts and tartar emetic.

Acid, hydrocyanic, with copper, iron, and silver salts, mercuric oxide, morphine solutions,and sulphides.

Acid, hypophosphorons, with mercuric chloride.

Acid, nitric, with ferrous salts, lead acetate, and many organic substances {e.g., carbolic acid), which it may, in strong solution, oxidise.

Acid, nitro-hydrochloric, with bromides, iodides, and lead and silver salts.

Acid, osmic, with alcohol, ether, ferrous salts, organic substances, and phosphorus.

Acid, oxalic, with calcium and iron salts and mineral acids.

Acid, phosphoric, with ferric chloride and lead acetate.

Acid, picric, with alkaloids and all oxidisable substances. Should on no account be compounded with phosphorus or sulphur, as it may be fatally explosive.

Acid, pyrogallic, with alkalies, copper and iron salts, and oxidising agents.

Acid, salicylic, with iron salts and spt. aether, nit.

Acid, sulphurous, with hyposulphites.

Acid, tannic, with albumen, alkalies, alkaloids, chlorates, emulsions, ferrous and ferric salts, gelatin, metallic salts, mineral acids, and tartar emetic.

Acid, tartaric, with ammonia,- lime and potash salts, lead and mercury compounds, and vegetable astringents.

Acids generally, with all alkalies and their carbonates, and with metallic oxides. As the combining powers of acids vary, one acid may displace another from a compound- e.g., mineral acids split up acetates (acetic acid being set free), and such organic acids as benzoic and salicylic are liberated from their salts by other acids.

Albumen, with acids, alcohol, mercuric chloride, and tannin.

Alkalies, with acids, alkaloidal salts, and most metallic salts.

Alkaloidal salts generally, with alkaline and earthy carbonates, borax, iodine and its compounds, double iodides of heavy metals (e.g., Donovan's solution), mercuric chloride, syr. pruni virg., tannin, and all vegetable astringents.

Alum, with alkalies and alkaline carbonates.

Ammonium acetate, with acids, potash and soda and their carbonates, lead and silver salts, and tr. ferri perchlor.

Ammonium benzoate, with acids and ferric salts.

Ammonium bromide, with mineral acids, alkaline carbonates, chlorine, potassium chlorate and bichromate, silver nitrate, sodium nitrite, calomel, and spt. aether, nit.

AmyI nitrite, with water behaves like spt. aether, nit.

Antimony and potassium tartrate, with acacia gum, acids, alkalies, soap, calomel, tannin, and all vegetable astringents.

Antimony, golden sulphurated, with acids, bismuth subnitrate, and sodium bicarbonate.

Antipyrin, with acids, alkalies, calomel, cinchona preparations, copper sulphate, sodium salicylate, spt. aether, nit., syr. ferri iodid., tannin, and all vegetable astringents.

Apomorphine hydrochloride, with alkalies, iodine, iron salts, potassium iodide, and tannin.

Aristol, with alkalies, ammonia, mercuric chloride, and metallic oxides, or anything that decomposes iodides.

Arsenium bromide and chloride are immediately decomposed by water.

Arsenium iodide, with acids, mercuric chloride, and morphine salts.

Aspirin with water decomposes into acetic and salicylic acids.

Atropine and its salts, with alkalies, salts of mercury, and tannin.

Barium chloride, with phosphoric and sulphuric acids and their salts, carbonates and tartrates, medicinal wines, and vegetable infusions.

Bismuth subnitrate, with alkaline bicarbonates, calomel, gallic acid, potassium or sodium iodide, sulphur, golden sulphide of antimony, and tannin.

Borax, with acacia mucilage, alka-loidal salts, glycerin, and mineral acids.

Bromides, with chlorine, also iron, lead and silver salts.

Caffeine and its salts, with all alkaloidal reagents except potassium iodohydrargyrate. Also with salicylates.

Calcium glycerophosphate, with sodium benzoate. Solutions of the glycerophosphate tend to hydro-lyse, calcium phosphate being precipitated.

Calcium hypophosphite, with ferri amnion, cit.