394

ELEMENTS OF MATERIA MED1CA,

burned with phosphorus are to be washed with a weak alkaline Solution, to re-move any adhering acid which might serve to keep up irritation.

1. TINCTUM ETHEREA CUM PIIOSPHORO, French Codex.— (Phosphorus 4 parts,Sulphuric Ether 200 parts by weight. Macerate for a month, in well-stopperedöottles covered with black paper, occasionally shaking. Preserve it in small bot-fles, well stoppered and covered with black paper. The quantity of phosphorusdissolved is about 4 grains for each ounce of ether. Dose from 5 to 10 drops.Some objection has been raised to the use of this preparation on the ground that,by the evaporation of the ether, the phosphorus will be set free in the stomach, andmight ignite.

PHOSPHORATM, Ph. Bonwiear- (Phosphorus dry and cut into smallpieces, gr. xij.; Almond Oil, recently prepared, 3j. Melt the phosphorus in theoil by the aid of warm water: then agitate until it appears to be dissolved.) Oneounee of oil dissolves about 4 grs. of phosphorus. Dose from 5 to 10 drops. Itshould be administered in some mucilaginous liquid, or made into an emulsion.It may be aromatized by a few drops of some essential oil, as of bergamot.

2. AC'IDUM PHOSPHOR'ICUM DILUTUM, £.—PHOSPHORIC ACID.

History. —Phosphoric acid was first distinguished by Marggraf, in 1740.Natural History. —(See Phosphorits.)

Preparation. —In the London Pharmacopoeia, diluted phosphoric acid is or-dered to be thus prepared:—

Take of Phosphorus, gj.; Nitric Acid, f^iv.; Distillcd Water, fgx. Add the phosphorusto the nitric acid, rnixed with the water, in a glass retort placed in a sand-bath ; then applyheat until eisjht fluid ounces are prodaced [distilled.] Let these be ngain put into the retortthat eight fluid ounees may distil, which are to be rejeeted. Evaporatc the remaining liquorin a platinum capsnle until only two ounces and six drachms reniain. Lastly, add to theacid, when it is cold, as mucli distilled water as may raake it accurately measure twenty-eight fluid ounces.

In this process six equivalents or 90 parts of phosphorus react on five equiva-lents or 270 parts of nitric acid, and abstract fifteen equivalents or 120 paits ofoxygen, with which they form six equivalents or210 parts of phosphoric acid,while five equivalents or 150 parts of the binoxide of nitrogen are evolved.

MATERIALS.

5 eq. Nitric Acid

270

COMPOSITION.

5 eq. Nitrogen ..

10 eq. Oxygen ....

. 15 eq. Oxygen ----

70)

BOj

120.

6 cq. Phosphorus......... 96

368

■ 5 eq. Binox. Nitrogen ...... 150

6 eq. Phosphoric Acid...... 216

366

If strong nitric acid be employed, instead of the dilute acid ordered in thePharmacopreia, the re-action is so energetic that explosion and combustion aresometimes the consequence. In such cases some nitrate of ammonia is usuallydeveloped: the ammonia being formed by the union of the nitrogen of the acidwith the hydrogen of the water.

Properties. —The aqueous Solution of phosphoric acid [acidum phosphoricumdilutum, Ph. L.) prepared as above, is a colourless and odourless liquid. Itpossesses the usual characteristics of an acid; that is, it is sour to the taste, red-äens litmus, and neutralizes bases. Its sp. gr., according to the London Pharma-copoaia, is D064. By evaporation it acquires the consistence of treacle (hydratedphosphoric acid:) and when exposed to a higher temperature, it loses water andbecomes pyrophosphoric acid. At a dull red heat a farther evolution of watertakes place, and a Compound is formed, called melaphosphoric acid; this is fusi-ble, and by cooling concretes into a transparent solid, called glacialphosphoricacid.

Characteristics. —If phosphoric acid be saturated with an alkali (soda) so as to