" Take of bruised heart-leaved cinchona, seven pounds; sulphuric acid, nine ounces; purified animal charcoal, two ounces; hydrated oxide of lead, solution of ammonia, distilled water, of each, as much as may be required. Mix four ounces and two drachms of the acid with six gallons of distilled water, and add to them the cinchona; boil for an hour, and strain. In the same manner, boil the residue with the same quantity of acid and water for an hour, and strain. Finally, boil the cinchona for three hours in eight gallons of distilled water, and strain. Wash the residue frequently with fresh quantities of boiling distilled water. To the liquors mixed together add the oxide of lead, still moist, to saturation. Pour off the supernatant fluid, and wash the precipitate with distilled water. Boil down the liquors (including the washings) for a quarter of an hour, and strain: then gradually add solution of ammonia to precipitate the quina. Wash this until no alkali be perceptible. Let the residue be then saturated with sulphuric acid diluted. Afterwards digest with two ounces of animal charcoal, and strain.

Finally, all the charcoal being washed, evaporate carefully the liquor that crystals may form."

In this process, the kinate of quina is taken up more readily by the acidulated water than it would be by simple distilled water. The addition of the hydrated oxide of lead frees the quina from the sulphuric acid, which is precipitated in the form of sulphate of lead, leaving the kinate of quina in solution." The ammonia abstracts the kinic acid and forms with it a soluble kinate of ammonia, whilst the freed quina, being little soluble, is thrown down. The disulphate is the result of the addition of the acid to this precipitate; it is freed from the colouring matter by digestion with the animal charcoal. The salt readily crystallizes. The Quantity of the di-sulphate obtained is very variable: it is mixed with a small proportion of disulphate of cinchonia.

This salt is chiefly manufactured in Paris, whence, Dumas informs us, 120,000 ounces are annually exported. It is frequently adulterated either with sugar, or gum, or starch, or sulphate of lime, or acetate of lime. The sugar is readily detected by dissolving the suspected salt in water, and precis pitating the quina by liquor potassae; as this destroys the bitterness of the solution, the presence of the sugar becomes obvious by its taste. Gum and starch are detected by digesting the salt in strong alcohol: the disulphate is dissolved and the impurities are left. The sulphate and acetate of lime are detected by exposing the suspected salt to a strong heat; the disulphate of quina is totally consumed, whilst the lime of the adulterating salts remain.

Qualities. - The disulphate of quina crystallizes indelicate acicular crystals, inodorous, and impressing a bitter taste on the palate. They require for their solution 740 parts of water at 60°, and 30 parts at 212°: but 80 parts only of cold alcohol of sp. gr. 850. They dissolve freely in alcohol at 212° : and effloresce when exposed to dry or heated air. The constituents of the salt are 2 eq. of quina = 329.1 + 1 of acid = 40.1 + 10 eq. of water = 90; making the equivalent 529.2 : or of 74.31 parts of quina + 9.17 of acid + 16.52 of water in 100 parts.

Disulphate of quina is incompatible in prescriptions with alkalies and their carbonates, lime-water, chloride of calcium, the salts of baryta, those of the oxide of lead, and astringent vegetable infusions and decoctions. It may be administered with sulphate of iron, and all the sulphates, and with acetate and hydrochlorate of morphia.

Medical properties and uses. - Disulphate of quina is a stimulant, tonic, and antiperiodic. It excites the tissues to which it is applied, and being taken into the circulation, augments the vigour and regulates the action of the heart and arterial system. Owing to its topical influence, in irritable states of the mucous membrane, and when over-dosed, it disorders the digestive organs, causing heat in the epigastrium, foul tongue, nausea and headach; and, in plethoric habits, haemorrhages. In doses, not exceeding a grain, dissolved in f iss. of acidulated infusion of roses, or of the confection of roses, it is an excellent tonic in dyspeptic affections; and in doses of two grains to three grains given every second hour, in the intervals of the paroxysms of ague, it rapidly checks the progress of the disease.

Some practitioners administer from grs. viij. to grs. x. immediately before the accession of the paroxysm; but my own experience is in favour of small doses at short intervals. M. Sadillot recommends it to be administered in the following form, in combination with opium : - Quinae Disulphatis grs. xij.; Opii grs. iij.; Confect. Rosae q. s. fiant pilulae x.; one every hour or two in the intermission of ague. As a general tonic, when the mucous membrane is in an irritable condition, or when diarrhoea is present, the decoction of the bark is preferable to the disulphate of quina. The dose as a simple tonic is from gr. j. to grs. ij.; as an antiperiodic, from grs. ij. to grs. xij.