OX′YCRATE. Syn. Oxycratum, L. The old name of a mixture of vinegar and water, dulcified with honey.
OXYCRO′CEUM. See Plasters.
OX′YGEN. O. Syn. Oxygen gas, Dephlogisticated air†, Empyreal a., Vital a.†; Oxygenium, L. An elementary body discovered by Scheele and Priestly in 1774. It is remarkable that, although this substance forms a large proportion of our atmosphere (nearly one fourth), and confers upon it the power of supporting respiration and combustion, and also constitutes the principal portion of the water of our rivers and seas (eight ninths), and enters largely into the composition of the majority of the various mineral bodies that form the bulk of our globe, its existence should have remained unsuspected, or at least undetermined, until a comparatively recent date. Oxygen is an essential constituent of all living organisms. It is absorbed by animals during respiration, and evolved in a free state by growing vegetables when exposed to sunlight. The oxygen gas of the atmosphere is mechanically mixed, not chemically combined, with the nitrogen.
Prep. 1. From red oxide of mercury, heated over a spirit lamp or a few pieces of ignited charcoal. The operation is usually performed in a small green-glass retort, or in a short tube of hard Bohemian glass, closed with a perforated cork furnished with a piece of bent glass tube of small bore, to convey the liberated gas to the vessel arranged to receive it. Pure. 1 oz. yields about 100 cubic inches.
2. From chlorate of potassium, as the last. Pure. 100 gr. yield nearly 100 cubic inches (Brande; 115—Ure). This is the plan adopted in the P. Cod. The decomposition occurs with both the above substances at a heat below that of redness.
3. From a mixture of chlorate of potassium (in coarse powder), 3 parts; powdered binoxide of manganese, 1 part; both by volume. Pure. 100 gr. of the mixture yield about 110 cubic inches as oxygen. This method, which has received the approval of Faraday, is exceedingly convenient. The gas is evolved with a rapidity which is entirely at the command of the operator by simply increasing or lessening the heat. The residuum in the retort may be kept for another operation, if not exhausted; or it may be at once washed out with a little warm water, and the manganese, which is uninjured by the process, reserved for future use. Red lead, black oxide of copper, red oxide of iron, and several other substances, answers nearly as well as binoxide of manganese.
4. From a mixture of bichromate of potassium, 3 parts; oil of vitriol, 4 parts; gently
heated, as before. Yields pure oxygen very freely, and with a rapidity entirely at the will of the operator. (Balmain.)
5. From binoxide of manganese and oil of vitriol, equal parts; as the last. 44 gr. of pure binoxide of manganese yield 8 gr., or 24 cubic inches, of oxygen; 1 oz. yields 88 gr., or 256 cubic inches. (Liebig.)
6. (On the large scale.)—a. From nitre exposed to a dull red heat in an iron retort, or gun-barrel. 1 lb. yields about 1200 cubic inches of gas, contaminated, more or less, with nitrogen. (Ure.)