Several conditions are requisite to enable a body to become oxygenated, or to permit oxygen to enter into combination with it. In the first place, it is necessary that the particles of the body to be oxygenated shall have less reciprocal attraction with each other than they have for the oxygen, which otherwise cannot possibly combine with them. Nature, in this case, may be assisted by art, as we have it in our power to diminish the attraction of the particles of bodies almost at will by heating them, or, in other words, by introducing caloric into the interstices between their particles; and, as the attraction of these particles for each other is diminished in the inverse ratio of their distance, it is evident that there must be a certain point of distance of particles when the affinity they possess with each other becomes less than that they have for oxygen, and at which oxygenation must necessarily take place if oxygen be present.
We can readily conceive that the degree of heat at which this phenomenon begins must be different in different bodies. Hence, on purpose to oxygenate most bodies, especially the greater part of the simple substances, it is only necessary to expose them to the influence of the air of the atmosphere in a convenient degree of temperature. With respect to lead, mercury, and tin, this needs be but little higher than the medium temperature of the earth; but it requires a more considerable degree of heat to oxygenate iron, copper, &c. by the dry way, or when this operation is not assisted by moisture. Sometimes oxygenation takes place with great rapidity, and is accompanied by great sensible heat, light, and flame; such is the combustion of phosphorus in atmospheric air, and of iron in oxygen gas. That of sulphur is less rapid; and the oxygenation of lead, tin, and most of the metals, takes place vastly slower, and consequently the disengagement of caloric, and more especially of light, is hardly sensible.
Some substances have so strong an affinity with oxygen, and combine with it in such low degrees of temperature, that we cannot procure them in their unoxygenated state; such is the muriatic acid, which has not hitherto been decomposed by art, perhaps even not by nature, and which consequently has only been found in the state of acid. It is probable that many other substances of the mineral kingdom are necessarily oxygenated in the common temperature of the atmosphere, and that being already saturated with oxygen, prevents their farther action upon that element.
There are other means of oxygenating simple substances besides exposure to air in a certain degree of temperature, such as by placing them in contact with metals combined with oxygen, and which have little affinity with that element. The red oxyd of mercury is one of the best substances for this purpose, especially with bodies which do not combine with that metal. In this oxyd the oxygen is united with very little force to the metal, and can be driven out by a degree of heat only sufficient to make glass red hot; wherefore such bodies as are capable of uniting with oxygen are readily oxygenated, by means of being mixed with red oxyd of mercury, and moderately heated. The same effect may be, to a certain degree, produced by means of the black oxyd of manganese, the red oxyd of lead, the oxyds of silver, and by most of the metallic oxyds, if we only take care to choose such as have less affinity with oxygen than the bodies they are meant to oxygenate. All the metallic reductions and revivifications belong to this class of operations, being nothing more than oxygenations of charcoal, by means of the several metallic oxyds. The charcoal combines with the oxygen and with caloric, and escapes in form of carbonic acid gas, while the metal remains pure and revivified, or deprived of the oxygen which before combined with it in the form of oxyd.
All combustible substances may likewise be oxygenated by means of mixing them with nitrat of potash or of soda, or with oxygenated muriat of potash, and subjecting the mixture to a certain degree of heat; the oxygen, in this case, quits the nitrat or the muriat, and combines with the combustible body. This species of oxygenation requires to be performed with extreme caution, and only with very small quantities; because, as the oxygen enters into the composition of nitrats, and more especially of oxygenated muriats, combined with almost as much caloric as is necessary for converting it into oxygen gas, this immense quantity of caloric becomes suddenly free the instant of the combination of the oxygen with the combustible body, and produces such violent explosions as are perfectly irresistible.
By the humid way we can oxygenate most combustible bodies, and convert most of the oxyds of the three kingdoms of nature into acids. For this purpose we chiefly employ the nitric acid, which has a very slight hold of oxygen, and quits it readily to a great number of bodies by the assistance of a gentle heat. The oxygenated muriatic acid may be used for several operations of this kind, but not in them all.
I give the name of binary to the combinations of oxygen with the simple substances, because in these only two elements are combined. When three substances are united in one combination I call it ternary, and quaternary when the combination consists of four substances united.
Table of the combinations of Oxygen with the compound radicals.
| Names of the radicals. | Names of the resulting acids. | |
| New nomenclature. | Old nomenclature. | |
| Nitro muriatic radical | Nitro muriatic acid | Aqua regia. |
| (A) | ||
| Tartaric | Tartarous acid | Unknown till lately. |
| Malic | Malic acid | Ditto. |
| Citric | Citric acid | Acid of lemons. |
| Pyro-lignous | Pyro-lignous acid | Empyreumatic acid of wood. |
| Pyro-mucous | Pyro-mucous acid | Empyr. acid of sugar. |
| Pyro-tartarous | Pyro-tartarous acid | Empyr. acid of tartar. |
| Oxalic | Oxalic acid | Acid of sorel. |
| Acetic | {Acetous acid | Vinegar, or acid of vinegar. |
| {Acetic acid | Radical vinegar. | |
| Succinic | Succinic acid | Volatile salt of amber. |
| Benzoic | Benzotic acid | Flowers of benzoin. |
| Camphoric | Camphoric acid | Unknown till lately. |
| Gallic | Gallic acid | The astringent principle of vegetables. |
| (B) | ||
| Lactic | Lactic acid | Acid of sour whey. |
| Saccholactic | Saccholactic acid | Unknown till lately. |
| Formic | Formic acid | Acid of ants. |
| Bombic | Bombic acid | Unknown till lately. |
| Sebacic | Sebacic acid | Ditto. |
| Lithic | Lithic acid | Urinary calculus. |
| Prussic | Prussic acid | Colouring matter of Prussian blue. |
[Note A: These radicals by a first degree of oxygenation form vegetable oxyds, as sugar, starch, mucus, &c.—A.]