Hydrogen, as its name expresses, is one of the constituent elements of water, of which it forms fifteen hundredth parts by weight, combined with eighty-five hundredth parts of oxygen. This substance, the properties and even existence of which was unknown till lately, is very plentifully distributed in nature, and acts a very considerable part in the processes of the animal and vegetable kingdoms. As it possesses so great affinity with caloric as only to exist in the state of gas, it is consequently impossible to procure it in the concrete or liquid state, independent of combination.
To procure hydrogen, or rather hydrogen gas, we have only to subject water to the action of a substance with which oxygen has greater affinity than it has to hydrogen; by this means the hydrogen is set free, and, by uniting with caloric, assumes the form of hydrogen gas. Red hot iron is usually employed for this purpose: The iron, during the process, becomes oxydated, and is changed into a substance resembling the iron ore from the island of Elba. In this state of oxyd it is much less attractible by the magnet, and dissolves in acids without effervescence.
Charcoal, in a red heat, has the same power of decomposing water, by attracting the oxygen from its combination with hydrogen. In this process carbonic acid gas is formed, and mixes with the hydrogen gas, but is easily separated by means of water or alkalies, which absorb the carbonic acid, and leave the hydrogen gas pure. We may likewise obtain hydrogen gas by dissolving iron or zinc in dilute sulphuric acid. These two metals decompose water very slowly, and with great difficulty, when alone, but do it with great ease and rapidity when assisted by sulphuric acid; the hydrogen unites with caloric during the process, and is disengaged in form of hydrogen gas, while the oxygen of the water unites with the metal in the form of oxyd, which is immediately dissolved in the acid, forming a sulphat of iron or of zinc.
Some very distinguished chemists consider hydrogen as the phlogiston of Stahl; and as that celebrated chemist admitted the existence of phlogiston in sulphur, charcoal, metals, &c. they are of course obliged to suppose that hydrogen exists in all these substances, though they cannot prove their supposition; even if they could, it would not avail much, since this disengagement of hydrogen is quite insufficient to explain the phenomena of calcination and combustion. We must always recur to the examination of this question, "Are the heat and light, which are disengaged during the different species of combustion, furnished by the burning body, or by the oxygen which combines in all these operations?" And certainly the supposition of hydrogen being disengaged throws no light whatever upon this question. Besides, it belongs to those who make suppositions to prove them; and, doubtless, a doctrine which without any supposition explains the phenomena as well, and as naturally, as theirs does by supposition, has at least the advantage of greater simplicity[40].
Table of the Binary Combinations of Sulphur with Simple Substances.
| Simple Substances. | Resulting Compounds. | |
| New Nomenclature. | Old Nomenclature. | |
| Caloric | Sulphuric gas | |
| {Oxyd of sulphur | Soft sulphur. | |
| Oxygen | {Sulphurous acid | Sulphureous acid. |
| {Sulphuric acid | Vitriolic acid. | |
| Hydrogen | Sulphuret of hydrogen} | |
| Azote | azote} | Unknown Combinations. |
| Phosphorus | phosphorus} | |
| Charcoal | charcoal} | |
| Antimony | antimony | Crude antimony. |
| Silver | silver | |
| Arsenic | arsenic | Orpiment, realgar. |
| Bismuth | bismuth | |
| Cobalt | cobalt | |
| Copper | copper | Copper pyrites. |
| Tin | tin | |
| Iron | iron | Iron pyrites. |
| Manganese | manganese | |
| Mercury | mercury | Ethiops mineral, cinnabar. |
| Molybdena | molybdena | |
| Nickel | nickel | |
| Gold | gold | |
| Platina | platina | |
| Lead | lead | Galena. |
| Tungstein | tungstein | |
| Zinc | zinc | Blende. |
| Potash | potash | Alkaline liver of sulphur with fixed vegetable alkali. |
| Soda | soda | Alkaline liver of sulphur with fixed mineral alkali. |
| Ammoniac | ammoniac | Volatile liver of sulphur, smoaking liquor of Boyle. |
| Lime | lime | Calcareous liver of sulphur. |
| Magnesia | magnesia | Magnesian liver of sulphur. |
| Barytes | barytes | Barytic liver of sulphur. |
| Argill | argill | Yet unknown. |
Sect. VIII.—Observations on Sulphur, and its Combinations.
Sulphur is a combustible substance, having a very great tendency to combination; it is naturally in a solid state in the ordinary temperature, and requires a heat somewhat higher than boiling water to make it liquify. Sulphur is formed by nature in a considerable degree of purity in the neighbourhood of volcanos; we find it likewise, chiefly in the state of sulphuric acid, combined with argill in aluminous schistus, with lime in gypsum, &c. From these combinations it may be procured in the state of sulphur, by carrying off its oxygen by means of charcoal in a red heat; carbonic acid is formed, and escapes in the state of gas; the sulphur remains combined with the clay, lime, &c. in the state of sulphuret, which is decomposed by acids; the acid unites with the earth into a neutral salt, and the sulphur is precipitated.