C̈uS⃛² + 10H² O.
Now this Formula expresses the following propositions:
‘That the salt consists of one atom of copper-oxide combined with 2 atoms of sulphuric acid and with 10 atoms of water; that the copper-oxide contains two atoms of oxygen; and that the sulphuric acid contains 3 atoms of oxygen for one atom of sulphur; that its oxygen is three times as much as that of the oxide; and that the number of atoms of oxygen in the acid is 6; and that the number of atoms of oxygen in the water is 10; that is, 5 times the number in the oxide; and that finally the salt contains, of simple atoms, 1 copper, 2 sulphur, 20 hydrogen, and 18 oxygen.
[68] System of Mineralogy, 1816.
[69] Jahresbericht, 1824, p. 119.
‘Since so much is expressed in this brief Formula, how very long would the explanation be for a more composite body, for example, Alum; for which the Formula is
K̈ S⃛² + 2A⃛l S⃛³ + 48H² O.
It would take half a page to express all which this Formula contains.
‘Perhaps it may be objected that it is seldom that any one wants to know all this at once. But it might reasonably be said in reply, that the peculiar value of the Formula consists in this, that it contains answers to all the questions which can be asked with regard to the composition of the body. 362
‘But these Formulæ have also another application, of which I have sometimes had occasion to make use. Experiments sometimes bring before us combinations which cannot be foreseen from the nomenclature, and for which it is not always easy to find a consistent and appropriate name. In writing, the Formula may be applied instead of a Name: and the reader understands it better than if one made a new name. In my treatise upon the sulphuretted alkalies I found Degrees of Sulphur-combination, for which Nomenclature has no name. I expressed them, for example, by KS6, KS8, KS10 and I believed that every one understood what was thereby meant. Moreover, I found another class of bodies in which an electro-negative sulphuretted metal played the part of an Acid with respect to an electro-positive sulphuretted metal, for which a whole new nomenclature was needed; while yet it were not prudent to construct such a nomenclature, till more is known on the subject. Instead of new names I used formulas; for example,
KS² + 2As S³,