1815.) On Dalton’s Theory of Chemical Composition. 373 
planation of a connected agreement in these five compounds, which 
would be destroy ed bya small variation in the composition of any 
one of the five 
In the following nine ebinpounds, seven of which are solids, the 
same principle is found to prevail with as much uniformity as in the 
gaseous fluids and water, which we have been comparing. 
1. 100 grains of sulphurous acid contain 50 grains of sulphur * 
and 50 grains of oxygen; that is, nearly in the proportion of 14 
sulphur to 14 oxygen, 
2. 100 grains of sulphuric acid contain 40°6 grains of sulphur 
and 59°4 grains of oxygen ; ghat is, nearly in the proportion of 14 
‘wilpbiar te 21 oxygen. 
3. 100 grains of black oxide of iron contain 78 grains of iron t 
and 22 grains of oxygen; that is, nearly in the proportion of 50 
iron to 14 oxygen. 
4. 100 grains of red oxide of iron contain 704 grains of iron t 
and 29: grains of oxygen; that is, nearly in the proportion of oA 
iron to 21 oxygen. 
5. 100 grains of sulphuret of iron contain 78 grains of iron ig 
and 22 grains of sulphur; that is; nearly in the proportion of av 
iron to 14 sulphur. 
6. 100 grains of magnetic pyrites contain 64 grains of iron || aiid 
36 grains of sulphur ; that i is, nearly in the proportion of 50 iron to 
28 sulphur. 
7. 100 grains of pyrites of Soria contain 54°3 grains of iron I . 
and 45:7 grains of sulphur; that is, nearly in the proportion of 50 
iron to 42 sulphur. 
8. 100 grains of common pyrites contain 47.grains of iron {| and 
53 grains of sulphur; that is, nearly in the proportion of 50 iron 
to 56 sulphur. 
9. 100 grains of sulphate of iron contain 49°78 grains of red 
oxide of iron ** and 50°22 grains of sulphuric acid; that is, nearly 
in the proportion of 71, red oxide of iron to 70 sulphuric acid. 
If we suppose, as before, the relative weight of an atom of 
oxygen to be as 7, and if we further suppose those of sulphur and 
iron to be respectively as 14 and 50, we shall have, 
Ist. In sulphurous acid, each atom of sujphur united to twoatoms 
of oxygen. 
2d. In sulphuric acid, each atom of sulphur united to three atoms 
of oxygen. 
3d. In black oxide of iron, each atom of iron united to two atoms 
- of oxygen. 
Ath. In red oxide of iron, each atom of iron united to three atoms 
of oxygen. 
* Davy, 274. + Berzelius, Ann, de Chim, Ixxviii, 44, 
t Davy, 110. § Vauquelin. 
|) Hatehett and Proust, Nich. Jour, x. and xi, 
** Berzelius, Ann, de Chim, Ixxviii, 218, 
