24 CHEMISTRY. 
carbon, phosphorus, sulphur, selenium, and silicium ; all the rest are metals. 
As far as any brief generalities can be made respecting the combinations 
of these simple substances, we may say that almost all the non-metallic 
elements combine in definite proportions with the metallic when brought 
together in a liquid state, while the non-metallic bodies, as well as the 
metals, either come together in any proportion, or else do not unite directly 
into a homogenevus whole. The instruments in which experiments of the 
kind are conducted, are retorts (pl. 30, fig. 25, and 26), matrasses (figs. 
27, 28, 29), and crucibles (figs. 30, 32, and pl. 31, fig. 57), the application 
of all which has already been explained. 
lV. CuemicaL SyntTHEsis AND ANALysis. Tur AppARATUS REQUIRED. 
It has already been remarked that simple bodies do not often combine 
with compound, but compound unite with compound just as simple with 
simple. In by far the most cases we have in chemistry to deal with the 
combinations of compound bodies, and in chemical analysis we obtain two 
binary compounds as the result, as for instance a combination of oxygen 
and a metal on the one hand, and of oxygen and a non-metallic body on the 
other. The compounds of oxygen with the non-metallic bodies, sulphur, 
carbon, nitrogen, are generally acids; the combinations of oxygen with 
metals are rarely acids, and exhibit in most cases a great tendency to 
unite with acids to form asalt. Potash, for instance, consists of carbonic 
acid and oxyde of potassium or pure potassa; the former being composed 
of carbon and oxygen, the latter of oxygen and potassium. This potassa 
has so great a tendency to combine with carbonic acid as to seize hold of 
it whenever the two come into contact, to form the carbonate of potassa. 
These oxydes which stand in such a relation to acids are called bases, the 
compound itself is a salt. The tendency of one base to combine with two 
or more different acids is very different, this difference being indicated by 
the terms greater or less chemical affinity. It is hence readily intelligible 
that an acid which has a greater afhnity for one base than another, may 
take the former from a combination which it may already have formed. 
On this principle depends the development of carbonic acid gas in the 
generating apparatus (p/. 31, fig. 46), which at the same time constitutes 
avery simple gasometer. In the glass cylinder A is placed a second 
cylinder, B, whose superior opening is fastened to the cover of AA, and, 
connected with a pipe provided with a cock, may be closed or opened by 
means of a cock at a, seen also in fig. 45. The wire C is suspended from a 
small hook in the tube, and carried beneath the bottom D, which is thus 
suspended a little above the lower end of B. By placing pieces of carbonate 
of lime (limestone, marble, or chalk) in the bottom D, and filling the cylinder 
A about half full of dilute sulphuric acid, the liquid will rise in A as soon 
as this is set in B. On opening the cock a, the dilute acid will rise still 
higher in B, driving out the inclosed air and covering the carbonate of 
lime. As sulphuric acid has a greater affinity for lime (oxyde of calcium) 
454 
