of potash, that it is scarcely possible scdialhliadae ae eta: 
are) waa suger Soda, it is said, attracts humidity from 
Oo! less rapidly than potash. 
Tris by their combinations, however, that they are principally: Je 
tinguished. The salts, in particular, which soda forms with the _ 
acids, are totally different in their properties from those that have 
potash for their base. It forms glass with silex in the same manner 
as potash. 
Soda is obtained as well as potash by burning vegetables. Tt is, 
however, only sea plants, or those that grow by the sea shore, that afford 
it: it has therefore been supposed, that these plants may contain sea= 
salt, or poriniat 20a; wedi, aa tees Sie deaaapataat of this: 
salt that the soda is derived. =~ a 
The third of these alkalies, AMMONIA, differs inuch from the 
others. It can never be obtained in the solid or fluid form, but when 
pure, is always in a state of gas: it is absorbed in great quantity 
by water, and thus forms a solution of pure ammonia. Its smell is 
extremely pungent: it is also volatile, escaping gradually from the 
water in which it has been dissolved : hence it has received the g 
pellation of volatile alkali. It is considered as a less powerful alkali 
than either of the others: it does not combine with the siliceous 
earth ; it acts more feebly on animal matter, and it ; 
acids with much less force. es 
Ammonia i is com of azot and h 0) 
121 of the f ae deesde laser droge, the in reat qcaistie beg 
ty by exposing animal substances to heat : they are ons ae = 
part of their hydrogen and azot combining, form ammonia. ee? 
~The alkalies are all used in medicine, and their ‘Ss 
form some ‘of the most important axtibbes of the materia medica, 
They are also important pharmaceutic agents. 
With the alkalies, earths, and metallic ‘oxyds, the acids Soins 
and form an order of compound termed NEUTRAL SALTs. In these, _ 
the properties of the acid, as well as of the base with which it is uni- 
ted, are in general lost; ‘the compound acquires some new proper- 
ties : it has in general a considerable attraction for water, and itis _ 
capable of assuming a crystalline form. The acids adhere with very oe 
different degrees of force to these bases; in general the attractions 2 
of the earths to the acids are greater than those of the metallic oxyde; 
and those of the alkalies greater than of the earths. . 
_ Phe names of the neutral salts are taken partly from the acid, and — 
partly from the base ; the generic name is derived from the acid, the 
specific from the base to. which it is united. ‘Thus, all the salts 
composed of the sulphuric acid, are poe ga together under the 
name of sul phats ; and each species is named from ab Fx: 
which the acid is united, as the sulphat of ae the sulj 
lime, &c.: and as each acidifiable basecan be combified with ; 
ent proportions of oxygen, so as to form acids of different qua 
the salts formed by these are distinguished by a variation, in the 
mination of the generic name. ‘Thus, the salts by 
eee ¢ compourid. i is een ideal: oe 
ay remains to notice he analysis of the vecerasul 
a 
_ = Z 
