12 INTRODUCTION. 
tallic oxides, and earths, and of forming with them 
certain compounds called salts. 
24. Sulphuric Acid, or Spirit of Vitriol, as it is com- 
monly called, is a liquid of a somewhat oily consistence, 
transparent and colourless as water, formed by a com- 
bination of oxygen (21) with sulphur (46). Like other 
acids, it never occurs in nature in a pure state, for it 
can no sooner be formed than it unites with earths (31), 
alkalies (42), or metals, and forms, with them, several 
well-known salts, which have the name of sulphats. 
Thus alabaster (192) and Epsom salts (199) are re- 
spectively formed by an union of sulphuric acid with 
lime and magnesia, and are denominated by chemists 
sulphat of lime and sulphat of magnesia. In like 
manner, blue vitriol (209) is sulphat of copper ; green, 
vitriol (208), sulphat of iron; and white vitriol (210), 
sulphat of zinc. 
25. Phosphoric Acid is produced by a combination of 
oxygen (21) with phosphorus (47); and, when obtained 
in a state of purity, is not a fluid, but a white and flaky 
substance. This acid, when combined with mineral 
productions, forms those salts which have the name of 
phosphats. It is very soluble in water ; and, in dissolving, 
makes a hissing noise, similar to that produced by 
plunging hot iron into water. 
26. Carbonic Acid is a compound of oxygen (21) and 
carbon, or pure charcoal (48): and in a state of gas (20) 
it forms a constituent part of the atmospheric air. It is 
also emitted in great abundance from wine, beer, and 
other liquors, in a state of fermentation, and is some- 
times found in the lowest parts of mines, where it is 
known to the miners by the name of choke damp, from 
the circumstance of its immediately extinguishing 
