The unsaturated acids also received much attention, and he discovered the internal anhydrides of oxyacids, termed lactones.
Five species of oxides may be distinguished: (I) basic oxides, (2) acidic oxides, (3) neutral oxides, (4) peroxides, (5) mixed anhydrides and salts.
A typical member is nitric oxide; carbon monoxide and nitrous oxide may also be put in this class, but it must be remembered that these oxides may be regarded, in some measure at least, as the anhydrides of formic and hyponitrous acid, although, at the same time, it is impossible to obtain these acids by simple hydration of these oxides.
Mixed anhydrides are oxides, which yield with water two acids, or are salts composed of a basic and acidic oxide of the same metal.
Examples of mixed anhydrides are C10 2 and N02, which give chlorous and chloric acid, and nitrous and nitric acid: 2C102+ H20=HC102+HC103, 2N02+H20=HN02+HN03; and of mixed salts Pb203 and Pb304, which may be regarded as lead metaand ortho-plumbate: Pb0 Pb02, 2PbO Pb02.