Aldehydes
in chemistry, pounds formed by the oxidation of alcohols, and are reconverted into alcohols by the action of nascent hydrogen; by further oxidation they are converted into acids. They differ from alcohols in having two atoms less of hydrogen, which are removed from the carbon atom containing the radical HO' (hydroxyl) con connected to it in the alcohol; thus the aldehyde monatomic radical is (O=C-H)'. Many aldehydes of monatomic alcohols have been prepared by oxidation of the alcohols, or by distilling a mixture of the potassium salt of the corresponding acid with potassium formate, which yields potassium carbonate and the aldehyde. Aldehydes form crystalline compounds with acid sulphites; they also unite with aniline. Ketones are aldehydes in which the atom of hydrogen united to the radical (CO)" is replaced by a hydrocarbon radical.