Alkali

"Closely allied to, and sometimes regarded as identical with, the alkalis, was the group of earths. These bodies were known to neutralise acids and affect colouring matters like alkalis, but they were much less soluble in water than the alkalis."

"It was taught by some chemists that an alkali is hidden in every earth, and by others that an alkali is an earth refined by the presence of acid and combustible matter. Black's exact quantitative investigations tended to disparage all such explanations as these; but it yet remained to find the precise composition the alkalis and the earths."

"Lavoisier thought that these bodies must be compounds; but, as he had no means of proving this, he classed them with the elements, while suggesting that the earths were probably compounds of oxygen with unknown metals."

"In 1807 Davy decomposed two alkalis, and soda, by passing an electric current through these substances when molten; and a year later he succeeded, by the same agency, in separating the earthy bodies lime, baryta, and strontia, into oxygen and, in each case, a metal."

"The name alkali is now generally applied to the compounds of and oxygen with one or other of the five metals, , , , , cæsium (v. Alkalis, Metals of the); an aqueous solution of is also regarded as containing an alkali, viz. a compound of hydrogen and oxygen with the radicle ' (v. Ammonium Compounds)."

"The alkalis are classed with the s, i.e. compounds of hydrogen and oxygen with a third element, rather than with the hydrates, i.e. compounds of water with an oxide or a salt. (v. Hydrates)."

"The general formula of the alkalis is written MOH rather than M2OH2O; M = Li, Na, K, Cs, Rb, or NH."

"The alkalis are very soluble in water; these solutions neutralise acids forming salts, and also precipitate most of the heavy metals from their solutions in the form of oxides or hydrated oxides; aqueous solutions of the alkalis act corrosively on animal and vegetable substances, and also alter the tint of many colouring matters."

"When moist, the alkalis, with the exception of , readily combine with to form s."

"Lithia is much less soluble in water than the other alkalis."

"The solid alkalis are not decomposed by the action of heat alone."