"Take of solution of carbonate of ammonia, any quantity; expose it, in a proper apparatus, to a stream of carbonic acid gas, extricated from white marble by diluted muriatic acid; when the effervescence is over, the crystals are to be dried without heat, and preserved in closely stopped vessels."

The theory of this operation requires no explanation: the result is a salt, a carbonate, crystallized in small six-sided prisms, having scarcely any odour, and less taste than the sesquicarbonate. It is volatilized by heat; dissolves in eight parts of water; and is decomposed by potassa with the disengagement of ammonia. It may be obtained by the exposure of the sesquicarbonate to the air. According to Mr. Phillips, it is a compound of 55.70 of carbonic acid, 21.52 of ammonia, and 22.78 of water, in 100 parts: or of 2 eq. of carbonic acid (22.24x2) =44.48+1 ammonia = 17.15 +2 water (9x2) = 18, making the equivalent = 79.63.

Medical properties arid uses. - The same as those of the sesquicarbonate. Its dose is from six to twenty-four grains. It may be given in combination with sulphate of magnesia.