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METHOD OF OBTAINING LIME.

violent a heat, if the native carbonate of lime were perfectlypure; but as this is seldom the case, an extreme degree of heatproduces a commencement of vitrification in the mixt stone, andenables it to preserve its solidity, and it no longer retains thequalities of lime, for it is covered with a sort of crust whichprevents the absorption of the water when it is attempted to beslaked. This is called over-burnt lime.

Remark. ..It is probably owing to tire first circumstance, thatthe lime prepared by Lord Stanhope, is so far superior to thatmet with in general.

In order to obtain lime in a state of great purity, the follow-ing method may be had recourse to.

Take Carara marble, or oyster-shells, reduce them to powderand dissolve the powder in pure acetous acid, precipitate the so-lution by carbonate of ammonia. Let the precipitate sub-side, wash it repeatedly in distilled water, let it dry and then ex-pose it to a white heat for some hours.

Rationale. ..The acetous acid in this operation unites to thelime and forms acetite of lime, disengaging at the same time thecarbonic acid, which flies off in the gazeous state: on adding tothe acetite of lime carbonate of ammonia, acetite of ammonia,and an artificial carbonate of lime are formed, from the latterthe carbonic acid is again expelled by exposure to heat, and thelime is left behind in a state of perfect purity.