478 OF OURCKZLIME

pouring upon this re/fduum, therefore, fome nitrous or muriatic acid,#nd treating it as directed§ 13, p. 508, the calcareous earth that was in the gyp/um will be now entirely diffolved; fo that when it is filtered and dry, the difference between the weight of this refiduum, and what it formerly was, is the real weight of the gyp/um originally contained in the lime ftone.

N.B. If the alkali employed to decom- pofe the gypfum was in a mild ftate, the calcareous earth that remains will effer- veice ftrongly when it is diffolving in the acid;—but if a cauftic alkali has been em- ployed, the{olution will be effe@ted with- out any effervefcence at all.

“\s vitriolated tartar is not readily foluble in water a confiderable quantity of water requires to. be employed, which ought’ al- ways to be hot, that the folution may be effected the more readily.

§ 3.

ft has alfo been faid,(§ 30, p. 274) that

the only extraneous matter contained in

hime-ftone is fand. But although fand, in general does predominate fo much over the other extraneous matters in lime-ftone, as to authorife the expreffion i general, yet there