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1. These salts with an earthy basis are discovered, bydissolving the marine salt in water, and dropping in a so-lution of any alcaline salt. The earth, of whatever kindit be, precipitates; the acid, which held it dissolved,quitting it, to unite with the superadded alcali; so that bycontinuing to drop in more of the alcaline solution, till itceases to occasion any precipitation or cloudiness, we pro-duce in the liquor, instead of the salt with an earthy basis,a true neutral salt with an alcaline basis.

2. In some sorts of marine salt, the acid united with theearth is the vitriolic. This may be known, by dropping,into a solution of the salt, a solution of chalk, or othercalcareous earth, made in the nitrous, marine, or vegetableacids. The vitriolic acid quits the earth which it was be-fore combined with, and joins itself to the calcareous earctl,forming therewith a selenitic concrete, not dissoluble orexceeding sparingly, and which therefore settles to thebottom in a powdery form; so that by continuing to dropin a due quantity of the calcareous solution, all the vitriolicacid may be separated with the calcareous earth, while themagnesia, now combined with the acid in which the cal-careous earth was before dissolved, remains in the liquoralong with the marine salt.

3. There is another method in which we can separatethe vitriolic acid, and this without communicating anyforeign impregnation to the liquor. Add to the solutionof the marine salt, some strong lime-water: the vitriolicacid unites and precipitates with the lime; and the mag-nesia, thus deprived of its acid solvent, precipitates also.Though this simple process effectually purifies the saltIrom the combination of vitriolic acid and magnesia (com-monly called bitter salt, or bittern) it does not answer sowell, tor merely distinguishing that acid, as the foregoingmethod; lime-water producing a turbidness and precipi-tation in many liquors which contain no vitriolic acid.