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riated magnefia by lime, and of Glauber’s faitby muriated lime, that Gren has propofed aningenious method of feparating the deiiquelcentearthy muriats from brine, and increaling theproportion of common fait, by the addition oflime, or Glauber’s fait, or both, according tothe following cafes:

r. If the brine contains, befkles commonfait, only muriated lime, the addition of Glau-ber’s fait is fufficient, which by decompofingthe calcareous muriat produces felenite. andcommon fait, as already mentioned.

2. If the lime contains, befides common fait,Glauber’s fait and muriated magnefia, the ad-dition of lime alone will fuffice, which, as wehave before defcribed, firft decompofes themuriated magnefia, and the refulting muriat oflime then decompofes the Glauber’s fait.

3. If the brine contains, befides commonfait, only muriated magnefia, both lime andGlauber’s fait mull be added, for obviousreafons.

4. If the brine contains, befides commonfait, fulphat and muriat of magnefia, lime andGlauber’s fait mud alfo be added.

5. If the brine contains, befides commonfait, fulphat and muriat of magnefia, and ful-phat of foda, lime alone will be fufficient ifthe Glauber’s fait be in fufficient quantity, ifnot, an additional quantity of the latter faitmuft alfo be added.

We know not whether any of thefe methodshave been adopted in the manufa&ure of faitin the large way, neither would they be re-quired in the Englifh rock fait and brine workson account of the very fmall proportion of im-purities, and which do not appear to throwmuch obftacle to the goodnefs of the fait, butin the falterns from fea-water, where the faltsof lime and magnefia are abundant, the ingeni-ous ideas of Gren might be adopted to advan-tage. The greateft objection would be in thecoll of Glauber’s fait, but it might be probablycollefted in winter, from fulphat of magnefiaand common fait, at a moderate expenfe, andfrom the remaining muriat of magnefia, theearth might then be precipitated by a carhonatedalkali.

Sulphat of foda is largely ufed in medicine,being a very ufeful, powerful, and cheap pur-gative. It is no otherwife ufed in manufacturethan as a material from which the foda may beextraCled by any of the methods already de-fcribed under the article muriat of foda.

When fulphat of foda is diffolved in dilute

fulphuric acid and fet afide to cryftaliize, Itdepofits large rhomboidal cryftals, d which con-tain an excefs of acid, and are therefore a fuperfulphat of foda.

If dry fulphat of foda is heated in a glafs orplatina vefl'el with concentrated fulphuric acid,they melt together as the mixture of fulphat ofpotafh and fulphuric acid do, but the acid inthis cafe is readily driven off by a moderatecontinuance of heat, and the remaining fait re-difl'olved in water, yields cryftals of commonGlauber’s fait.

But a mixture of equal parts of fulphat ofpotafh and foda retain an excefs of fulphuricacid almoft as obftinately as fulphat of potafhalone does. In all thefe cafes the excefs ofacid may be got rid of moft accurately, with-out affeCting the neutral fait, by diffolvingthe whole in water, fuperiaturating it with car-bonat of ammonia, evaporating the mixturecarefully to drynefs, and then applying a mo-derate red heat. A denfe white fmoke arifesbefore the mixture is red-hot, which is fulphatof ammonia, and by continuing the heat aslong as a particle of vifible fmoke rifes, all theexcefs of acid is volatilized along with the am-monia, and the neutral fulphat of potafh orfoda, remains perfectly pure, white and dry.It is probable however that a fmall portion ofthe neutral fait would be found to have beenvolatilized along with the fulphat of ammonia,but this lofs can only be very fmall, and theaCtual quantity might be eafily afeertained by afew comparative experiments.

Sulphat of Ammonia. Glauber's SecretSal-Ammoniac.

This fait has not been found native. It maybe prepared by faturating moderately dilutefulphuric acid with ammonia, and evaporatingconfiderably. It then cryftallizes on cooling,in hexahedral prifms terminated by hexahedralpyramids, or often in filky needled cryftals.This fait is produced in the manufacture of fal-ammoniac, but only as an intermediate product,and is immediately decompofed by commonfait, producing Glauber’s fait and muriatedammonia.

Sulphat of ammonia is very foluble in water,requiring only twice its weight of cold, andmuch lefs of boiling water. This fait is veryllightly deliquefeent in the air. It generatesmuch cold during folution.

When a quantity of this fait is heated per fein a retort, and all the products received in

Thomfon.