TRIPLE
SALTS.

§ 75.

The compound ſalts hitherto enumerated are ſuch as are compoſed of two ingredients only; but ſometimes three or more are ſo united as not to be ſeparated by chryſtallization. The vitriols that we are acquainted with are hardly ever pure, and two or three of them ſometimes are joined together.

Sometimes likewiſe it happens that neutral ſalts join earthy ſalts, and earthy ſalts metallic ones. I generally diſtinguiſh compound ſalts according to the number of their principles, whether the ſame acid be joined to ſeveral baſes, or the ſame baſis to different acids; or laſtly, whether ſeveral menſtrua and ſeveral baſes are joined together. Hence ariſe ſalts triple, quadruple, &c. which the diligence of after times muſt illuſtrate. I ſubjoin the moſt remarkable examples of triple and quadruple native ſalts which have occurred to me.

§ 76.

ALKALI MINERALE Salitum (common ſalt) contaminated by magneſia ſalita. The common ſalt when pure does not deliqueſce, but this degree of purity is ſeldom found, and in the native foſſil production (ſal gem) never.

§ 77.

MAGNESIA vitriolata (Epſom ſalt) contaminated by ferrum vitriolatum[[36]] (vitriol of iron.)

§ 78.

ARGILLA vitriolata (alum) native, contaminated by vitriol of iron. In the aluminous ſchiſtus it ſometimes effloreſces in a feathery form. Is this the plumoſe alum of the antients?