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ing it up to the surface, leaves the full quantity of the pla-tina to shew its colour in the acid liquor. By this me-thod, a most minute proportion of platina may be distin-guished, a little of this metal giving a high colour to a sur-prisingly large quantity of the menstruum.

The method of preparing the æther is described bymany chemical writers, but the most safe, easy, andcertain process I have met with, is that which Dr. Morrishas favoured the publick with in the medical observationsand inquiries of a society of physicians in London. Nineparts by weight of oil of vitriol are poured, by two ouncesat a time, at intervals of a quarter of an hour, into eightparts by weight of rectified spirit of wine, in a large stonebottle : after standing for a night, the mixture is decantedfrom one vessel to another three or four times, and thenconveyed, through a long-necked funnel, into a retortcapable of containing three times the quantity. Theretort is set on a little sand in an iron pot, and moresand put round it up to the height of the mixture : alarger receiver being luted on, with some strips of wetbladder, a small hole is made in the luting with a pin :the fire is raised somewhat hastily, till an ebullition ac-companied with large bubbles is observed in the mixture;aster which the fire is to be entirely removed, the heat ofthe sand being sufficient for completing the distillation.The distilled liquor is put into a clean retort, with twoor three ounces of fixt alkaline fait: about half the liquoris drawn off, by a very gentle heat, into a large receiver;and this being shaken with an equal quantity of pumpwater, the pure æther rises immediately to the top.

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