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pfatina. When thrown into water it gives outpure oxygen gas, and passes to the state ofpotash as before mentioned. When it is heatedvery strongly upon a platina support protectedby muriat of potash, oxygen gas is given out, 0and there remains a grey difficulty-fusible sub-*tance, vitreous in its fracture which disssolvesin water with much heat but without any ef-fervescence, and renders the water alkaline.This grey vitreous substance is considered bySir H. Davy as pure potash, free from wateror any foreign hody, and it is the only knownmethod of obtaining quite pure uncombinedpotash.
This yellow oxyd has a very striking actionon all combustible bodies, to all of which itaffords its excess of oxygen : in doing so itreturns to the state of potash, and the alkalithus generated often unites with some or otherof the products. Some particulars of these ex-periments we shall mention.' 1
Phosphorus heated with the peroryd in anatmosphere of azotic gas produced a very vividcombustion, so as to redden the whole of theplatina capsule in which it was contained. Theazote was unchanged. Part of the phosphoruswas burnt and part only volatilized. The pro-duct did not effervesce with water and withdifficulty dissolved in it, though the salts of lime-and barytes gave considerable precipitates. Theproduct of this combustion was probably sub-phosphat of potash.
Sulphur heated in like manner with the per-oxyd gave a compound which no longer effer-vesced with water {and therefore contained nouncombined oxygen) and smelt of liver of sul-phur, and at the same time gave a copious pre-cipitate with nitrat of barytes, and hence- con-tained a mixture of a little sulphuret of potash,with much sulphat.
Charcoal and the peroxyd heated togethergave carbonat of potash.
The following metals, namely, tin, arsenic,antimony, zinc, copper, bismuth, lead and iron,all in fine filings, were separately heated withthe peroxyd. In all the peroxyd was reducedto the state of potash but with some variationin the attending circumstances. With the tin,antimony, and arsenic, there was a great dis-engagement of heat and light, particularly withthe former, so that both the capsule of platina on.which the materials were placed and the glassvessel that confined them were made red-hot.The zinc and copper were but feebly ignited, and
the bismuth, lead and iron not at all. The lier.t*-was applied in all these cases with a spirit lampson the outside of the glass vessel. By putting,the product in water all the metallic oxydswere obtained except those soluble in the alkali:generated in the experiment.
The peroxyd and potassium heated togetherin the same way produced potash with muchdisengagement of light and heat..
The peroxyd was introduced into an atmos-phere of hydrogen confined by. mercury. No-effect was produced at a common temperature,but en heating it a rapid, absorption of gastook place with abundance of moisture which-streamed down the sides of the vessel, the per-oxyd whitened and gradually became changed',into pota.sh. No light was disengaged.
Phosphuretted and sulphuretted hydrogenheated with the peroxyd produced in like man-ner water and potash, and sulphuret and phos-phuret- of potash.
With ammoniaoal gas and the peroxyd theproducts Were water and azotic gas.
The peroxyd was heated with muriatic acid-gas.. Much of the. gas was absorbed; drops ofwater trickled down the sides of the vessel,oxygen gas was given qut, and yellowish white-muriat of po'tash was formed, but no oxymuri—atic acid, nor was any light produced..
With carbonic aaid gas the peroxyd whenheated gave out oxygen gas, and carbonat ofpotash was produced which strongly effervescedwith acids, but no water was generated.
The peroxyd was heated with sulphureous,acid gas and the experiment was- conducted ,with much care.- The gas was carefully dried,and had the- specific gravity of 2,2553 (com-mon air being 1.) the quantity of it as well as ;that of the peroxyd of potassium was weighed,,as also was each of the products after the expe-riments. As soon as the heat was applied a;brisk inflammation took place and an abundant-absorption of gas. Sulphat of potash was;formed, and a little oxygen gas, but not a trace-of aqueous vapour.. The oxygen was then se-parated from the undecomposed sulphureous,acid, and the weights of the two gasses, addedto that of the sulphat of potash, , were found to -equal that of the sulphureous acid gas and of.tlie peroxyd of potassium employed.
The peroxyd was heated in nitrous gas, butwithout any particular estimation of quantities.Much absorption took place, very red nitrousacid gas appeared, and a salt was melted to the