ALR

A LK

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'bottom of the retort which was nitrite of pot-•ash. Nitrous oxyd produced no alterationwhatever on the peroxyd of potassium.

The peroxyd may be made by heating po-tassium either in oxygen or in nitrous gasor in nitrous oxyd. In the latter cases, thepotassium becomes highly oxydated at first,but on continuing the heat, seems to returnto the state of alkali, and nitrite of potash isformed.

The French chemists, whose experiments weare now describing, consider the peroxyd ofpotassium as containing three times as muchoxygen as the quantity necessary to convert po-tassium into potash; so that if potash consistsof 84. parts by weight of potassium to 16 ofoxygen, the peroxyd of potassium will consistof 84 of potassium to 48 of oxygen, or 03.64per cent, of potassium and 36.36 of oxygen.

Potassium and Hydrogen . These combineneither at a common temperature nor at a red-heat, but readily at an intermediate degree,such as is produced by a spirit-lamp. Potassiumthus heated in hydrogen gas absorbs it rapidly,but gives it out again with equal ease whenthe proper degree of heat is exceeded. Theactual quantity of hydrogen absorbed seems tovary considerably, but on an average it appearsto be about a fourth of the quantity whichwould be produced by immersing the potassiumin water. This Hydruret of Potassium is grey,unmetallic in appearance and infusible. It in-flames in common air or in oxygen only whenheated. It is entirely decomposed into hydro-gen and potassium when heated per se in aclose vessel, and when in contact with hotmercury it is still more rapidly destroyed, thehydrogen flying off and the potassium amal-gamating with the mercury.

. Phosphorus unites readily with potassium.Tins compound is made by introducing the■two into a glass tube filled with azotic gasand gently wanning them. But little light isgiven out. The phosphuret of potassium hasan unmetallic appearance, is of a chocolatecolour, and when thrown into water producesphosphuretted hydrogen gas, which sometimesbut not always inflames.

Sulphur forms a very intimate union withpotassium, and the combination takes placewith much more heat and light than in thephosphuret, so as to endanger the glass vessel,unless the sulphur and potassium are placedupon a platina dish within the tube, which lastshould be filled with azote. This sulphuret issometimes yellow, sometimes red. It has the

smell and taste of rotten eggs, is soluble inwater without the production of any gas, butwith acids it is readily decomposed with evolu-tion of sulphuretted hydrogen gas.

When potassium is melted in sulphurettedor phosphuretted hydrogen gas, a sulphuret orphosphuret of potassium is formed, and thehydrogen remains pure.

Alloys of Potassium and the Metals.

Potassium very readily unites with many ofthe metals, as was first ascertained by Davy,and indeed this circumstance is one that isbrought forward as an argument of the metal-lic nature of this singular substance. Some ofthese alloys, as described by the discoverer, wohave already mentioned ; the following experi-ments are given by M. M. Gay Lussac andThenard. The alloys were made either byheating the substances in a small bent glasstube over mercury and filled with azotic gas,or by introducing the potassium into a smallglass tube closed at one end, covering it withthe metal in powder, then drawing out theother end of the tube over a lamp and sealingit hermetically, and finally uniting the metaland potassium by a due heat over lighted char-coal.

Potassium 2 measures, lead in powder 8 mea-sures, gave a solid brittle fusible fine-grainedalloy. Exposed to air it decomposed gradually,and in water, suddenly. In either case potashwas produced and the lead resumed its metallicstate. Potassium 2 measures, bismuth 8 mea-sures, a solid brittle alloy in small facets : de»composed as the last. Potassium 2 measures,antimony 8 measures: this mixture alloyed withgreat ease, giving out light in the process: de-composed as above.

Potassium 2 measures, tin 7 measures. Somelight is given out during the union, which re-quires almost red heat to be effected. Thisalloy must be made in azotic gas as it is imme-diately decomposed in the air. When the tinis in a less proportion than the above, the alloygenerally takes fire the moment it is attemptedto be pulverized.

Potassium and zinc alloy with difficulty onaccount of the volatility of the potassium atthe heat required.

Potassium and mercury will unite in anyproportions. When the former was to the lat-ter as 212 by weight to 3069, the amalgamremained fluid at a mean temperature. Withtwice the above quantity of potassium muchheat was excited on mixture, and the amalgamwas solid at a common temperature and easily