A L K

ALK

( S3 )

not exceeding 15 or 20 grains could be used,making the distance between the electric polesnot more-than j- or T V of an inch.

The Basis of Potash has been named by thediscoverer Potassium , and the Basis of Soda,Sodium , which term has been universally a-dopted.

The principal properties of Potassium dis-covered by Sir H. Davy in his first series of-experiments, are the following.

When exposed to the air a white' crust ra-pidly collects on the surface, tarnishing itsmetallic lustre, and this continues to be pro-duced till the whole is converted to this whitecrust, which is found to be pure potash. Whenglobules of Potassium are confined in commonair, or especially in oxygen, at a common tem-perature, the. same crust is formed, but notbeing removed by .deliquescence, the process isstopped, the interior part of the globule beingprotected by the crust of regenerated alkalifront further change. But when the tempera-ture is raised highly, a rapid and brilliant com-bustion takes place, and the whole is changedto solid dry potash. Oxygen gas alone is ab-sorbed in this change, the azotic admixturebeing in no degree affected, and the weight ofthe potash considerably exceeds that of the-potassium decomposed.

Potassium is a soft and malleable solid of thelustre of polished silver at 50° Fabr/at 32 s itrt is hard, brittle, and exhibits in its fracturedsurface beautiful facets of a perfect metallicwhiteness. At 60° it begins to soften and be-come pasty, and at 100° it is perfectly fluid, sothat the globules will run together. At a redheat it is converted into vapour, but in closevessels it condenses unaltered on cooling.

It is a very perfect conductor both of heatand electricity.

One of the most remarkable circumstancesrelating to potassium is its very great levity.Though resembling the metals in outward ap-pearance, in opacity and lustre, it is not onlylighter than any of them, but even than water,ether, naphtha, or almost any known fluid. Theexact determination of its specific gravity is at-tended with difficulty, but Sir H. Davy esti-mates it at about 0.6 (water being 1.)

The action of water upon potassium is verystriking. When a globule of it is touched witha drop of water, it instantly burns with a brightflame and a solution of potash is left. If thissimple experiment be performed on paper tingedyellow with turmeric, the spot where the com-bustion and generation of alkali takes place is

VOL. ill.

strongly marked by a deep brick-red stain.When potassium is decomposed by water inclose vessels, a gas is found among the pro-ducts, which is pure hydrogen. So strongis the affinity of potassium for oxygen, thatit decomposes water wherever it exists, andthus discovers the watery admixture in thepurest alcohol and ether, in both of which thepotassium produces potash and hydrogen gas.

In the liquid acids potassium is immediatelydecomposed. In the sulphuric, it produces atonce a white salt (probably sulphat of potash)with a yellow coating, which appears to besulphur.. In the nitric and muriatic acids itproduces nitrat and muriat of potash.

As potassium cannot exist for a moment un-altered in water or any fluid containing water,nor for any length of time in air, it was a mat-ter of difficulty to find some mode of preservingit. It was found however that naphtha recently-distilled will preserve it unchanged for a suf-ficient length of time, though even in this fluidit gradually oxydates and forms a kind of pot-ash soap with the naphtha, that collects roundthe globule and prevents it from floating in thisfluid. It also slowly forms an alkaline soapwhen confined in any of the oils. ■

Potassium unites with many of the metalswith great ease, forming very peculiar alloys.It amalgamates readily with mercury and re-markably reduces its fluidity.for when unitedwith 30 times its weight of mercury, the alloyis hard and brittle; The fluid amalgam dissolvesall tlie ; metals, forming a- triple alloy of mer-cury, potassium and the other metal employed.When the amalgam is thrown into water, ahissing noise is produced, hydrogen gas is givenout, potash is generated, and the mercury re-turns unaltered to its original state.

Potassium will equally well unite with gold,silver and copper, and it is equally separablefrom these alloys by mere moisture, which re-generates the alkali.

Potassium readily reduces many of the me-tallic oxyds, and when in excess it unites withthe metal thus reduced.

It decomposes the metallic oxyds in flint-glassand green-glass at a low red-heat; but it also^gradually changes perfectly unmetallic glasswhen heated in such vessels, slowly alkalizingitself and corroding the glass.

These are the principal properties of this,singular substance as given by the illustrious,discoverer in his first memoir on the subject,by which it appears that potassium has by farthe strongest affinity for oxygen of any hitherto-.

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