ALK

A L K

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are to be introduced and pushed on to the bentpart r. The tube, carefully luted is then tobe placed in a small furnace, nine or ten inchesin diameter, and provided with a pair of doubleblast bellows, the pipe from which is shown'at f. The next step is to insert the tube a inits place, after having put into it H parts ofpure potash recently fused. The whole ap-paratus should be perfectly clean, dry, andimpervious to air. A strong heat is nowto be excited in the furnace, and while thisis doing, the tube containing the potash aswell as the opposite end of the barrel shouldbe kept cool by ice. When the barrel hasattained a white heat the potash in a may bemelted by a small portable furnace. It willthen flow by the small hole upon the ironturnings. Much hydrogen gas will be evolved,and when this slackens we may remove thesmall furnace from beneath the tube a and in-crease the heat in the furnace d, in order torestore to the iron turnings at c, the tempe-rature proper for decomposing more potash.These operations may be repeated alternatelytill no more gas is produced, but last of all theheat in the furnace should be strongly raisedto drive off some of the potassium that adheresstrongly to the iron turnings.

When the furnace is quite cold, the safety-tube e is to be removed, and its place suppliedby an iron plug. If the end of the gun-barrelprojecting from this side of the furnace hasbeen kept carefully cooled during the experi-ment the metal will be found adhering to it inthe form of brilliant laminae. In order to ex-tract it, the gun-barrel is to be cut off at thebeginning of the part that has been kept cool,where the greatest quantity will be found.Another portion will be found close to theplug, and this adheres so slightly to the gun-barrel that the least effort serves to detach it.It is even partly oxidated by the air that enterson cooling the furnace, and when the whole iscovered with naphtha the oxidized part is de-tached in laminae, exposing a white and bril-liant metallic surface. The potassium whichis condensed nearest the furnace must be sepa-rated by a sharp chissel in the largest pieceswe can possibly break ofF. In the middle ofthe guti-barrcl we shall find an alloy of potas-sium and iron which becomes green on expo-sure to the air, the potassium returning to thestate of potash.

The potassium prepared in this way if thealkali is pure hardly differs from that obtained

* Rechvrches, ‘ A

by galvanic electricity, except that its specificgravity is somewhat higher, being to that -ofwater as 796. to 1000.

Having already described the leading proper-ties of potassium as first observed by Sir H.Davy , we shall proceed to give an abstract ofa very long and minute series of experimentson the same subject carried on by Messrs. GayLussac, and Thenard/ most of which furnishresults very nearly similar to those of the emi-nent discoverer of the alkaline metals, but othersare different and throw new light on the natureof these curious bodies.

Action of Water on Potassium . When alittle water is confined in a jar over mercury,and a portion of potassium is passed up (en-closed in paper) the potassium swims on thewater, moves about and lessens rapidly, andsoon disappears, leaving the water very alka-line, and a considerable quantity of hydrogengas is produced. When this experiment is per-formed, merely by throwing some pieces ofpotassium on water they soon become red hotwhile decomposing on its surface, which formsan amusing experiment. To determine theexact proportion of hydrogen produced by theconversion of potassium into potash by meansof water, a small iron tube was filled with2-213 grammes of potassium, and covered witha glass plate, and thus introduced under a bell-glass full of water. The decomposition tookplace with great rapidity, and, when complete,the hydrogen was measured and found to be0.66(1 litre at 15° centigrade therm, and 0.7455*metre bar. The experiment was repeated withthe same result, whence it follows that .100parts by weight of potassium absorb 19 945parts of oxygen to pass to the state of potash ;and hence 100. parts of potash consist of 85.571of potassium, and 16.629 of oxygen. Theseproportions closely correspond with those givenby Davy and Berzelius. 1 ’

Messrs. Gay Lussac, and Thenard give a sim-ple method of dividing potassium into equal por-tions without the trouble and loss attending theprocessof weighing thisdecoinposable substance,namely, by compressing it into a cavity made in asmall block of brass, on which another blockexactly fits so as to exclude every atom of po-tassium except that which fills the cavity. r lhequantity of hydrogen given by this portion ofpotassium in ten different experiments variedonly from 78.5 to 79.4 measures, and henceassuming 79. as the average, and comparingthis result with the former above mentioned

n. CUim. Tom. 80. p. 245,