XXIV. Account of the décomposition of POTASH and production of POTASSIUM, by heat: by THOMAS COOPER, Esq. Professor of Chemistry in Carlisle College, Pennsylvania, communicated to the Editor by Mr. WILLIAM HEMBEL, Jun'r. PHILADELPHIA, 12th July, 1811. Dr. Bruce, SIR, THE many abortive attempts which have been made by different chemists in our country to obtain potassium, gives a value to the accompanying letter (which I received from Thomas Cooper, Esq. of Northumberland, Pennsylvania) which in my opinion merits publicity. Should you, Sir, be of my sentiment, be pleased to give it a place in your useful Journal. I remain, Sir, With great esteem, your ob't servant, "The specimen you sent me of Potassium by Mr. Reuben Hains, procured by Mr. Johns, by means of his apparatus, in England, arrived here in full perfection; protected by the Naphtha. It appeared to be inveloped in a soapy coating, formed by the union of the external surface of Potassium partially reconverted into Potash, and united with the oleaginous matter of the Naphtha. But on cutting it, the blue mercurial metallic brilliancy was evident; and it decomposed water with a vivid pink-coloured flame, and a gyratory motion, as you described it. "I was so struck with the phenomena attending its decomposition of water, that I determined to make some if I could, and invited Mr. Hains to assist me in the progress of the experiment, to which he willingly consented. "I looked over the method of making it at the Royal Institution in England, as described in Nicholson's Journal, and the improvement on that apparatus, which Mr. Johns had published in Tilloch's Magazine; and adopted the latter. "Dr. Priestly's Laboratory was well furnished with gunbarrels. I took one, and had it filled with melted lead, for the purpose of giving the necessary curve; but this did not succeed. "The lead was melted out, and by repeated red-heats, and careful hammering, the required curvature was produced; but the barrel was too thin, and it cracked in the operation. "I took another, which seemed to answer very well. I had another piece of gun-barrel ground to it as an alongé : the further extremity being furnished with a brass cock, to which was connected by means of a cork, a glass tube, the further end of which was immersed in a small basin of linseed oil. An intermediate tube of sheet-iron, for the purpose of collecting the distilled Potassium (about six inches long) was inserted half within the curved tube, and half within the alonge, which was carefully and accurately ground, to fit the curved tube. The curvature within the furnace, was filled, for the length of nine inches, with chippings of malleable iron; for I could procure neither clean iron filings, or turnings. The other end of the gun-barrel (at the breech) was stopped by the common screw used in all gun-barrels. "The apparatus thus made, was fixed in a portable airfurnace, of nine and an half inches, internal diameter, furnished with a dome, and a pipe of about four feet in length. The filings were exposed to a full white heat, in this (very excellent) air-furnace, and then, the screw at the breech being taken out, about an ounce of fused caustic potash VOL. I. S was gradually put in; the projecting end of the tube next the breech being previously exposed to red heat. "Having no perfectly pure alkali, and not being satisfied with Berthollet's process of procuring it, by dissolution in alchohol, either in point of ease or purity, I made it myself, thus: "I took about a pound and an half of lime; I exposed it in a large black-lead crucible to a full red heat, for four hours; I mixed one pound of this, with one pound of good pearlash; I poured on it one and an half gallon of boiling water, and after stirring it, left it to subside for two hours, On adding an acid to a small quantity of the clear solution, not the smallest appearance of effervescence was observed. I poured off the clear liquor, filtered it through cotton, washed the remaining sediment with one and an half gallon more of boiling water, filtered it, then evaporated the whole over a charcoal fire in the open air. This was done in a large copper basin, silvered with the common mixture of muriate of silver one part, whiting one and an half part, cream of tartar one and an half part. Being evaporated nearly to dryness, it was tried with an acid, a slight effervescence appeared, probably from the absorbtion of carbonic acid from the atmosphere, during four hours evaporation. The nearly dry solution was then put in a clean iron crucible, gradually boiled, and then melted in a low red heat. It was then cast on the copper basin, and whilst hot, broken into pieces, and put into a glass bottle. In this way, a pound averdupois, of pearlash, will furnish nearly four oz. troy, of solid fused caustic alkali. "The curved part of the gun-barrel, containing the filings, being of a white heat, and six inches of the breech end which projected out of the furnace being brought to a red heat by the application of hot charcoal, the potash (about one ounce) was put in, and the breech closed with its screw. "All the other joints were luted with fat lute (lime and linseed oil.) Hydrogen gas came over abundantly; the heat was continued for half an hour, the apparatus cooled, taken to pieces, examined, but not a particle of potassium ! "On carefully examining the gun-barrel, three small holes appeared to have been burnt into it. To which the failure was attributed. Another gun-barrel was taken, bent, ground, filled with iron chippings, the experiment was conducted as before, but the barrel was not accurately ground to the straight joint or alongé; this failed also. "A thick well made rifle-barrel was then taken, it was filled with a faggot of clean iron wire; the experiment was conducted as before. The caustic alkali was distilled over in substance, chiefly undecomposed, but the surface of the cake of alkali exhibited unequivocal signs of potassium ; the scrapings taking fire in the air, and most vividly on water. "Monday, June 4th, finding the interstices between the wire too great, I directed the wire to be cut into small pieces of about an eighth of an inch long; the curvature of the gun-barrel was lessened; it was filled with these cuttings; an ounce of dry, fused, caustic potash was used; the alongé furnished with a brass cock, was screwed to the curved barrel by three small screws. All the joints were luted with fat lute. The white heat was given to the curvature of the barrel, the red heat to the projecting end of the breech. The potash was put in at twice; this took ten minutes; much hydrogen gas escaped, both at the breech and the glass tube, which was now immersed in olive-oil. The heat was kept up about fifteen minutes. In half an hour the apparatus was taken out, cooled, taken to pieces, and as much potassium procured as would fill one fourth of an ounce vial. was of the purest and most brilliant silvery lustre. It took fire in the air, and vividly in water. It was soft, spread under the knife, and appeared to have all the most perfect qualities of the purest potassium hitherto made. I could not weigh it, but I am not beyond the mark in saying we procured sixty grains. It ." I had not half sufficient naphtha to cover it. It decomposes olive-oil, with great frothing; and was quickly dete riorated. It sunk in ol. tereb. decomposing it, and producing constant streams of gas, which gave a frothy appearance to the spirits of turpentine, and in about three hours, turned of a dark brown colour, the potassium still retaining its silvery metallic lustre. How it will arrive at Philadelphia, I know not. Mr. Hains will bring you the whole result. "The chippings of wire are bright; they are no longer iron; they are not steel. I send them to you. What becomes of the oxygen? for certainly caustic potash is a metallic oxyd, There is no appearance of oxydated iron from the curved tube, nor of what Dr. Priestly and the English workmen call finery cinders. "I am as yet unable to give an opinion. I finished my successful experiment this morning, and Mr. Hains goes off at 6 o'clock to-morrow morning. I shall write further to you when I know more. "In the mean time I am with very kind respect, "THOMAS COOPER." References to Plate I. Fig. I. A, B. An earthenware furnace, 2 feet in height, which may be separated at C. Diameter of the furnace: at A. 5 inches; at B. 7 inches; at C. 11 1-2 inches. D. The ash pit. E. Door to supply the fuel. F. Sheet-iron bent, to contain a charcoal fire, outside the furnace, at the end of the present apparatus. a. b, c. d. e. A bended gun barrel, divisible by an air tight joint at d. within which is inserted a tube of sheet iron, f. g. extending 3 inches each way from the joint, |