246 ALKALIES. 



nace ; a stop cock and tube of glass bent downward at right angles, 

 are fixed at the other end ; the glass tube dipping into oil ; both ends 

 are kept cold by water or ice, till a great heat is raised by a powerful 

 bellows blowing with a large orifice, so as to introduce abundance of 

 air ; the potash which should have been previously ignited, before 

 its introduction into the tube, is then slowly melted by a portable 

 furnace, and running down upon the ignited iron, is decomposed ; 

 its oxygen is fixed in the iron, and hydrogen gas being abundantly 

 disengaged from the tube, holding potassium in solution, and being 

 spontaneously inflammable, it flashes frequently and with intense 

 brightness ; the potassium rises in vapor and congeals in the cold 

 end of the tube ; it is then cut out by a knife dipped in naptha and 

 is preserved under that substance. It may be melted beneath it, 

 and is readily moulded by the fingers smeared with naptha, into any 

 form and into pieces of convenient size. 



The great difficulty is in preserving the gun barrel from oxidation 

 and fusion.* 



Curaudau of Geneva, in the same year, shewed that potash might 

 be decomposed by charcoal alone, by mixing it in powder with twice 

 its weight of dry carbonate of potash, and heating the mixture strong- 

 ly in an iron tube or spheroidal iron bottle. Prof. Brunner has im- 

 proved this process. His apparatus is a spheroidal wrought iron 

 bottle, of one pint in capacity, and half an inch thick ; a bent gun 

 barrel, ten or twelve inches long, screws into the mouth of the bottle ; 

 the apparatus is well luted, and the gun barrel protected by iron wire 

 wound around it, dips into a vessel of naptha, kept cold by ice. In 

 one experiment, 6 oz. of iron filings, 2 of charcoal, and 8 of fused 

 carbonate of potash, were intimately mingled and heated in a furnace, 

 when 140 grains of potassium were obtained. It appears, accord- 

 ing to the original observation of Sir H. Davy, that " potash or pearl- 

 ash is easily decomposed by the combined attractions of charcoal and 

 iron ; but, it is not decomposable by charcoal, or, when perfectly dry, 

 by iron alone. Two combustible bodies seem to be required by their 



* For improved processes, see Ann. of Phil. New Series, VI, 233 ; Quarterly 

 Journal of London, XV, 379; and Annales de Chim. XXVII, 340; also, Am. Jour. 

 Vol. VIII, p. 372. It would be difficult, without an amount of detail which is in- 

 consistent with the limits of this work, to state all the circumstances that influence 

 the success of this difficult process. Soon after the discovery of this method of ob- 

 taining potassium, and for several years after, I labored much in this field, having 

 gone many times, through every part of the operation, from the preparation of the 

 caustic alkali to its decomposition, and the evolution of its metal ; I was a coadju- 

 tor at different periods, in these experiments, with Dr. Hare, Prof. Dewey, and 

 Prof. Olmsted. The statements of Gay Lussac and Thenard, are extremely pre- 

 cise and very full ; perhaps I might have added some things from my own expe- 

 rience, but it is rendered unnecessary by the fact, that easier means have been 

 discovered, and potassium, from being one of the dearest of all substances, is now 

 within the reach of every one. 



