ALKALIES. 245 



THEORY OF THE PHENOMENA. 



These decompositions agree perfectly with those which have been 

 before described ; oxygen is evolved at the positive wire, and the 

 combustible with which it was united at the negative. When the 

 solid potash or soda was decomposed in glass tubes, the new sub- 

 stances were always evolved at the negative wire, and the most deli- 

 cate examination proved that the gas liberated at the positive wire 

 was pure oxygen, and, unless more water was present than was ne- 

 cessary to give conducting power to the alkali, no gas whatever was 

 given out at the negative wire.* The synthetical proofs were equal- 

 ly satisfactory. 



The bases of both alkalies, when exposed to the atmosphere, be- 

 came tarnished and covered with a white crust, which immediately 

 deliquesced ; water was decomposed, a farther oxidizement took 

 place, more white matter was formed, and the whole became a sat- 

 urated solution of fixed alkali. When the metallic globules were 

 confined over mercury in oxygen gas or common air, an absorption 

 took place, a crust of alkali instantly formed, and, for want of mois- 

 ture the process stopped, the interior being defended from the action 

 of the gas. " When the substances were strongly heated, confined 

 in given portions of oxygen, a rapid combustion with a brilliant white 

 flame was produced ; and the metallic globules were found convert- 

 ed into a white and solid mass, which, in the case of the substance 

 from potash was found to be potash, and in that from soda, soda." 



2. BY THE FURNACE. 



(a.) The next spring, 1808, potash was decomposed in a gun 

 barrel, in Paris, by Gay Lussac and Thenard. 



S6.) Vary many precautions are necessary to secure success. -\ 

 c.) Principal particulars. Provide a clean sound gun barrel 

 bent, so that the middle shall be curved a little downward, while the 

 end in which the potash is to be placed, shall incline gently upward, 

 and the other end downward ; it must be protected by a very refrac- 

 tory lute, made of coarse siliceous sand and potter's clay, with as much 

 sand as can possibly be worked in, and dried with extreme slowness ; 

 place the tube across a furnace ; potash in fragments is put into the 

 elevated end out of the furnace ; this is the breech of the gun barrel, 

 and the breech pin is now put in with a lute ; clean iron turnings are 

 introduced into the belly of the tube in the part which lies in the fur- 



* Some have supposed that the hydrogen combines with the pure alkali to 

 form the metals. 



i Sec Recherchcs Physico-Chimiqucs; also, my translation of the Memoir of Gay 

 Lussac and Thenard, in the Boston Edition of Henry's Chemistry, 1814 ; also An- 

 nales de Chimie, LXV, 325; Memoires d' Arcueil, H, 299. 



