252 M. Fleitmann on a new Mode of preparing Oxygen. 



Fleitmann describes* a method of preparing oxygen gas, to 

 which he was led by the observation that a concentrated solution 

 of bleaching-powder in contact with a trace of freshly precipitated 

 moist peroxide of cobalt is completely decomposed into chloride 

 of calcium and oxygen. It is known that there are several oxides 

 of cobalt ; and the explanation of the above process is doubtless 

 that the lower oxide continually takes oxygen from the hypo- 

 chlorite of lime, passes into a higher oxide, and then is resolved 

 into oxygen and a lower oxide. The action of the peroxide is 

 thus quite analogous to that of binoxide of nitrogen in the 

 sulphuric acid manufacture. 



The same quantity of peroxide serves for the decomposition of 

 fresh quantities of hypochlorite of lime ; and the quantity required 

 is extremely small, one-half to one-tenth per cent, of the chlo- 

 ride is sufficient. It is not even necessary to have freshly preci- 

 pitated peroxide ; a few drops of any soluble cobalt-salt added to 

 a solution of hypochlorite of lime produces at once a corre- 

 sponding quantity of hydrated peroxide. 



Unfortunately it is essential to have a clear solution of hypo- 

 chlorite ; for otherwise it froths up. The clear solution is best 

 obtained by decantation, the liquid used for exhausting a first 

 portion being applied to a second, and so on. The vessels used 

 may be filled with the liquid to the extent of 7 § of their capacity. 



Ste.-Claire Deville has given the name of dissociation to the 

 phenomenon which many bodies exhibit of partially decompo- 

 sing into their constituents when heated at a considerably lower 

 temperature than that at which they are completely decomposed, 

 or at which their constituents unitef. In two recent commu- 

 nications J he has furnished additional instances of this pheno- 

 menon. 



The electric spark decomposes many substances, doubtless 

 in consequence of the great heat which it disengages ; and if a 

 reunion of the separated constituents does not ensue, this is 

 probably due to the circumstance that on their decomposition 

 they come into contact with a relatively cold atmosphere ; for 

 the path of the spark is very short as compared with the mass 

 of the gas, whose temperature is scarcely changed. 



Deville has devised a plan by which the same conditions are 

 attained without the aid of electricity. A porcelain tube is laid 

 through a furnace in which a very high temperature can be pro- 

 duced ; its ends are provided with corks in which are two perfora- 

 tions. In each cork is fitted a small tube, serving at the one end to 



* Liebig's Annalen, April 1865. 



f Phil. Mag. S. 4. vol. xx. p. 448 ; vol. xxv. p. 536. 



X Comptes Rendus, vol. lix. p. 8/3; vol. lx. p. 31/. 



