On the action of Marsh and Olefiant Gases on Metallic Oxides. 225 



obtains in the generality of modern trompes ; and the third 

 obtains in the trompe described by Francois, in trompes with 

 very shallow cisterns, in trompes in which the water before 

 leaving the cistern receives rotatory motion, either by the stream 

 which supplies the cistern entering at an angle to the water- 

 surface, or by some other cause, and in all trompes with in- 

 clined tubes (of which, as stated above, Kircher had seen forty 

 prior to the year 1655). 



I consider the most economical, and in every way the most 

 efficient form of trompe to be the old form, in which there are 

 no air-holes, and the air enters by a conical cavity in the water- 

 above the orifice from which the descending stream issues. It 

 will be seen from the above experiments that by this method we 

 obtain nearly double the amount of air obtainable by other 

 means. The construction of such a trompe, moreover, is com- 

 paratively easy; there is no need to have the tubes perfectly 

 vertical, and less spray is carried into the furnace than by the 

 form of trompe now in use. 



20 Great Marlborough Street, London, 

 July 28, 1864. 



XXVI. Chemical Notices from Foreign Journals. 

 By E. Atkinson, Ph.D., F.C.S. 

 [Continued from vol. xxvii. p. 506.] 



MULLER* has investigated the action of marsh-gas on several 

 metallic oxides at high temperatures. The marsh-gas was 

 prepared by heating in a charcoal fire a mixture of acetate of soda, 

 potash, and lime in a coated retort, by which almost the theore- 

 tical quantity of gas was obtained. 



Pure sesquioxide of iron, Fe 2 O 3 , heated in a hard glass tube 

 in a stream of the gas, soon became black, while a large quantity 

 of water was formed. Subsequent investigation and quantita- 

 tive analysis of the altered substance showed that it was proto- 

 sesquioxide of iron, Fe 3 O 4 . When sesquioxide of iron placed in 

 a porcelain tube, through which passed a current of marsh-gas, 

 was heated in a charcoal fire, protosesquioxide was obtained, which 

 contained, however, a larger quantity of protoxide. 



Protosesquioxide of manganese was easily attacked by the 

 gas and reduced to protoxide of manganese. 



The oxide of cobalt, Co 6 O 7 , by heating in a current of marsh- 

 gas, was reduced to metallic cobalt with formation of water. 

 Oxide of copper was likewise reduced to metallic copper, while 

 oxide of tin and oxide of zinc remained unchanged. 



* Poggendorff's Annalen, May 1864. 



