the Decomposition of the Earths, &c. 195 



electrified by iron wires under naphtha, by the same methods, 

 and with the same powers as those employed for the de- 

 composition of the fixed alkalis*. In these cases, gas was 

 copiously evolved, which was inflammable; and the earths 

 where in contact with the negative metallic wires became 

 dark coloured, and exhibited small points having a metallic 

 lustre, which, when exposed to air, gradually became white; 

 they became white likewise when plunged under water, and 

 when examined in this experiment by a magnifier, a greenish 

 powder seemed to separate from them, and small globules of 

 gas were disengaged. 



In these cases there was great reason to believe that the 

 earths had been decomposed ; and that their bases had 

 combined with the iron, so as to form alloys decomposable 

 by the oxygen of air or water; but the indistinctness of the 

 effect, and the complicated circumstances required for it, 

 were such as to compel me to form other plans of operation. 



The strong attraction of potassium for oxygen, induced me 

 to try whether this body might not detach the oxygen from 

 the earths, in the same manner as charcoal decomposes the 

 common metallic oxides. 



I heated potassium in contact with dry pure lime, barytes, 

 strontites, and magnesia, in tubes of plate glass; but' as I 

 was obliged to use very small quantities, and as I could not 

 raise the heat to ignition without fusing the glass, I obtained 

 in this way no good results. The potassium appeared to act 

 upon the earths and on the glass, and dark brown substances 

 were obtained, which evolved gas from water; but no di- 

 stinct metallic globules could be procured : from these cir- 

 cumstances, and other like circumstances, it seemed pro- 

 bable, that though potassium may partially de-oxygenate the 

 earths, yet its affinity for oxygen, at least at the tempera- 

 ture which I employed, is not sufficient to effect their de- 

 composition. 



I made mixtures of dry potash in excess and dry barytes, 

 lime, strontites, and magnesia, brought them into fusion, 

 and acted upon them in the voltaic circuit in the same man- 



* See Phil. Mag. vol. xxxii. p. 4. 



N 2 ner 



