Page:Experimental researches in electricity.djvu/176

150 to keep it all fluid caused a quicker action on the crucible, which was soon eaten through, and the experiment stopped.

534. In one experiment of this kind I used borate of lead (144, 408). It evolves lead, under the influence of the electric current, at the anode, and oxygen at the cathode; and as the boracic acid is not either directly (144) or incidentally decomposed during the operation, I expected a result dependent on the oxide of lead. The borate is not so violent a flux as the oxide, but it requires a higher temperature to make it quite liquid; and if not very hot, the bubbles of oxygen cling to the positive electrode, and retard the transfer of electricity. The number for lead came out 101.29, which is so near to 103.5 as to show that the action of the current had been definite.

535. Oxide of bismuth.—I found this substance required too high a temperature, and acted too powerfully as a flux, to allow of any experiment being made on it, without the application of more time and care than I could give at present.

536. The ordinary protoxide of antimony, which consists of one proportional of metal and one and a half of oxygen, was subjected to the action of the electric current in a green-glass tube (524), surrounded by a jacket of platina foil, and heated in a charcoal fire. The decomposition began and proceeded very well at first, apparently indicating, according to the general law (414, 432), that this substance was one containing such elements and in such proportions as made it amenable to the power of the electric current. This effect I have already given reasons for supposing may be due to the presence of a true protoxide, consisting of single proportionals (431, 428). The action soon diminished, and finally ceased, because of the formation of a higher oxide of the metal at the positive electrode. This compound, which was probably the peroxide, being infusible and insoluble in the protoxide, formed a crystalline crust around the positive electrode; and thus insulating it, prevented the transmission of the electricity. Whether, if it had been fusible and still immiscible, it would have decomposed, is doubtful, because of its departure from the required composition (432). It was a very natural secondary product at the positive electrode (514). On opening the tube it was found that a little antimony had been separated at the negative electrode; but the quantity was too small to allow of any quantitative result being obtained.