14 
PROFESSOR DANIELL AND DR. MILLER ON THE 
(x.) A salt of the same order, viz. the sesquisulphate of iron (Fe 2 0 3 , 3S0 3 ), was 
prepared with great care, and its solution treated exactly in the same way as the last. 
It conducted well, and 13 cubic inches of oxygen were collected from the zincode in 
twenty-eight minutes. On neutralizing the liquid of the platinode cell with ammo- 
nia, very slight traces of sesquioxide of iron appeared. The sesquioxide of iron had 
therefore resisted the transfer as well as the sesquioxide of aluminum. 
(y.) We next tried salts of the more ordinary constitution of single equivalents of 
acid and base. The zincode and connecting cells were charged with solution of sul- 
phate of copper (CuO, S0 3 ), and the platinode cell with dilute sulphuric acid. The 
combination conducted well, 23 - 6 cubic inches of oxygen were collected from the 
zincode, and an equivalent of hydrogen from the platinode ; but the platinode plate 
was scarcely covered with a very thin film of copper, the metal not having been 
transferred in any considerable quantity. Upon neutralizing the solutions on the 
two sides by carbonate of soda, it was found that an equivalent of sulphuric acid had 
travelled to the zincode. Upon reversing the arrangement, oxygen was collected as 
before from the zincode, and an equivalent of copper was thrown down upon the 
platinode, but no hydrogen was evolved. 
(z.) The last experiments were varied by the substitution of solution of sulphate of 
potassa for the dilute sulphuric acid in combination with the sulphate of copper. When 
the copper solution was placed at the zincode, none of the metal passed over to the 
platinode, but a full equivalent of hydrogen was collected with alkali and acid at their 
respective electrodes. When the position of the two salts was reversed, the potassium 
travelled into the platinode cell, and was at once indicated by a precipitate of hy- 
drated oxide of copper. The platinode plate was also covered partly with coherent 
copper, and partly with pulverulent metal, and only 3 cubic inches of hydrogen 
were collected for 71 cubic inches of mixed gases in the independent voltameter. 
None of the copper solution had penetrated to the zincode cell. 
Thus it appeared that copper refused to exchange places with potassium in the 
circuit, as it had before refused to exchange with hydrogen, and so to pass from the 
zincode to the platinode. 
(a. a.) Sulphate of zinc (ZnO, S0 3 ) was next subjected to the same treatment, 
and the results were exactly similar ; the metal in all cases refusing like the copper 
to pass from the zincode division of the diaphragm cell to the platinode in any con- 
siderable quantity. 
To ascertain whether the passage of the current from one electrolyte to another 
was in any way concerned in preventing the transfer of the base, we now resolved to 
employ sulphate of copper in solution throughout the whole arrangement, and having 
carefully ascertained the proportion of copper in solution, we placed 1500 grains of 
the liquid in each cell ; metallic copper was thrown down on the platinode, and on 
precipitating the oxide from the liquid in the cell by potash, we found exactly the 
same amount of copper (taking the united quantities obtained from the oxide preci- 
