April, ’89.] history society of Wisconsin. 
201 
more than a gram or so ol the metal. In those experi¬ 
ments an alumina lined clav crucible was used containing 
25 to 30 pounds of the salt with carbon cathode at the 
bottom of the crucible and a similar carbon anode pass¬ 
ing in at the top. A tight fitting cover prevented access 
of air from the top. Drawing the electrodes farther apart 
increased the yield of metal from the same number ol 
amperes. Mechanical agitation or boiling of the liquid 
would also tend to convey some of the A1 through the 
molten mass and thus bring it in contact with the liber¬ 
ated fluorine. Crv^olite, when solid, has a higher specific 
gravity than Al, but when liquid the A1 will sink to the 
bottom of it. It is doubtless true that with the temper¬ 
ature very high the liberated Na from the cryolite does 
not reduce the Al but passes off as a vapor at the top of 
the bath or reunites with the fluorine and thus only a 
vStnall amount of Al would be deposited at the cathode. 
I think it hardly probable that the reduced Al converts 
the AbF 6 of the cryolite to a lower fluoride. 
It is probable that AI 2 Fq when pure is not an electro 
lyte, as the resistance increases as other salts presen 
decreases. Prof. W. Harnpe gives experimented proof in 
the Chemiker Zeitung August 3,1887, that the pine c 1 or 
ides, bromides and iodides are not electrolytes. ^ 
been my experience with carefully prepared puie 2 ( * 
I attempted to pass the current from a 30 cell Gro\e a 
ery in series, using carbon electrodes a sixteent o 
inch apart in Al 2 Cl 6 without any deflection 0 e 
needle of a sensitive galvanoscope. The melting 
Al 2 Cl 6 was made to take place, and the circuit c ^ ’ 
nnder paraffin and also in glass vessels in w luc 1 er 
no access of air. On account of the great \o a y 
the salt an exit was allowed lor the large amoun o 
vapor passing off in the melting. It is still more improb¬ 
able that the oxide of Al is an electrolyte, althoug 1 - 
yarded as such by Heroult in U. S. patent, August, c 
