1891.] On Electrical Evaporation. 103 



Palladium 9'00 



Silver 7-88 



Tin 7'76 



Lead 6-61 



Gold 5-18 



Cadmium 3'72 



Copper 2-52 



Platinum 2'02 



Nickel 1'29 



Iron 0-71 



Iridium 0'47 



Aluminium and magnesium appear to be practically non- volatile 

 under these circumstances. 



The order of metals in the table shows at once that the electrical 

 volatility in the solid state does not correspond with the order of melt- 

 ing points, of atomic weights, or of any other well-known constant. 

 The experiment with some of the typical metals was repeated, and 

 the numbers obtained did not vary materially from those given above, 

 showing that the order is not likely to be far wrong. 



It is seen in the above table that the electrical volatility of silver 

 is high, while that of cadmium is low. In the two earlier experi- 

 ments, where cadmium and silver were taken, the cadmium negative 

 electrode in 30 minutes lost 7*52 grs., whilst the silver negative 

 electrode in 1J hours only lost 0'19 gr. This apparent discrepancy 

 is easily explained by the fact (already noted in the case of cadmium) 

 that the maximum evaporation effect, due to electrical disturbance, 

 takes place when the metal is at or near the point of liquefaction. If 

 it were possible to form a negative pole in vacuo of molten silver, 

 then the quantity volatilised in a given time would be probably much 

 more than that of cadmium. 



Gold having proved to be readily volatile under the electric current, 

 an experiment was tried with a view to producing a larger quantity 

 of the volatilised metal. A tube was made having at one end a nega- 

 tive pole composed of a weighed brush of fine wires of pure gold, and 

 an aluminium pole at the other end. 



The tube was exhausted and the current from the induction coil put 

 on, making the gold brush negative ; the resistance of the tube was 

 found to increase considerably as the walls became coated with metal, 

 so much so that, to enable the current to' pass through, air had to be 

 let in after a while, depressing the gauge f- mm. 



The weight of the brush before experiment was 35*4940 grs. 

 The induction current was kept on the tube for 14J hours ; at the 

 end of this time. the tube was opened and the brush removed. It now 

 weighed 32'5613, showing a loss of 2'9327 grs. When heated 



