On Copper Electrolysis in Vacuo. 73 



The following tables are not arranged in the order in which the 

 experiments were made. 



Table IV includes four experiments in which the current density 

 was approximately O007 ampere per square centimetre of " active " 

 cathode, or 1 ampere to 135 sq. cm. All the experiments gave the 

 vacuum deposit higher than the air deposit, and the percentage differ- 

 ences agree fairly. The mean value = 0'16 per cent, at a mean tem- 

 perature of 18'l. 



Table V includes three experiments in which the current density 

 was 0'006 ampere per square centimetre. It will be seen the vacuum 

 deposit is higher than the air deposit in the three experiments. Mean 

 value of difference = O10 per cent, at a mean temperature of 16'5. 



Table VI includes four experiments at a current density of 

 0*005 ampere per square centimetre. Again the vacuum deposit is 

 higher than the corresponding air deposit. Mean value of difference 

 = 0'14 per cent, at a mean temperature of 17'5. 



Table VII includes five experiments at a current density of 

 0'004 ampere per square centimetre. All the vacuum deposits are 

 higher than the corresponding air deposits. Mean value of the 

 difference = 0'17 per cent, at a mean temperature of 19. 



Table VIII includes five experiments at a current density of 

 0'0033 ampere per square centimetre. Again deposit in vacuo is 

 higher than the deposit in air. Mean value of difference = 0'14 per 

 cent, at a mean temperature of 15'5. 



Table IX includes seven experiments at a current density of 

 0'0027 ampere per square centimetre. The same results obtained 

 here as in the preceding tables ; but the experiments of April 12 and 

 13 do not agree very well with the others. Mean value of difference 

 = 0'16 per cent, at a mean temperature of 16'6. 



Table X includes nine experiments in which the strength of current 

 was approximately O'Ol ampere per square centimetre. This table is 

 very interesting, as showing that near this particular current 

 density the previously observed differences cease to exist. The nine 

 experiments never gave a greater difference between corresponding 

 deposits than 1 tenth-milligram. The voltameters were carefully 

 tested for leakage before and after these experiments ; and the 

 experiment of April 7 (Table IX), in which there was a percentage 

 difference of 0'12, follows that of April 5, without any alteration in 

 the arrangement of the apparatus. In addition, the experiments of 

 December 2 and 3 were made with a different bell-jar and a different 

 arrangement from that used in the previous experiments. It may be 

 fairly concluded that at this density no difference in the deposit exists. 



Table XI includes three experiments at a density of 0'02 ampere 

 per square centimetre. It will be seen that there is practically no 

 difference between the deposits. 



