ELECTRIFICATION OF AIR, VAPOUR OF WATER, AND OTHER GASES. 221 

 ELECTRIC Densities in C.G.S. Electrostatic Units. 



Gas. 



Air 



11 

 Carbonic acid 



Greatest electric density, 



while working electric machine 



and pump. 



O877 x 10 ' negative 

 0-370 X 10-* positive 

 1-17 xlO~* 

 0-833 x 10-* 

 0-63 x 10-* negative 



Percentage loss in stated time. 



73 per cent, in 90 minutes 

 92-7 ., 120 

 93-1 ., 14, hours 

 96-1 U 

 98-8 14- 



Diffusion of Electricity from Carbonic Acid Gas into Air. 



75. We next tried a scries of experiments to find if an electric charge given to 

 carbonic acid gas diffused from the gas into air. The method of experimenting finally 

 adopted was as follows : 



Carbonic acid gas was slowly passed from an upright pressure cylinder into the 

 metallic can, A, by aperture No. 6 ; atmospheric air was freely admitted through 

 aperture No. 7 ; while 12,000 cub. ceutims. of mixed carbonic acid and air were 

 drawn out per minute from aperture No. 2, and 6100 cub. centims. of air from the 

 top aperture (No. 5) ; the other openings in the can being kept closed. 



In these conditions, it was found that air entered abundantly through No. 7, 

 showing that the volume drawn off from (2) and (5) was much greater than that of 

 the carbonic acid gas entering by (6). Hence there must have been nearly pure 

 carbonic acid gas below the level of aperture No, 7, separated by a very thin 

 transitional stratum from nearly pure air, above the level of No. 7. Nos. 7 and 2 

 were on the same level. The air drawn oft' from No. 5 passed through the iusulated 

 standard filter, E (already described), which was connected to the insulated terminal 

 of the quadrant electrometer, F. The Voss electric machine, C, was worked to give a 

 brush discharge from the needle point, B, the charging potential being indicated by 

 the vertical electrostatic voltmeter, D. Within 15 seconds after starting the machine, 

 a decided electrical effect was observed, the reading of the quadrant electrometer 

 almost immediately rising to a maximum rate of deflection of 55 divisions per minute 

 when the needle was charged positively, and 50 divisions per minute when it was 

 charged negatively. The electrification observed was not sensibly affected by 

 stopping the supply of carbonic acid gas. But when the working of the electric 

 machine was stopped and the charging wire to the needle removed, and whether the 

 supply of carbonic acid gas was continued or stopped, the electrical effects noticed on 

 the electrometer rapidly fell, and 3 minutes after the electric machine was stopped, 

 no further electrification was detected. The sensibility of the electrometer was 

 117 divisions per volt. 



