1897.] Newly Prepared Gases. 351 



the water in A, and a deflection of 29 divisions negative per 

 minute was obtained as the gas entered /. 



(6) The tube connecting A and B was removed and a tube 

 containing glass wool was substituted. With the same current 

 through the cell a slight cloud was seen over the water in B and 

 the deflection was reduced to 6 divisions per minute. The elec- 

 trification of the gas was thus reduced to i of its original value 

 by passing through 15 centimetres of glass wool. The amount of 

 spray carried through this length of wool must have been ex- 

 tremely small but the cloud was distinctly visible. 



(c) The tube containing the glass wool was heated with a 

 Bunsen burner, and its discharging power was considerably 

 increased as the spot of light then gave only 2 divisions per 

 minute and no cloud was observed over the water in B. 



It is thus evident that the formation of the cloud and the 

 presence of the charge are phenomena which accompany one 

 another. 



(7) The clouds which are formed are slightly different in 

 appearance and for equal electrifications those formed in oxygen 

 are whiter than those formed in hydrogen. A difference is also 

 to be noticed in the positive and negative oxygen clouds, that 

 formed in the latter being the whiter. This would point to the 

 fact that the drops formed in the negative oxygen are larger than 

 those in the positive, and that those formed in either positive or 

 negative oxygen are larger than those in the hydrogen. A fairly 

 approximate value for the radius of the drop may be obtained by 

 observing the rate at which the cloud falls in a vessel. The 

 velocity of the drop through the gas was obtained by taking two 

 photographs of the cloud allowing some minutes to elapse between 

 the two exposures. Figure 3 represents two such photographs 

 taken of the cloud formed by bubbling the charged oxygen from 

 a sulphuric acid electrolyte through water. Three minutes were 

 allowed to elapse between the two exposures, and the scale shows 

 that in that time the cloud had fallen between 9 and 10 milli- 

 metres. Similar experiments were made with the other gases, 

 but in the case of the hydrogen the outline of the cloud never 

 became so distinct as it did in the oxygen. 



The sizes of the drops were obtained from the formula 

 fiaV = %Tra 3 g (Lamb, Motion of Fluids, p. 229). 



This gives for the radius of the drop in the positive oxygen 

 6'8 x 10 -5 , the rate of fall being 10 millimetres in 3 minutes, and 

 the radius of the drop in negative oxygen 7 "9 x 10 -5 the rate of fall 

 being 18 millimetres in 4 minutes. 



