1895.J Electrification of Air, tyc. 9 by bubbling through Water. 343 



of thin sheet copper, leaving an air space of about 3 mm. all round 

 between its edge and the inner surface of the jar, about 3 cm. above 

 the liquid surface, was used to prevent spherules of the liquid from 

 being tossed out of the jar by the bubbling. 



17. In the following short summary of our results the duration 

 of each experiment was 10 minutes. The effect of blowing air 

 through water and other liquids is summarised in 18 to 27, and of 

 blowing other gases than air through water in 28 to 31. 



18. The jar contained 200 c.c. of the Glasgow town-supply water 

 (from Loch Katrine). A mean of seventeen experiments showed an 

 electrification oF the jar to 4 volts positive when air was blown 

 through it for 10 minutes. 



19. A solution of zino sulphate of different strengths was now 

 used instead of the pure water. Three experiments, with 150 c.c. 

 of water containing one drop of a saturated solution of the zinc 

 sulphate, gave half the positive electrification that would, under 

 similar circumstances, have been obtained from water only. With 

 five drops no definite electrification was obtained. With greater 

 proportions of the zinc sulphate solution up to saturation (twenty- 

 four experiments altogether) the electrification was on the average 

 slightly negative. 



20. Twelve experiments were then made to test the effect of 

 adding a solution of ammonia to the water. One drop reduced the 

 electrification to one-half; two drops brought it down to one-quarter. 

 With larger proportions of ammonia than this, up to a saturated 

 solution, we found a very slight positive electrification, never amount- 

 ing to more than a small fraction of a volt, and therefore negligible 

 in the circumstances. 



21. Seven experiments with sulphuric acid of different strengths 

 all showed small positive electrification, the amount gradually de- 

 creasing from J volt, in 10 minutes, with 0'5 per cent, acid in water 

 to -^Q volt, in the same time, with acid of full strength. 



Seven experiments with hydrochloric acid solution of different 

 strengths all showed a small negative electrification, the amount 

 gradually increasing from ^ volt, in 10 minutes, with -^ per cent, acid 

 solution in water to 1^ volts, in the same time, with acid solution of 

 fall strength. 



Nine experiments with calcium chloride solution were made. A 

 saturated solution and a solution diluted to 75 per cent, of full 

 strength gave no result; but solutions of gradually diminished 

 strength, from 50 per cent, down to -^ per cent., showed a negative 

 electrification from fully -J volt, in 10 minutes, down to ^ volt. 



Additions of very small quantities of washing soda to water greatly 

 reduce the positive electrification obtained. 



Loch Katrine water, supersaturated with carbonic acid, and placed 



