NUCLEAR CONDENSATION OE CERTAIN ORGANIC VAPOURS. 
in the value of the expansion is an indication that the ester has acted on the rubber. 
Acetic acid and inactive amyl alcohol (iso-butyl carbinol), when tested in this way, 
and when tested directly, were not found to act on the rubber used in the writer’s 
apparatus. 
All the vapours tried condensed more readily in air on the positively charged nuclei 
than on the negative, as is seen below. Iiontgen rays were the ionising agent. 
Vapours which Condense with a Smaller Supersaturation on the Positive Nucleus 
than on the Negative. 
Ethyl acetate, methyl butyrate, propyl acetate, acetic acid, amyl alcohol (“ in¬ 
active ”). 
Przibram (loc. cit.) has found in addition to the above :—- 
Methyl alcohol, ethyl alcohol, iso-amyl alcohol, heptyl alcohol, chloroform, ethyl 
iodide. 
It is remarkable that there is only one vapour (water) so far known which 
condenses more readily on the negative than on the positive ion. 
Bubbling Experiments. 
Lenard* showed that when water splashes against a metal plate it charges the 
plate positively and the surrounding air negatively; a little later Lord Kelvin! 
observed the electrification produced by air in bubbling through water—the air 
became negatively and the water positively charged. The air near the Niagara Falls 
is known to be strongly negatively charged. Professor Thomson^ has suggested a 
double-layer theory to account for these observations. “ When air bubbles through 
water, or when the area of a drop is suddenly increased by the splashing of the drop 
against a plate, a virgin surface of the water is exposed to the air; if, as seems to be 
the case, a double layer of electricity is formed at this surface, and if the ions in the 
layer next the air come from the air, then there must be left in the air an excess of 
negative ions if the outer coating is positive, and of positive if the outer coating is 
negative.” On this view for a water drop the negative layer is next to the water 
and the positive layer to the air. 
Professor Thomson^ has further pointed out that if this double layer exists at the 
surface of an ionic condensation nucleus, and if the layers are in the same order on 
both positive and negative nuclei, then the relative efficiency of the nuclei will not lie 
the same. For example, if the water nuclei have the negative layer inside, as 
indicated by the bubbling and dropping experiments, then the negative ion will be a 
* ‘ W 1ED. Ann.,’ 46, p. 584 (1892). 
f ‘Roy. Soc. Proc.,’ 57, p. 335 (1895). 
| ‘ Conduction of Electricity through Gases,’ 2nd Edition, p. 428. 
§ Loc. cit., p. 186. 
