4:'?A Professor Sir James Detvar [June 8, 



of another kind is the facility with which an electrified glass rod 

 clears up ordinary opalescent liquid air by attaching the finely sus- 

 pended impurities of ice crystals, solid carbonic acid, and organic matter 

 to its surface when moved about in the liquid. The same thing may 

 also be done by moving about a crystal of nitrate of uranium, which 

 by cooling becomes highly electrified without the need of direct 

 friction as when glass is used. 



The Spheroidal State of Liquid Air on the Surface of Liquids, 



As volatility depends on vapour pressure, of two liquids that having 

 the higher vapour pressure at any given temperature is necessarily 

 the more volatile. The difference in the facility of condensation of 

 the vapours produced by different liquids may easily be demonstrated 

 by the use of liquid air. 



A series of Uquids with different boiling points, like : tetrachloride 

 of carbon ; water ; caustic potash solution ; benzoic ether ; and strong 

 sulphuric acid ; were selected, and each placed to the depth of about 

 an inch in a number of shallow cylindrical cups, as shown in Fig. 2, 

 the surfaces of which could in succession be projected on a screen by 

 means of a horizontal lantern. 



On allowing drops of liquid air to fall on the surfaces of these 

 Uquids, best by filtration through a small filter-paper funnel, they 

 immediately assume the spheroidal state, and the projection through 

 the liquid showed they were moving about with considerable rapidity, 

 impinging on the sides of the vessel and getting deflected like an 

 elastic body, while followed by clouds of condensed vapour, the 

 relative amount of which may be taken as roughly proportional to the 

 volatility of the liquid. With water the cloud was very dense, being 

 less so in the case of the alkali solution, more so for the tetrachloride 

 of carbon and least for sulphuric acid. On the sulphuric acid the 

 drops moved about slowly owing to the high viscosity of the liquid, 

 but with hardly any cloud, while on the surface of benzoic ester, a 

 lively agitation accompanied by a light cloud was observed. In the 

 case of the tetrachloride of carbon, the effect was most striking : 

 dense clouds swayed to and fro over the surface, and the drops of 

 liquid air shot to the walls of the vessel at all angles of incidence and 

 rebounded, followed by tails of vapour, making them look like 

 miniature comets. In order to secure a good view of the move- 

 ments, it is necessary occasionally to blow the fume away from the 

 upper part of the vessel by a current of dry air. Care must be taken 

 to avoid the fall of too much liquid air in one place, which would 

 cause a rapid local cooling of the liquid attended with solidification, 

 which inevitably arrests all spheroidal motion. This may be prevented 

 to a great extent by having the liquids in the vessels used for pro- 

 jection slightly lieated before the experiments are begun. 



