JO JOURNAL OF THE 



to be the same as that produced by forcing a current of air across 

 the surface of the disulphide. In farther experiments with the ther- 

 mometer the paper was discarded as uselessly cumbrous, the ther- 

 mometer was hung just touching the liquid, and evaporation was 

 started by blowing through a tube obliquely into the disulphide so 

 that the little waves struck against the bulb. The formation of the 

 snow-like solid soon commenced. The blowing could then be 

 stopped, and the growth went on rapidly until it reached a height of 

 5-6 cm., above the surface. If a current of air was directed upon 

 this growth, it increased most rapidly on the side exposed to the 

 current, forming little tufts resembling miniature, compactly-formed 

 trees and reaching in some cases a length of 7 — 8 mm. One point 

 observed was that the amount of moisture in the air had a decided 

 effect upon the ease of causing this formation and the rapidity of the 

 growth. 



A simple and effective mode of showing as a class experiment the 

 abstraction of heat by the rapid evaporation of the disulphide, or 

 more properly speaking, by the formation of the hydrate, is to take 

 a small glass tube with thin walls about 90 m. m. long and having 

 a diameter of 10 m. m. This tube is provided with a collar of cop- 

 per wire having two projecting points which turn easily in the ends, 

 bent into rings of a strong copper wire attached to a support. The 

 ring of one of the ends of the longer and stouter wire should not 

 be closed, so that the tube can be easily unmounted. This arrange- 

 ment gives stability and the tube is much easier to tilt than 

 when simply suspended by threads. The tube is wrapped with a 

 single layer of filter paper for two-thirds its length, the paper ex- 

 tending about 1 cm. beyond the closed end. This lower edge dips 

 just beneath the disulphide when the tube is in position. The tube 

 is filled about half or two-thirds full of water, is placed in its swing 

 and in a few minutes the water will be frozen and will not flow out 

 when the t ube is inverted. In one experiment, with the tube arranged 

 as above, the water was frozen within four minutes. The original 

 temperature of the water was 30° c, and the relative humidity of 

 the surrounding atmosphere was 74 per cent. 



Ballo has recorded one or two experiments to prove that this cau- 

 liflower-like growth is a hydrate and not solid frozen carbon disul- 

 phide. The following experiment confirms his results, and may be 

 regarded, I think, as conclusive of the dependence of this body for 

 its formation upon the moisture of the air. An open-necked bell- 

 jar, ground, greased and tightly fitting to a ground glass plate, was 

 provided with a large rubber stopper which was pierced with two 



