5o6 



NATURE 



iMarch 31, 1881 



infusible, because when pressed against tlie liot glas? it at once 

 splashed out, freezing again in long thin flakes when it obtained 

 free space for evaporation. All the heat passing to the ice is 

 U5ed up in volatiIisin| it, and increase of the source of heat merely 

 increases the rate of evaporation, as in the case of water boiling 

 under atmospheric or other constant pressure; provided the 

 condenser be efficient. These experiments were repeated with 

 different thermoiieters and thickne-;ses of ice, varying from 

 4 inch to the thinnest film, -^^ inch, or thereby, and the tempe- 

 rature of the ice was always dependent up:)n the temperature of 

 the receiver (when vacuous) and quite independent of the tem- 

 perature surrounding it ; the btter merely determining the rote 

 of evaporation. Whenever a hole appeare 1 in the ice covering 



the thermometer the latter rose, and if close to the hot glass rose 

 rapidly. When the ice wore away, as shown at D, the temper- 

 ature registered by the thermometer could be made either over or 

 under zero. If the source of heat was made to play upon the top 

 of the tube, then the temperature would read over zero siy 6°, and 

 if made to play on the bottom it would read - 8°, the receiver being 

 - 12°. When however the ice was made to he on the upper side 

 of the thermometer by turning the latter round, the tem;ierature 

 could not be raised over zero, and sometimes not over - 4°. 

 These experiments were repeated by exhausting with a Sprengel 

 pump, and it was invariably found that the pressure of the gas 

 (■r vapour in the receiver determined the temperature of vola- 

 tilisation of the ice, and when the "vacuum" contained only 



water vapour the temperatures of the receiver and of the ice round 

 the thermometer (however far apart they were placed) were prac- 

 tically the same. For instance, let the receiver be — 5°, then 

 the thermometer in the ice is also - 5° or - 4° ; now let the 

 receiver be suddenly cooled to - 14° while the flame round the 

 ice is urged^ to a higher temperature ; the ice will nevertheless 

 fall to - 13' or thereby ; in short, the temperature of the " bail- 

 ing" ice is determined by that of the receiver, while the raieoi 

 its "boiling" is determined by the temperature of the tube 

 sun-ounding it. The ice remains perfectly dry, but if air be 

 admitted or the receiver be raised above 0°, melting takes place. 



As it has been objected that the thermometer might yield 

 anomalous readings under such conditions (though why I cannot 

 see), another method was tried, as shown at E. A small bulb 



blown on the end of a tube open at the other end, and containing 

 a little water, had ice frozen round it, as in the case of the ther- 

 mometer, and was then placed in the flask as before, so that 

 there was a piece of ice under ordinary atmospheric conditions in- 

 cl'ised in the ice in 7uicuo. The tube round the outer ice was now 

 raised to the softening point, but the ice in the bulb did not melt, 

 and continued solid till the bulb was denuded of external ice by 

 evaporation, showing tliat the ice in vacito was never over o . 

 It appears then that ice cannot be raised ab^ve 0° under any 

 circumstances, and that the pressure determines the volatilising 

 or "boiling" points of both solids and liquids, as Regnault's 

 work would lead us to suppose. 



J. B. Hannay 

 Private Laboratorj', Sword Street, Glasgow 



Being a reader of Nature, I have become quite interested 

 in Mr. Thos. Carnelley's experiments with hot ice. Although 

 Mr. Carnelley's experiments would seem to be sufficiently accu- 

 rate to prove that the ice was in a heated condition, I would 

 still like to offer an additional meth id to heat the ice, and alsi 

 a method to test for heat in the ice. To heit the ice I would 

 suggest a small coil of fine platinum wire placed in position in th : 

 tube where the water is to be frozen, and the two ends of the 

 coil passed through the side; of the tube and hermetically 

 sealed. 



If now the water be frozen around the coil, and a current 

 of electricity passed through the wire of sufficient amount to 

 heat the wire as much as might be determined upon, and the 



ice yet remain frozen, there would seem to be no doubt about 

 the ice having become heated by contact with the hot platinum 

 wire. 



The method I would suggest to test for heat in the ice would 

 be to take a couple of pieces of heavy platinum wire and pass 

 through the sides of the tube and hermetically sealed as before, 

 except to have a small space between the two ends of the wire 

 on tire inside of the tube, of one-eighth or one-quarter inch, or 

 as much space as might be thought best. 



If now the water be frozen between the ends or all round the 

 ends of the wire, and a small battery and galvanometer be put 

 in circuit with the terminals of the platinum wire, and a gas 

 jet be applied to heat the ice, if the ice becomes heated the 



