Intelligence and Miscellaneous A?>ticles. 79 



ON THE DETERMINATION OF THE SOLIDIFYING-TEMPERATURE OF 

 LIQUIDS, AND IN PARTICULAR OF SULPHUR. BY D. GERNEZ. 



The determination of the temperature at which the passage of a 

 body from the solid to the liquid state is effected, or inversely, 

 presents, notwithstanding its apparent simplicity, uncertainties 

 which have only been dissipated for a relatively restricted number 

 of substances, even when the change of state takes place abruptly — 

 that is to say, when the solid becomes suddenly liquid through an 

 infinitesimal change of temperature. The slowness with which the 

 fusion of a body is produced in a bath at a constant temperature but 

 little above the fusing-point, and the imperfect conductivity of the 

 substances (which permits certain parts of the liquid to attain 

 temperatures above that of the part not melted), have led physicists 

 to substitute for the determination of the fusing-point that, supposed 

 identical, of the point of solidification : only it often happens in this 

 case that the measurements are found to be falsified in consequence 

 of the phenomena of surfusion. As I will show, these phenomena 

 can be utilized to determine the solidifying-temperature of liquids 

 with a precision only limited by the patience of the experimenter. 



For this purpose, into a glass tube 3 centims. in diameter, closed 

 at one end, such a quantity of the solid is put that in the liquid 

 state it forms a column 5 or 6 centims. in height ; along the axis 

 of the tube a thermometer, held by a cork, is arranged, the bulb of 

 which, sufficiently small to have only a negligible effect on the 

 temperature of the surrounding liquid, descends to within a few 

 millims. of the bottom, without touching the tube. The fusion of 

 the body is then determined by putting it into a bath of water or 

 paraffin at a temperature a few degrees higher than the presumed 

 point of solidification. "When the body is entirely melted, the tube 

 is brought into a bath at a constant temperature lower than the 

 temperature sought ; and we wait until the indications of two 

 thermometers (one internal, the other external) differ only very 

 little. The result is accelerated by turning the tube on its axis — 

 which does not provoke solidification, unless in the movement the 

 thermometer rubs against the sides of the tube bathed by the liquid. 

 The body being thus in the state of surfusion, a fine glass needle 

 with its extremity covered with a small quantity of the material in 

 the pulverulent state is introduced through a second aperture in the 

 cork, and this extremity brought into the liquid, the solidification of 

 which is immediately determined. To urge on the phenomenon, the 

 cork is rotated about its axis, which moves the stem and carries the 

 crystalline germs cylindrically round the thermometer, the indica- 

 tions of which are then followed, it soon attaining a maximum 

 certainly not higher than the solidifying-point, but possibly lower. 

 The experiment is then recommenced, the preceding maximum being 

 chosen for the temperature of the surrounding bath ; and by ope- 

 rating in the same manner the solidification of the liquid is deter- 

 mined : it is found that the thermometer rises to a maximum higher 

 than the previous one. After two or three trials of this sort, 

 temperatures are arrived at which differ from one another by only a 



