[ 79 ] 

 XII. Intelligence and Miscellaneous Articles. 



ON THE SOLIDIFICATION OF CERTAIN SUBSTANCES. 

 BY M. L. DUFOUR. 



TN a preceding communication it has been shown that water, kept 

 -*- in suspension in a liquid of its own density, could be cooled much 

 below 0° without solidifying. It was probable that other bodies 

 placed in similar conditions would experience a similar retardation of 

 solidification. The following are three examples : — 



Sulphur. — The persistence of this body in the fluid state below 

 115° has been already noted (M. Person and Prof. Faraday), but it is 

 an exception not frequently mentioned. 



It is easy to prepare a solution of chloride of zinc which has the 

 same or a little higher density than that of liquid sulphur. This 

 solution can be heated to 115° without boiling; sulphur may be 

 melted in it, and then floats in spheres. In order to keep the 

 spheres surrounded by liquid, a layer of oil may be poured on the 

 solution. On cooling, the solidification scarcely ever takes place at 

 the melting-point. The liquid globules usually sink to 70°, 50°, 

 &c. before solidifying. The solidification is spontaneous, or it 

 may be provoked by the contact of a solid body, especially of a 

 fragment of sulphur ; but in the special conditions of these experi- 

 ments the liquid state presents a remarkable stability. At 60°, salts, 

 metallic wires, &c. may occasionally be introduced into globules 6 

 millims. in diameter without inducing an immediate solidification. 

 Globules of | a millim. in diameter frequently remain fluid at 5°, 

 and persist in that state for several days. 



When the spheres of sulphur remain liquid at 50° or 60° below 

 the ordinary temperature of solidification, it is truly interesting to 

 see their change of state. The fluid mass, which is transparent and 

 of a deep red, suddenly changes into a hard, opake yellow fragment. 

 This experiment, which is very pretty and easily performed, is 

 exceedingly well adapted to exhibit the curious phenomenon of 

 superfusion. 



Phosphorus. — M. Desains has already noted the conservation of 

 the liquid state by this body below 44°. The method which serves 

 for sulphur is perfectly applicable to phosphorus. The solution of 

 chloride of zinc of a suitable density is covered with a layer of oil 

 in order to avoid contact of the air. The liquid transparent glo- 

 bules of phosphorus are easily seen, and their solidification does not 

 take place till far below 44°. Globules, \ to 2 millims. in diameter, 

 frequently sink to 5° or even to 0°. The liquid state is also remark- 

 ably stable, and the change of condition gives occasion for observa- 

 tions analogous to those relative to sulphur. 



Naphthaline. — The fusion and solidification of this body usually 

 take place at 79°. It has almost exactly the same density as water, 

 but is somewhat less dense in the liquid state. With suitable 

 precautions the phenomenon of superfusion may be easily produced. 

 It is merely requisite to melt the body in a flask filled to the neck 

 with boiled water, and then to incline the flask so that the liquid 

 napthaline lodges in the upper part of the flask, pressed, but feebly 



