Manchester Memoirs, Vol. xlii. (1898), No. 5, 



V. On a Method of Determining the Thermal Con- 

 ductivities of Salts, with some results of its 

 application. 



By Charles H. Lees, D.Sc. 



Received and read December 14th, ^^97- 



In the course of a recent investigation on the 

 thermal conductivities of mixtures of substances, and 

 their dependence on the conductivities of their con- 

 stituents, I required the conductivities of crystallised zinc 

 sulphate and some other salts, and had to devise a means 

 of determining them. The methods usually adopted in 

 determining a thermal conductivity, require a disc or 

 plate of the substance, and are therefore difficult to apply 

 to salts in the form of powder or discontinuous crystals. 

 A method of experimenting which has often been used 

 for the determination of the physical properties of small 

 bodies of irregular shape, may, however, be used with 

 advantage. This consists of immersing the body in a 

 liquid which possesses the particular physical property to 

 be determined, to nearly the same extent as the -body to 

 be tested, and observing whether the property of the 

 liquid is changed in magnitude by the presence of the 

 body. If a change is perceived, another liquid is tried, 

 till eventually one is found for which no change occurs, 

 and which, therefore, possesses the property in question 

 to the same extent as the immersed body. 



In applying this method to the determination of the 

 thermal conductivity of a salt, the salt in a rather fine 

 state is mixed with water, or with a mixture of water and 



May iph, i8g8. 



