4 Lees, Thermal Conductivity of Salts. 



For comparison, I give the mean values quoted by 

 Graetz* for metals, and the values found by me for sulphur.f 



Cu '9 



Al -5 



Mg -4 



M 3 



Fe -16 



Ni -I 



Pb -oS 



S "0004 to '0006 



The values for salts whose conductivities lie 

 between those of water and alcohol, have been determined 

 by the method described, those above that of water by 

 interpolation on the assumption that NaCl in particles 

 has the same conductivity as in bulk (rock salt). The 

 latter, as absolute values, may be wrong to a consider- 

 able extent, but the order of the various substances in the 

 above tables is not likely to be seriously affected by 

 subsequent more accurate work. 



From the above results the following conclusions can 

 be drawn : — 



(i) A good conducting metal does not always confer 

 good conductivity on its salts. 



(2) The presence of water of crystallisation in a salt 



seems to bring the conductivity near to that 

 of water. 



(3) The chlorides of the alkali metals are good thermal 



conductors. 



(4) Sulphides and oxides of the metals are com- 



paratively good conductors. 



(5) No direct connection appears to exist between 



the thermal conductivity of a salt and the con- 

 ductivities of its elements. 



* Winkelmann, Handbuch der Physik, Bd. III. 

 + Phil. Trans., 1892 and 1897. 



