314 Profs. J. A. Fleming, and J. Dewar On the 



140' 















f CAUSTIC POTASH, 



5% 









too* 



ft 











CO 

 Z 



< SO' 



II 



1. 









8- 



1 j 













O 



2 40-J 



f CAUSTIC 











-J 



bJ 



Q 



2Q\ 



i 







! 





CAUSTIC 5 



y 



OB A Sat. ^ _y 















-200° -150° -100° -50° O 



TEMPERATURE IN PLATINUM DEGREES. 



Fig. 5. — Curves showing the variation of dielectric constant of frozen caustic 

 alkali solutions with temperature. 



On examining these values for the dielectric constants of the- 

 frozen caustic alkali solutions, it will be seen that there is a remark- 

 able difference between these last bodies and the other electrolytes 

 examined by us, in that the values of the dielectric constant of the- 

 caustic alkalis are relatively very high at the low temperature of 

 liquid air. In this respect the 5 per cent, solution of caustic potash 

 is especially remarkable. For the same temperature, viz., —185° C.,. 

 and varying concentrations, the 5 per cent, solution of caustic potash 

 shows a maximum value for the dielectric constant of about 130, 

 whereas the dielectric constant of the sulphate of copper, chloride 

 of sodium, potassic cyanide, perchloride of iron, sulphuric and 



