518 Prof. J. G. MacGregor and Mr. E. H. Archibald on 



concentration unity the conductivity of the double salt 

 solutions is appreciably less than that of the equivalent 

 mixtures. 



With the object of securing an enlarged basis for a judg- 

 ment as to whether or not the differences of the above table 

 are due to the merely approximate values of the a's and fi^s 

 used in the calculations, observations were made of the con- 

 ductivity of mixtures of equal volumes of equi-molecular 

 solutions of each constituent of the above double salt and 

 another sulphate, zinc sulphate solutions being mixed with 

 those of copper sulphate and sodium sulphate solutions with 

 those of potassium sulphate. The following table gives the 

 results. 







Conductivity of mixtures. 







Concen- 















tration of 

 constituent 

 solutions. 



iCuS0 4 and*ZnS0 4 . 



iK 2 S0 4 and£Na 2 S0 4 . 

















Observed. 



Calculated. 



Difference 

 per cent. 



Observed. 



Calculated. 



Difference 

 per cent. 



1000 



245-4 



2451 



-012 



568-5 



5700 



+026 



•909 









526-6 



528-1 



+0-29 



•850 



215-3 



215-6 



+6i3 









•750 



199-7 



199-4 



-0-15 



452-8 



4519 



-019 



•6666 









414-4 



413-3 



-0-26 



•6000 



170-5 



1701 



-0-23 









•5000 



147 3 



1475 



+012 



324-6 



323-8 



-0-24 



•4000 



1245 



124-6 



+008 



2672 



267-7 



+0-19 



•2000 



73-20 



73-30 



+0-13 



147-3 



147-1 



-013 



•1000 



42-83 



42-76 



-0-16 



81-49 



81-40 



-0-11 



•0850 



37-63 



37-68 



+0-13 









•0800 









66-70 



66-82 



+0-18 



•0750 



33-88 



33-82 



-o-i7 



63 02 



63-12 



+015 



•0600 



28-55 



28-50 



-017 



51-67 



51-60 



-0-13 



•0500 



2401 



2405 



+016 



43-51 



43-48 



-007 



•0400 



2036 



20-32 



-019 









•0200 



12-05 



1203 



-0-15 









•0125 



7-830 



7-837 



+008 









It will be seen that in the case of both series of mixtures 

 the differences between observed and calculated values are 

 within the limits of error of the observations up to a concen- 

 tration of 1 gramme-equivalent per litre. They have neither 

 the large values found in the case of the double salt solutions 

 nor the slightly smaller values observed in the case of the 

 equivalent mixtures. In the calculation of the conductivity 

 of each of these series of mixtures one set of the values of the 

 a's and /ju^s used in the calculations of the double salt 

 solutions were of course employed. If, therefore, the differ- 



