AQUEOUS SOLUTIONS.—MCKAY. 327 
inches. The electrodes were of stout platinum and supported 
by platinum wires passing through the ebonite covers of the 
cell. The diameter of the electrodes was 14 inches. The second 
cell was a cylindrical vessel of diameter 1} inches. The elec- 
trodes, whose diameter was nearly as great, were also of 
platinum. The platinum wires leading from them were fused 
into glass tubes, in the interior of which they made connection 
through mercury with the outside wires. The glass tubes were 
moveable through holes in the cover of the cell so that the 
distance between the electrodes could be adjusted. For any 
given adjustment the tubes were held in place with sealing- 
wax. The solutions, whose conductivity could be measured in 
this cell, ranged from the most dilute to, in the case of sodium 
chloride, about .02 gramme-equivalent per litre. The range of 
of NaCl solutions which could be measured in the first cell 
varied from 0.1 to 5 gramme-equivalent per litre. The electrodes 
of both cells had been platinized in a solution containing 1 
erm. of platinum tetrachloride and .008 grim. of lead acetate to 
30 grm. of water. 
Measurements were made near the temperature 18°C, almost 
always within 0.3 degree of that temperature. The thermometer 
could be read to .01 degree, and was corrected by compari- 
son with a standard thermometer tested at the Physikalisch- 
Technische Reichsanstalt, Berlin. The thermometer was kept in 
a separate tube in the bath; and it was found, on several occa- 
sions, by placing another chermometer in the cell itself, that the 
temperature of the liquid in the cell could be read off from the 
thermometer in the tube in almost all cases to less than 0.1 
degree. Where the measurements were not made at exactly 18°, 
correction was made by means of the temperature coefhcients 
given in Fitzpatrick’s Table in the British Association Reports.* 
The bridge wire was calibrated by Strouhal and Barus’ 
method. The resistances for this purpose were made of German 
silver wires, whose ends were soldered to short pieces of thick 
* Nottingham, 1893. 
