Electrolysis of Alkali Salt- Vapours. 209 



The end of this electrode was closed by a conical platinum 

 cap which was about 9 centims. down the tube TT'. 



At T' the platinum tube was fitted tightly into a glass 

 tube through which air charged with spray of a salt-solution 

 entered. The spray was produced by a Gouy sprayer S, 

 which projected the spray into a glass bulb G, about 8 centims. 

 in diameter, from which the air and spray were led through 

 an inverted U-tube, in which the coarser spray settled. The 

 salt-solution was contained in a reservoir, the level of the 

 surface being 30 centims. above the nozzle of the sprayer. 

 The greater part of the spray settled in the bulb and first 

 half of the U-tube, and was returned to the reservoir through 

 a tube up which the liquid was forced by compressed air. 



The supply of compressed air used was obtained by means 

 of two water-injector pumps similar to the one used in the 

 previous work on the conductivity of flames. Some of the 

 air was allowed to escape by bubbling through mercury 

 which served to keep its pressure nearly constant, and the 

 rest was passed through a large carboy to smooth out small 

 oscillations in the pressure. 



The air-pressure at the sprayer was measured by means of 

 a water manometer, and was kept constant at 50 centims. 

 This arrangement gave enough air to work the sprayer and 

 also the furnace, except at temperatures above about 1100° C, 

 when the air-s apply to the furnace was supplemented by 

 oxygen from a cylinder, by means of which a temperature of 

 1400° C. could be obtained. 



The temperature of the tube was measured by means of a 

 platinum platinum-rhodium thermo-couple, which was simply 

 connected through a resistance-box and commutator to an 

 Ayrton-Mather dead-beat galvanometer G 2 of about 500 ohms 

 resistance. 



The platinum wire served to support the tube, and the 

 Pt/Rh wire was fused on to the tube at a point on its upper 

 surface so that the tube itself formed one of the elements of 

 the couple. The couple was standardized by determining 

 the galvanometer deflexion corresponding to the melting- 

 point of K 2 S0 4 , which melts, according to Heycock and 

 Neville, at 1066° C. The K 2 S0 4 was introduced into the 

 tube on a small platinum spatula, and the temperature 

 gradually increased until it was seen to melt, and the cor- 

 responding deflexion noted. Then by maintaining the tube 

 at a series of constant temperatures near the M.Pt. and find- 

 ing at which the K 2 SO i melted, it was possible to obtain two 

 temperatures very near together, at one of which the K 2 S0 4 

 melted and at the other remained solid. The mean of the 



Phil. Mag. S. 6. Vol. 4. No. 20. Aug. 1902. P 



