Mfc F. E. SMITH OX THE NORMAL WESTOX CADMIUM CKLL. 3y? 







about 17C., but the irregularities were afterwards traced by COHEN* to a transition 

 which the 14'3 per cent, amalgam which was used undergoes at 23 C. The solution 

 has also been investigated by H. v. STEINWEHB,! who failed to confirm any transition 

 point at about 17 C. Cadmium sulphate is very soluble and increases very little in 

 solubility over the ordinary range of temperature. As purchased, the crystals are 

 generally acid, and in all cases it appeal's necessary to purify by recrystallisation. 



Setting up of the Cell. 



We have employed the Rayleigh H form of cell in nearly all our work. A 

 platinum wire was fused into the lower end of each limb, and the parts of the wire 

 inside the vessel were amalgamated by passing an electric current from a platinum 

 anode through an acid solution of mercurous nitrate to each of the wires in turn. 

 The vessel was washed out twice with dilute nitric acid, and several times with 

 distilled water ; it was dried in an oven. A small pipette was used for the intro- 

 duction of the amalgam, and a small thistle funnel for the insertion of the mercurous 

 sulphate paste and cadmium sulphate crystals. The main stock of amalgam was 

 flooded with very dilute sulphuric acid, and melted over a water bath ; a little was 

 then introduced into one of the limbs of the H vessel. After the amalgam had 

 solidified the limb containing it was washed out several times with distilled water, 

 care being taken not to wet the interior of the other limb. A little distilled water 

 was then added, and the amalgam again melted by immersing the H vessel in 

 hot water ; after solidification it was washed once more. Into the other limb 

 of the vessel sufficient mercury was added to cover the amalgamated platinum 

 wire and then the mercurous sulphate paste was introduced. The paste consisted 

 of mercurous sulphate mixed with about one-fourth its volume of powdered 

 recry stall ised cadmium sulphate, and about one tenth its volume of pure mercury. 

 (The latter was not added when the mercurous sulphate was prepared electrolytically 

 or by means of fuming sulphuric acid.) To this mixture sufficient saturated cadmium 

 sulphate solution was added, so that when well mixed the whole formed a thin paste. 

 After the introduction of some of this paste into the limb containing the mercury, 

 powdered crystals of cadmium sulphate were added to the contents of each limb, and 

 after an interval of one hour sufficient saturated cadmium sulphate solution was 

 inserted to fill the vessel to the top of the cross-connecting-tube. The cells were 

 hermetically sealed with the aid of a blow-pipe. For the comparison of their electro- 

 motive forces the cells were immersed in paraffin oil and were maintained at an 

 approximately constant temperature of 17 C. The comparisons were made by means 



* E. COHEN, ' Zoitschr. f. Phys. Chem.,' 34, p. 621, 1901. W. JAEGER and ST. LINDECK, ' Ann. 

 d. Physik (4),' 3, p. 366, 1900; also ' Zeitschr. f. Phys. Chem.,' 35, p. 98, 1900. 

 t H. v. STK.IMVEJIR, 'Ann. d. Physik, pp. 1046-1053, 1902. 



