CONTRIBUTION TO STUDY OF HYDROXYLAMINE. MACKAY. 331 



This cell showed itself to be greatly superior to that con- 

 structed of bare platinum, but still slightly decomposed the 

 solution. Thus in a couple of hours an approximately N/5 

 solution in the platinum and tin cells decreased in resistance as 

 follows : — 



With platinum. With tin. 



Initial resistance 3555 ohms. 3717 ohms. 



Final " 2636 " 3201 " 



Difference 919 " 516 " 



For solutions 1/10 Normal and more dilute, a second cell 

 with pure tin electrodes of larger size and closer together, was 

 fitted up b}' fusing pieces of stout tin wire to two tin plates 

 about 25 sq. cm. in area, and arranged in the same manner as 

 the Arrhenius cell. The wire was protected by glass tubes 

 passing through holes in the wooden cork and held in place by 

 sealing wax, and as the wire could not be fused into the glass it 

 was left bare for about 25mm. abov^e the electrodes. Of course 

 with this arrangement it was necessary to always introduce the 

 same amount of liquid into the cell so that the same area of the 

 surface of the wires would always come into play. Twenty-five 

 cc. measured from a pipette was the amount used. This cell did 

 not give such a good minimum point with the telephone as the 

 electroplated one. 



Before making an observation the cell was first carefully 

 cleaned with pure water, the electrodes suspended at some dis- 

 tance over an electric lamp to dry, the cell rinsed with the 

 solution, the requisite amount put in, and the whole placed in a 

 large thermostat of the form recommended by Ostwald^, with a 

 stirrer rotated by a small air engine. A thermometer graduated 

 to the 1/50 of a degree and calibrated by the Physikalisch- 

 Technische Reichsanstalt, Berlin, was placed in the bath. By 

 the addition of cold water, or the application of a very small 

 flame under the bath, the temperature of the whole could readily 

 be kept constant to within 1/50 degree of 18", at which temper- 



1. Ztschr. phys. Chem., 2, 565 (1888). 



