Ii | 
when brought home, is rigidly connected to an overlapping cap, 
screwed on the outside of the cylinder. By turning the handle A 
backwards with cock K closed, cap and plunger are turned too and | 
the latter is therefore drawn a little out of the cylinder. The liquid 
may thus be drawn up into the electrode tube, and by swinging the 
Fig: 17: 
handle A gently to and fro the equilibrium between platinum elec- 
trode, liquid and hydrogen can be easily established. Dead space and 
mistakes are avoided by the arrangements C and D on cock and 
frame. The protruding piece D allows the turning out of the plunger 
only, if the cock is shut and the quadrant C on the top of the cock 
is then in the position, shown in the figure. The same arrangement 
clearly helps to avoid the mistake of opening the cock and thus 
admitting the hydrogen, when the plunger is not turned home. 
After shutting the cock, establishing equilibrium as described 
above, and adjusting the liquid in the electrode tube (by slightly 
turning the handle A) in such a way, that it just touches the point 
of the platinum wire, the whole apparatus is lifted up and placed 
on the wooden block of Fig. 16, the electrode tube dipping in the 
KCl-cup. 
Another improvement was the carrying out of all these operations 
in an air-thermostat (Fig. 18), in which all the apparatus, shown 
Q* 
