328 



MR. W. C. D. WHETHAM ON THE IONIZATION OF 



The apparatus is filled from a platinum vessel, which is an exact model on a larger 

 scale of the filling machine used to add stock solution and is shown in fig. 2. The 

 vessel is arranged to hold 250 grammes of water, and about that quantity 'is 

 collected in it and accurately weighed. The long limb of the vessel being 

 introduced into the cell, a slight increase of pressure is given by removing the 

 platinum stopper and placing a tube of thick india-rubber lightly on its top. At 

 the other end of the india-rubber is a glass tube, part of which is packed tightly 

 with cotton wool. A slight puff of air at the glass tube is then sufficient to start 

 the water siphoning over into the cell. This goes on till the whole quantity of 

 water has entered the cell. 



2. 



Fig. 3. 



The water is then left for some hours till its temperature has sunk nearly to the 

 freezing point. This process can be much accelerated if desirable by the ether 

 apparatus. It is then necessary to adjust the level of the liquid. This is done by 

 means of the glass emptying vessel (shown in fig. 3), through the cork of which pass 

 two tubes. One of them is connected by means of india-rubber with another glass 

 tube, which carries a short piece of very fine platinum tubing at its end. The 

 bore of this is so small that a fine needle will only just enter it. The glass stem 

 will pass into the platinum tube which forms the side entrance to the cell in 

 fig. 1. At its upper end is fixed a glass ring which is too big to enter, and lies 

 on the top of the platinum. When this ring is pressed home, the bottom of 

 the fine platinum tube is in a perfectly definite position inside the cell. In order 

 that it should always withdraw to exactly the same level, it is necessary that the 



