17 
the tube. The tube is then closed at the upper end with a cork 
and sealed at the lower end before removing the connection 
with the coal gas delivery tube. The cylindrical part is now 
sealed. There still remains in the tube a considerable 
quantity of air. To absorb this, the sodium is melted at a 
gentle heat over the flame, allowed to cool, and the operation 
performed repeatedly for two or three days, the tube being 
held in a horizontal position. The sodium is now filtered 
through the glass wool into the pear-shaped bulb. This is 
done as follows : The sodium is first melted and the tube 
tilted with the bulb end downwards. On heating the bulb, 
bubbles of gas are driven through the melted sodium, and 
on cooling, the tube being still held vertically, the sodium 
passes slowly into the bulb through the glass wool, which 
retains the unmelted oxide. This process of filtration may 
be hastened by warming at the same time the upper part of 
the tube. If sufiicient time has been allowed, and the 
remelting of the sodium often enough repeated, the metal 
runs through and has a bright metallic surface. Out of a 
large number of tubes prepared in this way only two were 
successful. The glass easily cracks on warming the metal 
when firmly adhering to the walls. The pear-shaped bulb 
is now sealed off and the sealed ends doubled round in the 
form of hooks. The bulb is placed in one compartment of 
a tube drawn out in the middle ; the other compartment is 
filled with phosphoric anhydride and separated by a plug of 
glass wool, as in the diagram. This tube is connected with 
the hydrochloric acid apparatus, the compartment containing 
the bulb being attached to the phosphoric acid tube of the 
hydrochloric acid apparatus. The other end is connected 
with a wash bottle of concentrated sulphuric acid. Ail the 
joints having been carefully secured, hydrochloric acid gas 
