MICROLITER DI\TER TECHNIQUE 353 



4. Fuse the end of a glass thread to form a drop, and fuse the 

 drop to the bottom of the bulb by heating the drop to a bright red 

 heat and the very bottom of the bulb to a medium red heat, and 

 then joining the two with a slight pressure. 



5. Remove from the flame and pull out the glass tail at once 

 {E, Fig. 118). If the bulb is too hot, its shape will be spoiled while 

 pulling the tail; if too cold, the glass drop will not fuse into the 

 bottom and the tail will break off. Test the strength of the fusion 

 by applying a lateral pressure to the tail. 



6. Cut off the excess at the neck and tail with a diamond point. 

 To prepare a conical diver [D, Fig. 116) heat only the side walls 



of the bulb after the tail has been fused on, and collapse and draw 

 into the conical shape. 



Cleaning the Diver. Holter ( 1943, page 429) has recommended 

 the following procedure for cleaning the diver after an experiment: 



1. Rinse the outside of the diver with distilled water. 



2. Remove the neck seals separately with soft filter paper cut 

 into short narrow strips and rolled between the fingers to form tight 

 smooth rolls. Take particular care to remove the paraffin oil as 

 completely as possible. 



3. With a finely drawn pipette having a 2-3 ml. capacity, fill 

 the diver with glass-distilled water and blow about 2 ml. water 

 through the diver in a brisk stream. Stop before air gets into the 

 diver so that filling with the next liquid will be easier. 



4. Repeat the washing with acetone, toluol, acetone, and twice 

 with glass-distilled water in the order given. Leave the toluol in the 

 diver for a few min. before replacing it with acetone. If the diver 

 had a neck ring of wax, rinse two to three times with toluol. 



If the diver is unusually dirty, treat as described and then fill it 

 with freshly prepared 1% potassium permanganate in cone, sul- 

 furic acid, and let stand overnight. Replace the solution with water, 

 wash with strong hydrochloric acid, and flush well with glass-dis- 

 tilled water. 



5. Blow air through the diver to remove as much water as 

 possible after the final washing. 



6. Dry the outside of the diver with filter paper and place in an 

 oven at 120°. 



7. Holding the diver by the tail with forceps, heat only the 

 neck of the diver by moving it slowly two to three times through 



