14 



At this temperature, the color of the wire is a bright yellow. 1 current of 7^ 

 amperes may be used for #26 platinum wire. 



The heater is adjustable in position and should be set squarely under the glasa 

 rod. The heater can be raised and lowered and the loops bent in and out. If the 

 heater is too low or too open at the top of the loops the heat will not be main- 

 tained long enough as the glass rises, and the final taper may be too short or 

 the tip broken. On the other hand if the heater is too high the final taper will 

 be too long or the tip fused. 



Sj. lalCHCJ Of M» t fc 



Fl« 9 



One other adjustment that can be made is the position, up and down, of the bar 

 -hat locks the machine while the glass is being clamped in place. The lower the 

 bar is adjusted the less will be the initial tention on the glass. It should be 

 kept fairly low. 



It will be seen that each of these adjustments affects the others. Thus an increase 

 of heater current or a raising of the heater, or a lowering of the locking bar will 

 all act to increase the heat delivered to the glass. The main thing seems to be a 

 rather intense heat at the start, maintained as the glass rises until just before 

 the pull-out. ^he exact setting however, can only be made experimentally. 



With the machine adjusted to give the type of point desired, it is possible to 

 turn out pipettes or needles at the rate of four to six per minute. This machine 

 is now in use in Dr. Chambers' laboratory. I>u Bois, 1931. 



