CHAPTER VI 



GLASS-WORK REQUISITES AND HOW TO 



MAKE THEM 



How to make a Glass-Cutting Knife. 



Take an ordinary pocket-knife, heat the blade until it 

 becomes white hot in the flame of a blow lamp, and im- 

 mediately plunge it into cold water, keeping it there until 

 it has become quite cold ; the edge should then be whetted 

 on a rough stone. This process will give it a rough cutting 

 surface, capable of scratching ordinary glass tubing, etc. 



When the rough edge wears off, it can always be renewed 

 by re whetting it on the stone. 



Glass Tubing. 



For the making of capillary pipettes, etc., tubing of 

 about 5 millimetres external diameter is usually used. The 

 glass should be of the best kind if we desire to make 

 pipettes uniform in shape and calibre, and, as the glass 

 itself is quite inexpensive, there is no need to use inferior 

 quality. 



Method of making Capillary Pipettes. 



Take a piece of glass tubing, cut it into lengths of about 

 9 centimetres. This is done by holding a piece of glass 

 tubing in the right hand and against the ball of the thumb, 

 while the same hand is armed with the glass-cutting knife, 

 the edge of which is made to rest firmly upon the glass 

 tube. With the left hand the tubing is now rotated, and 



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