no 



Laboratory Arts 



in a similar manner, at the other end and on the opposite side to that 

 already completed, wrapping in cotton-wool as before. 



The whole difficulty in this exercise is to keep the glass from 

 cracking, and this can only be accomplished by maintaining at the 

 same temperature the whole circuit of glass while the joining is 

 proceeding, and after the junction is successfully made, heating 

 the whole to an even temperature, and then annealing in cotton- 

 wool and cooling very slowly. 



EXERCISE 16. To make an ozone tube. 



Select a piece of 27-25 mm. tubing about 30 cm. long, and one 

 about 20-18 mm. about 25 cm. long. Seal a side piece into the 



FIG. 102. Stages in the construction of an ozone tube. 



former about 7 cm. from one end, and slightly contract this end 

 by drawing!out, and blowing a thin bulb which is to be subsequently 

 removed. 



Draw out one end of the smaller tube, and seal up the end in the 

 shape of a hemisphere ; also blow a slight bulb near the open end, 

 which will just prevent the small tube passing the constriction of 

 the wider one (Fig. 102 (2) ). 



Wrap a strip of paper round the narrow tube and push it into 

 its place in the wider one, sealing the joint in the usual way, as in 

 Exercise 12, by heating both during rotation until softened, pressing 

 together and blowing in successively at each open end until the final 

 shape is that shown in Fig. 102 (3). 



