n6 Laboratory Arts 



blue tint observed on looking through a quantity of it. Thus 

 the ends of a Jena tube are blue, but little if any colour is 

 noticed by looking across the tube. 



This particular tubing is difficult to work, and there 

 appears to be a great deterioration or prolonged keeping 

 such tubing cracking when suddenly placed in a blowpipe 

 flame. 



To cut the tube it should be wrapped with moistened paper 

 applied in two parallel strips with a space of about |" between, 

 as described on p. 71, heated between these with a blowpipe 

 flame, and plunged under water. All cut edges should be 

 rounded before use, and if possible, bordered by inserting and 

 rotating a carbon cone in the hot tube. 



Jena glass can only be worked i.e. bent or blown in 

 the oxy-gas flame, a somewhat difficult flame to work with 

 owing to its small size and high temperature, the latter being 

 sufficiently high to devitrify the glass if kept long under its 

 influence. 



By means of an oxy-coal gas flame, or even an oxy-ether 

 flame, it is possible to blow bulbs, make T or Y pieces, and 

 perform several of the operations already described for soda- 

 glass work with almost equal ease, though it is difficult to obtain 

 glass of convenient dimensions. 



It should be remembered that an oxy-coal gas flame can 

 be produced by supplying the ordinary blowpipe with oxygen 

 from a cylinder through a regulator instead of air from a 

 blower. The flame to be aimed at is a long, noiseless one, 

 practically colourless, and intensely hot, particularly near the 

 blowpipe the absence of nitrogen in the flame making it 

 almost solid, and removing the hottest point from two-thirds 

 of the length of the flame from the blowpipe, to about one- 

 twentieth of that distance. 



The heat being so great, it is difficult to keep the glass 

 from devitrify ing if this point of maximum temperature be 

 freely used ; consequently it is well to use the flame half 

 way up, and gradually bring the work nearer the blowpipe 

 as the higher temperature is needed, taking care, however, 

 not to localize the heat too much unless this is specially 



