112 



Laboratory Arts 



from its stand and used as a hand blowpipe. Some little dexterity 

 is required, but this comes with practice. 



Finally, bought taps may be sealed on to the upper ends of the 

 side pieces, or use made of broken burette taps, for the same 

 purpose. As an alternative, the ends might be drawn out, and 

 indiarubber connections closed by spring clips be affixed, suitable 

 jets being inserted beyond the clips. 



For the bottom ends, it will only be necessary to shrink a glass 

 tube upon a platinum wire welded to a 25 x 5 mm. piece of 



(A) 



Welded, 

 Joint 

 Ptwire 



FIG. 104. 

 Enlarged 

 view of 

 electrode 

 for Fig. 

 103. 



! ft. Stopper 



\air-hole 



FIG. 105. Enlarged views of alternative 

 electrodes for voltameter. 



N. B. The small air-hole in (A) is to per- 

 mit the expansion of the air during the seal- 

 ing of the lower end. 



platinum foil (see p. 61), and to pass this through a single-holed 

 indiarubber stopper. The glass carrying the electrodes may be 

 sealed into the tube, as in Exercise 12, but this is additional 

 work to little purpose, it being an advantage for the tubes to have 

 removable and replaceable electrodes, for cleaning and other 

 purposes. The platinum wire may be sealed into the tube, as 

 shown in Fig. 104, leaving a loop for the battery connection, or 

 it may be wrapped round a stout copper wire and soldered, the tube 

 being subsequently bent in the form of a U and partly filled with 



