Laboratory Arts 



The needle will serve to hold the platinum axially should it show 

 a tendency to move. 



EXERCISE 19. To make a percolator. 



Take a piece of 26-24 mm. glass tube, about 30 cm. long, seal up 

 one end hemispherically, and without allowing it to cool, join to it a 

 lo-cm. piece of 12-io-mm. tube, by pressing the two together while 

 red hot, and well softened, blowing alternately in each end and 

 heating the junction strongly until quite secure. Before cooling, seal 

 in to the side (near the bottom) of the wider tube a small tube 3 mm. 

 external diameter, and about 30 cm. long. Bend this tube round, 

 take it up the side of the wide tube, turn it about 10 cm. from the 

 junction, and let it return by the side of the first portion. 



Blow out an opening in the side of the lower piece of tube and 

 seal in a second piece of the narrow tube bent downwards on the 



FIG. 108. Stages in the construction of a percolator. 



inside, held in place meanwhile with a perforated cork, arranging 

 the portion outside parallel to and touching the down pipe already 

 connected to the upper tube, as shown in Fig. 108 (5). 



On the opposite side join in at right angles a piece of lo-mm. 

 tubing, bend this, carry it up, and join in at the top, as shown. 

 The lower curve must be heated at the time of pressing together 

 the tubes to make the upper junction, consequently the order of 

 procedure will be 



(i) Blow out the upper opening ; (2) bend the tube at right 

 angles, at A, and cut off at the correct length; (3) bend again 

 at right angles at B, and keep A hot meanwhile ; (4) press 

 together at A, keeping B hot ; (5) seal up the joint and allow all 

 to cool. 



The last joint to be made is that between the two small tubes. 



