120 



85. 



BASES A^-D ACIDS WITH REAGENTS. 



With the aid of the burette, put 20 c.c. of the standard 

 sulphuric acid in the bulbed tube C (fig. 5), and add 

 water until the bulbs are about ^\^ filled ; the quantity of 

 the liquid should not be so great, however, as to incur any 

 danger of loss when the gases evolved from the combus- 



tion-tube pass rapidly through, or 



when, as sometimes 

 A 



Fig. 5. 



happens, there is a sudden retrograde current towards the 

 combustion-tube at the close of the operation. 



When the bulbed tube is properly filled, hold it so that 

 the liquid rises higher in one arm than in the other, con- 

 nect it with the combustion- tube by the soft, well-fitting 

 cork, that has been already fitted to the small horizontal 

 tube of the bulbed apparatus, and lay the combustion- 

 tube on a level table ; if the connection is not tight, the 

 acid will slowly assume the same level in both arms of 

 the bulbed tube. 



The apparatus being tight throughout, and a small fur- 

 nace full of live charcoal coals being ready, the combus- 

 tion-tube is introduced into the iron combustion-furnace 

 (fig. 5), so that only about 5 cm. of the tube remains out- 

 side the furnace at B, and the whole is slightly inclined 

 towards that end, so that any water, condensing in the 

 small tube of the bulbed apparatus, will flow down into 

 the bulb beyond. 



A movable screen bemg placed over che tube in the 

 furnace, about 8 cm. from the end B, this end is surround- 



