90 



62. BASES AND ACIDS WITH REAGENTS. 



tube, a / the rubber tube he should be about 8 cm. long, 

 and have a clamp on it ; d is another narrow caoutchouc 

 tube, 15 cm. long. The neck of the jar B is ground on 

 the outside so that a rubber tube slipped over it will 

 more readily make a tight joint ; a small glass tube, ^, 

 is connected with the jar by the stop-cock h and rubber 

 tubing ; another glass tube, ^, bent at an obtuse angle, and 

 reaching above the level of the stop-cock ^, is fastened in 

 tlie tubulure m of the jar by a good cork. This last- 

 mentioned tube being in place, open the stop-cock h^ pour 



a little boiled 

 water into the jar 

 through the tube 

 /, and then pour 

 in mercury until 

 it rises to the 

 lower rim of the 

 rubber tube f on 

 the neck of the 

 jar ; close the 

 stop-cock, put the 

 jar in the mercury 

 trough so that 

 the mercury rises 

 above the tubnlure, and remove the glass tube I and 

 the cork ; now, by means of a pipette, the lower end of 

 which is bent so that it can be inserted in the tubulure, 

 introduce 50 c.c. of well-boiled rriilk of hme, and then 

 cover the mercury in the trough with water to the depth 

 of about 3 cm. 



The solution of the nitrate in x\, which must be neutral 

 or alkaline, is boiled down to a small volume, while the 

 open end of d is immersed in water ; when the bubbles of 

 gas escaping from A are completely condensed in passing 

 through the water, showing that all the air has been ex- 

 pelled from the liquid in A, close the clamp on 5c, and 



Fig. 4. 



