CHEMICAL APPARATUS. 



Fig. 528. 



time to time, is indicated 

 by a graduated glass tube, 

 which runs on the outside 

 from the top to the bottom 

 of it. When the gas hold- 

 er is full, screw on again 

 the end of the tube at bot- 

 tom. When the gas is 

 wanted for use, it may 

 either be drawn off by the 

 cock on the side, or on the 

 top, being careful to open 

 before either of them the 

 cock in the middle, and 

 keep the cistern filled with 

 water, as this is wanted to 

 occupy the receiver when 

 the gas is drawn out. 



Price, $6.50 to $10. 



Preparation of Gases. 

 (Fig. 529.) To procure 

 hydrogen from iron, sul- 

 phuric acid, and water. Put 

 into a wine bottle a few iron 

 nails, add some water, and 

 then sulphuric acid, equal 

 in quantity to one-fourth of 

 the water; the iron nails 

 will in a minute or two be 

 covered with bubbles of gas, 

 which will rise to the top of the 

 vessel. Hold a candle near the 

 gas as it passes away from the 

 mouth of the bottle, and by its 

 taking fire it will be known to 

 be hydrogen. It may be col- 

 lected either with a bent tube 

 passing under the shelf of the 

 pneumatic trough, or by a bladder fastened to the mouth of 

 the bottle. 



Fig. 529. 



