CHEMICAL APPARATUS. 



Tongs. (Fig. 521, as below.) Chemical tongs are made 

 of iron. One pair straight, and another crooked should be 

 obtained, and of the shape shown in the plate. Their use 

 is so well known that further description is unnecessary. 



Price, $1.00. 



Fig. 521. 



Fig. 522. 



The Pneumatic Trough (\g. 522.) 

 This consists of an oblong japanned 

 tin vessel, which is filled within one or 

 two inches of the top with water ; just 

 below the surface of the water is 

 fixed a shelf, and also a sliding shelf 

 supported by two wires, having a funnel on the under side ; 

 the sliding shelf may be set at any distance across the 

 vessel ; there is also a small spout at the side to prevent the 

 water overflowing. The use of the pneumatic trough is in 

 collecting gases. Supposing gas is issuing out of the beak 

 of a retort, and that beak were placed beneath the funnel, 

 the shelf being covered with water, it is evident that the 

 gas would pass through the funnelled hole, and ascend into 

 the air if the hole were uncovered, or else into a gas jar or 

 other vessel placed over the hole. Also in passing through 

 the water, the gas becomes purified and cooled. 



Price, - $2.00. 

 larger, $2.50. 



Cooper's Mercurial Tube. (Fig. 523, next page.) This 

 small instrument supplies the place of a mercurial trough. 

 It consists of a bent tube, closed at top, open at the foot, 

 supported in any manner which may be convenient, and 

 filled previous to use with mercury. The open end is then 

 connected with a retort, or alembic, which is giving off the 



