PNEUMATO-CIIEMICAL APPARATUS. 15 



nected with a Leyden phial to the rings of the 

 wires, the spark will pass through the interrupted 

 space between the two wires, and explode the 

 gases. These instruments are called ea:ploding 

 tubes. 



In compound distillations, or when a decompo- 

 sition of the materials subjected to this process 

 takes place, and gases are formed, some of which 

 are absorbable by water, some by alkalis, and 

 others are not capable of being absorbed at all, it 

 is often required to preserve separate the several 

 new substances procured. The apparatus invented 

 by Lavoisier for this purpose is the most con- 

 venient. 



A (Plate 2. fig. 1.), is a glass retort, the beak 

 of which is adjusted to a double tubulated balloon, 

 or receiver, B. To the upper tubulure of tliis re- 

 ceiver is fitted a glass tube, C, the other extremity 

 of which is conveyed into the Hquor contained in 

 the glass vessel, D : with this vessel, D, which has 

 three tubulures, are connected two or three other 

 similar vessels, by means of glass tubes fitted into 

 their tubulures, and to the last tubulure of the 

 range of vessels is adapted a glass tube which is 

 conveyed under a receiver placed upon the shelf 

 of the pneumatic cistern. Water is put into the 

 first of these vessels, caustic potash into the next, 

 or such other substances as are necessary for ab- 

 sorbing the gases, and the joinings are w^ell luted. 

 Sometimes it will happen that a re-absorption of 

 gas takes place; and in this case, that there may 

 be no danger of the water in the pneumatic tub 

 entering rapidly into the vessels through the tube, 

 E, a capillary tube is adapted to the middle tubu- 

 lure of each vessel, which goes into the liquid con- 



