GALVANIC INSTRUMENTS. 



341 



having two holes in the bottom, through which are inserted 

 two screw cups for receiving wires from the galvanic bat- 

 tery, and which terminate on the inside of the glass vessel 

 in platina wires, or strips of platina plate ; over these are 

 suspended by a frame resting on the rim of the glass vessel, 

 two small receivers, for collecting the separate gases. The 

 tube collecting the hydrogen will be found to contain double 

 the volume of that collecting the oxygen ; the hydrogen 

 and oxygen gases being in water exactly as two to one in 

 their proportions. 



Price, $4.00 ; larger size, $5.00. 



Tubes for the Decomposition of Fi g .405. 



Water by the Galvanic Battery. 

 (Fig. 405.) This apparatus consists 

 of a glass tube, c, bent in the form 

 of a V, to each end of which a cork, 

 D D, is fitted, air tight, through 

 which cups with binding screws are 

 fixed, and on the interior are solder- 

 ed slips of platina ; in the bend of 

 the tube is a small hole for the es- 

 cape of water. To use, the instru- 

 ment is filled with water usually containing a little salt 

 and the poles of a powerful galvanic battery applied to the 

 cups. The decomposition of the water will rapidly take 

 place ; the hydrogen occupying the one tube, and the oxygen 

 the other. 



The instrument is represented in the cut on a mahogany 

 base, having a wire support. 



Price, with stand, $2.00 ; without stand, $1.50. 



Decomposition Tubes. (Fig. 406.) This fig. 406. 

 apparatus, used to show the decomposition of 

 a neutral salt by galvanism, consists of a glass 

 tube in the form of a letter V, having corks 

 fitted to each end, with small binding screws to 

 receive wires from the battery, and wires or 

 slips of platina descending into the tubes ; the 

 whole is mounted on a stand. The solution of 

 a neutral salt, colored by litmus, is poured into the tube ; a 

 galvanic current being made to pass from wire to wire 

 through the liquid, decomposes it, drawing the alkali to one 

 pole, and the acid to the other, as is made visible by the 

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