. Elements of chemistry ... remove it from the zinc,the chemical process will cease, leaving- b nearly filled withhydrogen. The brass tube d: is cemented to the neck c,and furnished with a stop-cock. The box e, contains theplatina sponge at the end of the tube. When a light is wanted, nothing more is necessary thanto open the stop-cock d, and let a jet of the gas blow uponthe sponge, which becoming immediately red hot, a match,and then a candle may be lighted. By permitting thehydrogen to escape, the acid again comes in contact withthe zinc, and thus another portion of the gas is formed, andre
. Elements of chemistry ... remove it from the zinc,the chemical process will cease, leaving- b nearly filled withhydrogen. The brass tube d: is cemented to the neck c,and furnished with a stop-cock. The box e, contains theplatina sponge at the end of the tube. When a light is wanted, nothing more is necessary thanto open the stop-cock d, and let a jet of the gas blow uponthe sponge, which becoming immediately red hot, a match,and then a candle may be lighted. By permitting thehydrogen to escape, the acid again comes in contact withthe zinc, and thus another portion of the gas is formed, andretained until wanted. 296. Decomposition of Metallic Oxides by Hydrogen.—Many metallic oxides when heated slightly in hydrogen gas,give off their oxygen to form water with that gas, at thesame time the oxide is decomposed by the loss of one of itscomponents. Thus, while one compound is decomposed,another is forming from one of its elements, and by proceed-ing carefully we can detect the exact composition of each. Fig. 297. The apparatus, Fig. 61, is designed for this consists of the flask a, in which the hydrogen is slowlygenerated by first introducing pieces of zinc, and then pour-ing through the pipe 6, sulphuric acid much diluted. Ingeneral a little water in the form of vapor rises with the Why does not the acid constantly act upon the zinc ? When one portionof the gas escapes, in what manner is another portiom generated ? 146 WATER. hydrogen, for the collection of which the two bulbs c, c, aredesigned. If the gas still contains vapor, this is entirelywithdrawn by passing through the tube d, which containsdry chloride of lime, a salt having a remarkable attractionfor water. It therefore passes into the globe e, in a perfectlydry state. The ball e, contains the metallic oxide to be decomposed,that of copper, for instance. After the apparatus is filledwith hydrogen, this ball is heated by means of a spirit lamp,until the oxj^gen begins to be evolved, when unit
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