Chemical lecture experiments . inverted under the bucketswill cause the wheel to rotate. Paper wheel (Pig 125, p. 313) ; liter cylinder of H. 10. Determination of the specific gravity. — By means of abalance weighing two centigrams a very satisfactory demon-stration of the fact that hydrogen is approximately lighter than an equal volume of air may be made. On one arm of a lecture-balance a clean, dry, graduatedliter flask is suspended mouth downwards (Fig. 18) by meansof a harness of fine wire. After bringing the balance intoequilibrium hydrogen, dried by passing through a gas wash-i
Chemical lecture experiments . inverted under the bucketswill cause the wheel to rotate. Paper wheel (Pig 125, p. 313) ; liter cylinder of H. 10. Determination of the specific gravity. — By means of abalance weighing two centigrams a very satisfactory demon-stration of the fact that hydrogen is approximately lighter than an equal volume of air may be made. On one arm of a lecture-balance a clean, dry, graduatedliter flask is suspended mouth downwards (Fig. 18) by meansof a harness of fine wire. After bringing the balance intoequilibrium hydrogen, dried by passing through a gas wash-ing-bottle containing sul-phuric acid, is allowed topass through a fine tubeinto the inverted a few minutes theair will have been en-tirely replaced by thehydrogen, and it will befound necessary to g. on the flat bottomof the inverted flask inorder to bring the sys-tern to equilibrium the weight of a liter of air at the laboratory tem-perature and standard barometric pressure as g., it. HYDROGEN 49 will be seen that the weight of a liter of hydrogen is thedifference between and or .085 g. On dividingthe weight of air under these conditions, , g. by theweight of an equal volume of hydrogen, , .085 g., thequotient is , or the air is times heavier thanhydrogen. In filling the flask with hydrogen the tube should leadclear up to the bottom and should be withdrawn while thegas is still flowing through it. If the graduated flask has along narrow neck, the rate of diffusion is so slow that thereis no appreciable change of weight in bringing the balanceinto equilibrium. In fact, it will be some time before enoughair will have diffused into the flask to disturb the equilibriummaterially. If desirable, a rubber stopper can be balancedwith the flask and inserted after withdrawing the tubedelivering the hydrogen. Current of dry H ; liter graduated flask; lecture-balance andweights. 11. Use in balloons.—The use of
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