. The principles of chemistry . is point with a sharp properties, together with their impermeability, transparency, hardness, and regu-larity of bore, render glass tubes most useful in experiments with gases. Naturally theymight be replaced by straws, india-rubber, metallic, or other tubes, but these are moredifficult to fix on to a vessel, and are not entirely impervious to gases. A glass gasdelivery tube may be hermetically fixed into a vessel by fitting it into a perforated cork,which should be soft and free from flaws, and fixing the cork into the orifice of thevessel. To protec
. The principles of chemistry . is point with a sharp properties, together with their impermeability, transparency, hardness, and regu-larity of bore, render glass tubes most useful in experiments with gases. Naturally theymight be replaced by straws, india-rubber, metallic, or other tubes, but these are moredifficult to fix on to a vessel, and are not entirely impervious to gases. A glass gasdelivery tube may be hermetically fixed into a vessel by fitting it into a perforated cork,which should be soft and free from flaws, and fixing the cork into the orifice of thevessel. To protect the cork from the action of gases it is sometimes previously soakedin paraffin, or it may be replaced by an india-rvibber cork. 10 PKINCIPLES OF CHEMISTRY tially differ from air in many respects ; for instance, a burning taperis extinguished in it as if it had been plunged into water. If weighinghad not proved to us that some substance had been separated, theformation of the gas might easily have escaped our notice, for it is. Fig. 1.—Apparatus for the decomposition of red mercury oxide. colourless and transparent like air, and is therefore evolved withoutany striking feature. The carbonic anhydride evolved may be weighed,^^and it will be seen that the sum of the weights of the black copperoxide and carbonic anhydride is equal to the weight of the coppercarbonate ^^ originally taken, and thus by carefully following out the Gases, like all other substances, may be weighed, but, owing to their extreme light-ness and the difficulty of dealing witla them in large masses, they can only be weighedby very sensitive balances; that is, in such as, with a considerable load, indicate a verysmall difference in weight—for example, a centigram or a milligram with a load of 1,000grams. In order to weigh a gas, a glass globe furnished wnth a tight-fitting stop-cock isfirst of all exhausted of air by an air-pump (a Sprengel j)ump is the best). The stop-cock is then closed, and the exhaust
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Keywords: ., bookcentury1800, bookdecade1890, bookpublis, booksubjectchemistry
