A manual of elementary chemistry : theoretical and practical / by George Fownes.

  • George Fownes
Date:
1869
Catalogue details

Licence: Public Domain Mark

Credit: A manual of elementary chemistry : theoretical and practical / by George Fownes. Source: Wellcome Collection.

    38/882 (page 34)
    The determination of the specific gravity of gases and vapors of volatile liquids is a problem of very great practical importance to the chemist: the theory of the operation is as simple as when liquids themselves are con- cerned, but the processes are much more delicate, and involve besides cer- tain corrections for differences of temperature and pressure, founded on principles yet to be discussed. It will be proper to defer the considerations of these matters for the present. The method of determining the specific gravity of a gas will be found described under the head of Oxygen, and that of the vapor of a volatile liquid in the Introduction to Organic Chemistry. in the text. It results from the theorem of Archimedes, that if any solid be immersed in water and then in any other liquid, the loss of weight sustained in each case will give the relative weights of equal bulks of the liquids, and on dividing the weight of the liquid by the weight of the water, the quotient will be the specific gravity of the liquid experimented on. For in- stance, Jet a piece of glass rod (fig. 10) be suspended from the balance pan and exactly counter- poised, then immerse it in water and restore the equipoise by weights added to the pan to which the glass is suspended, the amount will give the loss of weight by immersion or the weight of a bulk of water equal to that of the stopper. Now wipe the glass dry, and having removed the additional weights, immerse it in the other liquid, and restore the equipoise as before; this latter weight is the weight of a bulk of the liquid equal to that of the water. The latter divided by the former gives the specific gravity. For example:— The glass stopper loses by immersion in water 171 grains. The glass stopper loses by immersion in alcohol ...... 143 ±ffl - .836, the specific gravity required. —R. B.]