Treatise on general and industrial inorganic chemistry / by Etore Molinari ; third revised and amplified Italian edition translated by Ernest Feilman.
- Ettore Molinari
- Date:
- 1912
Licence: In copyright
Credit: Treatise on general and industrial inorganic chemistry / by Etore Molinari ; third revised and amplified Italian edition translated by Ernest Feilman. Source: Wellcome Collection.
56/734
![DETERMINATION OF THE DENSITIES OF VAPOURS AND GASES The density of gases is given by thè relation between thè weight of a given volimie of gas and that of an equal volume of air, measured under thè same conditions and taken as thè unit of comparison. It would be more rational to refer thè density of gases to that of hydrogen. The gases must be compared at thè same temperature and pres- sure, and it is convenient to com- pare all gas volumes, Vo at zero temperature and at thè normal pressure of 760 mm. Then by combining thè two formulse repre- senting thè laws of Boyle and of Gay-Lussac respectively (see pp. 23-24) and noting thè coefficient of dilatation of gases, \ve arrive at a single generai formula for any temperature : V = ^ (p — ^ì ^ 760 (1 -f 0-00367 t) where V indica tes thè volume of gas at thè temperature t and pres- sure p observed in mm. by thè mercury barometer. But it is necessary to take into account thè vapour tension of thè liquids over which thè gases are measured ; thè tensions, k, for water are indicated in thè table which is given in thè chapter on Water. There are various methods of determining thè densities or specific weighls of gases and vapours, but in al] these it is necessary to take into account thè observation of Amagat, that gases and vapours follow thè laws of Boyle and of Gay-Lussac thè more exactly thè further thè vapour is removed from thè tem- perature of condensation or lique- faction, that is, thè hotter it is. Gay-Lussac’s Method (1816). A weigliod quantity of a liqiiid or solid substanco is introduced into a gra- duatcd glass tube {see Fig. 8) full of incrcmy and standing in a batli of mercury. The tubo is surrounded by a largo glass cylinder in which a liquid is placed (water, oil, &c.), which boils at a more elevated temperature tlian thè point of ebullition of thè substancc under examination. The oidvr liquid is then boiled by raising thè mercury to a sulticicntly high temperatine and thè amount of vapour formed by thè substance under examination is then measured, thè tenqieraturc and pressure to which it is subjected being also noted. A. ir. Hofmann s Method (1868). This is an improvement upon Gay-Lussac’s metliod, hecause thè graduateci tube containing thè mercury is 1 m. liigh (Fig. 0), and thè substance Fig. 8. Fig. 9. Fig. io.](https://iiif.wellcomecollection.org/image/b28134187_0058.jp2/full/800%2C/0/default.jpg)
