This is a very simple method. Take a small bottle with a long neck and weigh it acurately ; then put into the bottle 1000 grains by weight of Q distilled water, and mark its height on the neck with a file. As distilled water is the standard by which
Qthe comparative weights of other substances are known, the same bulk of any other liquid, weighed at the same temperature, will give its specific gravity. Thus suppose that on filling the bottle up to the mark at which the distilled water weighed 1000 grams, with a sulphuric acid, thislast should be found to weigh 1850 grains; then the specific gravity of sulphuric acid is to water, as 1850 to 1000, or nearly double. If filled up to the same mark with alcohol, it might weigh 800 grains. The specific gravity of alcohol then would be 800, water being 1000 ; and so of any other liquid. The strength of proof spirits may be told in this
of glass terminated at each end with a bulb, one of which is half full of water. It is perfectly exhausted of air and hermetically scaled; the consequence is that the water is always disposed to evaporate. This evaporation however, does not proceed so fast as to freeze the water; but if the empty ball be cooled by some artificial means, so as quickly to condense the vapour which arises from the water, the heat is carried off so suddenly by the evaporation, that the water freezes. This may be done in warm weather, and affords a very curious experiment.
A bell glass receiver fig. 11, is of indispensible use in making' experiments on air, or the gases. It is a glass vessel of tbe shape seen in the figure. The knob at the upper part is for a handle, by which it is removed. It is U9ed for confining any kind of elastic fluid on which experiments are made. A large tumbler is a good substitute.
The Dropping tube fig. 12, is a glass tube blown into a ball in the middle. It is filled by putting the small end iDlo the liquid, and exhausting the air by sucking with the mouth at the other end. The thumb is then placed on the upper orifice, which keeps the liquor t from running out. On raising the thumb carefully the liquor is expelled in drops.
Obs. The ammoniacal gas cannot be collected and retained in the usual way over water, because it is immediately absorbed by that fluid. This is also the case with several of the other gases. Chemists are therefore obliged to make use of a mercurial, instead of a water bath in experimenting on these gases.
By the following method such gases as cannot be retained by water, and are of less specific gravity than the atmosphere, may be collected and submitted to experiment without the aid of a meicurial bath.
^ Take a flask a, fig. 13, put into it a mixture of
equal parts of slacked quicklime and muriate of ammonia, 4ioth separately reduced to a fine powder. Adapt to the mouth of the flask a cork, pierced with a hot iron, with a glass tube 10 or 12 inches high, passed through the aperture. Invert over the tube the bell glass b in such a manner that the upper extremity of the tube reaches the bottom of the receiver. Then apply to the bottom of the flask the heat of a lamp. The ammoniacal gas will he produced, in consequence of the combination which takes place between the muriatic acid of the muriate of ammonia and the quicklime t this sets the ammonia at liberty, and being lighter than atmospheric air, it rises up, expels the air from the bell glass, and gradually takes its place. Experiments may be made on it by introducing other gases up into the receiver in the same way.
GAS APPARATUS.