as to form two right angles, one end extending close to the bottom of the
bottle B as shown.

Having fitted up the apparatus, about two ounces of hyposulphite of soda
are placed in the bottle A, while the bottle B is about three-fourths
filled with water--distilled or melted ice water is to be preferred; some
sulphuric acid--about two ounces--is now diluted with about twice its bulk
of water, by first putting the water into a dish and pouring in the acid in
a steady stream, stirring meanwhile. It is well to set the dish in a sink,
to avoid any damage which might occur through the breaking of the dish by
the heat produced; when cool, the solution is ready for use and may be kept
in a bottle.

The cork which serves to adapt the bent tube to the bottle A is now just
removed for an instant, the other end remaining in the water in bottle B,
and about two or three ounces of the dilute acid are poured in upon the
hyposulphite, after which the cork is immediately replaced.

Sulphurous acid is now evolved by the action of the acid on the hypo, and
as the gas is generated it is led as a series of bubbles through the water
in the bottle B as shown. The air space above the water in bottle B soon
becomes filled by displacement with sulphurous acid gas, which is a little
over twice as heavy as air; so in order to expedite the complete saturation
of the water, it is convenient to remove the bottle A with its tube from
bottle B, and after having closed the latter by its cork or stopper, to
agitate it thoroughly by turning the bottle upside down. As the sulphurous
acid gas accumulated in the air space over the water is absorbed by the
water, a partial vacuum is created, and when the stopper is eased an inrush
of air may be noted. When, after passing fresh gas through the liquid for
some minutes, no further inrush of air is noted on easing the stopper as