Each
two apertures receive the glass tubes used in gas washing bottles, while
the third holds a dropping funnel. It is filled with dilute hydrochloric
acid, and after the expulsion of the air by a current of gas, plentiful
quantities of chromous acetate are passed into the bottles. When the
current of gas has been passed in for some time, the hydrochloric acid
is let enter, which dissolves the chromous acetate, and thus, in the
absence of air, produces a solution of blue chromous chloride. It is
advisable to use an excess of chromous acetate or an insufficient
quantity of hydrochloric acid, so that there may be no free hydrochloric
acid in the liquid. To keep back any free acetic acid which might be
swept over by the current of gas, there is introduced after the washing
apparatus another washing bottle with sodium carbonate. Also solid
potassium carbonate may be used instead of calcium chloride for drying
the gas. If the two apertures of the washing apparatus are fitted with
small pinch cocks, it is ready for use, and merely requires to be
connected with the gas apparatus in action in order to free the gas
generated from oxygen. As but little chromous salt is decomposed by the
oxygen such a washing apparatus may serve for many experiments.
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