. Introduction to inorganic chemistry . owdered man-ganese dioxide. The flask containing the mixture is heated by meansof a bath containing hot water (Fig. 66). The gas is passed througha washing bottle containing water, in order to remove some hydro-gen chloride which may be carried over. It may be dried, if neces-sary, in a second washing bottle containing concentrated sulphuricacid. It cannot be collected over water on account of its solubility, sothat jars are usiially filled with it by downward displacement of air. CHLORINE AND HYDROGEN CHLORIDE 171 The chemical change used here is somewh
. Introduction to inorganic chemistry . owdered man-ganese dioxide. The flask containing the mixture is heated by meansof a bath containing hot water (Fig. 66). The gas is passed througha washing bottle containing water, in order to remove some hydro-gen chloride which may be carried over. It may be dried, if neces-sary, in a second washing bottle containing concentrated sulphuricacid. It cannot be collected over water on account of its solubility, sothat jars are usiially filled with it by downward displacement of air. CHLORINE AND HYDROGEN CHLORIDE 171 The chemical change used here is somewhat complex. When anacid (here HCl) interacts with an oxide (here MnOj), the hydrogen ofthe former unites with the oxygen of the latter, giving water. Weperceive at once that to combine with 20, 4H, obtainable only bytaking 4HC1, will be required. Hence the equation might be : MnOj + 4HC1 -^ 2HjO + MnCl^. : This is probably what happens in the first place. The productsactually obtained, however, are water, manganous chloride (MnClj) and. Fig. 66. chlorine. The manganese tetrachloride is decomposed by the heating,the chlorine escapes, and the other two products remain in the vessel. MnOj + 4HC1 -^ 2HjO + MnCl, + 2C1. (1) We owe the chlorine to the fact that the tetrachloride is unstable. When the mixture is surrounded by ice and saturated with chlorine, it can beshown with some degree of certainty that it contains the tetrachloride. If it isquickly poured into water, hydrated manganese dioxide is precipitated (Waoker).The decomposition of the tetrachloride is reversible : MnCl, ^ MnClj + Cl„ and is driven back by the excess of chlorine. The tetrachloride is hydrolyzed by MnCl^ + 2H,0 + xHjO -* MnO„ xHjO + 4HCL 172 INORGANIC CHEMISTRY The action (1) is of a type very, common in chemistry. It is morecomplex even than double decomposition (p. 99), and, unlike this, itsresults cannot be anticipated by guessing. If we had used manganousoxide (MnO), we should hare had a double deco
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