Barium Subchloride, BaCl

Barium Subchloride, BaCl, is obtained by heating together barium and barium chloride at 850° C. It forms brown microscopic crystals which decompose water with the evolution of hydrogen. It is also formed in the electrolysis of barium chloride, using a carbon anode. By heating barium chloride with excess of sodium at 1000° C., a double salt, NaCl.BaCl, is formed. By shaking this with mercury, decomposition must take place because barium amalgam is obtained. If the double salt be heated in vacuo at 700° C., sodium volatilises and barium chloride is left. By heating the subchloride strongly, barium volatilises and the chloride remains. By heating to redness in hydrogen or nitrogen, the hydride and nitride respectively are formed.

Haber and Tolloczko represent the reactions between barium and chlorine by the following thermochemical equations: -

Ba + Cl = BaCl + 115.8 Cal.
BaCl + Cl = BaCl₂ + 81.2 Cal.
Ba + BaCl₂ = 2BaCl + 34.6 Cal.

According to Marino, the behaviour of these compounds may be explained by supposing them to be solid solutions of metallic barium or sodium, or suspensions of pulverised metal, in the ordinary barium chloride.