DEMONSTRATION OF EQUILIBRIUM M. C. HAYS. of Lyons Township High School, LaGrange, Illinois, sends in the following demonstration of equilibrium in answer to a previous inquiry.' The demonstration is not new and will probably be recognized by some. "A few ml. of an HCl solution of SbCls are added to about 25 ml. of water in a beaker (400-ml. or larger).
1
J. CHEM.Eouc., 17. 346 (July. 1940).
A white precipitate forms immediately, according to the equation: SbCL
+ K O G Sb(OH)CI>+ 2HC1
When sufficient concentrated HCI is added, the precipitate dissolves. The point of equilibrium may be changed by the addition of either water or concentrated HC1, and the class can easily see the effect of concentration in an equilibrium reaction."
