Thusfive hundred and sixty-three pounds of a seventeen-per-ccnt. grade of lithopone will be precipitated, from which the soda liquor may be filtered and then washed out. Fifty six pounds of sodium hydrosulfid may then be recovered from the solution, if no further treatment thereof is contemplated, by any suitable evaporating process. By employing sodium sulfate and suitably altering the reaction I have also produced lithopone and sogo dium sulfid. The products of these reactions will be found to be of unusual purity and require no subsequent treatment for placing them upon the market.

The process described is seen to consist of preparing separate solutions of readily-soluble salts of zinc and barium together with a third salt, which will further the reaction and at the same time upon uniting the solutions produce by one set of combinations lithopone and a marketable byproduct. This process, moreover, insures the greatest purity of the substances produced and avoids the expense attendant upon more difficult methods in common use. Thisis particularly true with respect to the manufacture of various grades of lithopone, since by properly calculating the amounts of the ingredients used, as above illustrated, any desired quality of lithopone may be produced without mixing additional substances to increase or decrease the percentage of zinc sulfid. The entire product, too, is an absolutely uniform mixture when prepared in accordance with my process.