The Manufacture And Comparative Merits of White Lead And Zinc White Paints

same as those described for the Dutch process. It will be understood from what has been said that this process is somewhat empirical, and that it was bound to occur to the minds of chemists to replace it by a rational method based on science. It is to Thunard, in 1801, that the first scientific method of preparing white lead was due?a method more generally known under the name of the Clichy process, which, towards 1830, was more often still called the French process. THE FRENCH, OR CLICHY PROCESS. It rests on the following chemical reaction :?A current of carbonic acid gas traversing a solution of basic acetate of lead precipitates carbonate of lead and regenerates the normal acetate which can dissolve fresh oxide of lead to form the basic acetate, which is in its turn treated with gaseous carbonic acid. The reaction can thus be rendered continuous. It is always the same acetic acid which figures in the reaction, with the exception of inevitable loss, which a well-constructed apparatus is capable of rendering almost negligible. In the beginning the Clichy process was wrought thus. In a wooden vat, tarred so as to prevent the disintegration of the wood, litharge was dissolved in acetic acid. An agitator was fitted to the vat to keep the particles of oxide of lead in contact with the acid liquid, and thus assist solution and the formation of basic acetate. When this solution marked 17 to 18 B., the agitator was stopped and the liquid allowed to settle. ...