Preparation of Potash Dyes.

The Scientific American 10, 7.3.1868

"I take yellow prussiate of potash, or the first crystallization, and dissolve in hot water and make the solution to 20 deg. by Baumé's hydrometer, then pass a stream of chlorine gas through the solution, but not more to be introduced than will prevent precipitation, as may be tested by persulphate of iron, when it is ready to be barreled for shipment or use. In this mode of preparation a larger amount of chlorine is retained which, in the preparation of red prussiate of potash, is dissipated in the process of evaporation and exposure. This loss is by the present new process avoided and by that means a great reduction in labor and cost is effected, and a superior article produced being in value, as yellow prussiate of potash, a saving of nearly seventy-five per cent, in red prussiate of potash, fifty per cent. One hundred pounds of yellow prussiate of potash, or first crystillization, make four hundred pounds of the improved solution." Patented by John Reynolds, San Francisco, Cal.