Technikatörténeti szemle 19. (1992)

KÖNYVISMERTETÉS - Papers of the First „MINERALKONTOR” International Conference on the History of Chemistry and Chemical Industry (Veszprém, 12-16 August, 1991)

a conveyor, and after mixing with water, the sample was treated with acid in a small reactor. The pressure of the evolved carbon dioxide controlled the position of a piston which regulated the feeding rate of the shale, changing the speed of the driving motor. 6. Waste water pH-control system by Kufferath (34) 1940 A pfl control system, was used for the regulation of the neutralisation process of the waste water in the paper industry in the forties, in Germany (34). The lights of the white, red, green lamps indicated wether the pH of the liquid stream was appropriate or higher, or lower than the acceptable one respectively.