Basf Aktiengesellschaft

Lothar Diehl

Bernd Leutner

Peter Kroetzsch

Andreas Brunold

Fluorine compounds which are contained in the vapors obtained when evaporatively concentrating phosphoric acid are removed by scrubbing with an aqueous solution of fluosilicic acid under reduced pressure at a temperature at which condensation of steam is substantially avoided. The aqueous fluosilicic acid solutions are injected, at a speed of from 15 m/s to 40 m/s, into the upper part of a scrubbing zone, finely dispersed over the entire cross-section of the latter. The vapors are passed through the scrubbing zone at a speed of from 5 to 30 m/s, in co-current with the fluosilicic acid solutions. The residence time of the vapors in the scrubbing zone is from 0.4 to 1.5 s. The fluosilicic acid taken off the scrubbing zone contains from 20 to 28% by weight of H.sub.2 SiF.sub.6.

Isolating fluorine compounds from the vapors obtained when evaporatively

Sulfur concrete which exhibits improved compressive strength and flexural strength, and improved corrosion characteristics, is manufactured by mixing sulfur, dicyclopentadiene and aggregate at from 120.degree. to 160.degree. C. The period for which the sulfur and dicyclopentadiene interact should not exceed certain limits.

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Ludwigshafen, Germany

Lothar Diehl