A rapid concentrating still.

Lw the apparatus described here aqueous solutions can be concentrated at rates of 12-14 1./hr. at temperatures not exceeding 360C. Under these conditions many enzymes, bacterial toxins and other substances can be recovered in high yield. No novelty is claimed for this apparatus; it is a laboratory application ofthe climbing film still used in industry, and it is closely modelled on an apparatus described by Mitchell, Shildneck and Dustin (1944). See also Kemmerer (1945), Ames (1946), Muirhead (1946) and Reavell (1946a, b). The apparatuA is described here because it can be made from parts (mainly standard) supplied by a British firm, and because it is thought that a detailed description of its operation would be useful to those concerned with the isolation of small amounts of biologically active substances from large volumes of solution.