PROF. THIEL is to be congratulated on the clear and comprehensive account which he has given of his work on the application of colorimetry, which has enabled him to elaborate a technique whereby many inorganic and organic substances can be quantitatively determined optically with an accuracy not before achieved by this method of analysis.
Von Prof. Dr. A. Thiel. (Arbeitsmethoden der modernen Naturwissenschaften.) Pp. xv + 215. (Berlin: Walter de Gruyter und Co., 1939.) 10.80 gold marks.