Water and Its Impurities

most versatile and sensitive tools for micro-chemical studies of biological material. Since the publication of Volume I, which covers this topic very briefly, many advances have been made both in the development of new procedures and in the adaptation of existing ones to the micro-chemical level. Although the latter deficit is recognized by Dr. Glick in the preface to Volume II, it is unfortunate that a supplement to the Volume I chapter on fluorometric techniques could not have been included. I hope that future revisions of this series will place both flame photometry and fluorometry in a more realistic perspective. Excluding these deficits, both volumes serve as a reference for specific procedures and as a summary of micro-histochemical and cytochemical procedures in general. Volume II deals primarily with micro-spectrophotometric techniques, although some consideration is given to titrimetric, flame photometric, and microbiological techniques. In each section, consideration is first given to apparatus and special manipulations; where special equipment is commercially available, the manufacturer is cited; when it must be custom made, original references are cited and, in many instances, a detailed and well-illustrated description is presented. Much of the equipment employed for micro-chemical studies is modified and adapted by the individual researcher to meet the specific problem at hand. Such descriptions are, however, of value to the researcher in designing equipment to meet his special needs. Following discussion of the apparatus, a particular assay or series of assay procedures are considered both in theory and in practicality. Such discussions provide a useful guide for the researcher in the selection of the most appropriate procedure. Following this, the specific procedures that have been employed in micro-histochemical and cytochemical work are presented in "cook book" fashion. The sensitivity range for most procedures is given, although in a few cases one must go to the original source. The two-volume series is well documented with recent references (1962 for Volume II) and a total of 68 pages is devoted to bibliography. Within the limitations mentioned above, this series should provide a valuable reference for those already engaged in micro-chemical studies, and an excellent introduction to the field for those considering the use of micro-chemical procedures in future investigations.