tion of the copper group sulfides from those of the tin group. This solution is prepared as follows: To 30 cc. of (NHp)aSprepared as described, add 10 cc. of concentrated ammonium hydroxide and 1 g. of powdered sulfur. Shake the mixture vigorously until all the sulfur is dissolved and then dilute the resulting solution with 60 cc. of water.
Handbook of Science Museum. Museums need not be mere storehouses of inanimate objects; a thoughtful staff can do much to build around the sppcimens in their care the reflection of a human setting, thus enabling the significance of the exhibits to be appreciated by an ever-widening circle of interested visitors. An example of such treatment is afforded by the recently issued handbook of the collections in the Science Museum, South Kensington, illustrating industrial chemistry (London: H. M. Stationerv Office. Price Is.. net). This volume, althounh containinn- a descri~tivecatalazof the collections, differs from previous catalogs in that considerably more than half the book is devoted to illustration of the development which has taken place in that branch of science. Hence there is provided a background of human interest against which the exhibits themselves may be studied, and some idea of the course of evolution of a areat modern industry may be gained. The museum authorities, and in particular the compiler, Mr. A. Barclay, are t o be congratulated on producing a handbook which is not unworthy of a permanent place in m y library of historical chemistry. The scene surveyed is, of course, so wide in its extent and so varied in its aspects that even the principal portions of it can receive but brief treatment and incomplete illustration. That such should inevitably be the case detracts in no way from the advantage of the method of presentation adopted or from the interest of the exhibits-nearly one hundredwhich are t o he found in Gallery LXVI of the Science Museum. The Handbook deals with the origin and early history of industrial chemistry; technical chemistry in the Middle Ages; industrial chemistry in recent times; mineral acids, alkalies, and allied products; coal-tar distillation products; explosives; artificial dyes; artificial silk; fermentation processes; mineral oil products; and one or two other examples of chemical technology. The catalog differentiates between inorganic and organic processes, and gives a technical account of the corresponding exhibits. There are described, for example, models of various types of plant for the manufacture of sulfuric acid, including the first type of plant to have sulfur burners separate from the leaden chamber. A model of a Cheshire salt plant illustrates the manufacture of blocks of common salt from brine by evaporation in open pans, as carried on in Cheshire a t the present day, while other exhibits represent the cement kiln erected by William Aspdin, son of the inventor of portland cement, and a modern ~ l a nincludinp: t the rotary kiln. Yet other models depict processes for the production of black powder, guncotton, nitroglycerin, and trinitrotoluene. Early specimens of artificial silk made by the cuprammonium, nitrocellulose, and viscose processes, and samples illustrating the acetate process arc included in the collection. Stills for the preparation of whiskey, the manufacture of alcohol, and for the refining of mineral oils are shown, together with oil shale retorts, and certain examples of general plant. The handbook is well illustrated by photographs of actual operations as well as of certain of the museum exhibits.Natzrre, 124, 315 (Aug. 24, 1939).
