It is evident that the double salt can exist in stable equilibrium with its own saturated aqueous solutions as the line drawn from the origin representing the composition of the salt cuts the curve of the double salt at X. The three-component system ZnCl2, KCl, H2O was also investigated. The curves obtained with the solubility data from which the curve in Fig. 4 was constructed are given below. The electromotive force of the cells containing either the double salt alone or potassium sulphate, and the double salt in the solid phase, varied considerably. Their electromotive forces at 25° were 1.46965 and 1.48680 respectively. Zn Amg (K2SO,ZnSO4.6H2O), Hg2SO, | Hg Zn Amg | (H2SO4ZnSO4.6H2O) S' ་ ” Hg2SO4 | Hg The saturated solutions of the double salt alone or potassium sulphate, and the double salt, seem to hydrolyze the depolarizer, and this fact may account for the inconstancy of these two combinations. On the other hand, if the combination Zn Amg (K2SO,ZnSO4.6H2O) Hg2SO4 Hg is used, this difficulty of hydrolysis of the Hg2SO, is overcome. The electromotive force of this cell was found to be 1.41976 at 25°, with a negative temperature coefficient of 0.00133. Since the investigation on the cadmium chloride cell, employing calomel as depolarizer with cadmium chloride as salt, gave results which for constancy and reproducibility left nothing to be desired, it was decided to investigate cells containing the chloride double salt. The constancy and reproducibility of the combination Cd Amg | (2KCICdCl2. 6H2O), HgCl2 Hg is given in Table III: The temperature coefficient of this combination was +0.00015 at 18° C. The electromotive force of the combination Zn Amg | (2KCIZnCl2.6H2O), Hg2Cl2 | Hg was 1.01857 at 25. The double salt although crystallized in a beautiful form when brought into solution, did not seem to be stable and hydrolyzed. Laboratory of Physical Chemistry Princeton, N. J., Aug., 1915 Elements of General Science. By O. W. Caldwell and W. L. Eikenberry. 20 X 14 cm; pp. 14 + 308. Boston: Ginn & Company, 1914. Price: $1.00. In the preface the authors say, "Science instruction in the first year of the high school has presented one of the most serious problems in secondary school work. First-year pupils do not possess a large fund of information about the common phenomena of nature, or they may not attempt a scientific interpretation of these phenomena. This lack in abundant, concrete, and rationalized experience has made it extremely difficult to secure the desired results from the first science course through presentation of any one of the differential sciences. Experiments have been under way in different parts of the United States for several years with the purpose of securing an organization of science materials and a method of presentation which shall prove more educative. It has been the object of these experiments to develop a more usable fund of knowledge about common things and a more scientific attitude in interpreting common problems, and to discover and utilize interest and ability in such ways that more effective and more profitable work may thereafter be done in the differentiated sciences. These experiments have shown uniformity in their attempt to use the point of view of the relatively uninformed pupil, and while they have followed several lines of effort in the main they have come to use a similar body of knowledge. "The course presented in this book is the result of six years of experiment with a number of pupils, averaging about one hundred per year. During this time several persons have assisted in teaching the course and have made contributions to it. Teachers of subjects other than science, and particularly the administrative officers who are studying the efficiency of the whole high-school curriculum, have been constant observers and critics of the experiment. The success of the course has been such as to justify its presentation, with the hope that it may prove helpful in increasing the efficiency of science teaching." The subject is divided into five parts: the air; water and its uses; work and energy; the earth's crust; life upon the earth. Under the general heading of the air the special chapters are: some characteristics of the air; temperature changes and the seasons; the water of the air; the weather; structure of air; composition of air; relation of air to food manufacture; dusts, molds, and bacteria of the air; distribution of bacteria and other disease germs. Under water and its uses the special chapters are: ice, water, and steam; water pressure; climatic influences of bodies of water; commercial relations; water supply and sewage disposal. Under work and energy the chapters are: work by running water; work; mechanical energy. In the fourth section, dealing with the earth's crust, the chapters are entitled: natural forces upon the surface of the earth; physical structure of the soil; soil water, drainage, and irrigation; erosion and sedimentation; life in the soil. Under the general heading of life upon the earth, the special topics are: the plant covering of the earth; absorption from the soil by plants; the world's food supply; utilization of food in the plant; nutrition of animals; hygienic aspects of nutrition; reproduction in plants and animals. For pupils who are not going to college a course in general science is much more important than a course in a single subject like physics or chemistry. The reviewer is inclined to believe that a course of this sort is also desirable for the minority who expect to go to college. A general survey is an admirable preparation for a more detailed study. It gives the student a point of view and also shows him something about the interdependence of the sciences. The authors appear to have done their work very well. Some of the chapters seem a trifle scrappy; but the proof of the pudding is in the eating, and it is quite possible that the test of experience will justify the authors in their allotment of space. A few errors have crept in. On p. 20 the authors say that "The rays of the sun pass through the glass with little loss, but the heat which is given off by the objects in the greenhouse, after they have been warmed by the sun, does not easily pass through the glass. The heat is therefore retained in the greenhouse." This view has been overthrown by Wood's experiments. The account of freezing mixtures on p. 116 is not very happy. It is no longer true to say, p. 134, that "neither the submarine nor the dirigible balloon has passed beyond the experimental stage." The worst thing in the book is an introduction by Charles H. Judd which is in very bad taste and which might profitably be omitted in future editions. Wilder D. Bancroft By O. W. Caldwell, A Laboratory Manual for Work in General Science. W. L. Eikenberry and C. J. Pieper. 20 X 27 cm; pp. xi + 134. New York: Ginn & Company, 1915. Price: 50 cents. The publishers announce that this volume provides laboratory work to accompany Caldwell and Eikenberry's "Elements of General Science." "The exercises are the result of the co-operative work of several high-school teachers throughout several years and have been tried with more than a thousand pupils. Only those exercises have been included which have proved their value for use in the first year of high school." There are 108 experiments in all. The first two show whether air can occupy space and whether air can be made to exclude water. The last two deal with the relation between the weights of the grains and of the cob in ears of corn and with the questions whether variations in parents are transmitted to offspring. The last experiment involves a study of data obtained by Galton In fact, a good many of the experiments consist in a study of data obtained from the Weather Bureau or other sources. The experiments seem to be well selected. Wilder D. Bancroft Metallurgy of Copper. By H. O. Hofman. 17 X 24 cm; pp. xiv + 556. New York: McGraw-Hill Book Company, 1914. Price: $5.00. This very complete treatise is of the same high standard as the author's General Metallurgy. It is packed full of information not only of a general nature but also of details that are as valuable as they are scarce in books of this nature. The book covers. properties of copper and its alloys, impurities and their effects, chemistry of copper compounds, roasting sulphide ores, smelting in blast furnaces, reverberatory furnaces and converters, smelting oxide ores and native copper, fire refin ing, leaching of copper ores, matte and metallic copper, electrolysis by series and multiple systems. The footnotes are not only very numerous, but up to date as well, many 1914 references being given H. W. Gillett |