VOL.
4, NO. 3
WCENT
A Collection of Chemical Lecture Experiments. H. F. DAVISON. The Chemical Catalog Co., Inc., New York City, 1926. First edition. 139 pp. 23 figures. 12.5 X 19 cm. $2.50 net. In a preliminary note to the reader this little book is gracefully dedicated by L. A. Bigelow to the Teaching Profession as the last work of one who was called only too suddenly from our ranks. Those who were fortunate enough to hear Prof. Davison's paper on "The Art of Lecture Table Demonstrating," delivered before the Division of Chemical Education a t the recent Baltimore meeting of the American Chemical Society, will be particularly interested in the introductory chapter which bears the same title. I n i t the author, a very able demonstrator himself, has given a very clear exposition of the fundamental rules which he believes must be observed. There follow descriptions of 69 experiments, grouped in the index under the titles: Gases (5). Combustion and Oxidation (12), Hydrolysis (4), Colloidal Chemistry (8). The Atmosphere (41, Solubility and Solution (7). Ammonia and Its Compounds (10). Time Reactions (3), Activity of the Elements (6). and Miscellaneous (11). The author has limited himself almost wholly to experiments designed for a relatively small class in general chemistry and, as he announces in the preface, does not attempt to make the list complete. Drawings of set-ups are abundant and well executed. Some of the experiments admit of multiple application to which attention is not called. For enample, Experiment 45, "The Time Reaction of Iodic Acid," could serve also to illustrate the preparation of iodine, the oxidizing power of iodic acid and the effect of temperature an the speed of chemical action. The simplicity of the apparatus and the minuteness of the directions indicate that each experiment must have received careful preliminary testing. Included in the list are original devices as well as
unique modscations of time-honored lecture experiments. Although explanations of the principles involved and references to the original literature are frequently missing, this collection of experiments should he in the hands of every teacher of general chemistry. R. A. BAKER The Hydrous Oxides. HARRYB. WEISER. McGraw-Hill Book Co.. Inc.. New York City, 1926. x 452 pp. 14 X 20 cm. $5.00.
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The literature on hydrous oxide gels and sols is voluminous and has been unavailable in compact form until the appearance of Prof. Weiser's unique book. Following a short but comprehensive review of the theories of gel structure, the properties of precipitates, suspensions,and sols of the following elements are described-iron, chromium, aluminum, gallium, indium, thallium, copper, cobalt, nickel, silver, gold, beryllium, magnesium, zinc, cadmium, mercury, silicon, germanium. tin, lead, titanium, zirconium. thorium, vanadium, columbium, tantalum, antimony, bismuth, molvbdenum, tunasten, uranium, manganese, the rare earths, and the platinum family. There are also chapters on tanning, mordants, water purification, cement, and soil. Dr. Weiser has undertaken a difficult task and has produced a valuable contribution to chemical literature. He has given not merely a "scissors and paste" compilation but has discussed his subject critically. His point of view is that of the mechanistic schwl of colloids. Colloids are shown to he small particles of matter possessing little or no chemical reactivity; they merely adsorb. I t is a pity that the conception of "hydrous oxide" colloids, as pure oxides which adsorb, or are "peptized" by electrolytes or their ions, should he so vigorously defended by the author against such good physico-chemical evidence as composition of the electrophoresced micelles and electrode potential measurements which show
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that they are far from being pure oxides plus adsorbed ions. For example, Pauli's measurements have well verified Duclaux's opinion that the dispersed phase in hydrous iron oxide sol made by hydrolysis of ferric chloride, or by peptization of precipitated hydrous ferricoxide by hydrochloric acid, is a very complex aggregate of what might be termed ferric oxychloride, or of a series of ferric oxychlorides. If this view is too radical then, criticizing from another angle, ferric oxide hydrosol can hardly consist of iron oxide partides which have adsorbed the hydrogen ions of the peptizing hydrochloric acid, or the ferric ions of the peptizing ferric chloride, because this simple picture leaves the chloride ions free in solution. I t has been found (Pauli) that the actual chloride-ion concentration of such a sol may be vanishingly small although containing a large proportion of chloride. Furthermore, the "colloid" electrically deposited a t the cathode has been shown t o contain a considerable amount of chloride. An example of Weiser's resistance to the concept of chemical reactivity of a colloidally dispersed phase is found on pages 6 7 4 8 in the discussion of the so~ a l l e dadsorption of arsenious acid by hydrous ferric oxide. The convincing calculation of Reychler which showed Biltz's adsorption constant t o be the hydrolytic equilibrium constant for the hydrolysis of ferric arsenite is ignored. I n a criticism of the chemical theory of mutual precipitation of hydrosols Prof. Weiser admits that the mutual reaction between negative sulfur and negative arsenious sulfide sols is chemical in nature, vet. . . in connection with his criticism of similar evidence for oppositely charged sols, he makes the fallowing statement (page 64), "Such an interpretation of the mechanism of the mutual precipitation process would not account for the repeated observation of mutual predpitation of sols where interaction between the peptizing agents is impossible or improbable." The author stops here. Such ~
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OF CED a statement would he strengthened by citation of a specific example. None is cited. Evidently for the purpose of effectively brushing aside quantitative chemical evidence, the author states-"Thus, to obtain data to support a purely chemical mechanism involving the stabilizing agents, it seems necessary t o choose the experimental conditions t o fit the case." The reviewer fails to see the justice of this criticism since in all quantitative determinations, the conditions must be chosen t o fit the case as, for example, in the precipitation of magnesium ammonium phosphate. The chapter on tanning hardly belongs in this book because hydrous oxides do not tan. For one thing they cannot diffuse through the compact hide protein structure. This is proper colloidal behavior. I n this chapter, incidental to the resistance t o a chemical point of view, the author commres curves of Thomas and Kelly on combinations between hide suhstance and chromium with curves for the adsorption of arrtic acid from toluene solution by charcoal. Thomas and Kelly's "adsorption" curve has been erased from their published diagram as reproduced in Fig. 21, while their chrome-collagen composition curve, obtained by an entirely different technic, is erroneously reproduced as their "adsorption" curve. The deleted "adsorption" curve was identical in character t o the acetic add-toluene curve cited in argument in Fig. 22. This missing curve proved the futility of the common practice of measuring adsorption by the "by-difference" technic in certain systems. While the reviewer takes issue with the author in some instances, he would emphasize the fact that Weiser's book is a very useful discussion of a field of inorganic chemistry that has been neglected by writers of books. It is filled with interesting information which deserves wide circulation.
AnTHua W. THOMAS
