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NEW BOOKS Theoretical and Applied Colloid Chemistry. B y Wolfgang Ostwald. Translated by M . H . Fischer. 23 X 16 cm; p p . xvi 232. New York: John W i l e y and Sons, Inc., I p 7 . Price: $2.50.-This book is based on lectures given by the author in America during the winter of 1913-1914. In the preface the author says: “There already exist a number of strictly scientific text-books treating of colloid chemistry and a number of more or less valuable introductions to colloid chemistry of a popular or semi-popular nature. So far as I know, however, none of these has tried to establish the right of modern colloid chemistry to existence as a separate and independent science while emphasizing a t the same time its great possibilities of scientific and technological application. The attempt to give a general survey of modern colloid chemistry as a pure and as an applied science and in a form readily intelligible to the general reader seems t o be new.” The first lecture deals with: fundamental properties of the colloid state; colloids as examples of dispersed systems ; methods of preparing colloid solutions. The subjects treated in the second lecture are: classification of the colloids ; the physico-chemical properties of the colloids and their dependence upon the degree of dispersion. The third lecture is devoted t o the changes in state of colloids and the fourth lecture to some scientific applications of colloid chemistry, while some technical applications of colloid chemistry are discussed in the fifth lecture. The lectures must have been very interesting ones to attend because of the large number of surprisingly good experiments which were shown. Since these lectures were primarily popular ones, their first mission was t o be interesting. How successful they were in this respect may be judged from the following quotations, pp. 179, 187 : “The clothes you wear are plant gels, be they wool, cotton, or silk. They are dyed with colors which are often colloid in type, as the indigos and the blacks for instance. In the process of dyeing, adsorption and other colloid-chemical reactions take place between the colloid substrates of the fabrics and the colloid dyes which color them. The leather of your shoes is a n animal gel, closely related in its general properties t o that prototype of the colloids, gelatine. Leather is tanned with substances of which the majority are colloids, and the whole process of tanning is punctuated with the colloid phenomena of hydration, dehydration and adsorption. The wood of the chairs in which you rest is made of cellulose, which in all its various forms is colloid in nature. The colloid swelling of wood, as I emphasized earlier, was used by the old Egyptians t o aid their quarrying of stone. The woods of your chairs are held together by glue or with metals. You already know glue to be a colloid; b u t it may surprise you to learn that colloid chemistry has much t o say in metallurgy and that steel, for instance, is a colloid solid solution. The paper upon which you write is essentially cellulose, in other words, again colloid. It has been given a body by being mixed with water-glass, with rosin or some similar material, in other words with various colloids. The ink in your fountain pens is probably also colloid if it is

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the ordinary iron tannate, and colloid, too, is the hard rubber of your penholders, prepared from that notoriously colloid mother-substance, soft rubber. “I could continue this list indefinitely, pointing in this manner to one colloid after another in your immediate surroundings and belonging to the since yesterday’s things of your every-day life. Perhaps you think-perhaps lecture you think you know-that I am possessed of a colloid mania because I see colloids everywhere. Let me admit that I do see colloids everywhere, only I do not believe that because of this I must be adjudged insane. I t is simply a fact that colloids constitute Ihe mosl universal a n d the commonest of all things we know. We need only to look a t the sky, a t the earth, or a t ourselves to discover colloids or substances closely allied to them. We begin the day with a colloid practice-that of washing-and we may end it with one in a bedtime drink of colloid tea or coffee. Even if you make it beer, you still consume colloid.. . . .. “An interesting illustration of color due to a colloid element is seen in the case of ultramarine. There still rages an old debate concerning the causes for the color in this mixture of different silicates, borates, etc., with sulphur or sulphur compounds. Even recently, nothing short of desperate efforts have been made to explain the color of this dye substance on the basis of its ‘chemical constitution.’ I say desperate because not only are the quantitative relationships found in the different ultramarines totally different; but uncolored, gray, yellow, red, blue, and even green ultramarines can be produced by heating the normal ultramarine. On the basis of differences in chemical constitution we would have to assume that each of these different colors represented a different chemical compound. “What we observe is entirely analogous to what we discussed previously when dealing with the photohalides. \Ve can produce blue and green solutions of sulphur by simply introducing this element into molten sodium chloride, into a borax bead, into liquid ammonia, or into hot organic liquids like glycerine. These facts render it most improbable that ultramarine is blue because of the existence in it of a specific blue sulphur compound. We have therefore come to the conclusion that ultramarine represents a solid solution of highly dispersed sulphur. The degree of dispersion may oscillate between molecular and colloid dimensions, and as this happens there are produced the different colors discussed above, which represent different degrees in the dispersion of the element sulphur. “Of the many facts which confirm this view, I would like to emphasize the analogy between the production of ultramarine and the production of ruby glass, of blue rock salt, etc. In making ultramarine the necessary salts and the sulphur are melted together a t a high temperature. This yields the grayish white or yellowish ‘mother of ultramarine.’ This product is then reheated, cooled, and reheated again, just as in the case of ruby glass, until the requisite color is obtained. The original product is obviously a molecularly dispersed solution, the particles of which, through reheating, are permitted to condense to colloid dimensions. Support for the correctness of this view may be found in mineralogy. Mineralogists are familiar with a complex, sulphur-rich, silicate compound known as hauynite, which appears in different colors ranging from colorless to green and blue. It has been shown that the colorless varieties may be colored blue or green by heating them with sulphur in a closed tube, a n experiment entirely analogous to the production of blue rock salt by heating this with metallic

sodium. There exist reasons for believing that with many of the so-called sulphur dyestuffs (dyes produced by melting together sulphur and different organic compounds in the presence of alkali) we have also to do with similar solid solutions of highly dispersed sulphur. There certainly exists little hope of explaining their colors on the basis of chemical constitution. Let me, in passing, emphasize that the alkali used in the preparation of either the inorganic or the organic sulphur systems tends to increase their degrees of dispersion. In other words, i t has a peptizing or stabilizing influence.” Wilder D . BancrofL Laboratory Manual of General Chemistry. By William J . Hale. 19 X 23 cm; p p . xii f 474. N e w York: The Macmillan Company, 1917. Price: $1.50. -In the preface the author says: “In experimental general chemistry we find but few laboratory manuals which make any pretense to a general systematic study of the elements. Whatever criticism they may have received must lie primarily in the lack of correlation of the experimental work, for the fact remains t h a t modern chemistry demands a thorough and rigorous training in experimental general chemistry as a prerequisite for all other courses in the science.” It is evident to anybody who does not teach general chemistry that one should emphasize somewhat the reactions which are to be used later in qualitative analysis. It is one of the good features of this manual t h a t this point is kept in mind throughout. The author has a strong prejudice against note-books and has arranged this manual so that each question must be answered in a small blank space on the opposite page. This ingenious method does not appeal to the reviewer at all. The student will never use i t in later life because his probIems do not ordinarily appear in the form of printed questions. The only advantage of the form adopted by the author seems to be a financial one, because the manual cannot be resold t o a subsequent freshman. Another idiosyncrasy is the use of the word ionogen instead of electrolyte. The reviewer has noted but few actual errors. Copper is not obtained when a cupric chloride solution is electrolyzed, p. 172,and nickel does not ordinarily precipitate copper from solutions of copper salts, p. 468. It hardly seems a good illustration of filtration to boil a solution of litmus with powdered charcoal and then filter, p. 46. The showy part of the experiment illustrates something else. It is true but obscure to say that a n increase in the volume of the solvent reduces the concentration of the ionic substawes and, therefore, increases the dissociation, p. 156. The reviewer is unable to answer Question 3 about disWilder D . Bancroft tillation, p. 45; but perhaps the student can. Standard Table of Electrochemical Equivalents and Their Derivatives. B y Carl Hering and Frederick H . Getman. 19 X 12 cm; $9. vii 130. N e w Fork: D . Vun Nostrand Co., 1917. Price: $2.00.-1n the preface the authors say: “The chief purpose of this publication is t o serve as a reference book on account of the tables and other data given in it, and not as a treatise on electrochemistry in general; sufficient explanatory text has, however, been added to enable the d a t a t o be used for most purposes without the need of further treatise on the subject. To make the data available also to the student, electroplater, engineer, and others who may not have made a special study of chemistry and electrochemistry, the descriptive text has been given in elementary and easily understood terms.”

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The subject is presented under the following headings: fundamental laws; fundamental data and description of the tables; electrochemical equivalents by weight; grams per ampere hour in the order of magnitude; electrophysical equivalents by volume; valences of the elements in their combinations; calculations involving electrochemical equivalents; electrolysis; the electronic theory; valence; elementary principles of chemical reactions and calculations ; conversion factors used in electrochemical calculations; glossary of terms. The tables are admirable and the chapter on the electronic theory is good, though incomplete. The rest of the text is interesting chiefly as showing what the senior author considers a simple and helpful way of presenting things. The reviewer is quite unable to do justice to the eccentricities of the text otherwise than by quoting a few passages, pp. I , 5 , 103, without comment. “The simplest and most basic law of electrolysis refers to the elements when they are in their gaseous state, or in the state of vapor. When in this state it is true alike for every element that to set free a liter of this gas or vapor requires the same constant amount of electricity in coulombs or ampere-hours when there is one atom to the molecule and when the change of valence is unity. For those elements in which there are two or more atoms to the molecule it will require two or more times this constant quantity of electricity, in direct proportion; and for any other change of valence the constant must also be increased in direct proportion. . “The valence of any element in its free, uncombined state must be considered to be zero, because the term valence, in Faraday’s law a t least, must be interpreted t o mean the number of bonds per atom which hold it in combination with another element; hence, when the element is no longer combined, these bonds, of course, no longer exist. Therefore, when an element has been set free by electrolysis it means that it has changed its valence from what it had in that compound to zero; in that specific case, therefore, and only in that case, is t h e valence numerically equal to the change of valence and it is only this particular case and not the more general one, that the text-books can refer to when they give Faraday’s law in terms of valence instead of more broadly and more correctly in terms of the change of valence. . , . . . . . “According to the more modern electronic theory, however, it is the negative electricity which is conceived t o flow in the opposite direction, a positive charge being then the result of a loss of negative electrons; a loss of a charge, therefore, means that it was a negative charge. And according to the modern dissociation theory, before any current is applied and before they reach the electrodes the ions have already been dissociated or ionized, whereby they have received their charges; dissociation means decomposition, hence a reduction of the cation. The true chemical reduction of the cations, therefore, really took place during this process of dissociation, and as they are then left with a positive charge there has been a reduction or loss of negative electrons during the actual chemical reduction. The final freeing of an element is not an essential part of reduction; ferric salts are correctly said to be reduced to ferrous, yet nothing is set free thereby. The final freeing of the dissociated ions is a different and subsequent W i l d e r D . Banc>oft process, and is not the real reduction.”

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An Elementary Study of Chemistry. By W i l l i a m McPherson and W . E . Heqideuson. Second uenised edition. rg x 14 cm; p p . x i i 576. Boston: Ginn G- Company, 1917. Price: $1.00.-Some alterations have been made in the presentation. “Carbon and carbon dioxide are presented at a n earlier point; the chapter on neutralization is preceded by a brief chapter devoted to a metal (sodium) and a base (sodium hydroxide), and one devoted to a nonmetal (chlorine) and an acid (hydrochloric acid); the space given to the compounds of carbon has been extended a little, and the material has been brought forward into its appropriate place in the text.” In the chapter on the colloidal state, the authors mention sols and gels, coagulation of colloids, preparation of colloidal sols, colloids and hydrolysis, nature of colloids, colloids and the industries, emulsions, and fogs. On p. 386 the authors say: “It is probable that each particle of a typical colloid consists of thousands of molecules, but that these are clumped together without any special order. When the particles assume an orderly arrangement, they constitute crystals, and crystalline particles continue to grow in size, precipitating from the solution in definite solid form. On the other hand, the colloid clumps teiid to form networks or sponge-like forms that enclose water and constitute Wilder D . Bancroft jellies.”

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Practical Pyrometry. By E . S. Ferry, G. A . Shook, and J . R. Collins. X 15 cm; p p , vii I47. New York: John W i l e y and Sons, Inc., 1917. Price: $I.jo.--This book is primarily a text-book €or a course in high temperature measurements required of students of chemical engineering at Purdue Cniversity. The preface states also that it is designed to meet the needs of technically trained men dealing with processes requiring such measurements, and for less-trained observers who may make the measurements. The physical principles underlying the measurement of temperatures by resistance pyrometers, thermocouples, radiation and optical pyrometers are described in the standard manner of a text-book in physics. The likeness to a text-book of physics is further manifest by the rigid exclusion of any discussion of how to apply a pyrometer to any sort of industrial furnace. There is a page and a half of generalities on “the selection of pyrometers for particular uses.” After assimilating this book one could write a good report on the subject in a college course in physics; but he would have to look farther for useful information on how to install and protect his apparatus in order t o get correct readings and reasonable life in industrial work. Evidently the student is not supposed t o desire any further information on any point covered by the book, for there is an entire absence of references to the literature. The subject is neither so fully, practically, nor interestingly covered as is done by Burgess. The book might satisfy a pure physicist, but the chemist who needs i t a t all needs a lot that is not included which is just as important t o him as what has been set forth. A book that would live up t o the title “Practical Pyrometry” would be a distinct acquisition, but in this case the title is camouflage. H . W . Gillett 20

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