IiEW B0 0 K S Diatomaceous Earth. Bji Robert C a h r l . 83 X 16 c m ; 7 ) p . 2.71. S e w York: Chemicol (’atalog Company, 1930. Price . I n the preface, p. 9, the author says: “The present of diatomaceous earth are attributable t o its unique uses as well as the future possi properties. Diatomaceous earth consists of the fossil remains of an order of unicellular plants called Iliatomacme. The individual particles of the earth are so small that forty million of a given species may be contained in one cubic inch. Yet the microscope shows each one of the millions to be delicately fashioned into a highly ornate structure, with numerous channels, perforations, and nodules, all combining t o give an extensive surface area. The composition is nearly pure silica and, consequently, is infusible a i a red heat.” The subject is presented under the headings: introduction; present status of the industry; occurrence of diatomaceous earth; mining and preparation of diatomaceous earth for the market; physical properties of diatomaceous earth; filtration medium of diatomaceous earth; filtration of sugar solutions; miscellaneous filtrations with diatomaceous earth; diatomaceous earth in the petroleum industry; action of alkalies upon the diatomaceous earth; diatomaceous earth as an admix in Portland cement and plaster; diatomaceous brick; miscellaneous insulating compositions containing diatomaceous earth; thermal conductance and loss of heat throuKh furnace walls; diatomaceous enrth as absorbent; miscellaneous uses of diatomaceous earth. Fullers’ earth must he distinguished from diatomaceous earth, p. 15. “The two earths are different in origin, composition, density, uses, and properties. Yet they are often confused in the general thought. Fullers’ earth is of mineral, diatomaceous earth, of vegetable origin. Fullers’ earth is a clayey substance, diatomaceous earth nearly pure silica. The one has an unctuous, greasy feel, the other is chalky. In compact form, fullers’ earth weighs more than I O O pounds t o the cubic foot, diatomaceous earth, 15 to 40. Fullers’ earth has sufficient adsorptive power to be useful as a decolorant of oils; diatomaceous earth, unless specially treated, has little adsorptive power and functions in filtrations largely mechanically, as a straining agent, to remove insoluble suspended matter.” “Some diatoms live in fresh, some in salt water. Pome lie at anchor. Others of the so-called plankton type float freely. Some appear under the microscope as almost naked skeletons while others show a pronounced gelatinous covering. Searly all varieties are alike in secreting silica and accumulating a droplet of oil. . . . On the decay of the diatoms, the oil and the silica remain. Occasionally the conditions of growth, wind, or current favor the settling of the silica into great deposits that are only slightly contaminated. A similar concentration of diatom oil, either the primary oil or oil formed by decomposition of the vegetable matter of the diatom, is responsible for much of our petroleum. Certainly such vegetable growth is sufficient in quantity to produce enormous pools of oil, by suitable chemical decomposition. Card and Dun describe a deposit of mud no less than four hundred miles long by one hundred and twenty miles broad, found at a depth of between two hundred and four hundred feet, on the flanks of Victoria Land in 70” south latitude. This deposit is composed of diatom ooze, its thickness is unknown. In the Antarctic Regions the sea is often thick with Diatornacear which also tinge it and the ice a dull yellow. Instances are on record of shallow estuarine harbours being choked by their rapid accumulation,” p.18. “The present importance of diatomaceous earth is due largely t o the widespread use of the powder for filtering raw cane sugar solutions and as a n addition to concrete and of diatomareous brick for thermal insulation. These represent the major uses of diatomaceous earth,” p. 25. “rlpproximately zoo0 tons of diatomite are mined annually at Carlin, Kevada, over three-quarters of which are for insulation purposes, as it is claimed that the best grade material will stand an exceptionally high temperature without shrinkage. A good insulation brick is made using magnesium chloride as a binder. It does not make a good cane-sugar filter medium as the diatoms are too small, but the coarsest is used for beet sugar and
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molasses, also for clarifying dirty oils from rrank-cases, etc. It makes an excellent silver polish and is also used in finger-nail polishes and tooth pastes, as well as for fillers, etc,” p. 49. According to Patty and Glover, “the overburden is removed and the thus exposed diatomaceous earth is quarried by hand, stacked outdoors to dry, milled by impact pulverizers, and conveyed by blowers through a pipe line over a series of hoppers into which the powder settles according to the size of the particle. The very fine dust which does not settle, even in the last hopper, is separated from the air stream by filtration through cloth in a so-called “bag-house.” The powders thus obtained are packed in burlap sacks and sold according to grade. . . The product which settles in the single dust chamber or in any of the four hoppers is of satisfactory grade for the regular grade for the regular commercial uses. The fine dust which separates in the cyclone or in the cloth bags is exceedingly fine, free from grit, and much desired by the manufacturers of various polishes, particularly those for lacquered automobiles,” pp. 69, 81. “An excellent absorhent, diatomite is a poor adsorbent. I t does not adsorb vapors o r gases readily. Keither does it decolorize, to an important degree, liquids filtered through i t . That it does adsorb in certain instances is true. For example, an alkaline, alcoholic solution of phenolphthalein, if poured into diatomaceous earth, loses its bright pink color a t once and becomes colorless. Also, powdered diatomaceous earth in filtering raw sugar probably retains much colloidal matter and raises the purity of the raw sugar,” p. 93. “Finally, a removal of bacteria and enzymes is sometimes effected by filtration through powdered diatomaceous earth. Brewers of “near-beer” arrest the fermentation, when the alcoholic content approaches that allowed by law, by adding diatomaceous earth to the brew and filtering. Calvert and Knight have found that sugar syrups Eltered through diatomaceous earth and then kept in fermentation tubes do not develop gas as quickly as unfiltered syrup. Owen, in very careful tests, has found such filtration removes 99 per cent of the bacteria,” p. 100. “Originally, varnish v a s ‘cleared’ by the simple process of settling out the undissolved gums and other solids. Centrifuging was more convenient but did not accomplish an absolute, positive clarification of the varnish. Some of the suspended gums and other solids are so finely divided and so light in weight as to defy every attempt a t removal hy centrifugal force. Therefore, it was but natural that filtration with pressure filters should persist for the clarification of the higher grades of goods, especially in the larger companies with reputations for the appearance and durability of their product. The absolute certainty of clear goods from the filter-press offsets, in a large measure, the objections accompanying the added labor, floor space, and handling of ‘excess varnish.’ At the same time, it \vas recognized that these objections are serious ones, and in many of the smaller varnish factories centrifuges were adopted and were accepted as an answer to the whole problem of clearing varnish. “Recent developments have changed entirely the position which filter-presses hiterto have held in varnish manufacture. These improvements are, namely, the development for and the application to the varnish industry of the filter-aid Super-Cel which has materially changed the aspect of varnish filtration. Varnish makers are said to he able, through the use of Super-Cel, to accomplish tasks which previously were considered impossible. Ease of filtration, high capacity and more nearly continuous operation of filter-presses are the advantages claimed for the use of Super-Cel, together with greater clarityof product,” p. 139. “Of all the alkalies, lime has perhaps the most interesting effect upon diatomaceous earth. Lime gives a quick change in appearance and a product of interesting though unexplored possibilities. Diatomaceous earth, shaken with water and allowed to stand, settles slowly. With the usual grade of earth, the supernatant liquor will be turbid after even a day of subsidence. But, if lime is added to the suspension and the mixture boiled, coagulation occurs immediately. Now, on even brief settling, the supernatant liquor becomes quite clear. As the boiling is continued for an hour or more, the lime in solution apparently combinea with the surface silica of the particles of diatomaceous earth, with attendant enormous swelling.
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“The properties of the lime-treated earth are quite different from those of the original earth. A Io-gram sample of diatomaceous earth that settles in distilled water to a volume of 33 cc. has been found, after boiling for three hours with j o per cent of its weight of lime in aqueous suspension, to occupy a volume of 375 cc. The increase in volume of settled material is over 1,000 per cent. Furthermore, Calvert finds the lime-treated diatomaceous earth to filter water a t 4,600 per cent of the rate for the untreated earth. Also, the swollen product after being baked can adsorb vapors of volatile liquids, whereas the original earth has practically no adsorptive capacity. “The product, when dried a t ordinary temperature, is slightly whiter and smoother to the feel than the original diatomaceous earth. Also, the dry lime-treated material weighs only 5 pounds to the cubic foot, as compared to 7 or 8 for the untreated earth packed in the same manner,” p. I 56. “Admixture of powdered diatomaceous earth with plaster produces a notable increase in spreading power. Admixture of the earth with Portland cement causes such conspicuous improvements in the quality as to justify the belief that the use in concrete may soon constitute the largest single demand for diatomaceous earth. Already this use is very important,” p. 160. “The firing of diatomaceous brick, in the usual manner, above 1900°F. converts a part of the silica (which comprises more than 90 per cent of the earth) into cristobalite, a highly objectionable, crystalline form. Cristohalite undergoes an abrupt change in volume a t certain transition temperatures, as it pasees from one crystal form to another. One such change amounts t o approximately I per cent in length and occurs when the cristobalite undergoes a temperature change of only a few degrees a t the critical point. If the cristohalite is cooled through this critical range, the change of I per cent in length is one of contraction. If it is warmed, the change is an expansion of a like amount. This, perhaps, explains why insulating bricks that have been improperly made will often spa11 when only a match flame is applied to the corner ot the brick. “To avoid the formation of cristobalite and consequent spalling, Coss fires his brick in the presence of an agent that favors, it is said, the formation of tridymite instead of cristobalite. Thus, he fires in the kiln to 2500’F. or higher without producing a spalling brick. He seems to obtain a large proportion of the desired tridymite, which, unlike cristobalite, has no transition temperatures at which it undergoes such sudden change of volume as to crack the brick. “The agent which is used to cause the transformation of amorphous silica of the natural earth into tridymite of this brick is usually I to 3 per cent of lime. As a hinder, there is used 2 to 7 per cent of a refractory of clay-like composition, such as feldspar. A grog of calcined material, for example, 12 per cent, and a small amount of plastic clay may also be used, p. 185. “The user of diatomaceous insulation is interested more in the thermal conductivity and the amount of heat that will be saved by the use of the insulation than in the methods of manufacturing it. He is interested, for example, in such results as those obtained from the insulation of 90-ton annealing furnaces in a large malleable iron works. The insulation of walls, arches, and doors with a 4-1/2-inch course of Nonpareil insulating brick decreased the fuel oil consumption, for each ton of product, to 40 gallons as compared to 60 gallons in the older type of uninsulated furnaces. On a total production of 60 tons a day, the fuel saving is 1,200 gallons a day. At 3 cents a gallon this saving amounts to more than $10,000 a year,” p. zoo. “The solidifying of alcohol by diatomaceous earth is an interesting illustration of the high degree of porosity of the earth, the amount which may he absorbed being very large. Thus, IOO cc. of the wet paste can be made to contain 86.4 cc. alcohol without being so fluid as to allow leakage of the alcohol from the paste when the container is inverted, either while cold or while the alcohol is burning and the composition is, therefore, warm. To make such a solidified alcohol one mixes, for example, 30 grams of diatomaceous earth, of the quality known as Filter-Cel, with 86.4 cc. alcohol. Although the diatomaceous earth when
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dry, is very bulky, the actual net volume of the 30 grams of silica composing the skeletons is 30 divided by 2.2 (the approximate specific gravity of such silica) or only 13.6 cc. “Alcohol thus absorbed in diatomaceous earth is being marketed in Germany, it is said, under the name ‘Lithosprit.’ I n the United States, solidified alcohol or ‘canned heat’ is now preferably made by allowing a warm solution of soap in alcohol to set to a gel on cooling or by the precipitation of pyroxylin in a dilute alcoholic solution,” p. 221. “Silica per se is a poor catalyst as compared with the oxides of iron or aluminum or with many other oxides. Yet the very large extent of surface in diatomaceous earth, its condition of neutrality, insolubility, and inertness under most conditions, its low density, and slow rate of settling from solutions make diatomaceous earth an excellent supporting agent for catalysts,” p. 23 j. The photomicrographs are good. The reviewer was especially interested in Fig. 2 of Wilder D. Bancroft diatoms from New Zealand. Tables annuelles de constants et donndes numdriques de chimie. (Annual Tables of Constants and Numencal Data, Chemical, Physical, Biological and Technological). Edited by Ch. Marie. Published by the International Committee appointed by the Seventh Congress of Applied Chemistry. Vol. V I I , Parts 1 and 2 , 1925-1926. 28 X 23 cm; p p . Part 1 , xxxu 916, Part 2, zu 960. ,Vew Fork: McGraw- Hill Book Company, 1930. Price: $26.00. The new volumes of tables give a very valuable survey of the numerical data discovered in the years 1925-26. As was the case for the earlier volumes, the tables are divided into more than fifty sections, each written by specialists who are well known in their respective fields. Two new sections have been introduced into Part 2 on Explosives and Explosions in Gaseous Mixtures and two old sections, those on Photography and Geophysics, have been omitted. The specialists in charge of the last two sections prefer that these subjects be dealt with once in every two volumes. Since there is a large amount of explanatory description given with some of the tables, the various chapters partake somewhat of the nature of monographs. The descriptive matter makes the tables more valuable in that it will not be found so necessary to refer from them to the original literature. When this is necessary, as in the case of details of preparation of new compounds, the reader is aided by being given the number of the page on which the new substance is described. One feature of the tables which increases their value to the searcher through the literature is the bibliography of papers whose contents cannot readily be expressed in tabular form. It is of interest to note to what extent the attention of the scientific world is being directed to the study of spectra. More than 450 pages are devoted to data on emission and absorption spectra, out of a total of 1896 pages. The chapters on dielectric constants and on X-ray analysis of crystals are also very largely augmented. The Secretary of the International Committee, Dr. Marie, announces that Volume VI11 for the years 1927-28 is already in the press and should appear very shortly. After the publication of this volume, it is proposed to commence a yearly publication of the annual tables. The International Committee is to be congratulated on the manner in W . E . Garner which they have overtaken the arrears of publication.
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Jahrbuch des Forschungs-Instituts der Allgemeinen Elektriziuts-Gesellschaft. Vol.1, 1828-1929. 30 X 22 cm: p p . $40. Berlin: Julius Springer, 1990. The scope of the research
work of the laboratories of those great corporations whose interests depend on applications of pure scientific knowledge is year by year growing wider, and their outlook more philosophic. It pays, in every good sense of that much-ahused word, to take the long view. And so we find engineering companies fostering research on surface-forces in liquids, and telephone research laboratories enlisting the aid of physicists, physiologists and psychologists. Now we welcome the first volume of the Yearbook of the A. E . G . The range covered by the papers is remarkable, and to attempt to consider it in any detail within the limits of a brief review is an impoeaihle task. Briefly, the volume is made up of some thirty-five papers grouped together under seven headings-Akustik, Elektrotechnik,
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Elektronenphysik, Atomphysik, Atomchemie, Stoff-physik and Elektro-optik. Subjects so diverse as sound-films, contact potentials, the application of electron-waves to the analysis of crystal structure, the frequency curves of memhranes, and the electrical conductivity of molten silicon-to name hut one or two titles-are discussed both experimentally and mathemat,ically, and the volume closes, appropriately enough with an essay under the heading “Sollen die technisch-physikalischen Forschungslaboratorien der Industrie rein wissenschaftliche Forschung hetreiben?” The volume is well-produced and hound, and the illustrations, whether line drawings or photographic reproductions, are excellent of their kind. A . Ferguson Solvents. B y Thos. H . Durrans. 22 X 1; cm; p p . xu X 144. A-ew Y o r k : D. 1-an Soslrand Company, 1930. Price: 86.00. I n the preface, p. vii, the author says: “Both the number of organic solvents which are available to industry and the extent to vhich they are used have increased greatly during the recent years, and there is in consequence a need for a scientific exposition of the technical application of solvents, more particularly in connection with the cellulose-lacquer industry. . . . “The first part of this book takes the form of a more or less connected series of chapters dealing with the fundamentals in a broad and simple manner. The second part is of a more utilitarian nature and deals comprehensively with individual solvents, mainly with the view of facilitating the intelligent use of these solvents in the cellulose-lacquer industry.” The chapters in the f i s t part are entitled: introduction; solvent action; solvent power; plasticising solvents; solvent balance; viscosity; vapour pressure; imflammability ; toxicity. In the second part of the chapters are: introduction; hydrocarbons; alcohols; ketones; esters; glycols; cyclohexane derivatives; chloro-compounds; furfurals; plasticising solvents. It should be noted that the solutions which the author discusses are practically exclusively colloidal solutions. “It is well known that certain varieties of cellulose nitrate are soluble in a mixture of alcohol and ether, although not soluhle in either liquid separately. Neither of these liquids contains any group, such as rarbonyl, which usually imparts solvent properties, as, for instance, does acetone or amyl acetate,” p. I . “If to a solution of cellulose nitrate a miscible non-solvent he gradually added, a dilotion is ultimately reached, a t which the cellulose nitrate begins to be thrown out of solution either as precipitate or as gel. The solution is said to ‘tolerate’ the addition of this definite proportion of the diluent under the conditions of temperature and cellulose-nitrate content obtaining. It is common to regard tolerances or dilution ratios as a measure of the solvent power of a solvent,” p. 5. “Plasticisers are solvents which are practically non-volatile; they may be liquids or solids, the latter being known as ‘solid-solvents.’ The term ‘solid-solvent’ arose from the use of the solid, camphor, which is a ketone a n d , like many other ketones, dissolves cellulose nitrate. If a solution of a cellulose ester be allowed to evaporate so as to leave a film, a certain hut diminishing quantity of the aolvent remains in the film according to the conditions obtaining, This small quantity of solvent imparts t o the films a degree of softness or plasticity depending on the solvent and the quantity of it which is present,” p. 9 . “The terms ’plasticiser’ and ’softener’ are not quite happy ones, for \,.hat is really desired is not a soft or plastic film but a stable, highly elastic, non-shrinking film with a hard non-scratchable surface. A soft film is one which is susceptible t o deformation of its surface; a plastic one retains such deformation; a n elastic film returns quickly to its original form,” p. IO. “Platicisiers have a pronounced effect on ‘secondary flow,’ a loose term applied to the very slow smoothing effect which takes place shortly hefore the film sets and no longer is capable of flowing. The gloss of a film is largely governed by this secondary flow and it is for this reason that high-boiling solvents tend to produce glossy films! the slow rate a t which the solvent evaporates allowing time for microscopic irregularities of the surface to disappear,” p. 11. “For many years it was not possible to make satisfactory factory lacquers with the cellulose nitrates then available, since those nitraies gave solutions of excessively high viscosity
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when prepared in a state sufficiently concentrated to ensure films of the desired thickness and strength. Many, more or less successful, attempts were made to reduce this viscosity by employing various solvents, hut this generally resulted in introducing other undesirable characteristics. I t was not until the introduction of the low-viscosity cellulose nitrates, such as the well-known ‘half-second cotton,’ took place, that the Tidespread use of such lacquers became possible; even now i t is common practice to ‘load’ the lacquer with resins for the purpose, among others, of giving’body’to a film without of necessity producing unduly viscous solutions. “The viscosity of a lacquer may be adjusted in several ways; thus mixtures of different cellulose nitrates may he employed, these being available in grades giving a wide range of viscosity, or the viscosity may be varied by suitable choice of solvent or solvent mixture. Viscosity and vapour pressure are apparently to a considerable extent concomitant properties, thegreater thevapour pressureof asolvent the lower theviscosityof its solutions,” p. 18. “The lowering of temperature of a solvent evaporating in free air causes the air in its immediate neighhourhood to fall in temperature, and if the humidity of this air he sufficiently great a temperature beloir. that of the dew-point may be reached and water \ d l he deposited. If the solvent contain a substance insoluble in w t e r , for instance, cellulose nitrate or resin, this deposition of water may cause their precipitation with the consequent formation of a white opaque film on the surface of the solution; this effect is known as ‘chilling.’ If the solvent is one ahle to dissolve water to a considerable extent, such as ethyl lactate, diacetone alcohol or ethyl alcohol, this chilling effect may be delayed, since the water may be dispersed in a greater depth of the solution. If, on the other hand, water is completely insoluhle in the solvent no chilling can occur, since the water will merely deposit on the surface and not penetrate at all,” p, 30. “It is safe to say that the vapours of all volatile substances are toxic or at least narcotic, if they be inhaled in a sufficiently concentrated state for a sufficient length of time. K i t h some the effect is merely that of suffocation caused hy the deprivation of oxygen, others cause anesthesia, whilst a third class includes those definitely poisonous by reason of some physiological action, causing functional derangement of the metabolism. The three classes are not closely defined hut merge one into the other and vary with the individual. The majority of lacquer solvents belong to the earlier classes, the term ‘solvents’ being taken to include the diluents. . . “The poisonous effects of most solvents is not cumulative, and their vapours can he inhaled without any apparent effect, provided that they are present in a sufficientlydiluted state; prolonged inhalation of such dilute vupours has been known to give immunity to the poisoning by concentrations normally lethal. I t has been found, for instance, that workmen constantly employed in the manufacture of ether cannot be anaesthetised in the normal manner by this substance. I t should, however, he realised that the continual inhalation of quite small quantities of solvent vapours cannot but have a deleterious effect on the general health, although the effect may not he sufficiently pronounced t o he apparent; generally speaking the risk is not greater than that obtaining in other industries, but the importance of adequatt ventilation is to be emphasised. “With some solvents, however, the effect is cumulative, notably with methyl alcohol! tetrachloroethane, tetrachloroethylene and carbon disulphide, although some persons are insensitive to the action of the last-named. Prolonged exposure to benzene vapour has also been found to be highly dangerous, especially to persons of advanced age. Turpentine vapour is poisonous t o some, and it would appear that the poisonous action of lead-pigmented paints may have heen wongly ascribed in some instances to the lead pigment: 4 to 6 mg. of turpentine per litre of air can produce symptoms of poisoning; 16 mg. per litre killed a cat within one hour. “Of the various classes of solvents employed, the chloro-compounds are undoubtedly the most poisonous, and they are potent anaesthetics. Carbon tetrachloride and tetrachloroethylene are definitely poisonous, causing enlargement of the liver. This disease, when produced by the action of the latter solvent, is notifiable in England. I n Germany,
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the use of tetrachloroethylene is forbidden. Tetrachloroethane is also said to be highly poisonous, but trichloroethylene is relatively harmless, whilst di-chloroethylene causes dermatitis,” p. 40. “In many cases it is not desirable or expedient that a chemically-pure substance should he used for lacquers. In some instances the presence of ‘impurities’ considerably enhances the desirable properties of a solvent. On the other hand, the cost of removing certain impurities is out of proportion to the advantages to be gained,” p. 45. The second part contains chiefly data concerning the different substances used as solvents, plasticisers, etc. V i l d e r D. Bancrojt Application of Interferometry. By W . Ettcart Williams. 19 X f8 em; p p . it’. i- 10;. London: Methuen and Co.. Ltd., 1980. Price: 2 shillings, 6 pence. This small monograph, written for advanced students, contains a clear and correct presentation of the fundamental principles of interferometry. The different methods of obtaining interference effects are divided into such in which the interfering beams start out from a primary line or point light-source or from’a similar secondary source, such as a narrow slit (“division of wavefront”) and such in which a broad beam is divided by a partially reflecting surface and later is re-united (“division of amplitude”) . For the physical chemist, instruments in the former category are particularly important (the Rayleigh interferometer and the designs worked out by Haber and Lowe are of thls type). The methods for size measurement of microscopic and ultramicroscopic objects, worked out by Gehrcke, 0. v. Baeyer and Gerhardt, employ the same principle, and are analogous to the method developed by Michelson for the determination of the angular diameter of the stars. The Jamin and Mach instruiLients, belonging to the second category are also of interest to the physical chemist, applicable as they are to the investigation of reaction rates in gaseous systems. Finally, the various interferometers for the examination of the fine structure of spectral lines (Fabry-Perot; Lummer-Gehrcke) are of importance t o the modern Jpectroscopist. The manifold possibilities offered by interferometry for purely physical measurements of length and of thickness, form the main theme of the present small volume, and it should be a real stimulus for physical chemlsts to see set out so clearly the close relations which exist between their own interferometric experiments and the most precise measurements of modern physics. Fritz Weigert
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178. Easton: T h e German for Chemists. By Louis de Vries. 23 X 16 cm; p p . ti Chemical Publishing Co., 19?29. Price: 8S.00. I n the preface the author says: “This text contains material taken from the works of well-known Chemists, such as Emil Fischer, Wilhelm Ostwald and others. The different chapters embrace many phases of chemistry. including Organic, Inorganic, Analytical, Biophysical, Physiological and Nutritional, Soil, Plant, and Enzyme Chemistry. The reader, prepared for the use of students who wish to acquire a reading knowledge of G e m a n , gives in addition to practice in reading the language, an introduction to German chemical literature.” The selections are well made and the reviewer ronfesses both to pleasure and profit from reading the book. I n the vocabulary verbs with separable prefixes have a hyphen between verb and prefix. That simple little detail will make life a good deal easier for the student. There are several misprints which should be corrected in future editions: Vergrosserung, p. v; kapilla, p. 17; Gesets, p. 25; Kekule, p. 43 and elsewhere; versichieden, Wurts, p. 45; urnstandilch, p. 66; Herteroeyklus, p. 7 6 ; nebeneiander, p. 7 7 ; Zukkerarten, p. 103;geblidet, p. 104. These are obvious misprints but they might bother the beginner. The author has Inhalt in the vocabulary and Jnhalt in the text, p. 8. The reviewer thinks that Deutsche chemische Gesellschaft, p. v, should not be written with three capitals. Wilder D. Bancrojt
