NOTICES OF BOOKS Price 6d. net. Education, Scientific and Humane. Edited by FREDERIC G. KENYON. London: John Murray. 1917. Pp. 32. THIS pamphlet has been issued at the request of the Council for Humanistic Studies, and is the outcome of an endeavour to arrive at a general agreement regarding the principles and main ourlines of secondary education, so that future discussion of details may show a less extreme and more tolerant spirit than in the past. The Conference, representative of the Classical, English, Geographical, Historical, and Modern Language Associations, drew up a series of resolutions upon which the Methematical Association and the Association of Public School Science Masters expressed their opinion, at the same time outlining their own aims. The statement of the latter Association regarding the value of scientific teaching in fostering a love of truth and in giving a valuable knowledge of the employment of the forces of nature and the sequence of cause and effect will be generally approved. So far the main points of agreement seem to be that early speciali. sation should be avoided, and that the doors of all subjects should be open to all pupils. In a later conference between the Sub-Committee on Education of the Board of Scientific Societies and the Council for Humanistic Studies, the question was again discussed, and a series of resolutions drawn up representing a further advance towards agreement. CORRESPONDENCE. SIMILARITY OF CARBON AND PHOSPHORUS. To the Editor of the Chemical News. SIR, In the CHEMICAL NEWS for October 23, 1914 (vol. cx.. p. 210), which I recently came across, I find a letter by F. H. Loring calling attention to the close resemblance of the properties of the two elements carbon and phosphorus. This similarity between these two elements is very striking, and it is brought out very forcibly in the series of intermetallic compounds formed by these elements respectively with iron. The well authenticated compounds formed by these elements with iron are set out below: MISCELLANEOUS the new accommodation for the British Industries Fair British Industries Fairs, 1918. As it is possible that (Glasgow), 1918, may not be entirely completed by February 25th, and as it is of great importance that the British Industries Fairs in London and Glasgow should be held simultaneously, the Board of Trade have decided to postpone the opening of both Fairs for two weeks. Accordingly, the period for which the British Industries Fairs in London and Glasgow will be open will be March II to March 22. NOTES AND QUERIES. Our Notes and Queries column was opened for the purpose of giving and obtaining information likely to be of use to our readers generally. We cannot undertake to let this column be the means of transmitting merely private information, or such trade notices as should legitimately come in the advertisement columns. "The Homunculus "-A correspondent wishes to know where he can either borrow or purchase a copy of "The Homunculus." Vinegar. Can any reader supply recipes for making pure malt vineAlso the name of a book (and the publisher) dealing with the manufacgar and vinegar proper-that is, such as is not styled "malt "vinegar. ture of vinegar and its by-products-to wit, yeast?-H. T. Books Required -Could any reader tell me how I could get the following:-"Die Technik der Rosanilinfarbstoffen" (O. Mülhäuser, 1889) and "Derivate des Naphthalins " (Täober and Norman, 1896), or any other good books which will give me detailed information on the manufacture of phthalic anhydride and the rosaniline dyestuffs (especially fuchsine)? I should be most grateful to anyone who can get me these. Should these two books not be as suitable as others kindly advise me.-S K. Decomposition and Solution of Minerals.-(Reply to "Perplexed").-Your correspondent may find an answer to his query in the chapter on "Silica " in Low's "Technical Methods of Ore Analysis" (Chapman and Hall). Little difficulty has been experienced with many minerals when-(1) The substance is very finely powdered; (2) as a preliminary step before fusion, as much as possible is extracted from the mineral by HCl assisted by HNOg; (3) any residue unattached in the fusion is powdered up again and re-melted with fusion mixture, NagCO3+ KgCO3.-F. BROWNE. MEETINGS FOR THE WEEK. MONDAY, 21st.-Royal Society of Arts, 4.30. (Cantor Lecture). THURSDAY, 24th.-Royal Institution, 3. "Generalship-a Campaign of Napoleon's (1806)," by Prof. Spenser Wilkinson. Royal Society. "Graphical Solution for Highangle Fire," by A. N. Whitehead "Flocculation," by S Pickering. "Revolving Fluid in the Atmosphere," by J. Aitken." Ultra-violet Transparency of the Lower Atmosphere and its Relative Poverty in Ozone," by Hon. R J. Strutt. ས The Pressure in the Solar Spectrum of the Watervapour Band A 3064" by A. Fowler. "The Ultraviolet Band of Ammonia and its Occurrence in the Solar Spectrum," by A. Fowler and C. C. L. Gregory. FRIDAY, 25th-Royal Institution, 5.30. "Motion of Electrons in Gases," by Prof. J. S. Townsend. SATURDAY, 26th.-Royal Institution, 3. "The Chemical Action of Light," by Prof. W. J. Pope. SOCIETY OF CHEMICAL INDUSTRY JOURNAL, set; also Vol. I or No. 1 (1882), or run including. CH MICAL SOCIETY OF LONDON, Memoirs and Journal, set or any portions of 1841 70. IRON AND STEEL INSTITUTE JOURNAL, set, or 1869-71, 1878 (Pt. 2). QUARTERLY JOURNAL MICROSCOPICAL SCIENC, Nos. 122, 133, 139, 146, 147, 149, 150; £ each offered, or buy run including. PHILOSOPHICAL MAGAZINE 1881, 1888, 1801, or run. TEXTILE ME CURY, Vols. 1-32 (1889-1905). TEXT LE RECO DER, set. TEXTILE MANUFACTURER, set. PERFUMERY AND ESSENTIAL OILS RECORD, Vols. 1 to 8. JOHN WHELDON & CO., 38, Gt. Queen Street, London, W.C. 2. Telephone-Gerrard 1412. UNI CHEMICAL NEWS AND JOURNAL OF PHYSICAL SCIENCE Proprietor and Editer, Sir Wm. Crookes, O.M., FR.S.] (WITH WHICH IS INCORPORATED THE "CHEMICAL GAZETTE ""). [Established Published Weekly. Annual Subscription. free by post Entered at the New York Post Office as Second Class Mail Matter. Transmissible through the Post-United Kingdom, at Newspaper rate; Canada and Newfoundland, at Magazine rate. 44 48 The Ores of Copper, Lead, Gold, and Silver, by C. H. Fulton.. .... CAPPER PASS & SON, LIM, BRISTOL, are buyers of LEAD ASHES, SULPHATE OF LEAD, LEAD SLAGS, ANTIMONIAL LEAD, COPPER MATTE, TIN ASHES, &c., ORES, DROSS, or RESIDUES containing TIN, COPPER, LEAD, and ANTIMONY. NEW TYPE Particulars from OZONAIR LIMITED, 96, Victoria Street, London, S. W. 1. SULPHUROUS ACID and SULPHITES. Liquid SO2 in Syphons, for Lectures, &c. PHOSPHORIC ACID and PHOSPHATES. CARAMELS & COLORINGS for all purposes. G. ROSSI. G. SILVESTRI. R. BELASIO. F. BARBONI. Translated by T. H. POPE, B. Sc., A.C.G.I., F.I.C., Univ. of B'ham. By ARTHUR MARSHALL, A.C.G.I., F.I.C., INDUSTRIAL ORGANIC ANALYSIS. By PAUL S. ARUP, B.Sc., THE SYNTHETIC USE of the METALS in ORGANIC THE PLANT ALKALOIDS. By T. A. HENRY, D.Sc., Supt. of MODERN STEEL ANALYSIS. Practical Methods. By J. A. THE PREPARATION of ORGANIC COMPOUNDS. By E DE BARRY A. BOAKE, ROBERTS, & CO. (LIMITED), JOHN J. GRIFFIN & SONS, LTD., Stratford, London, E. KINGSWAY, LONDON, W.c TABLES FOR MIXED ACIDS. ABC FIVE - FIGURE LOGARITHMS and Tables for CHEMISTS By C. J. WOODWARD, B.Sc. Logarithms of Numbers with Thumb Lateral Index - Instructions for using the Tables, with Examples and Exercises-Hydrometer Tables -Electrochemical Equivalents-Gas Correction or Nitrometer Tables from 680 to 799 mm. pressure and 7° to 23° C.-Thermometer Equivalents, -99° F. to +2990° F. in C. and vice versa-Weight and Measure Conversion, Imperial to Metric and vice versa-Factors and Logarithms of Factors for use in Gravimetric Analysis. All tables involving atomic weights calculated from the International Atomic Weights of 1917. LONDON: E. & F. N. SPON, 57, Haymarket. To comply with Regulation 8 (6) of the Defence of the Realm Act, advertisements from firms whose business consists wholly or mainly in Engineering, Shipbuilding, or the production of Munitions of War, or of substances required for the production thereof, must include the words "No person resident more than ten miles away or already engaged on Government work will be engaged."' Chinese Graduate, B.Sc. (London University), seeks Position as Chemist, either in Analytical or Manufacturing work.-Write, Y. T. C., care of 2, Kingston House, Fortess Road, Kentish Town, London, N.W. 5. Chemist, intelligent, elderly, at present em ployed in large Government Steel and Copper Works in Russia, seeks employment in this country.-Messrs. Symonds and Macdonald, Writers, Dumfries, N.B, will furnish all particulars. Wanted, Chemist (male or female) for large Dairy Firm in London.-Write, stating qualifications, experience, and salary required, to “D. E.," care of Street's, 30, Cornhill, E C. 3. Wanted, "Chemical News," 1863, 1864, 1869, 1892, 1895 to 1914 or part; General Index vols. 1-100; "Che mical Gazette," vol. 17 (1859); "Journ. Soc. Dyers and Colourists": Journ. Soc. Chem. Ind."; "Quarterly Journ. Chem. Soc."-Offers to "C. 186," CHEMICAL NEWS Office, 16, Newcastle Street, Farringdon Street, London, E.C. 4. Special Articles on PICTORIAL and Wanted, Modern SCIENTIFIC PHOTOGRAPHY. The best and brightest Photographic copy CHEMICAL TRADES JOURNAL dated January 6, 1917.-Address, R. C, BAGGE, Chance and Hunt, Ltd., Oldbury. Weekly for the Beginner or Advanced Wanted, "MEMORIALS OF THE GOOD. Worker. Office: 51, LONG ACRE, LONDON, W.C. MICA. WIN SANDS," by Mr. Gattie.-Address, W. S., CHEMICAL Telephone Vacancies in Heat Treatment Department of No. 2248 Avenue. large Steel Works for men of good Technical training and general knowledge of Metallurgy of Steel, including use of Pyrometers. Previous works experience an advantage, although not essential. Initiative and energy will lead to quick advancement and responsibility. No person already on Government work will be engaged.-Apply your nearest Employment Exchange, quoting reference No. A 4472, and giving full particulars as to age, previous experience, qualifications. and salary expected. dihydrate. In the ordinary setting of plaster the quantity of water is so small as to be capable of dissolving only a minute fraction of the calcium sulphate, but it is sufficient to form a layer of supersaturated solution around each particle of the hemihydrate, and when this layer deposits its excess of dihydrate the remaining water is available for the solution of a further quantity. It is certain that the above statement corresponds closely with the main facts of the setting of plaster of Paris of the composition 2CaSO4, H2O, as prepared by any of the usual technical methods. So far as the writer is aware, only one attempt has been made to explain the setting of plaster as a colloidal process. Rohland (4) has suggested that the water is taken into solution in the salt in a colloidal form, and has extended the same explana. tion to the caking of other salts when powdered and moistened, but the statement is not supported by evidence, and has not been accepted by others. There are, however, certain facts which indicate that ALTHOUGH the use of calcareous cements dates from a very early period of human history, and has attained to so high a development in modern times as to have given rise to an industry of the greatest importance, our knowledge of the scientific nature of the materials and processes involved is even yet imperfect, in spite of many excellent investigations covering various parts of the subject. It is the setting process is not quite simple. It was observed convenient, in a review of our present knowledge, to dis- by Cloez (5) that the heat evolved during the setting tinguish between the plasters and simple chemical cements, appears at two different stages, the initial rise of tempera-. such as the magnesia cements on the one hand, and the ture on mixing plaster with water being followed by a lime mortars, Roman and Portland cements, and similar products, on the other. The chemistry of the substances stationary period and then again by a rise of temperature. of the first group is now fairly well known, although the from that which might be expected from the known proMoreover, the density of the hydrated plaster is different plasters manufactured from gypsum have proved to be perties of calcium sulphate and its hydrates. The hemiunexpectedly complex, and there is little doubt that a correct explanation of the principal features of the setting and a calculation shows that the latter compound is formed hydrate has a density of 2.75 and the dihydrate of 2.32, process has been given. The case is different when we from its components with a contraction of 7 per cent, turn to the second group. It is only very recently that definite information as to the chemical constituents of fact on account of this property that plaster of Paris finds whilst in practice an expansion is observed, and it is in Portland cement clinker has been obtained, and even now some points remain in dispute, whilst two distinct explana-enabling it to fill the mould completely, and therefore to its application in the making of casts, the expansion tions of the setting process have been given, and the evidence in favour of either is by no means conclusive. In the present paper an attempt is made to examine these hypotheses and the evidence adduced in their support, and to indicate the nature of the observed discrepancies. The plasters are first, considered on account of their relative simplicity. A short section then follows on the magnesia and similar cements, and the third section is devoted to the setting of lime mortars and the complex cements. accompanied by a contraction, followed by a smaller extake an impression sharply. The setting is found to be pansion. The experiments of Davis (6) led him to the conclusion that the crystals of the dihydrate which at first separate are not identical with gypsum, but consist of a second, rhombic modification, which subsequently passes into the stable form. It may also be remarked that a part at least of the expansion is only apparent, and is due to the thrusting apart of the growing crystals, producing a porous mass. This effect is common in the growth of is obvious from the familiar porosity of a mass of hardened crystals from a supersaturated solution, and its existence plaster. The setting of the various kinds of flooring plaster, consisting largely of soluble 2nhydrite, is in all probability of of Paris only in regard to velocity. The addition of other a quite similar character, and differs from that of plaster salts may also bring about great changes in the rate of hydration and crystallisation of calcium sulphate, potassium sulphate, for instance, accelerating the process and borax retarding it. Rohland has shown (7) that the accelerators are substances which increase the solubility of gypsum, and the retarders are those which diminish the solubility. Colloidal substances may delay the setting con. iderably, and these facts are made use of in the preparaof many technical plasters. 1. Plaster of Paris and Gypsum Cements. It was shown by Lavoisier in 1765 (1) that the setting of plaster of Paris was essentially a process of recombination of the dehydrated gypsum with the water of which it had been deprived in the process of "burning," and that the strength of the mass after setting was the result of the formation of a confused mass of interlacing crystals. The mechanism of the process was not explained until 1871, when Professor H. le Chatelier (2) showed that the hemihydrate, 2CaSO,,H2O, readily dissolves in water, forming an unstable solution which is supersaturated in respect to the dihydrate, CaSO3,2H2O. Any particles of the latter salt which may be present, probably in the form of unburnt particles of the original gypsum, act as nuclei, and set up crystallisation of the stable dihydrate. It is characteristic of crystals separating from strongly super-tion saturated solutions that they tend to grow in radial fashion about the nucleus. When the nuclei are sufficiently near to one another, the radiating needles of neighbouring groups interlock, and a mass possessing considerable mechanical strength is obtained, which can only be broken across by breaking the individual crystals. That such a supersaturated solution is actually formed is not only proved by microscopical examination, but was shown by an experiment due to Marignac (3), who shook ground plaster of Paris with water and filtered after a short interval. The filtrate was five times as concentrated as a saturated solution of gypsum at the same temperature, but it soon became turbid and deposited crystals of the A contribution to a General Discussion on "The Setting of Cements and Plasters," held by the Faraday Society, January 14, 1918. II. Substances the Setting of which resembles that of It was also shown by Le Chatelier that other substances which are capable of forming unstable supersaturated solutions will set in the same manner as plaster of Paris. Thus, anhydrous sodium sulphate dissolves readily in water, and if precautions are taken to prevent too rapid solution and consequent rise of temperature, a highly concentrated solution may be prepared at practically constant temperature. This solution is unstable, and the hydrate separates in characteristic interlocking masses of crystals. Various cements composed of a mixture of an insoluble metallic oxide aud a solution of the chloride of some similar salt of the same metal are in technical use. For example, a mixture of zinc oxide with a concentrated solu. tion of zinc chloride yields a strongly supersaturated solution, from which the oxychloride slowly crystallises. Magnesium oxychloride, prepared in a similar manner, forms the basis of many cements, and may be assumed to set by a process of crystallisation, although Kallauner (8) considers that the ease with which the chloride is extracted from the solid mass by means of alcohol, and the fact that the free magnesia in the mixture cannot be completely converted into carbonate by carbon dioxide, points to the formation of a solid solution of hydroxide and chloride rather than of a definite exychloride. A microscopical study of the setting process does not appear to have been made, although it would have some interest in relation to the problem of the dental cements, some of which have an analogous constitution. Barium metasilicate is another salt which forms supersaturated solutions and is capable of setting when mixed with a small proportion of water. Tae product is the crystalline hydrated salt BaSiO3,6H20. The orthosilicate undergoes hydrolysis, forming the hydrated metasilicate, Ba2SiO4 + 15H20 BaSiO3.6H2O + Ba(OH)2,8H2O. Owing to the comparatively great solubility of the silicate the setting resembles that of plaster, and the mechenical strength of the product is not comparable with that of a hydraulic cement, although in the case of the orthosilicate the chemical reaction is quite similar to that which con stitutes the principal part of the hydration of a Portland cement. The product is crystalline, and consists of interlocking bunches of needles. III. Lime, Mortar, and Cements of the Portland Class. The hardening of a simple lime mortar, composed only of slaked lime and sand with water, is a mere process of desiccation. The calcium hydroxide forms an apparently structureless mass, which may be either colloidal or minutely crystalline, and the cohesion of this mass furnishes the necessary strength. The sand merely prevents the cracking which would otherwise take place during the contraction on drying, by sub-dividing the line into thin layers. As time goes on the calcium hydroxide may recrystallise to a certain extent, whilst those portions of the mass which come into contact with the atmosphere may be converted into the crystalline carbonate, but neither of these changes is essential to the hardening of the cement. There is no chemical reaction between the lime and the sand. On the other hand, when pozzolanic substances are added to the mortar, such as the volcanic earths of the Mediterranean which were used by the Greeks and Romans, the trass and ground tiles which were employed by the Romans in more northern regions, or the burnt brick and ballast added to this day in India, a chemical reaction takes place between the lime and the active or soluble silica which is the essential constituent of all pozzolanic materials, and calcium metasilicate is formed. Portland cement is a more complex material. The constitution of the clinker has been established by the brilliant investigations of the Geophysical Laboratory staff at Washington. The compounds which are or may be present are tricalcium silicate, 3CaO, SiO2; calcium orthosilicate, 2CaO,SiO2; tricalcium aluminate, 3CaO,Al2O3; pentacalcium trialuminate, 5CaO,3Al2O3; and free lime, CaO (9). Campbell has recently given reasons for believing (10) that tricalcium aluminate is rather to be regarded as a solid solution of lime in the pentacalcium trialuminate, but this does not materially affect the present problem. Not more than three of the above-mentioned compounds can be simultaneously present in the clinker in a state of equilibrium, but since the components do not reach the temperature of fusion during the process of manufacture, it is actually possible for small quantities of one or more additional constituents to occur in commercial clinker. It does not appear, however, that clinker made in a rotary kiln departs very widely from the state of equilibrium. An examination of the ternary equilibrium diagram shows that the clinker will contain a ternary eutectic, there being two such eutectics within the usual range of the composition of clinker. The microscopical examination of transparent sections of clinker does not reveal the presence of any eutectic, but this is simply due to the minuteness of the structure, much overlapping occurring even within the thickness of a thin section. When, however, the specimen is polished on one surface only and lighly etched, as in the examination of metals, the eutectic structure is clearly revealed. The writer has published one such photograph (11), and Mr. T. Hattori, working in the writer's laboratory, has since obtained very beautiful eutectic structure of Japanese clinker. The calcium aluminate which is chiefly present as a constituent of this eutectic is consequently in a finely divided form, and therefore in a condition to react readily with water. According to the explanation of the setting process put forward by Le Chatelier in 1887 the ground cement reacts with water in such a way that the silicates and aluminates are hydrolysed, the staple compounds being the hydrated metasilicate, CaSiO3,2·5H2O, and a hydrated tetracalcium aluminate, 4CaO,Al2O3,12H2O, the excess of lime liberated by the hydrolysis forming calcium hydroxide. Microscopical examination of the reactions of the constituents with water led to the conclusion that the process was strictly analogous with that of the setting of plaster, an unstable supersaturated solution of the basic silicate, for example, being formed initially, followed by rapid crystallisation of the stable phase in the form of radiating needles. In reference to this it should be remarked that the process is largely dependent on the ratio between solid and water, and that in hydration experiments on a microscope slide the quantity of water used is relatively much larger than in the gauging of cement in practice, and that this fact probably accounts for certain discrepancies recorded by different observers. The alternative hypothesis was proposed by W. Michaelis in 1893 (12), and expanded in a later paper (13). On this view, whilst the chemical reactions assumed are those which were shown to take place by Le Chatelier, the physical conditions are supposed to be different. The hydrated metasilicate is considered to form, not a mass of radiating crystals, but a gelatinous mass or gel, the gradual dehydration of which brings about the hardening of the cement with time. The aluminate crystallises much more readily than the silicate; but even this is regarded as forming a gel when the solution is sufficiently supersaturated that is when the quantity of water is small, as is the case in the practical utilisation of cement. The presence of gelatinous material at an early stage of the setting process is readily observed. It has been photographed by Stern (14), and the increase of size of the cement particles by absorption of water and consequent swelling of the gelatinous sheath which forms around them has been described by Ambronn (15), and may be readily confirmed. According to Colony (16), a reaction subsequently takes place between this early gelatinous material and the remaining constituents of the cement, and a secondary amorphous product is formed, the desiccation of which is the cause of the hardening, At a later stage crystals of calcium hydroxide, calcite, and zeolites make their appearance (17). An attempt to distinguish between the various possible colloidal products has been made by Keisermann (18), using the method of staining with organic dyes. The results indicate that the gelatinous sheath consists of calcium metasilicates, which compound also occurs in the form of small needles, whilst the calcine hydroxide and aluminate assume the crystalline form. These staining results with colloids depend largely on the concentrations of the substances concerned, and the writer, possibly not working under precisely similar conditions, has not succeeded in confirming all of Keisermann's results. The dependence of the observations of the size of grain has been pointed out by Wetzel (19). Other experiments in which stains were used led Blumenthal to the conclusion (20) that the metasilicate and aluminate were first formed |