between the electrodes. The large and abrupt fall of | just before his death in May, 1910, of a letter which he "Measurement of End-standards of Length." By Dr. P. E. SHAW. A continuation of work published in Roy. Soc. Proc. December 1, 1905). In recent years the authorities at the National Physical Laboratory have been required to measure and test end-standards with unprecedented accuracy. As a result, the faults of the standards and of the measuring machines have come to light. In this paper an account is given (1) of improvements in the planeness and parallelism of the standards; (2) of changes introduced in the writer's measuring machine to cope with the more accurate standards. It is easy to get consistent readings of length provided the standard is not moved; but if, as is required, the standard is moved, it is a difficult mechanical problem to provide a movement so nearly parallel that the readings before and after movement shall be consistent. Curves and tables are given showing the degree of accuracy at present obtained. A great advance in refinement is expected on the present lines of work. NOTICES OF BOOKS. An Introduction to the Chemistry of Colloids. By Dr. DR. PōSCHL's excellent little book on colloidal chemistry Technical Mycology. By Dr. FRANZ LAFAR. Translated by CHARLES T. C. SALTER. Vol. II. Eumycetic Fermentation. London: Charles Griffin and Co., Ltd. 1910. wrote to Prof. S. de Luca, and which appeared originally Manual of Practical Inorganic Chemistry. By A. M. Iron and Steel Analysis. Volume I. By A. CAMPION, THIS small book can be recommended for the use of evening students of practical chemistry, or of others who wish to obtain an elementary knowledge of the methods of iron and steel analysis in the shortest possible time. It is to be the first of a series of books on iron and steel analysis written by the author, and takes into consideration none but the ordinary constituents, e.g., silicon, carbon, sulphur, phosphorus, &c. As a rule one method only is given for each constituent, and that is described in sufficient detail THE delay in the appearance of the second volume of this for the average student to carry out the determinations treatise has been caused partly by the dilatoriness of the either without any or with very little supervision from a German publishers in supplying the final sheets, and partly teacher. The methods selected are those usually emby the magnitude and tediousness of the task of the trans-ployed, and may be regarded as the most rapid and accurate lator, who has, however, finally succeeded in accomplishing known, and in every case the method of working out the his aim and has made a valuable text-book of mycology results is carefully explained. accessible to English readers. The second volume deals with eumycetic fermentation, and gives a complete account of the culture of yeast, the life history and morphology of the saccharomycetes, ascomycetes, and the Fungi Imperfecti. The general editor is responsible for only a small section of the book, and has had the advantage of the collaboration of authors who are well known for their research work in mycology. The volume contains the complete bibliography and index to the whole work. Sketch of a Course of Chemical Philosophy. By STANISLAO CANNIZZARO (1858). Edinburgh: The Alembic Club. 1910. THIS Volume of the Alembic Club Reprints is a translation, to publish which permission was obtained from the author Diet and the Maximum Duration of Life. By CHARLES To the Editor of the Chemical News. SIR,-In your issue of January 6th, commenting on our new catalogue "Scientific Handicraft" you say:-"Messrs. Griffins are to be congratulated on having included the description of all their manufactures in one volume." As this may be somewhat misleading to some of your readers, we should like to point out that the catalogue to which you refer deals with physical apparatus only; we are at present at work on a new edition of our "Chemical Handicraft" dealing with chemical, metallurgical, and bacteriological apparatus, which we hope to publish next month, and which will form a companion volume to "Scientific Handicraft."-We are, &c., JOHN J. GRIFFIN AND SONS, LTD. Kingsway, London, W.C., January 13, 1911. 35 Boiling-point (°C.). Bromine Substitution and Addition (McIlhiney Process). Addition. Substitution. 149-155 155-171 A RAPID METHOD FOR THE IDENTIFICATION To the Editor of the Chemical News. SIR,-In the CHEMICAL NEWS for January 6th, 1911 (vol. ciii., p. 3) there, appeared a paper by Park and Worthing on the "Identification of Gas Oils," which is reprinted from the Chemical Engineer. The idea of using the bromine absorption test for this purpose was tried by us as far back as 1902, and was found to be unsatisfactory, as a considerable amount of secondary reaction undoubtedly takes place, and the amount of hydrobromic acid formed is not really a measure of substitution. Further, we have shown that the dehydrogenated naphthenes do not react quantitatively with either bromine or iodine. Thus, tetrahydronaphthalene after twelve hours only absorbs the equivalent of rather over one atom of a halogen instead of six. Further, the bromine absorption of any gas oil is not a constant unless the same limits of boiling-point are always adhered to. This, of course, is never the case in practice, the proportion taken for gas oils being dependent on the demands of the market for other classes of oil. The effect of variations in range of distillation can be readily seen in the accompanying table, which is drawn up from experiments made in 1902, the results of which have not previously been published. For the recognition of gas oils we have found (Soc. Chem. Ind., May, 1902; Analyst, Sept., 1906, and July, 1907) that a distillation test in which the fractions are separated at intervals of 20° C. in such a way as to have an even number for the second digit, combined with the determination of the specific gravity, refractive index, and specific refraction of each fraction, affords not only reliable information as to the origin of the oil, but also as to its suitability for gas making purposes. To see the reason of this it is only necessary to remember that the following facts hold good when comparing fractions of similar boiling-points obtained from different oils. Open-chain compounds (paraffins) have the best value for gas making purposes, the lowest specific gravity, the lowest refractive index, and a moderately high specific refraction. The presence of double bonds in the chain slightly decreases the gas making value, raises slightly the specific gravity and refractive index, but considerably lowers the specific refraction. As regards naphthenes, their utility for gas making purposes depends entirely on their degree of hydrogenation. Saturated naphthenes, e.g., of the type of deca-hydronaphthalene, are fair gas makers, but those of the type of tetra-hydronaphthalene are almost useless whatever temperature is used. Naphthenes must, of course, differ within themselves; thus, there is no doubt that two isomeric substances might differ very greatly in their gas making value if one contained a number of small side-chains and the other one long side-chain. The more the paraffin of the side-chain predominates over the simple or conjugated benzene nuclei the better the oil for gas making purposes. We are inclined to believe that the higher boiling ractions of most gas oils are largely made up of such naphthenes. The specific gravity and refractive index of such compounds would naturally conform to the rule that the longer the side-chain the lower the specific gravity and refractive index, and, conversely, the less hydrogenated, or the greater the predominance of the benzene nuclei, the higher the refractive index and specific gravity, always considered, of course, in relation to boiling point. in view. It is thus possible to identify and value an oil with a very great degree of certainty if these points are kept well An examination of our papers already quoted will make the foregoing statements quite clear.-We are, &c., RAYMOND Ross, JNO. P. LEATher. Public Analyst's Office, Burnley, January 11, 1911. CHEMICAL NOTICES FROM SOURCES. Hydrogenation of Isomeric Thujenes and of Sabinene.-L. Tchougaeff and W. Fomin.-By the direct hydrogenation of a and B-thujenes and of sabinene, hydrocarbons of formula C10H18 are obtained. They possess very similar physical properties, and apparently are saturated bicyclic compounds. Their composition is that of thujane, and the trimethylenic nucleus is evidently not altered by hydrogenation in presence of platinum black in the conditions specified by Wilstatter and Mayer. New Reaction of Morphine.-Georges Denigès.-To 10 cc. of a solution of morphine chlorhydrate 1 cc. of hydrogen peroxide is added, also I cc. of ammonia, and then a drop of copper sulphate solution containing 4 per cent of the crystalline salt. If the whole is well shaken both before and after adding the copper salt a pink or red colouration appears. This reaction seems to be due to the phenolic hydroxyl of the alkaloid. No. 24, December 12, 1910. Action of Nitric Acid on Aloïns.-E. Léger.-When nitric acid acts on the aloïns the products are chrysammic acid, picric acid, and oxalic acid; the first of these, however, is not formed directly, but results from the transformation of an intermediate product, viz., tetranitro aloemodine, the formula of which is C14 HO2(NO2)4(OH)2(CH2OH). Apparently tetranitrorheine, C14HO2(NO2)4(OH)2(COOH), is first formed, and is then changed into chrysammic acid. NOH The isomerisation of this oxime yields NOTE.-All degrees of temperature are Centigrade unless otherwise hexahydroacetanilide, C6H11.NH.CO.CH3. When hexaexpressed. Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. Vol. cli., No. 23, December 5, 1910. Decomposition of Hydrogen Peroxide by Light.— M. Tian.-The decomposition of hydrogen peroxide by heat is a bimolecular reaction. From the determination of the rate of decomposition when it is brought about by light it is found to be a monomolecular reaction. Thus it cannot be represented by the equation 2H2O2 = 2H2O+02, but to express all the facts the two equations H2O2 = H2O +0, 20+02 are necessary. The action of light is thus quite different from that of heat, and seems analogous to that of a catalyser. Brominated and Hydrobrominated Compounds of Silicon--A. Besson and L. Fournier.-When a rapid current of dry hydrobromic acid acts on amorphous silicon heated to a red heat, from the raw product of the reaction the following compounds can be isolated by distillation and subsequent sublimation under reduced pressure :1. SiBr4. 2. A white crystalline solid fusing at 95°, distilling without decomposition under ordinary pressure at 265°, and having the composition represented by the formula Si2Bг6. 3. A white crystalline substance of formula Si3Brs, fusing at 133°. 4. Si, Brro, which can be sublimed in vacuo, and appears to fuse at 1850; at this temperature it undergoes partial decomposition, leaving a white residue. hydroacetophenone reacts with acetic ether in presence of sodium ethylate, hexahydrobenzoylacetone, C6H11.CO.CH2.CO.CH3, is formed; it is a colourless liquid with a very penetrating odour. No. 25, December 19, 1910. This number contains no chemical matter. MEETINGS FOR THE WEEK. MONDAY, 23rd.-Royal Society of Arts, 8. (Cantor Lecture). “Etching," Royal Institution, 3. "Recent Progress in Astronomy," by F. W. Dyson, Astronomer Royal. FRIDAY, 27th.-Royal Institution, 9. "Radio-activity as a Kinetic Theory of a Fourth State of Matter," by Prof. W. H. Bragg, M.A., F.R.S. Reactions in the Electric Arc.-E. A. Salmon.-The author describes an apparatus for inducing two substances to react in the electric arc; it consists essentially of two electrodes pierced axially by channels; the gas is led down one channel and the products of the reaction escape by the other. Using this apparatus the author has made carbon unite directly with nitrogen, forming cyanogen, and water SATURDAY, can be decomposed by copper. Physical, 5. Demonstration of Phase Difference between the Primary and Secondary Currents of a Transformer by means of a Simple Apparatus, by F. T. Trouton. "Experimental Measurement of the High-frequency Resistance of Wires," by J. A. Fleming. "Measurement of Energy Losses in Condensers traversed by High-frequency Oscillations" and Some Resonance Curves taken with Impact and Spark Discharges," by J. A. Fleming and G. B. Dyke. 28th.-Royal Institution, 3. "Problems in the Career of the Great Napoleon," by Arthur Hassall, M.A. CHEMICAL NEWS, Jan. 27, 1911 Use of Calcium Carbide for Determining Moisture. THE CHEMICAL VOL. CIII., No. 2670. 37 A method based on this fact is now in use in Australia NEWS. for the determination of moisture in sheep's wool, having THE USE OF CALCIUM CARBIDE FOR DETERMINING MOISTURE.* By IRVINE MASSON, M.Sc.(Melb.). IN the determination of moisture in pure and in raw materials the methods which have been in use have generally proved accurate and reliable. They depend, for the most part, on removal of the water by heating the material, and measurement of the resulting loss of weight; sometimes the water driven off is collected and weighed. Often, however, the material dealt with is such that, when it is heated, it gives off vapours other than water; or it may be that some of the water evolved is the result of chemical decomposition. Again, certain substances gain weight by oxidation when heated in air. In all such cases it is obvious that weighing alone gives results which may lead to considerable error; other methods must therefore be sought which are free from objection. The introduction of calcium carbide as a commercial article has afforded a means of moisture determination which overcomes the difficulties mentioned. Since, however, the method has not attracted such general attention as it deserves, an account of it may be of interest to chemists, technical and otherwise. The great advantages of calcium carbide as a reagent in water determination may be summed up by saying that, of all substances dealt with in ordinary circumstances, water is the only one which has any chemical action on carbide; and this action is rapid, and generates a gas, whose quantity is readily ascertained and gives a direct measure of the action. The gas in question, acetylene, is produced according to Moissan's well known equation, CaC2+2H2O=Ca(OH)2+C2H2. It is apparent, then, that a good method of water determination should be obtained by allowing a weighed amount of the material under consideration to give up its water to excess of carbide, and measuring the acetylene evolved. Up to the present time applications of the foregoing principles have not been numerous. The first was described by H. A. Danne in 1900, before the Society of Chemical Industry of Victoria. Danne applied the method to various hygroscopic organic powders, for which the ordinary method of heating and weighing is unsuitable. The powder was weighed into a test-tube, and covered with a layer of sand, on top of which was a layer of carbide. On heating the tube, the moisture of the powder distilled through the sand, and acted on the carbide, generating acetylene, which was collected. The apparatus having been standardised with known amounts of water, the moisture in the material could be found from the volume of acetylene. A process which was substantially the same as that of Danne was described by P. V. Dupré (Analyst, 1906, xxxi., 213), for moisture determination in cordite and similar materials. It is to be noted that in this process the water is brought into contact with carbide after removal from the original material by distillation. It has been found, however, that such a process is unnecessary; and in later work a large excess of the carbide is simply mixed intimately, in the form of powder, with the material under examination. By the natural processes of diffusion all the moisture present rapidly reaches and reacts on the carbide. This has been established by direct tests. * Read before the Australasian Association for the Advancement of Science, January, 1911. been devised at the instance of a joint conference of pastoralists and workers held in 1908-1909. A detailed account is given by Orme Masson (Proc. Soc. Chem. Ind. Victoria, 1909). In carrying out a determination a fixed weight of wool clippings is introduced into a metal globe, which has a screw top provided with a tray below, and with a gas-exit tube. On the tray is placed a charge of finely powdered carbide in considerable excess of the theoretical amount; when the globe is shaken this falls on to the wool, and is brought into intimate contact with it, causing immediate evolution of acetylene. The quantity of gas was formerly obtained by measuring its volume when collected at atmospheric pressure; it is now found constant volume, by reading a mercury manometer attached more convenient to measure the increase of pressure at to the metal globe. All instruments are made of standard capacity, and the manometer is graduated in percentages of moisture. industrial materials seems to have been described, namely, Only one other application of the carbide method to that to petroleum containing water (Roberts and Fraser, Journ. Soc. Chem. Ind., 1910, xxix., 197). In this process excess of carbide is allowed to fall into a fixed quantity of dry paraffin oil. The volume of aeetylene is measured by the petroleum, which may be rendered fluid by addition of the quantity of brine which it displaces from a bottle, the necessary temperature correction being made. The results are stated to be reliable and accurate. The applications of the method so far discussed concern the determination of water present as moisture; that is, mechanically mixed with the material. In some cases, united with the material as water of crystallisation, and however, water is present in another form, chemically the question arises, is the carbide method applicable to the determination of combined water? To investigate the action of calcium carbide on water of crystallisation, the writer carried out experiments with numerous hydrated weight of hydrate was mixed with excess of carbide salts (Trans. Chem. Soc., 1910, xcvii., 351). A known powder, both being contained in a bent test-tube, the tilting of which brought about mixing; the gas generated passed into a nitrometer, where it was measured over mercury. Briefly, the results of the examination show that, as regards behaviour towards carbide, hydrated salts are roughly divisible into four classes. In the first are those, such as sodium carbonate and sodium sulphate decahydrates, which react at once and completely, being barium chloride dihydrate, react rapidly and completely rendered anhydrous. Salts of the second class, such as only on heating. The third class, which includes salts such as copper sulphate pentahydrate and the alums, react, either in the cold or on heating, in such a way as to lose only part of their water, leaving a hydrated residue which stable towards carbide even at 170° C. belongs to the fourth class, characterised by being quite In general, the stability is such as might be anticipated from the behaviour of the salts when they are heated alone; there are, however, interesting exceptions. It is noteworthy that ammonium salts do not lose ammonia, nor do crystalline acids react as such, when these are heated with carbide and the calcium hydroxide present as a result of the acetylene production; this is to be attributed to the complete absence of free water. From the analyst's point of view, the carbide method as applied to hydrated salts is quite satisfactory for the first, those cases where the method cannot be applied, it has second, and part of the third classes mentioned above. In been found that the usual process of heating and weighing determine the degree of hydration. s also inadequate, and indirect methods must be used to In conclusion, some instances in which the carbide method would prove of value may be indicated. These are mainly cases of technical materials whose water content is not easily obtainable by the ordinary means. For cotton, paper, fabrics, wood-pulp, tobacco, flour, the "wet wool" Enough has been said to show that calcium carbide affords a ready and reliable means for determining water, and is especially of value for that purpose with organic materials. THE PURIFICATION OF WATER BY OZONE. (OZONAIR SYSTEM). THE simplest and most certain method of purifying drinking water is sterilisation by ozone. It accomplishes its purpose without in any way altering the natural constitution of the water and at the same time leaves no trace of its presence. Water which previously was alive with dangerous organisms will after proper subjection to ozone treatment be in perfect condition for consumption. Moreover, its appearance and odour have been improved, and it will have a sparkling brightness which before the treatment was absent. In the methods hitherto adopted for effecting the sterilisation of water by means of ozone, mutual contact between the water and the gas has been made dependent upon either exposing the liquid in a thin film to the action of a current of the gas, or upon forcing the gas through the body of the liquid. By neither of these methods is it economically prac ticable to ensure a perfect result on a commercial scale, and the object of the Ozonair system is to provide an proved method and means whereby, so far as possible, thorough mutual contact may be simply and economically ensured between the liquid and the gaseous agent. SEPARATION OF OXYGEN BY COLD.* By JAMES SWINBURNE, F.R.S. THIS industry has arisen, almost by accident, out of that of the liquefaction of gases. It had long been the ambition of scientific men to liquefy first one gas and then another; the liquefaction of such gases as oxygen, hydrogen, and nitrogen being a sort of North Pole to be reached. It is doubtful whether reaching the North Pole is of any value to anybody but newspaper men, whereas the production of very low temperatures was bound to increase our knowledge very materially. Like most researches that appear at first to have purely increase of knowledge value, low temperature work has proved to be, in addition, of direct commercial importance. Though the separation of gases by cold has arisen out of the liquefaction of air, the two problems are not quite the same. Leaving out of account the details of the machine employed for the moment, we may consider the apparatus as a closed vessel, insulated to prevent heat getting in through the walls, and having three pipes. In at one pipe we may assume that air at the temperature of the room, but at a higher pressure, enters the machine; at a second and third, oxygen and nitrogen come out at the pressure and temperature of the room. Air under high pressure has less internal energy than the same mass of air at the same temperature and lower pressure, so that if air is continually going into the apparatus at the temperature of the room and at high pressure, and its constituents are coming out at the same rate at the temperature and pressure of the room, more energy is coming out of the apparatus than is going in. This is impossible as a permanent regime. It cannot be put right by less air coming out than goes in, because that would mean an accumulation of air. Å balance can be obtained by taking out most of the air at the pressure and temperature of the room, with a higher internal energy per kilo, while a little of the air comes out at a low temperature, with less internal energy per kilo. This portion may be quite small, and may be liquid. But the air is supplied under pressure, and comes out at the pressure of the atmosphere, so it must be expanded inside the apparatus, and as there is no way of getting the energy of expansion out of the apparatus as described, it must be converted into heat, provided it is expanded irreim-versibly. This means loss of power, which is a small point, and production of heat just where it is not wanted, which is a serious matter. If, therefore, in addition to the three pipes, there is communication by a shaft, and the apparatus may be arranged so that the expansion of the air works some sort of engine which turns the shaft so that work is given out, the yield of the liquid air must be larger. The ideal liquid air machine would therefore take in compressed air and give out air at the same temperature, but at the pressure of the atmosphere; and a stream of liquid air, and as much power as possible, would be given out mechanically through a shaft or other mechanical transmitter. It will be explained presently that the Linde separation process is nearly reversible, capable of being but little improved by giving out energy. In the Ozonair system the water is first atomised in presence of a stream of ozonised air within the upper portion of the apparatus, the minutely divided particles of liquid being allowed to fall upon the upper part of a pile of glass spheres, through the interstices of which the stream of ozone is caused to ascend whilst the liquid, already partially ozonised and sterilised, descends over the surfaces of the spheres in a very thin film. On reaching the bottom of the pile the water is allowed to fall into a tank through which the ozonised air is forced upwards in fine jets, the water being retained in the tank and subjected therein to this third ozonising process for any predetermined length of time according to require ments. It will be obvious from the above description that the Ozonair system ensures sterilisation, and that by no means can any portion of the water, however small, escape contact with the sterilising agent at some portion of its descent in the tower. The Ozonair system ensures the best treatment at the proper time, for the reason that, as the water descends through the tower, the concentration of the ozone gets more intense, until when, having fallen into the tank, it is subjected to a stream of ozonised air coming direct from the generator. The living bacilli falling into the tank are the most resistant and therefore need the strongest treatment. It is generally assumed that the problem of the separation of gases is substantially the same. This is not the case, however, and the overlooking of the difference has led inventors and designers of such apparatus into a series of absurd mistakes. Take the ideal apparatus for separating gases; we have a pipe leading in gas under pressure at the temperature of the room, and two pipes coming out; one carrying oxygen more or less pure and the other nitrogen more or less pure, at the temperature and pressure of the room. Now the internal energy of the gases coming out is greater than that of the compressed gas going in, and if the energy were alone to be considered, once the apparatus was started and got into running order as regards temperatures, air * A Paper read before the Faraday Society, December 13, 1910. |