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DOI:10.1039/AN96287FX021

出版商:RSC    

年代:1962

数据来源: RSC

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DOI:10.1039/AN96287BX023

出版商:RSC    

年代:1962

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN96287FP135

出版商:RSC    

年代:1962

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN96287BP149

出版商:RSC    

年代:1962

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JUNE, 1962 THE ANALYST Vol. 87, No. 1035 EDITORIAL The Feigl Anniversary Symposium THE Feigl Anniversary Symposium, held from April 9th to April 12th, 1962, at the Chemistry Department of the University of Birmingham, and organised on behalf of the Society by its Midlands Section, under the patronage of the International Union of Pure and Applied Chemistry, drew its speakers and delegates from all parts of the world. Four hundred participants from 28 countries attended to hear the lectures and join in the discussions, and to pay tribute to Fritz Feigl, who is undoubtedly one of the most talented and energetic analytical chemists of this, and any other, day. That this is so was attested by the attendance from countries as far away as Australia, Japan, Thailand, India, Israel, South America and the U.S.A., and from the great majority of European countries, from Spain in the West to the U.S.S.R.in the East, from Italy in the South to Finland in the North. Many dis- tinguished scientists, unable to attend, sent congratulatory addresses, as did several overseas Societies. Professor I. P. Alimarin, on behalf of the Analytical Chemistry Commission of the Soviet Academy of Sciences and of Moscow University, presented the M. V. Lomonosov medal-a singular honour awarded for the first time to a non-Soviet national-and Professor M. Ishidate of Tokyo presented the medal of honorary membership of the Japanese Society for Analytical Chemistry. The microchemists of the United Kingdom also paid their tribute through the presentation, by the Microchemistry Group chairman, C.Whalley, of a magnificent cut-glass vase with “built-in” spot-tests. Another presentation in memory of the event came from the Honorary President of the Symposium, Professor M. Stacey, F.R.S., in the form of a handsomely bound first edition of Faraday’s “Chemical Manipulations” to Professor Feigl, and of Griffiths “Use of the Blowpipe” to Mrs. Feigl, herself a chemist of considerable reputation. Industry was also liberal in its appreciation of Feigl’s contribution to analytical chemistry and in its support of the Society. In this connection the generosity of B.I.P. Chemicals, British Titan Products, The Dunlop Rubber Company, The Elsevier Publishing Company, Imperial Chemical Industries (Metals Division), Midland Counties Dairy, Mitchells and Butlers, and John and E.Sturge Ltd., deserve particular mention. All delegates were also received by the Lord Mayor of Birmingham, and the City acknowledged the presence of Professor Feigl and many distinguished scientists in its midst by arranging a civic reception for the delegates. The University itself provided the facilities and rooms free of charge, and donated freely the time and energy of many of its technical and teaching staff. The subject matter of the scientific programme was arranged in three concurrent streams of lectures and provided a wide-ranging bill of fare, from Feigl’s own beloved spot-testing and pyrolytic cleavage reactions for organic groups, through classical qualitative and quanti- tative microchemistry, to philosophical points such as the existence (or non-existence) of the uranyl ion, to deal with most branches of electroanalytical chemistry, activation and other nuclear methods of analysis, X-ray fluorescence, atomic absorption spectroscopy, visual and extravisual spectrophotometry, as well as chelate chemistry and most modern separation cum concentration methods such as ion-exchange, solvent extraction and chromatography in vapour and liquid phases.417 Several international honours were bestowed on our chief guest.418 PR0CEE:DINGS [Vol. 87 Lectures were very well attended and, because of the splendid co-operation of both lecturers and chairmen, the proceedings ran smoothly to time-table throughout so that delegates were able to interchange freely between the groups of two lectures that constituted each sitting.A full and absorbing discussion followed most lecture sessions. Whilst delegates were thus engaged, or were exchanging information more informally over coffee in the Refectory, Student’s Union or Halls of Residence, or were inspecting the extensive trade exhibition by some 50 firms in the laboratories adjoining the lecture theatres, their lady guests were catered for by a special programme. This included visits to places as diverse as the Houses of Parliament, Westminster Abbey, The Royal Brierly Crystal-Glass Works, The Barber Institute of Fine Arts, Coventry, and Coughton Court. On the evening of April 12th, the Symposium was formally closed by the President, Dr. Amos, who sent delegates and lecturers Cheerfully on their way home after a very full scientific and social programme, which was characterised throughout by its free informal atmosphere. Behind the scenes, the Symposium Committee still meets to attend to unfinished business, whilst the editors of the Proceedings, current1.y busy arranging manuscripts and discussion for publication, hope to have their work finished and in delegates’ hands by January. T. S. W.

ISSN:0003-2654    

DOI:10.1039/AN9628700417

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年代:1962

数据来源: RSC

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418 PR0CEE:DINGS [Vol. 87 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY DEATHS WE record with regret the deaths of Joseph John Valentine Backes Cyril Langley Hinton Harold Vivian Horton John King Edward Russell Harold Bernard Salt. NORTH OF ENGLAND SECTION AND BIOLOGICAL METHODS GROUP A JOINT Meeting of the North of England Section and the Biological Methods Group was held at 7.15 p.m. on Friday, April 6th, 1962, at the “Old Nag’s Head Hotel,” Lloyd Street, Man- Chester. The Chair was taken by the Chairman of the North of England Section, Mr. J. Markland, BSc. F.R.I.C. The meeting took the form of a discussion on “The Assessment of Psychostimulants” which was opened by M. W. Parkes, B.Sc., Ph.D. WESTERN SECTION A JOINT Meeting of the Western Section with the South Western Counties Section of the Royal Institute of Chemistry was held on Friday and Saturday, April 6th and 7th, 1962.The Chair was taken by Mr. R. C. Chirnside, F.R.I.C., Past President of the Society. The subject of the meeting was “Sampling” and the following papers were presented and discussed : “The Technique of Sampling”-film, introduced by W. T. Elwell, F.R.I.C. ; “Samp- ling of Ore with Special Reference to Imported Iron Ores,” by G. V. James, M.B.E., M.Sc., Ph.D., F.R.I.C. ; “Sampling of Soils and Crops,” by B. M. Dougall, M.Sc.Agric., F.G.S., A.R.I.C. ; “Sampling of Fertilizers, Foods and :Feeding Stuffs,” by F. W. Marston; “Sampling of Liquids,” by G. J. C. Nash, A.R.I.C.; “Sampling for Atmospheric Pollution,” by B. T. Commins, M.Sc., A.R.I.C. ; “Sampling of Air-borne Dusts,” by N. M. Potter, MSc., Ph.D. F.Inst.F., M.I.Min.E., F.R.I.C.June, 19621 PROCEEDINGS 419 MIDLANDS SECTION AN Ordinary Meeting of the Section was held at 7 p.m. on Thursday, April 5th, 1962, at the Wolverhampton and Staff ordshire College of Technology, Wulfruna Street, Wolverhampton. The Chair was taken by the Chairman of the Section, Dr. H. C. Smith, F.R.I.C., Dip. Ed. The subject of the meeting was “The Determination of Boron” and papers were presented by R. H. Biddulph, M.A., B.Sc., Ph.D., and H. J. Cluley, MSc., Ph.D., F.R.I.C.

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DOI:10.1039/AN9628700418

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年代:1962

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June, 19621 PROCEEDINGS 419 Obituary CYRIL LANGLEY HINTON CYRIL LANGLEY HINTON, formerly Superintendent of Research of the British Food Manu- facturing Industries Research Association, died on March E t h , 1962, at the age of 70. He was one of the three original members of the staff of the Association, from which he had retired at the end of 1958 after nearly 39 years of service. Hinton was trained at King’s College, London, qualifying in 1912 through the examina- tion in the Chemistry of Food, Drugs and Water of the Institute of Chemistry, of which he was elected a Fellow in 1916. He joined our Society in 1923, and served on the Council in 1954-55. When he joined the Research Association it was connected primarily with the con- fectionery and jam trades, and his work on variations in the melting-point of cocoa butter, on the manufacture of fondant and on the composition of fruits and jam was of outstanding importance.He became an authority on sugar analysis and was the author of the D.S.I.R. Food Investigation Special Report No. 48 on fruit pectins and of a paper on the polyuronides in the Annual Review of Biochemistry, 1951. At various times he was Chairman of the Technical Commission of the International Association of Confectionery Manufacturers, and was therefore largely responsible for the work leading up to the publication of “Methods of Analysis” by that body. For many years he was a member of this Society’s Analytical Methods Committee’s Sub-Commlttee on the determination of Metallic Impurities in Foodstuffs, and, later, in Organic Matter.He had a flair for foreign languages and became an acknow- ledged authority on international food legislation. After his retirement from the Association, Hinton found much to occupy his time and was the author of the first number in the F.A.O. Food Additive Control Series, “Food Additives Control in the United Kingdom.” He was at the time of his death engaged on another work for F.A.O. on the utilisation of sugar. L. E. CAMPBELL EDWARD RUSSELL EDWARD RUSSELL, one of the oldest members of our Society, died at his home in Clifton, Bristol, on March 13th, 1962, at the age of 92, after a week’s illness. A native of Shropshire, he proceeded in due course to Portsmouth, whence, in 1914, he was appointed Bristol City Analyst, a post which he held until his retirement in 1934.During his term of office he was also a lecturer in public health chemistry at Bristol University. He made a number of con- tributions to The Analyst, the most important of which were concerned with “The Composition of Cider’’ (1909), “The Composition of Malt Vinegar” (1910), “The Composition of British Wines” (191 l), “Unfermented Cordials” (Annual Reports issued between 1929 and 1934) and “The Composition of Egg Powder (1921), the last laying a useful foundation for work that was extended by others during the Second World War in connection with the widespread sale of spurious egg-substitute powders. A genial and lovable character, Russell was an active member of the Bristol Area Section of the Royal Institute of Chemistry, the meetings of which he continued to attend (come fog, come weather) until 1960. He was a keen pedal cyclist, continuing to cycle around Clifton until he was in his late 70’s. His elder son, Sir Lionel Russell, is Chief Education Officer for Birmingham, and his younger son, Ronald, is Director of the Little Theatre, Bristol. He is survived by his wife, two sons and two daughters. C. H. MANLEY.

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DOI:10.1039/AN9628700419

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年代:1962

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420 MACKENZIE AND MITCHELL : DIFFERENTIAL THERMAL ANALYSIS. A REVIEW W O l . 87 Differential Thermal Analysis A Review* BY R. C. MACKENZIE AND B. D. MITCHELL (The Macaulay Institute for Soil Research, Craigiebucklev, Aberdeen) SUMMARY OF CONTENTS Introduction Theory Apparatus Technique Inorganic materials Organic materials Analytical applications OF the various thermal methods of investigation available, differential thermal analysis has found most application in mineralogy, and particularly in clay mineralogy. The method is now, however, receiving more wide-spread recognition and is being used not only in inorganic and analytical chemistry but also, with controlled-atmosphere techniques, in organic chemistry. It is our opinion that many possible fields for. application in analytical chemistry still exist.The method is fundamentally simple. A sample of the material being investigated is heated up side-by-side with a sample of a thermally inert material in a suitable specimen holder, and the difference in temperature between the two is recorded as they are heated. When no reaction occurs in the specimen there is no difference between the temperatures of the two samples, but as soon as any reaction begins the specimen becomes hotter or cooler than the inert material, and a peak develops on the curve for difference in temperature (AT) against time (t) or temperature (T). In Fig. 1 , the peak is represented as BCD, and it should be noted that the reaction is not complete at C., but at some point, X, along the return portion of the peak, CD, whereas the maximum rate of reaction occurs at a point, E, along the line BC.The temperature of the specimen at point C, which is usually referred to as the “peak tem- perature,” is therefore not indicative of any specific stage of reaction, but, being the most easily observable point of inflexion, is usually the criterion quoted. The distance BD is referred to as the “peak width,” the perpendic3lar distance to C from a line joining BD as the “peak height’’ or “amplitude,” the angle :BCD as the “peak angle” and the area enclosed by BECXD as the “peak area.” It will be appreciated from the above brief description that the curve is not a true diferential curve, but simply a straightfoward diference curve. I t will also be appreciated that such a curve gives information on reactions occurring in the specimen when it is heated, rather than on the ultimate composition of the specimen.The name is therefore somewhat of a misnomer. Nevertheless, the usefulness of the method lies in the fact that the curve obtained for a specific compound is reasonably characteristic of that compound and that the peak area is related to the amount of reacting materia1.lJJ Although the method is usually traced back to early work on clays by Le Chatelier? it was in fact first developed by Roberts-Austtm5 for metallurgical studies. Adoption of the Le Chatelier - Saladin6 and Kurnakov’ recording devices in place of the rather cumbersome original arrangement of Roberts-Austen made the method more attractive for laboratory use, but up to the late 1930’s differential thermal analysis was not extensively used, except by restricted schools, and by far the greatest amount of work in this period was carried out in Russia, where the first book devoted largely to the subject was published in 1944.8 From the late 1930’s to the early 1950’s, most differential thermal studies related to clays or minerals, but this period also saw the first attempt at the derivation of t h e ~ r y .~ During the past decade there has been a much wider interest in the subject, and differential thermal studies have even been carried out in connection with such diverse subjects as criminologyl* and the determination of the efficacy of pyrot.echnics.11 * Renrints of this paper will be available short1.y. For dctails, please see p.512.June, 19621 MACKENZIE AND MITCHELL : DIFFERENTIAL THERMAL ANALYSIS. A REVIEW 421 Apart from the Russian book,s “Thermography, ” referred to above, several other books and booklets devoted entirely to differential thermal analysis have appeared, * namely, “Die Di$eYe~ztiaZt~ermoanalyse,”lz “Transactions of the First Congress of Thennography” (in Russian),13 “Diferenc‘ni Thermickd Analysa” (in Czech),14 “The Differential Thermal Investi- gation of Clays, ”15 “Differential Thermal Analysis”l6 and “Differential Thermal Analysis as Applied to Building Science.”17 In many books a considerable proportion of the contents is devoted to the subject (see Mackenzie15), and excellent reviews have recently been pub- lished.18J9 Comprehensive lists of references to papers dealing with differential thermal analysis have been given by several authors,12J6,20 and a punched-card “data index” is due to appear shortly.21 THEORY Although the method was originally entirely empirical, it was early appreciated that the peak area was approximately proportional to the amount of reacting material present, pro- vided that the experimental conditions were entirely reproducible.The first attempt to Te m pe r a t u re- Fig. 1. Formalised differential thermal curve (AT is the difference between the temperatures of the sample and inert materials1 find a theoretical basis for such a relationship was made by Speilg in 1945 and was later further developed in a paper22 by Kerr and Kulp,f. the final equation being- D where M is the mass of reacting material, H is the heat content of 1 g of reacting material, g is a geometrical-shape constant, k is the thermal conductivity of the specimen, T is tem- perature, t is time and AT& is the peak area on a AT/t plot of the curve, B and D having the significance indicated in Fig.1. This equation implies that the relationship will only hold for a AT/T curve if the rate of increase in temperature over the peak is always exactly B s” *Since this review was compiled, there has been published in the U.S.S.R. a valuable and comprehensive treatise by Professor L. G. Berg entitled “Introduction to Thermography” (Izd. Akad. Nauk. SSSR, Moscow, 1961). t Some unfortunate misprints in this paper make the argument rather difficult to follow.422 MACKENZIE AND MITCHELL DIFFERENTIAL THERMAL ANALYSIS.A REVIEW [VOl. 87 reproducible. heat involved in the reaction, Q, namely- A somewhat similar equation was derived by Yagfarov and Berg8 for the tl where I , d,, and G ? ~ are the length, the external and the internal diameter of the cylindrical specimen, X is the coefficient of heat conductivity and ATdt is the peak area. t i’ 1 Such theories involve many obvious oversimplifications, but the problems involved in deriving a more rigorous theory are formidable, since not only are heat capacity, heat con- ductivity and heat diffusivity involved, but conduction of heat away from the sample through the thermocouple wires, the nature of the specimen holder, the nature of the contact between the sample and the specimen holder and other factors difficult to assess have also to be taken into account.24 Although the attempt by A r e n ~ ~ ~ to develop a theory cannot unfortunately be accepted because of errors and i n a c c u r a c i e ~ , ~ ~ ~ ~ ~ many valid refinement~~~9~7 to 44 have been made; probably the most intensive study of the problem was made by S e ~ e 1 1 , ~ ~ who derived the equation- t2 f where J ((AT), - (AT) )dt ((AT), - (AT)},& == W(PJ - t 0 r defines the peak area and W(Pl) WP2) and W(P,) define the peak area t 1 functions, viz.- W(P) = (Pt - f ( P ) - T(P,t)}dt 1 t 0 where t is the time taken to attain temperature T , to and t , are initial and final times, /3 is the heating rate and Pl and P , are points in the wire passing through the test sample and in that passing through the inert material, respectively.From four equations determining W(P), Sewell concludes that the peak area is propor- tional to the heat of reaction per unit volume (of the sample and is independent of the heating rate (provided that this is linear), the rate at which the reaction occurs and the specific heat of the sample. On the other hand, the peak area does depend on the conductivities of the test sample and the other materials in the furnace and on the conductance between the surface of the specimen-holder block and the furnace wall. Accurate contemporary investigations suggest that the peak area is not in fact related to the amount of reacting material by a straight line, but by a curve.46~46~47 When the sample is diluted to less than 30 per cent. with inert material, however, this difficulty seems to disappeaP@~*~ and may be due, as Sewell arid Honeyborne2* suggest, to differences between the thermal characteristics of the specimen and the inert material.It should be mentioned that relationships between amount of reacting material and factors involving some criterion other than peak area, eg., peak height,50 the cosecant of the peak angle51 and the ratio of peak area to width at half height,62 have been found to give better results than peak area alone. Such relationships can usually be deduced as special cases of the area relationship. Despite recent advances in theoretical studies, all difficulties have not yet been overcome ; nevertheless, such studies suggest certain essential features that ought to be incorporated in any apparatus.These are, particularly, the necessity for accuracy in construction, reproducibility in all experimental operations-including reproducible positioning of theJune, 19621 MACKENZIE AND MITCHELL : DIFFERENTIAL THERMAL ANALYSIS. A REVIEW 423 specimen-holder in the furnace and reproducible (and if possible linear) control of heating rate-dilution of the specimen with inert material and the use of an inert material having thermal characteristics similar to those of the specimen. APPARATUS Because of the apparent simplicity of the method there has been little commercial development of suitable apparatus,* and most laboratories construct their own. This has the grave disadvantage that those constructing the apparatus are frequently not familiar with the precautions necessary for obtaining the best results.Such a procedure certainly has the advantage of cheapness, but whether this is sufficient compensation is extremely doubtful. Both from practice and from theory various desirable features of an apparatus can be deduced, and neglect of such information or saving of expense by use of too primitive an apparatus can lead to most unfortunate results.60 I t must be admitted that much of the criticism of the technique arises from those who have attempted to carry out precise work with crude apparatus-and who have naturally failed in their objective. Before discussing any particular type of apparatus, therefore, the fundamental precautions that must be observed in its construction16~67 ought to be considered, having regard to the minimum number of functional units.FURNACE- This must be so wound as to be capable of heating at the uniform rate decided upon (usually about 10" C per minute61) from room temperature to the maximum desired. The latter will vary with the application, the usual maximum being about 1000" C; a Nichrome winding permits cheap construction together with a maximum temperature of about 1100" C. The zone of uniform heat in the furnace should be as large as possible. Earthed metal shielding should be provided between the furnace winding and the specimen h01der.~7 SPECIMEN HOLDER- The specimen holder must be fabricated so that the wells for the sample and inert material are symmetrically placed in all directions with regard to the heat source.Further, some arrangement must be provided whereby the specimen holder is always exactly positioned in the same place in the furnace.66@ Both metal and ceramic holders have their own particular application~,6~~63~~@ but greater accuracy is possible with metal holders, as they are more homogeneous and can be machined more accurately. For high-precision work, metal specimen holders ought to be adequately earthed.56$57 The sample wells should not be too large or too small; the former may lead to pronounced non-linearity of the relationship between peak area and reacting material, and the latter to very small peaks. Optimum sizes may be assessed from several comparative studies.61 s66 s67 THERMOCOUPLES- It is generally most convenient to use a suitable thermocouple system for measuring T and AT, although thermometers68 3C9 and transducers7O have been employed.Thermo- couples must be rigidly placed in the wells of the specimen holder and so arranged that, on replacement, the beads are always in exactly the same position.66~71 In cylindrical wells * To our knowledge the firms listed below produce apparatus for differential thermal analysis- Eberbach Corporation, Ann Arbor, Michigan, U.S.A.15 (asymptotic heating rate; useful for field and rapid tests). Gallenkamp and Co. Ltd., London (based on apparatus described by Grimshaw, Heaton and Robertss3; no provision for control of gas atmosphere). Chemisches Laboratorium fur Staubtechnik, Goslar, Germany15 (combined dilatometer and dif- ferential thermal apparatus ; range of heating rates).Gebriider Netzsch, Selb/Bayern, Germany (development of the Linseis apparatuss4 ; permits control of enveloping gas a t atmospheric pressure). Technical Equipment Corporation, Denver, Colorado, U.S.A.65 (specification suggests excellent design; multiple specimen holders, a large range of heating rates and gas control). A. R. Bolton & Co. Ltd., Sighthill, Edinburgh, Scotland (development of Mitchell and Mac- kenzie'9 W apparatus, with plug-in units and gas control; alternative recording units available). Robert L. Stone Co., Austin, Texass8 (complete gas control in sample over a wide range of pressures). Metrimpex, Budapest, Hungary (based on Erdey, Paulik and Paulik'ds apparatus ; combines in one arrangement thermogravimetric, differential thermogravimetric and differential thermal techniques). Rigaku-Dewki Co., Tokyo, Japan (specifications awaited).424 MACKENZIE AND MITCHELL : DIFFEREXTIAL THERMAL ANALYSIS.A REVIEW p o l . 87 (which are the most common) it is preferable that the thermocouples be arranged longitu- dinally rather than radially to obviate spurious peaks with certain mate1-ials.7~ Thermocouple wires should be as thin as possible consistent with life and strength, in order to minimise conduction of heat away from the sample,24 and beads should not vary too much in size.6586 Thermocouples must be joined to the leads to the apparatus through some type of temperature equaliser,l6 and all leads should be of screened wire suitably earthed.66 TEMPERATURE CONTROL- Many suitable types of temperature controller are Ion the market and, with the advent of tran- sistorised circuits, can now be obtained relatively cheaply. The controller should be actuated from a thermocouple completely divorced from the specimen holder and situated close to the furnace winding in order to obviate lag in response.12~66~66 From practice, it has been found that large electrical surges in the heating coil must be avoided when high sensitivities On no account should manual control of the increase in temperature be used.I I I I 0 1 bbO ' 800 I000 Temperature, "C Fig. 2. Differential thermal curves for: A, 0.20 g of quartz; B, 0-35g of gibbsite. Both curves plotted on same scale. Each division on the AT axis is equivalent to 2' C are used, and probably the most satisfactory rneans of achieving this are by a servo system% or by use of a motorised autotransformer with two contacts set for the lowest voltage difference commensurate with control.66 Use of a motorised system without a suitable programme controller74 cannot be recommended, even with a constant-voltage arrangement, since it cannot accommodate minor random changes in the system. Some arrangement for accurate re-positioning of the control thermocouple with respect to the winding must be provided.A rather novel and inexpensive method of obtaining a uniform rate of increase in temperature has been proposed by Yagfarov and Berg.75 RECORDING SYSTEM- Two criteria have to be recorded, namely, T and AT. The former creates no difficulty; if the heating rate is reproducible and linear, a check every 5 minutes or so is all that is required (or a continuous record may be made on a conventional recorder).For AT, the system used must be sufficiently sensitive to give reasonably sized peaks for the types of materials and sizes of sample usedl5; instances are known in which it is difficult to assess the reality of peaks because of too low sensitivity. The recording system should preferably be more sensitive than is essential, so that it can be readily adapted for accurate measurement of smaller reactions than are customary by simple alteration of a series resistor or potential divider. The range of sensitivity desirable can be assessed from the curves for quartz, SiO,, and gibb- site, Al(OH), in the gamma form, shown on t'he same scale in Fig. 2; these curves representJune, 19621 MACKENZIE AND MITCHELL: DIFFERENTIAL THERMAL ANALYSIS.A REVIEW 425 the minimum and maximum changes in heat energy likely to be encountered from pure materials in normal work; for quantitative determination of quartz, a 20-fold increase in sensitivity is obviously desirable. Manual recording of galvanometer deflections against time or temperaturea is wasteful of time, and use of a recording drum together with a galvano- With present instrumentation, sufficient sensitivity may be obtained on pen-and-ink instruments without the construction of complex d.c. amplifier^.^^^^^ ,7s979 In this brief review it would be impossible to consider even a representative range of apparatus, especially as the number of different types in existence is of the same order as the number of laboratories employing the technique. A general system suitable for such an apparatus is shown diagrammatically in Fig.3, and, if the components for this were chosen to conform with the criteria mentioned above, operation should be satisfactory. In view of current developments, control of atmospheres0 is becoming virtually essential, and most well developed recently described sets of a~paratus56@,6~ ,78980 t o e+~ have provision for this. The advantages of controlled-atmosphere techniques are threefold : (a) an undesirable reaction may be suppressed, e.g., oxidation, by using an inert atmosphereJS6 ( b ) reactions may be enhanced, e.g., oxidation, by using an atmosphere of oxygen47 and (c) superimposed peaks may be resolved by varying the pressure of a gaseous product of reaction.s8~6s or a sensitive microvolt recorder57 is recommended.1 Recorder Recorder Controller - (AT) tT> (T) - - Recent tendencies in differential thermal analysis have been towards the use of small samples, with corresponding increase in sensitivity of r e c ~ r d i n g , ~ ~ , ~ ~ pg6 and use of rapid heating rates.86~87 The latter, although giving larger peaks, may not be so suitable for accurate mensurational work, as the peaks tend to broaden and neighbouring peaks coalesce; the technique also raises problems of accurate temperature control. Another development that may lead to considerable application in analytical work has been the design of an apparatus capable of measuring the evolution of gas from the specimen during heating88*s9; water vapour can also be measured with this apparatus by insertion of calcium hydride, which reacts with moisture quantitatively to yield h y d r ~ g e n .~ ~ , ~ ~ Such a system is equivalent to simultaneous differential thermal analysis and thermogra~imetry~~ ,90 and is probably simpler to operate. It should be possible also to develop this system to permit gas analysis of the decomposition products, alternative methods for determining which have also recently been d e s ~ r i b e d . ~ l , ~ ~ Sets of apparatus permitting simultaneous determination of several thermal characteristicsg~~Q4 may also have analytical applications. At a meeting in the Academy of Sciences, Prague, in May, 1961, and attended by one of us, severaI interesting papers were read on apparatus and technique; the pieces of apparatus described were advanced in design and are worthy of study by analyst^.^^426 MACKENZIE AND MITCHELL : DIFFERENTIAL THERMAL ANALYSIS.A REVIEW [vol. 87 Since differential thermal analysis is a dynamic method, it is essential that all aspects of technique be standardised in order to obtain reproducible results. Some basic recom- mendations on this topic were drawn up by a Sub-committee of Comit6 International pour 1'Etude des Argiles, in 1952,61 and these may still be regarded as a valid basis. The main factors involved are pre-treatment of specimen, particle size of specimen, packing of specimen, dilution of specimen and nature of inert material. As regards pre-treatment of the specimen, it is advisable to equilibrate finely particulate powders of hygroscopic materials at a definite relative humidity in order to standardise the amount of sorbed moisture present.Many materials, however, are not noticeably hygro- scopic, and therefore no significant error is introduced if they are investigated at atmospheric humidity. For equilibration, standing over a saturated solution of Mg(N0,),.6H20, (i.e., at a relative humidity of 55 per cent. at 65" F) is re~0rnmended.l~ Particle size of the specimen may also in many instances be a function of pre-treatment, and it is recommended that crystalline materials be ground to pass through a 100-mesh sieve. That particle size does affect differential thermal curves has frequently been ~ h o w n , ~ ~ , ~ ~ s ~ ~ , ~ ~ but for colloidal particles, such as clays, micelle size rather than sieve size is the critical feature.61 On the other hand, prolonged grinding is known seriously to aflect crystal structure and consequently the differential thermal ~ ~ r ~ e , ~ ~ t o ~ ~ ~ and any comminution must be carried out in the least destructive manner. Density of packing of the specimen is critical, as this influences not only the ease of egress of products of decomposition, but also the thermal characteristics of the specimen.Hard packing by hand,61 although the most satisfactory simple method, is liable to subjective errors, and comparative work ought to be carried out by the same operator. Careful tamping has been claimed to give an accuracy to within 1 per cent,60 but subjection of all specimens to a constant loadlo6 and use of a special plunger charging device65 have also been recom- mended; the last mentioned is probably the most satisfactory for general use.In order to ensure that the thermal characteristics of the specimen and inert material are as similar as possible, specimens should be diluted to less than 30 per cent. with inert This procedure should be adopted for all quantitative work. Placing the active material in a thin layer about the thermocouple junction, with inert material above and below, leads to enhanced sensitivity5GJ07; for quantitative measurements with this technique, the centre portion ought always to be the same weight.66 Considerations determining the type of inert material have been discussed by Mackenzie and Mitchell15; those in most common use are perhaps alumina, alundum powder and powdered kaolinite.Recently, quartz sand has been used successfully in certain investiga- tions,l08 since not only does the relatively coarse material permit rapid egress of gaseous products of decomposition, but the a + p inversion at 573" C provides a useful temperature- calibration point. Glass beads have also been used for low-temperature work.g1 TECHNIQUE Gentle grinding under liquid, or filing, may suffice.101 Dilution of the specimen has been referred to above. INORGANIC MATERIALS Although, as mentioned above, the development of differential thermal analysis has been closely linked with r n i n e r a l ~ g y , ~ ~ , ~ ~ and particularly with clay mineralogy,15 ,169109 ,l10 much work on inorganic compounds as distinct from minerals has been carried out in Russia since the earliest days of its development.An excellent review of such early work, together with a comprehensive bibliography, has been made by Berg, Nikolaev and Rode.8 More recently, numerous studies involving use of the method have been reported, particularly in Zhztrnal Neorganicheskoi Khimii. The number of such papers is so large that it would be impossible t o detail them here, but the compounds investigated range from alloyslll and simple com- pounds112 ,113 to very complex C O ~ ~ O U ~ ~ S ~ ~ ~ , ~ ~ ~ ~ , ~ ~ ~ and even to inorganic - organic com- plexes.117,118 In America also, the method is finding increasing application in inorganic chemistry, as is evidenced by the studies of Gordon and his collaborators,~~~119~120~121 Borchardt, Daniels and their co-workers,41J22J23J24J25 Markowitz and others,60,126,12',128,129 Murphy and his collaborator^^^^^^ 91303131 and Wendlandt and Bear.132,133 In Britain, application of the technique t o inorganic compounds as distinct from minerals and materials of ceramic im- portance has been rather neglected, and no schools comparable to those mentioned above have developed.Occasional papers have, however, appeared from continental sources.gfj~13QJune, 19621 MACKENZIE AND MITCHELL DIFFERENTIAL THERMAL ANALYSIS. A REVIEW 427 The major application of the technique in inorganic studies has probably been in checking the thermal stabilities of compounds, e.g., ammine s ~ ~ ~ s , ~ ~ ~ J ~ ~ J ~ J simple and complex selenates and seleniteslo 714491453146 and uranium cornpo~nds.55~1~9~147 to 153 Oxides and h y d r 0 ~ i d e ~ ~ ~ , ~ ~ , ~ 5 y 6 ~ , ~ ~ ,152 t o 155 and s ~ l p h i d e s l ~ , ~ ~ ~ to 161 have been investigated as much from the viewpoint of mineralogy as of chemistry; the last-named and some other corn pound^^^^^^^^ necessitate special attention to the gas atmosphere in the specimen.Other applications have been to check the identities of ~ o m p o u n d s ~ ~ ~ 9 ~ 6 ~ to l67 and to ensure that in a specific reaction a new compound is formed and that the product is not simply unreacted original material.16s to 173 Further, the technique presents an elegant method for investigating solid-phase reactions between inorganic substances174 t o l80 and phase transformations and inversions in single compounds .lS1 t o lS6 Its usefulness in the elucidation of fusibility phase diagramslS7 to lg4 is obvious, and much information may also be gleaned from its application in isothermal phase-diagram studies.lg5 t o The studies referred to above are essentially qualitative, but from the theoretical considerations already discussed it is clear that, given sufficiently refined apparatus and standardised technique, quantitative results are readily obtainable.Thus, much work has been carried out on calorimetric and more especially on reaction As might be expected, by far the most voluminous literature on differential thermal analysis is to be found in journals dealing with minerals, ceramics and clays.The position with regard to the last-named up to 1957 was critically reviewed in the book edited by Mackenzie,15 and an extensive bibliography up to 1958 was given by Smothers and Chiang.l6 Perhaps the most notable recent contribution is that of Ivan0va,~~7 which reproduces 506 curves for minerals determined on one apparatus. The card index previously mentioned21 contains about 1600 cards giving data and references for minerals, inorganic compounds and organic compounds. ORGANIC MATERIALS Investigations so far reported on organic materials have been largely exploratory, and, owing to lack of control of the atmosphere in the specimen, some results are of rather dubious value.69 v208 sZo9 The advent of controlled-atmosphere apparatus, however, has permitted much more valid results to be obtained, and several papers of major importance have appeared.The techniques currently in use are of two t y p e ~ l ~ ? ~ ~ : (a) in an oxidising atmosphere, which permits assessment of the burning characteristics and (b) in an inert atmosphere, which suppresses combustion, but allows observation of melting- and boiling-points, phase transi- tions and auto-oxidation reactions. Frequently, too, both differential thermal analysis and thermogravimetry are applied in conjunction. Many of the studies on organic materials have been related to substances of industrial importance, for example, fatty acids and their salts,211 t o 217 fats, oils and waxes,47,21* to 221 polymerss4 ,222 y z 2 3 and fuels, such as peat ,47 sZo9 P4 t o 227 y228 and coal.227 ,229 to 235 Simpler substances, such as hydrocarbon^,^^ carbohydrate^,^^^^^^ ,237 guanidine and related compounds238 and salts of ethylenetetraminediacetic acid239 have also received attention ; even anti- b i o t i ~ s ~ ~ o , ~ ~ have not been immune.In view of the amount of work on organic materials it is not surprising to find that many inorganic - organic117 s118 ,242 to 246 and mineral - organic complexesZ47 to 251 have been subjected to differential thermal analysis. The same provisos regarding furnace atmosphere apply to these as to organic compounds. Nevertheless, the method is a simple and rapid means of investigating the thermal decomposition of such compounds. As Andersonzz3 has pointed out, differential thermal analysis is less quantitative than is thermogravimetry, since endothermic peaks caused by bond breakage may be occluded by exothermic peaks arising from oxidation.This effect has been observed by Mitchell47 for cellulose in atmospheres of oxygen and nitrogen, but the intensities of the two reactions are vastly different, and this would not preclude quantitative determination of material from measurements of peak area. carbonates,l5,58,65,78,114,116,135 t o 139 chlorates and perchlorates,ll ,GO ,113,119,126,127,129,140,14l,143 kinetics.38,65,78,125,152,202 to 206 ANALYTICAL APPLICATIONS Differential thermal analysis cannot be used for ultimate analysis, as the curve obtained traces the solid-phase reactions occurring when the sample is heated and is therefore a reflec- tion of the structure of the compound or compounds being investigated.If the specimen428 MACKENZIE AND MITCHELL : DIFFERENTIAL THERMAL ANALYSIS. A REVIEW p o l . 87 is a mixture, the curve will be a summation of the curves for the individual species present, always provided that no solid-phase reaction occurs between these species. It can therefore be used for identifying compounds, and, although this aspect has not as yet been developed to any great extent in inorganic ~ h e m i s t r y , ~ ~ ~ s ~ ~ ~ it has so far been the most wide-spread use in mineralogy and clay minera10gy.l~ Because o€ this, the illustrations below are taken from the latter field. The differential thermal method is not, unfortunately, so diagnostic as, for example, X-ray diffraction examination, since certain limiting factors operate. Thus, two of the compounds in a mixture may give peaks that superpose, e.g., goethite, a-FeOOH, and gibbsite, y-Al( OH) 3, or kaolinite, Al,Si,O,,( OH) 8, and illite, (K,H 30) z( Si,Al) 8(Al,Fe,Mg)40,0( OH),.The constituents of the former mixture may be readily distinguished by subjecting the speci- men to a chemical pre-treatment that dissolves one compound without the other,Z53 and those 00 Temperature, “C Fig. 4. Differential thermal curves for 0-2-g samples of moiitmorillonites: curves A and B ‘‘ normal ’’ montmorillonites ; curves C, D, E and F, “ abnormal ” mont- morillonites. Each division on the AT axis is equivalent to 2” C of the latter (arguing from effects observed with carbonates68s66) could probably be resolved by varying the pressure of water vapour in the furnace atmosphere-which should affect the kinetics of decomposition of the two compounds differently.The occurrence of solid-phase reactions between components in a specimen:!64 is a factor that must always be considered in identification studies and can only be excluded by prior knowledge of the type of compounds involved. One limitation of the method may in certain circumstances be an advantage, since minor structural differences not observable on the X-ray diffraction pattern can be reflected in changes in peak temperature. This may cause difficulties in identification, but brings out significant differences that would otherwise be missed. A case in point is montmorillonite xM+.Si8(A1,Mg),020(OH)4, which occurs in “normal” (peak at 710 “C) and “abnormal” form, (peaks at 550” and 650” C or only at 550” C)--see Fig.4.256 These differences indicate that the energy needed to initiate de-hydroxylation varies, despite the fact that the energy involved in the de-hydroxylation process itself remains the same.266 Similar effects may be observed in the mica group of clay mineralslS and may in fact not be limited to natural materials. Analytical uses of the technique have been discussed by Garn and Fla~chen~7 and by Murphy.18 In inorganic studies generally, one of the main uses of the method has been,June, 19621 MACKENZIE -4ND MITCHELL : DIFFERENTIAL THERMAL ANALYSIS. A REVIEW 429 as mentioned above, investigation of the thermal stabilities of compounds; with some adjuncts, these studies can be extended, e.g., to measure the volumes of gases or vapours evolvedsS pS9 or to permit gas analysis of the decomposition prod~cts.~lJg~ s258 Such studies permit phase inversions or recrystallisation reactions to be distinguished from decomposition reactions.The technique is often used together with X-ray diffraction examination, as the material can be heated up in the differential thermal apparatus until a specific peak is com- plete, when it is removed and then examined by X-rays to check for structural changes.269 This technique is applicable even if the peaks to some extent overlap, as was shown during investigations on gibbsite.16 A possible qualitative use in analytical chemistry, which has so far not been developed, is as a rapid check on the formation of a specific reaction product.If the reaction product gives a curve different from that of the product expected then the synthesis has not succeeded. In industry it is extensively used to check the identity of batches, either of raw materials2s0 to 267 or of products2G8t0271; in this connection, it should be mentioned that not only can the technique be employed in the customary region of 0" to 1000" C, but also well b e 1 o ~ ~ ~ ~ and above270 Another fruitful application in analytical industrial practice is to investigate the reactions occurring during firing, as has been done for several glass systems.276 to 2so The method was originally developed for metallurgy,6 since it permitted easy recognition of phase changes, etc., occurring during heating; it is still employed in this field111J281s282,2~ for observing either phase changes or, with use of cooling curves, the miscibility of melts.Several other applications in inorganic chemistry will be obvious from the section on "Inorganic Materials," but use in the study of catalysts has not been referred to. In such investigations, the technique has been used not only to determine the constitution and thermal characteristics of catalysts,284 to 287 but also to determine the temperature at which catalytic activity is enhanced2S8 or destroyed2S9 and to determine the activities of catalysts in a specific Since, fundamentally, differential thermal analysis is a technique for measuring energy changes during heating, measurements of stored energy in irradiated materials292 ,293 is a logical application.Quantitatively, the method is ideally suited to the rapid determination of hygroscopic moisture in finely particulate materials; it has indeed been used for this purpose in industrial practice.294 Accuracy in such a determination is highly dependent on control of the heating rate at low temperatures and may be improved to the level required by strict attention to this factor (unpublished results by R. C. Mackenzie). The time needed varies from about 5 to 20 minutes per determination, depending on the heating rate. Control is probably more easily effected at slow rates, but, on the other hand, small differences in heating rate may not be so important in the higher ranges (100 "C per minute or greater). Calibration curves for peak area against weight of moisture should be constructed from results for materials identical with those used in practice, but with different moisture contents, since the intensity with which moisture is held depends on the surface properties of the materials.Provided that the compounds present in a mixture are known or can be directly deduced from the differential thermal curve- as is in many instances possible21-and that no solid- phase interactions occur, these compounds may be rapidly determined quantitatively with a fairly high degree of accuracy from calibration curves of peak area against amount of material.24 945 946948,49 The accuracy of such determinations is dependent largely on necessary attention being paid to constructional details of the apparatus and operating techniques, but, without undue complexity, should be within about +5 per ~ent.~53 Other quantitative applications include use of the method in ~alorimetric13,201s2~5~296 and similar investigations, and many studies on reaction kinetics, notably those by Webb,65 have been amenable to quantitative interpretation.In organic chemistry, melting- and boiling-points are readily determinable,56s218*227 and some attempts have been made under strictly controlled conditions of combustion47 to identify specific compounds. Quantitative determinations of calorific can be rapidly and easily made on small samples (about 10 mg) with a high degree of accuracy, and latent heat of fusion can be determined with an accuracy to within about +5 per cent.227 However, such applications are as yet in their infancy, and considerable advances can be expected with the advent of more highly developed instrumentation.this range. proceS.206,290,291430 MACKENZIE AND MITCHELL : DIFFERENTIAL THERMAL ANALYSIS. A REVIEW [VOl. 87 In conclusion, it is obvious that the technique of differentia1 thermal analysis has a large number of uses in analytical chemistry. Up t.o the present, most of these have been quali- tative, but quantitative applications are being developed as the method becomes more refined. In consequence of the important effects on results of factors involving apparatus and technique, no excuse is offered for occupying the largest part of this brief review with these two aspects, and it should be mentioned that the references given cover only a small part of the literature -to our knowledge, almost 1000 papers dealing with the technique have been published over the past 24 years.1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 16. 16. 17. 18. 19. 20. 21. 22. 23. 24. 26. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. REFERENCES Orcel, J., and Caillbre, S., Conzpt. Rend., 1933, 197, 774. Norton, F. H., J . Amer. Ceram. Soc., 1939, .22, 54. Berg, L. G., Lepeshkov, I. N., and Bodaleva N. V., DOH. Rkad. Nauk SSSR, 1941, 31, 577. Le Chatelier, H., Compt. Rend., 1857, 104, 141.3; Bull. SOC. Franp Minbr., 1887, 10, 204. Roberts-Austen, W. C., Proc. Inst. Mech. Engrs., 1899, 55. Le Chatelier, H., Rev. Mktall., 1904, 1, 134. Kurnakov, N. S., Zhzcr. Russ.Fiz.-Khim. Olshch., 1004, 36, 841; Z. anorg. Chem., 1904, 42, 184. Berg, L. G., Nikolaev, A. V., and Rode, E. Ya., “Termografiya,” Izd. Akad. Nauk SSSR, Moscow, Speil, S., Technical Paper, No. 664, U.S. Bureau of Mines, Washington, D.C., 1945, p. 1. Anon., Anal. Chem., 1959, 31, part 2 (Fcbruary), 2 1 ~ . Hogan, V. D., Gordon, S., and Campbell, C., Ibid., 1957, 29, 306. Lehmann, H., Das, S. S., and Paetsch, H. H., “Die Differe.lztiaZthermoanalyse,” Tonind.-Ztg. u. Berg, L. G., Editor, “Trzrdg Pervogo Soveshchaniya Po Ternzografii (Kazan, 1953))” Izd. Akad. Eli& M., Stovick, M., and Z?hradnik, L., “Chemickb rozbory nerostzcjch Surovin. SeSit 12-Dif- Mackenzie, K. C., Editov, “The Differential Thermal Investigation of Clays,” Mineralogical Society, 1944. Keranz.Rundschau, Beiheft 1, 1954. Nauk SSSR, hfoscow and Leningrad, 1955. ferentnizi thermickd analysa, London, 1957. Nakladatelst vi CcskoslovenskB Altademie VGd, Prague, 1957. Smothers. W. J., and Chiang, Y., “Differential Thermal Analysis,” Chemical Publishing Co., New York, 1958. Ramachandran, V. S., and Garg, S. P., “Differential Thermal Analysis as Applied to Building Murphy, C. B., Anal. Chem., 1958, 30, 867; 1960, 32, 1 6 8 ~ . Foldvan-Vogl, M., Ada Geol. Hung., 1958, 5, 3. Satava, S. V., Silikdty, 1957, 1, 232. Mackenzie, R. C., Compiler, “The Scifax Differential Thermal Analysis Data Index,” Cleaver-Hume Kerr, P. F., and Kulp, J. L., Amer. Mineralogist, 1948, 33, 387. Yagfarov, 31. Sh., and Berg, L. G., Izv. Kazaiz. FiZ. Akad. Nauk S S S R , Ser. Khim., 1957, No.3, 31; Bul. Inst. Polztehn. Iasi, 1958, 4, 361. Sewell, E. C., and Honeyborne, D. B., in Mackcnzie, R. C., Editor, op. cit., p. 65; references are given to nine earlier papers by Sewell in which this theory is developed. Arens, P. L., “A Study on the Differential Thermal Analysis of Clays and Clay Minerals,” Thesis, W‘ageningcn, Holland, 1951. Mackenzie, R. C., and Farmer, V. C., Clay Minevals Bull., 1952, 1, 262. Tsang, N. F.. in Smothers, W. J., and Chiang, Y., op. cit., p. 78. Vold, M. J., Anal. Chem., 1949, 21, 683. Smyth, H. T., J . Amer. Ceranz. SOC., 1951, 34, 221. Kronig, R., and Snoodijk, I?., Appl. Sci. Rcs., Hague, A , 1951, 3, 27. SoulB, J. L., J . Phys. Radium, 1962, 13, 516. Eriksson, E., Lantbr. Hugsk. Ann., 1953, 19, 127; 1953, 20, 117; 1954, 21, 189.Nagasawa, K., J . Earth Sci., Nagoya Univ., 1953, 1, 156. Boersnia, S. L., J . Amer. Ceranz. SOC., 1955, 38, 281. Berg, L. G., Editor, OF. cit., p. 59; see also in this volume papers by Yu. V. Sementovskii (p. 67), A. F. Kapustinskii and Uu. P. Barskii @. 82) and Yu. P. Barski’l, N. G. Fridman and R. 13. Ivnitskaya (p. 86). Allison, E. B., Clay Minerals Bull., 1955, 2, 242. Murray, P., and ?mite, J., Ibid., 1955, 2, 255. Kissinger, H. E., J . Res. Nut. BUY. Stand., 1956, 57, 217; Anal. Chem., 1957, 29, 1702. Deeg, E., Ber. dtsclz. keram. Ges., 1956, 33, 321. Ziegler, G., Ibid., 1956, 33, 363. Borchardt, H. J., J . Phys. Chem., 1957, 61, 827. De Jong, G. de J., J . Amer. Ceram. Soc., 1957, 40, 42. Tsuzuki, Y., and Nagasawa, K., Nendokagzku no Shimpo, 1959, 1, 144.Ojo, D. F., “The Physical Basis of the Method of Differential Thermal Analysis,’’ Ph.D. Thesis, University of Edinburgh, 1959. Sementovskii, Yu. V., in Tsvetkov, A. I., Editor, “Trud?j Pyatogo Soveshchaniya Po Eksperimentalnoi i Tekhnicheskoi Mineralogii i Petrografii,” Izd. Akad. Nauk SSSR, Moscow, 1958, p. 79; see also paper by same author in reference No. 36. Science,” Central Building Research Inst ttute, Roorkee, India, 1959. Press, London, 1962.June, 19621 MACKENZIE AND MITCHELL: DIFFERENTIAL THERMAL ANALYSIS. A REVIEW 431 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99.100. 101. 102. 103. 104. 105. 106. 107. 108. McLaughlin, R. J. W., Trans. Brit. Ceram. SOC., 1961, 60, 177. Mitchell, B. D., Sci. Proc. R. Dublin Soc., A , 1960, 1, 105; see also Mackenzie, R. C., Acta Univ. Grimshaw, R. W., and Roberts, A. L., Trans. Brit. Ceram. SOC., 1953, 52, 50. Sabatier, G., Bull. SOC. Franc. Mint%., 1954, 77, 963 and 1077. Gallitelli, P., Cola, M., and Alietti, A., Mem. Accad. Lincei, 1954, 4, 49. Dean, L. A., Soil Sci., 1947, 63, 95. Carthew, A. R., Amer. Mineralogist, 1955, 40, 107. Grimshaw, R. W., Heaton, E., and Roberts, A. L., Trans. Brit. Ceram. SOL, 1945, 44, 76. Linseis, M., Sprechsaal, 1952, 85, 423. Demarco, R. E., Heller, H. A., Abbott, R. C., and Burkhardt, W., Bull. Amer. Ceram. SOC., 1959, Mitchell, B. D., and Mackenzie, R.C., Clay Minerals Bull., 1959, 4, 31. Mitchell, B. D., Ibid., 1961, 4, 246. Stone, R. L., Anal. Chem., 1960, 32, 1582. Erdey, L., Paulik, F., and Paulik, J., Acta Chim. Hung., 1956, 10, 61. Markowitz, M. M., and Boryta, D. A., J . Phys. Chem., 1960, 64, 1711. Mackenzie, R. C., and Farquharson, K. R., Compt. Rend. X I X Congr. Gbol. Int., Algeria, 1952, McConnell, D., and Earley, J. W., J . Amer. Ceram. SOC., 1951, 34, 183. Webb, T. L., Nature, 1954, 174, 686. Mackenzie, R. C., Ibid., 1954, 174, 688. Webb, T. L., “Contributions t o the Technique and Apparatus for Qualitative and Quantitative Differential Thermal Analysis, with Particular Reference t o Carbonates and Hydroxides of Calcium and Magnesium,” D.Sc. Thesis, Pretoria, 1958. Stegmiiller, L., Sprechsaal, 1953, 86, 1.Dilaktorskii, N. L., and Arkhangelskaya, L. S., in Tsvetkov, A. I., Editor, 09. cit., p. 88. Glogoczowski, J. J., Hoczn. Pol. Tow. Geol., Krakowie, 1952, 22, 211. Gawel, A., Ibid., 1952, 22, 375. Anon., Lab. Practice, 1961, 10, 418. Berg, L. G., and Yagfarov, M. Sh., in Berg, L. G., Editor, op. cit., p. 53. Cole, W. F., and Rowland, N. M., Amer. Mineralogist, 1961, 46, 304. Wilburn, F. W., J . Sci. Instrum., 1958, 35, 403. Grim, R. E., and Rowland, R. A., J . Anzer. Ceram. Soc., 1944, 27, 65. Yagfarov, M. Sh., and Berg, L. G., Izv. Kazan. Fil. Akad. Nauk SSSR, Ser. Khim., 1957, No. 3, 27. Horte, C. H., and Wiegmann, J., Feingeriitetechnik, 1959, 8, 16. Theron, J. J., Heydenrych, J. C., and Anderson, F., J . Sci. Instrum., 1949,26, 233. Reisman. A., Anal.Chem., 1960, 32, 1566. Nagasaki, S., and Yonemitshu, K., Nendokagaku no Skimpo, 1959, 1, 159. Jonas, E. C., and Grim, R. E., in Mackenzie, R. C., Editor, op. cit., p. 389. Lloyd, S. J., and Murray, J. R., J . Sci. Instrum., 1958, 35, 252. Papailhau, J., Bull. Soc. Frang. Mint%., 1959, 82, 367. Lodding, W., and Hammell, L., Anal. Chem., 1960, 32, 657. Anderson, H. C., Ibid., 1960, 32, 1592. Mazikres, C., Compt. Rend., 1959, 248, 2990. Berg, L. G., and Rassonskaya, I.S., Dokl. Akad. Nauk SSSR, 1950, 73, 113. FoldvAri-Vogl, M., and Kliburszky, R., Geologie, 1957, 6, 542. Berg, L. G., “Skorostnoi Kolichestvennyi Fazovyi Analiz,” Izd. Akad. Nauk SSSR, Moscow, 1952. Berg, L. G., Teitelbaum, B. Ya., and Anoshina, N. P., in Berg, L. G., Editor, op. cit., p. 108. Powell, D.A., J . Sci. Instrum., 1957, 34, 226. Murphy, C. B., Hill, J. A., and Schacher, G. P., Anal. Chem., 1960, 32, 1374. Ayres, W. M., and Bens, E. M., Ibid., 1961, 33, 568. Keler. E. K., in Berg, L. G., Editor, op. cit., p. 239. Nedumov, N. A., Zhur. Fiz. Khim., 1960, 34, 184. Silika’ty, 1962, 6, No. 1. Sabatier, G., Bull. SOC. FranF. Minkr., 1950, 73, 43. Martin, R. T., in Milligan, W. O., Editor, “Clays and Clay Minerals: Proceedings of the Third National Conference on Clays and Clay Minerals,’’ Publication No. 395, National Academy of Sciences-National Research Council, iyashington, 1955, p. 117. Caillkre, S., and HCnin, S., in Mackenzie, R. C., Editor, op. cit., p. 207. Mackenzie, R. C., and Milne, A. A., Miner. Mag., 1953, 30, 178. Mackenzie, 13. C., Meldau, R., and Farmer, V. C., Bey.dfsch. keram. Ges., 1956, 33, 222. Takahashi, H., in Swineford, A., Editor, “Clays and Clay Minerals: Proceedings of the Sixth National Conference on Clays and Clay Minerals,” Pergamon Press, London, 1959, p. 279. -, Bull. Chem. SOC. Japan, 1959, 32, 381. Yamaguchi, G., and Sakamoto, K., Ibid., 1959, 32, 1364. Bruthans, Z., paper presented a t the Conference of the Silicate Industry, Budapest, October, 1961, (abstract No. 58 in the English list published by the Scientific Society of the Silicate Industry). Whitehead, W. L., and Breger, I. A,, Science, 1950, 111, 279. Talibudeen, O., J. Soil Sci., 1952, 3, 251. Dunne, J. A., and Kern, P. F., Amer. Mineralogist, 1961, 46, 1. Carol., Geol.. 1962, in the press. 38, 360. 1953, 18, 183. , , Clay Minerals Bull., 1953, 2, 57.--432 MACKENZIE AND MITCHELL : DIFFERENTIAL THERMAL ANALYSIS. A REVIEW Grim, R. E., “Clay Mineralogy,” McGraw-Hill Book Co. Inc., New York, 1953. Sudo, T., “Nendokubutsu,” (Clay Mineralogy), Iwanami-Shoten, Tokyo, 1953. Grigorev, A. T., Yui-Pu, E., and Sokolovskaya, E. M., Zhur. Neorg. Khim., 1961, 6, 1616. Maksimov, V. N., Semenenko, K. N., Naumova, T. N., and Novoselova, A. V., Ibid., 1960,5, 658. Zinovev, A. -4., and Krivtsov, N. V., Ibid., 1960, 5, 1418. Golovnya, V. A., and Kokh, L. A., Ibid., 1960, 5, 56. Tsin-Shen, M., and Tronev, V. G., Ibid., 1960, 5, 861. Chcmyaev, I. I., and Molodkin, A. K., Ibid, 1961, 6, 809. Fedorov, I. A., and Balakaeva, T. A., Ibid., 1960, 5, 1522. Lebedev, V. G., and Tronev, V. G., Ibid., 1960, 5, 1725.Gordon, S., and Campbell, C., Anal. Chem., 1055. 27, 1102. Campbell, C., Gordon, S., and Smith, C. L., Jbid., 1969, 31, 1188. Hogan, V. D., and Gordon, S., Ibid., 1960, 32, 573. Borchardt, H. J., Dissert. Abstr., 1956, 16, 1807. Horchardt, H. J., and Daniels, F., J. Phys. Chem., 1957, 61, 917. Daniels, F., Mathews, J. H., Williams, J. W., Render, P., and Alberty, R. A., “Experimental Borchardt, H. J., and Daniels, F., J . Amer. Chem. Soc., 1957, 79, 41. hlarkowitz, M. M., J. Phys. Chem., 1958, 62, 827. Markowitz, M. M., and Harris, R. l?., Ibid., 1959, 63, 1519. Markowitz, M. M., and Boryta, D. A., Anal Chem., 1960, 32, 1688. Markowitz, M. M., Boryta, I). A., and Harris, R. F., J. Phys. Chem., 1961, 65, 261. Murphy, C. B., and West, R. R., Ind. Eng.Chem., 1959, 51, 952. Hill, J. A., and Murphy, C. B., Anal Chem., 1959, 31, 1443. Wendlandt, W. W., and Bear, J. L., Anal. Chim. Acta, 1959, 21, 439. -- , J. Phys. Chem., 1961, 65, 1516. Pa& R., Ann. Chim., 1955, 10, 353. Dell, R. M., and Weller, S. W., Trans. Faraday Soc., 1959, 55, 2203. Berak, J., Guczalski, R., \T76jcik, J., and Zalwert, S., Przem. Chem., 1960, 39, 297. Ambrozhii, M. N., Luchnikova, E. F., and Siderova, M. I., Zhuv. Neorg. Khim., 1960, 5, 366. Spitsyn, V. I., Komissarova, L. N., Shatskii, V. M., and Pushkina, G. Ya., Ibid., 1960, 5, 2223. Chcrnyaev, I. I., Golovnya, V. A., and Ellen, G. V., Ibid., 1961, 6, 376. Freeman, E. S., and Anderson, D. A., J. Phys. Chem., 1959, 63, 1344. Zinovev, A. 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ISSN:0003-2654    

DOI:10.1039/AN9628700420

出版商:RSC    

年代:1962

数据来源: RSC

摘要:

June, 19621 RICHARDSON 435 The Determination of Manganese in High-quality Calcium Carbonate by means of Tetraphenylarsonium Chloride* BY 11. L. RICHARDSON (John & E. Sturge Limited, Lifford Chemical Works, Kings Norton, Birmi@zam 30) A solution of the sample in nitric acid is oxidised by potassium periodate at pH 6.3, and the resulting permanganate is allowed to react with tetra- phenylarsonium ion. The ion-association complex formed is extracted into chloroform, and the optical density of the blue-red colour is measured. The method is suitable for determining manganese in “luminescent quality” calcium carbonate, for which the manganese content is nominally less than 5 p.p.m., with an error of k0.l p.p.m. of manganese. None of the ions likely to react with tetraphenylarsonium chloride interferes; the method is therefore highly selective.The presence of salts aids the formation of the complex. THE production of permanganate by oxidation with persulphate, periodate, bismuthate, etc., is not sufficiently sensitive or reproducible at the level of manganese (0 to 5 p.p.m.) usually present in “luminescent quality’’ calcium carbonate. Calcium ions have an inhibitive effect on the oxidation of manganous ion to permanganate ion to such a degree that it is not visible or detectable with a spectrophotometer (4-cm cells) until about 10 pg of manganese are present in 50 ml of solution ( i e . , 0.2 pg of manganese per ml) ; increasing the weight of sample results in precipitation of calcium salts. Solvent-extraction methods for determining manganese, e.g., those involving the use of 8-hydroxyquinoline, acetylacetone, dithizone and diethyldithiocarbamate, are non-selective, the products are unstable and too high a pH for working in the presence of excess of calcium is usually required ; no satisfactory chelating agent was found for determining manganese at the low levels present in this grade of calcium carbonate.The use of non-ionisation complexes was therefore considered. Tetraphenylarsonium chloride1 to 7 has been successfully used for determining micro amounts of technetium and rhenium, but no reference was found describing its use for determining micro amounts of manganese. A procedure based on the reaction of perman- ganate ion with tetraphenylarsonium chloride, extraction of the reaction product into chloro- form and measurement of the optical density of the coloured complex was investigated In the method evolved, the oxidation to pennanganate was still subject to partial inhibition by the high concentration of calcium arising from the sample, but subsequent concentration of the manganese by solvent extraction resulted in a considerable gain in sensitivity.THEORY- a neutral extractable species, e.g.- The formation of an ion-association complex occurs when an inorganic ion reacts to form Mn0,- + (C,H,),As+ -+ (C,H,),As+ . MnO,- Reddish blue--soluble in chloroform For the complex to be appreciably soluble in an organic solvent, it must contain a large molecule. Presented at the meeting of the Midlands Section of the Society on Thursday, September 14th, 1961.This paper received the Elwell Award for 1961.436 RICHARDSON : DETERMINATION OF MANGANESE IN HIGH-QUALITY CALCIUM [Vol. 87 In general, ion-association complexes are less amenable to general theoretical treatment than are chelation complexes, but Bjerrum* derived a simplified expression for the formation constant, viz.- where a = distance between ion centres in tE.e complex, E = dielectric constant of the medium and T = temperature (OK). Hence a low dielectric constant favoured by the presence of acid or a salting-out agent will also favour complex formation. Low temperature will also favour complex formation, although temperature may also affect the dielectric constant (any change in dielectric constant owing to temperature in this reaction is, however, likely to be small) ; the sizes of the associating ions will also affect the stability of the complex.If a large organic molecule is involved then its solubility in organic solvents can be expected. Oxonium compounds are often more efficient solvents, because oxygen-donor atoms permit co-ordination of solvent molecules, within the metal-ion sphere, giving a product with a structural resemblance to the solvent. The efficiency of the solvent is usually in the order of relative basicity, Le., alcohols > ethers > ketones. High electrolyte concentrations (salting out) favour extraction of ion-association com- plexes for two reasons- (a) The dielectric constant of the medium is lowered, thus favouring ion-pair foimation. (b) The ions of the salting-out agents compete for water molecules with the ion pair.Thus Li+, Ca2+ and Mg2+ ions, which are highly hydrated, are very effective salt ing-out agents . EXPERIMENTAL OXIDISING AGENT- Potassium periodate9 was selected because it produces permanganate a t room temperature and no radicle need be used that would precipitate calcium or involve the addition of a large amount of acid. EFFECT OF pH- To establish the optimum pH for the oxidation, a series of solutions was prepared, each containing 50 pg of manganese, buffer solutions of different pH values and 3 ml of potassium iodate reagent in a volume of 100 ml; the mixtures were set aside for 1 minute. Universal buffer solutionslO covered the pH range 2 to 12 in increments of one unit, and only buffer solutions corresponding to pH 6 and 7 gave any marked permanganate colour.These tests were repeated over the pH range 5.4 to 7.0 in intervals of 0.2 pH unit and optical densities of the resulting solutions were measured at 532 mp. The optical density was found to be a maximum a t pH 6.4. To avoid use of a complex mixture, such as that present in the Universal buffer solution,lO with its possible subsequent interference, a simpler citric - phosphate11 buffer solution was tried (periodate is not affected by citric acid). The previous tests were repeated over the pH range 6.1 to 6.5 in intervals of 0.05 pH unit, and it was established that maximum optical density occurred at pH 6.30. This pH was used in all subsequent experiments. Optical-density readings over the pH range 6-31 to 6.5, measured after 1 minute, were- pH .. . . 6.1 6.15 6.2 6,,25 6.3 6-35 6.4 6-45 6-5 Optical density. . 0.036 0.043 0.048 0.052 0.054 0.050 0.032 0.027 0.027 It was not possible to repeat these spectrophotometric measurements in the presence of calcium ions, because the oxidation is inhibited and the optical density is so small that spec trop ho t ome t ric measurement in 4-cm cells is meaningless without concentration. Accordingly, at this stage calcium ions were excluded from the series of tests. However, because of the possibility that the optimum pH might be different in the presence of calcium ions, the tests with the citric - phosphate buffer solution were repeated in the presence of 10 g of calcium carbonate in the form of nitrate. The colours producedJune, 19621 CARBONATE BY MEAKS OF TETRAPHENYLARSONIUM CHLORIDE 437 in this series of solutions were examined in 100-ml Nessler cylinders and showed a similar gradation in colour to that in the previous series. STABILITY OF PERMANGANATE COLOUR- The tests described earlier were repeated at pH 6.3, and optical densities were measured after various intervals of time.Because of the subsequent solvent-extraction and spectrophotometric-measurement stages, optical-density measurement before 5 minutes’ standing was not considered, owing to the impracticability of making these measurements. It was found that the optical density after 5 minutes was constant for a further 5 minutes; it then decreased to give a half-life of 80 minutes. All subsequent optical-density measurements were made within 10 minutes of adding the potassium periodate reagent ; this reading was taken as the practical maximum optical density in view of the time required to carry out the subsequent stages.Varying the temperature of the test solution from 18” to 24” C had a negligible effect on the optical density. AMOUNT OF POTASSIUM PERIODATE- It was desirable to know the minimum amount of this reagent necessary to achieve complete oxidation of the manganese, because excessive amounts precipitate tetraphenyl- arsonium periodate. The earlier tests were repeated with different amounts of potassium periodate; optical densities were measured 10 minutes after addition of this reagent, this time being necessary to allow for the subsequent operations. The results were- Potassium periodate reagent (0.2 per cent.w/v) added, ml . . 0.5 1.0 1-5 2-0 2.5 3-0 3-5 4-0 4-6 5-0 Optical density . . 0.027 0,031 0.030 0.035 0.039 0.039 0.039 0.040 0.039 0.039 Optical densities rose to a maximum when 2.5 ml of 0.2 per cent. w/v potassium periodate solution were added and remained constant for increased amounts. A compromise of 3.0 ml of reagent was therefore chosen. A repeat of this series in the presence of calcium, with visual comparison of colours in Nessler cylinders, confirmed that the use of 3 ml of periodate solution was suit able. ACID SOLVENT- and hydrochloric acid decomposes permanganate. the solvent. Sulphuric acid was not permissible because of the formation of insoluble calcium sulphate , Kitric acid was therefore chosen as EXTRACTION OF THE COMPLEX INTO ORGANIC SOLVENTS AND DETERMINATION OF THE WAVE- Of the common organic solvents only chloroform extracted the coloured complex from an aqueous calcium nitrate phase.A large excess of tetraphenylarsonium chloride was used, and it was established that the chloroform extract had a maximum absorption at 532 mp. The extraction was found to be of constant efficiency in the pH range 5 to 7, so that no change in pH was necessary after the oxidation at pH 6.3. LENGTH OF MAXIMUM ABSORPTION- STABILITY OF THE COMPLEX IN CHLOROFORM- The organic phase was extracted from an aqueous calcium nitrate phase containing 50 pg of manganese as described under “Method.” The optical density was measured at 532 mp against time in 4-cm cells with chloroform in the reference cell, and it was found that the optical density fell from 0.172 to 0.135 in 10 minutes.It was therefore necessary to standardise the time interval preceding the optical-density measurement, and this was taken as exactly 5 minutes from the addition of chloroform. Variations in temperature of the test solution from 18” to 24” C had a negligible effect on the optical density.438 RICHARDSON DETERMINATION OF MANGANESE IN HIGH-QUALITY CALCIUM [VOl. 87 SHAKING TIME- Tests were carried out as described under “Method” in the presence of 50 pg of manganese with different times of shaking with chloroforni. It was found that the complex was com- pletely extracted after 50 seconds. A 60-second shaking period and optical-density measure- ment after 5 minutes from the beginning of shaking were adopted.PRECISIOX- Six determinations were carried out on sample F (see Table 11) as describedunder “Method,” but with the addition of 50 pg of manganese; the greatest variation in optical density was 3-2.0 per cent., corresponding to an error of + l a 0 pg of manganese. INTERFERENCES- Elements likely to form coloured complexes with tetraphenylarsonium chloride were examined. Determinations were made on sample F as described under “Method,” with the addition of 50 pg of manganese and the amounts of the various elements shown in Table I. TABLE I INTERFERENCE BY VARIOUS ELEMENTS Amourit of CLg Element element present, Molybdenum . . .. 20 Chromium ( C r 9 . . .. .. 20 Iron (Fe3+) .. Cobalt (Coz+) . . . . . . 20 .. * * { :: Tungsten mop2--) .. .. 25 Vanadium (VO,-) . . .. 25 Deviation from optical density (viz., 0.172) of standard 50pg of manganese + 0.003 + 0.005 - 0.003 - 0.005 - 0.005 - 0.002 + 0.003 Further tests were carried out separately in the presence of 50 pg of manganese and 10 g of sodium, potassium or ammonium nitrate. The presence of these salts had no obvious effect on the optical density, but they had a suppression or enhancement effect on the graph. It was not possible to determine manganese in the presence of similar amounts of magnesium, strontium or barium because of precipitation effects caused by the citric - phosphate buffer. METHOD KEAGENTS- All reagents must be of analytical grade. Nitric acid, 5 N. Ammonia solution, 5 N. Narrow-range indicator papers, pH 6.5 to 7.0.Chloro form. Bufer solution, p H 6.311-Place 135.3 ml of 0.2 M disodium hydrogen orthophosphate Potassium periodate solution, 0.2 per cent. w/v-Freshly prepared. Tetraphe?$ylarsonium chloride, 0.02 M. Calcium carbonate-Less than 1 p.p.m. of manganese. Standard manganese stock solution-Dissolve 4-08 g of manganous sulphate, MnS04.4H20, in 300 ml of 5 N sulphuric acid, and dilute wit:h water to 1 litre. and 64.5 ml of 0.1 M citric acid in a dry polythene bottle, and mix thoroughly. 1 ml 3 1000 pg of manganese. Standard manganese working solution-Dilute 10 ml of stock solution to 1 litre with water immediately before use. 1 ml = 10 pg of manganese. PREPARATION OF STANDARD GRAPH- Transfer 100 g of the calcium carbonate to a 1-litre beaker, add 100 to 150 ml of water, and boil; then add 5 N nitric acid slowly (about 420 to 450 ml will be required).Boil the solution after each addition of 50 ml of nitric ac:id, and continue adding acid until the solutionJune, 19621 CARBONATE BY MEANS OF TETRAPHENYLARSONIUM CHLORIDE 439 is neutral to litmus paper; then heat the solution to boiling-point to expel carbon dioxide. Check the pH with the narrow-range indicator paper, and adjust to pH 6-1 to 6.5 if necessary with 5 N nitric acid or 5 N ammonia solution. Cool the solution to room temperature, transfer it to a l-litre calibrated flask, and dilute to the mark with water. Transfer a 100-ml portion to a 250-ml separating funnel, add 50 pg of manganese (5.0 ml of standard manganese working solution), and proceed as described under “Procedure” from “Add 5 ml of buffer solution, pH 6.3, mix, .. .’, Repeat the above in turn with 40, 30, 20, 10 and 0 pg of manganese (Le., 4.0, 3.0, 2.0, 1.0, 0.0ml of standard manganese working solution). Plot a graph relating optical density to micrograms of manganese, and correct the graph for the reagent blank value. PROCEDURE- Transfer a 10-g sample to a 250-ml beaker, add about 25 to 30ml of water, and boil; then add 5 N nitric acid slowly from a burette until the solution is neutral to litmus. Heat the solution to boiling-point, and boil to expel carbon dioxide. Check the pH with narrow- range indicator paper, and if necessary adjust to pH 6-1 to 6.5 with 5 N nitric acid or 5N ammonia solution. Cool the solution to room temperature, transfer to a 250-ml separating funnel, and dilute to 100ml (see Note 1) with water.Add 5 ml of buffer solution, pH 6.3, mix, and then add 3 ml of potassium periodate solution. Immediately start a stop-watch, and then thoroughly mix the test solution. After exactly 5 minutes add 5 ml of 0.02 M tetraphenylarsonium chloride, and mix. Immediately add exactly 10 ml of chloroform, insert the stopper in the separating funnel, and shake gently for exactly 60 seconds. Allow the contents of the funnel to separate for 1 to 2 minutes (no longer). Dry the stem with filter-paper, and run off as much of the organic phase as possible into a dry stoppered test-tube. Transfer the contents of the test-tube to a 4-cm cell (see Note 2), and measure the optical density at 532mp exactly 10 minutes after the stop-watch was started.Use chloroform in the reference cell. Read the manganese content from the standard graph. TABLE I1 COMPARISON OF RESULTS BY DIFFERENT METHODS Sample A B C D E F G H I Calcium carbonate ( AnalaR) Manganese found by proposed method, p.p.m. 0.6 0.8 1.2 10.9 0.7 0.6 2.6 4.1 5.0 1.2 Manganese found by persulphate method, p.p.m. <1 <1 <1 10 <1 <1 1 3 4 - NOTES- 1. The separating funnel should be marked to indicate 100 +, 2 ml. 2. It is necessary to raise the cells about inch above the base of the cell basket, e.g., with a piece of thin Perspex (covered with filter-paper), so that the limited depth provided by the 10 ml of extract in the 4-cm cell fills the aperture of the cell basket. RESULTS The procedure was appliea to the samples listed in Table 11, and results agreed closely with those previously obtained by a method based on oxidation of manganese with ammonium persulphate and visual comparison against similarly prepared standards containing AnalaR calcium carbonate and known amounts of added manganese. By this earlier procedure440 RICHARDSON [Vol.87 results were of doubtful accuracy, because they were based on the addition of manganese to supposedly manganese-free calcium carbonate. Samples F and G were also examined by cathode-ray polarography, and manganese contents of 0.4 and 2.4 p.p.m., respectively, were obtained. CONCLUSIONS In “luminescent quality” calcium carbonate, the proposed method provides for the determination of manganese in the 0.1 to 5 p.p.m.range with an error of tO.1 p.p.m. It should be possible to extend the procedure to the determination of manganese in oxides, hydroxides, carbonates, nitrates, etc., of many other elements. The method is highly selective and more accurate, reliable and sensitive than any permanganate colorimetric procedure, and the presence of large amounts of salts aids the ion-association effect. I thank the Directors of John & E. Sturge Limited for permission to publish this paper. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. REFERENCES Tribalat, S., Anal. Chim. Acta, 1949, 3, 113. -, Ibid., 1950, 4, 228. Sandell, E. B., “Colorimetric Determination of Traces of Metals,” Third Edition, Interscience Tribalat, S., and Beydon, J., Anal. Chim. A ~ t a , 1952, 6, 96. Morrison, G. H., and Freiser, H., “Solvent Extraction in Analytical Chemistry,’’ John Wiley & Sons Inc., New York, and Chapman & Hall Ltcl., London, 1957, p. 217. Kemp, E. F., “Solvent Extraction in Analytical Chemistry,” Course 11, Lecture Summaries, Summer School in Analytical Chemistry, Royal Institute of Chemistry, London, 1959. Cornfield, A. H., and Pollard, A. G., J . Sci. Food Agric., 1950, 1, 107. Johnson, W. C., and Lindsey, A. J., AnaZyst, 1939,64,490; Vogel, A. I., “A Text-book of Quantita- tive Inorganic Analysis,” Second Edition, Longmans, Green & Co. Ltd., London, 1951, p. 872. McIlvaine, T. C., J . B i d . Chem., 1921, 49, 183; Vogel, A. I., op. cit., p. 869. First received June lSth, 1961 Amended, February 20th, 1962 -, Ibid., 1951, 5, 115. Publishers Inc., New York, 1960, p. 753. , , Ibid., 1953, 8, 22. --

ISSN:0003-2654    

DOI:10.1039/AN9628700435

出版商:RSC    

年代:1962

数据来源: RSC

摘要:

June, 19621 WILSON AND PHILLIPSON 441 The Determination of Aldrin in Fertilisers BY €3. N. WILSON AND M. PHILLIPSON (Imperial Chemical Industries Ltd., Billingham Division, P.O. Box No. 6, Billingham, Co. Durham) After the fertiliser has been separated from the aldrin by extraction with dilute acid, the aldrin is burnt in oxygen, the products of combustion are absorbed, and the chloride is determined by “dead-stop” amperometric titration ; from this result the aldrin content of the sample is calculated. The method is relatively rapid and accurate; a determination that previously took 6 hours can be completed in 90 minutes. THE pesticide aldrin (1,~,3,4,10,l0-hexachloro-1,4,4a,5,8,8a-hexahydro-l,4,5,8-dimethanonaph- thalene) is added to certain fertilisers, and a rapid method for its determination is desirable.In the method generally used, l o g of sample are placed in an extraction apparatus, and the aldrin is extracted by heating under reflux with light petroleum (boiling-point 120” C) for 3 hours. After the addition of 1-5 g of sodium and 5 ml of butyl alcohol, the extract is heated under reflux for 1 hour; 25ml of butyl alcohol are then added, and the solution is heated for a further hour to destroy the excess of sodium (Stepanow’s procedure). The chloride is transferred to an aqueous phase by treatment in a separating funnel with dilute nitric acid and water. From the chloride, which is determined by titration, the aldrin content of the sample is calculated. This method gives good results, but approximately 6 hours are needed for one determination.A procedure is described for determining aldrin in fertilisers. EXPERIMENTAL It was found that the duration of extraction could be decreased to 1 hour, but treatment of the extract with sodium remained lengthy. Attempts were made to extract the aldrin from a solution of fertiliser in water or dilute acid, but complete extraction proved most difficult to achieve; it could be done by repeated extraction with light petroleum, but this was not regarded as any great advantage. It was then decided to attempt the determination of the organic chlorine by combustion in oxygen in a closed flask.l This technique is applicable to small amounts of organic compounds, and the chloride produced can be titrated amperometrically on the micro scaIe,2 0.01 N or more dilute silver nitrate being used as titrant.Aldrin was purified by recrystal- lisation from light petroleum, and a suitable weight was burnt in oxygen in a flask; recovery was 98 per cent., which, owing to the relatively small percentage of aldrin in the fertiliser, was regarded as satisfactory. A 10-g sample of fertiliser was then extracted with light petroleum, and the extract was evaporated to about 10 ml, transferred to a 25-ml calibrated flask and diluted to the mark with light petroleum. After being mixed, some of this solution was transferred to a micro- burette, and 2.5 ml (equivalent to 1 g of sample) were allowed to drop slowly on to a piece of filter-paper (2 sq. inches) at a rate such that the light petroleum evaporated between drops; the paper was dried and burnt in oxygen as before, and the chlorine was determined.The sample was found by the usual method to contain 0-15 per cent. of aldrin; by combustion in oxygen, 0-13 per cent. This procedure was regarded as a considerable improvement and could be used with advantage if it were desired to determine aldrin in other insoluble materials. However, it was thought that extraction with light petroleum might be avoided by utilising the fact that aldrin is virtually insoluble in dilute nitric acid, whereas fertilisers are soluble. Samples prepared by adding known amounts of aldrin to l-g portions of untreated fertiliser were transferred to the filtration apparatus shown in Fig. 1, and the acid-soluble fertiliser was dissolved through the filter by washing with just warm 10 per cent.nitric acid previously saturated with aldrin. The filter was washed free from chloride, and the papers were removed, dried for 5 minutes at 100” C and burnt in oxygen; aldrin was determined as before. The results were- Experiments were made to abridge this procedure. Sample No. . . . . .. 1 2 3 4 Aldrin added, mg . . . . 5-59 6.96 10.00 15-59 Aldrin found, mg . . . . 5.66 7-10 10.00 15.78442 WILSON AND PHILLIPSON : DETERMINATION [Vol. 87 METHOD Filtration apparatus-This is shown in Fig. 1. APPARATUS- It consists of a 1-litre filter flask fitted with a rubber stopper and a cylindrical funnel 2 inches tall and 14 inches internal diameter. A filter cone is placed in the base of this funnel, and the top is closed by a rubber stopper into which is fitted the extraction tube and a stoppered tube (8 inch internal diameter) used for washing the outer portion of the filter-paper pad and equalising the pressure when necessary. The extraction tube is 34 inches long and 8 inch internal diameter; both ends are fire polished and at right angles to the axis of the tube.Combmtion fifZask-This is shown in Fig. 2 and comprises a Quickfit & Quartz 1-litre flask with a B24 socket and two stoppers. One is a standard B24 stopper, the other is made from a "drip cone"; the upper end is sealed, and the lower end drawn out and joined to a short length of Pyrex-glass rod. A platinum .wire fused into the glass rod has a t its lower end a piece of platinum gauze, 14 inches x 9 inch, bent over to hold the paper to be ignited.Amperometric-titration apparatus-As described by Price and Coe.2 -Extraction tube n Stoppered tube Filter-paper discs - Pad of filter-paper pulp Filter cone Fig. 1. Apparatus for filtration Fig. 2. Combustion flask REAGENTS- Silver nitrate, 0.01 N. Hydrogen peroxide, 20-vol~me. Nitric acid, dilute (1 + 9)-Transfer 500 nil of dilute acid (1 + 9) to a stoppered 1-litre Filter through a Whatman flask, add about 1 g of aldrin, shake well, and. allow to settle. No. 42 filter-paper before use. PROCEDURE- Make a fairly tight pad of filter-paper pulp about & inch thick on the filter cone (this pad is preferably prepared in three layers). Place three discs of Whatman No. 42 filter-paper over the pad, moisten, and press down firmly. Insert the stopper and extraction tube, and adjust the position of the tube so that it presses firmly on the discs of filter-paper to form a good seal.Quantitatively transfer 1 g of ground sample to the extraction tube, and wash it with the minimum amount (usually about 25 ml) of just warm (25" C) dilute nitric acid until all soluble material has been extracted. Wash the sample and pad with distilled water until the washings are free from chloride (the outer part of the pad is washed via the side tube). Continue to apply suction until as much water as possible has been removed from the pad, carefully remove the extraction tube and stopper, and withdraw the two upper discs of filter-paper. Wipe the inside of the tube with a small piece of filter-paper, place it with the two discs on a clean watch-glass, and dry in an oven at 100" C for 5 minutes, but no longer.June, 19621 OF ALDRIN IN FERTILISERS 443 Measure 5 ml of 20-volume hydrogen peroxide and 15 ml of water into the combustion flask, fill it with oxygen, and close with the B24 stopper.Fold the dried discs of paper, place them in the fold of the platinum gauze, insert a short length (1 inch x & inch) of filter- paper to act as a wick, and press the gauze to hold the paper gently. Ignite the wick, rapidly remove the stopper from the flask, insert the sample, and hold the stopper firmly in position until combustion is complete. (Although no explosions have occurred, the combustion is preferably carried out behind a safety screen.) Shake the flask vigorously, with a shaking machine if available, until no traces of mist remain (about 15 minutes), Transfer the solution to a squat 250-ml beaker, rinse the flask with distilled water, and add the rinsings to the main solution.Add 5 ml of nitric acid, sp.gr. 1.42, dilute to 150 ml with distilled water, mix well, and titrate amperometrically2 with 0.01 N silver nitrate. Repeat the titration with similar volumes of reagents to determine the blank value. 1 ml of 0-01 N silver nitrate = 0.6083 mg of aldrin = 0.06083 per cent. of aldrin on a l-g sample. RE s u LTS A series of samples of a compound fertiliser based on ammonium phosphate and containing approximately 28 per cent. of potassium chloride was analysed by both proposed and usual procedures. The results are shown in Table I ; the difference between the aldrin contents found by the two methods has no practical significance. TABLE I COMPARISON OF RESULTS FOR ALDRIN IN A COMPOUND FERTILISER Aldrin content found by- - % % Sample extrachon proposed No. method, method, 1 0.22 0.2 1 2 0.1 1 0.1 1 3 0.22 0.20 4 0.20 0.20 5 0.19 0.19 6 0-17 0.17 7 0.19 0-19 8 0-18 0.19 9 0.18 0.17 10 0.19 0.19 Mean aldrin content by extraction method = 0.2 16 ?& Aldrin content found by- - % % Sample extraction proposed No. method, method, 11 0-18 0.16 12 0.18 0.17 13 0.21 0.19 14 0-21 0.19 15 0.19 0.18 16 0-15 0.16 17 0.31 0.31 18 0.37 0.35 19 0-25 0.26 20 0.43 0-43 Mean aldrin content by proposed method =0-211y0 The proposed method was equally satisfactory when applied to aldrinated fertilisers based on superphosphate ; results for such samples were- Sample No. . . .. .. .. 1 2 3 4 Aldrin found by extraction method, yo 0-31 0.12 0.18 0.2 1 Aldrin found by proposed method, yo. . 0.29, 0-29 0.16, 0.16 0.20, 0.20, 0.19 0.23, 0.23, 0.22 REFERENCES 1. 2. Schoniger, W., iMikrochim. Acta, 1955, 123; 1956, 869. Price, D., and Coe, F. R., Analyst, 1959, 84, 55. Received November 27th, 1961

ISSN:0003-2654    

DOI:10.1039/AN9628700441

出版商:RSC    

年代:1962

数据来源: RSC