摘要:

Proceedings of the Society for Analytical Chemistry CONTENTS Reports of Meetings . . . . 129 Automatic Methods of Analysis. . I30 Solvent Extraction . . . . 138 Papers accepted for The Analyst 139 Membership changes . . .. 140 Publications Received . . .. 140 Notices .. . . . . . . 141 Forthcoming Meetings . . .. 142 Proc. SOC. Anal. Chem. Vol. I No. 12 Pages 129442 December 1964 Vol. I No. 12 December 1964 PROCEEDINGS THE SOCIETY FOR ANALYTICAL CHEMISTRY OF President of the Society D. C. Garratt Hon. Secretary of the Society S. A. Price Hon Treasurer of the Society D. T. Lewis C.B. Hon. Assistant Secretaries of the Society B. S. Cooper; D. W. Wilson Secretary Miss P. E. Hutchinson 14 BELGRAVE SQUARE LONDON S.W.1 Telephone BELgravia 3258 Editor J. B. Attrill Proceedings is published by The Society for Analytical Chemistry and distributed to members and all subscribers to The Analyst without charge Single copies may be obtained direct from the Secretary The Society for Analytical Chemistry at the above address (NOT through Trade Agents) price 2s.6d. post free. Remittances payable to “Society for Analytical Chemistry” MUST accompany orders Methods for the Analysis of Non-Soapy Detergent (NSD) Products by G. F. LONGMAN B.Sc. F.R.I.C. & J. HILTON B.Sc. A.R.I.C. (Unilever Research Laboratory Port Sunlight) Society for Analytical Chemistry Monograph No. I -0- This Monograph describes i n detail the methods of analysis developed in Unilever’s Laboratories for the identification and assay of components of NSD Products. -0- Available ONLY from The Editor “The Analyst,” 14 Belgrave Square London S.W. I (Not through Trade Agents) Price 15s. or U.S. $2.00 Post free A remittance made out to “Society for Analytical Chemistry” should accompany every order. Members of the Society may purchase copies at the special price of 5s. post free.

ISSN:0037-9697    

DOI:10.1039/SA96401FX039

出版商:RSC    

年代:1964

数据来源: RSC

摘要:

142 FORTHCOMING MEETINGS [Pvoc. SOC. Anal. Chem. January Friday 8th BRISTOL Tuesday 19th B I RM I N GH A M Friday 22nd GLASGOW Wednesday 27th LONDON Saturday 30th MANCHESTER Forthcoming Meetings WESTERN SECTION A. G. M. followed by Ordinary Meeting. “Editing a Scientific Journal,” by J . B. Attrill M.A. F.R.I.C. College of Advanced Technology Bristol; 6.30 p.m. MIDLANDS SECTION Discussion Meeting. “Analysis of Polyester Resins,” to be opened by C. H. Hughes A.R.I.C. Haworth Lecture Theatre The University Birmingham 15; 7 p.m. SCOTTISH SECTION A.G.M. More’s Hotel Glasgow; 1.45 p.m. MICROCHEMICAL METHODS GROUP Discussion Meeting. “The Feathers,” Tudor Street London E.C.4; 6.30 p.m. NORTH OF ENGLAND SECTION A.G.M. followed by the Address of the Ketir- ingchairman C. J . House B.Sc. A.R.C.S. F.R.I.C. Old Nag’s Head Hotel Lloyd Street Manchester; 2.15 p.m. PRINTED BY W. HEFFER 8r SONS LTD.. CAMBRIDGE. ENGLAND.

ISSN:0037-9697    

DOI:10.1039/SA96401BX041

出版商:RSC    

年代:1964

数据来源: RSC

摘要:

December I964 Vol. I No. 12 Analytical Methods Committee DETERMINATION OF FLUORINE THE Analytical Methods Committee has recently been considering the formation of a sub- committee to recommend standardised methods for determining both major-constituent amounts and impurity levels of fluorine. It has however not been possible properly to assess the general need for such methods. Any analyst who requires even if only infrequently to determine fluorine is therefore invited to communicate with the Committee. Details that would prove most helpful are- Level of fluorine to be determined. 128 130 AUTOMATIC METHODS OF ANALYSIS [Proc. Soc. Anal. Chem. Material in which fluorine is to be determined. Method at present used. Whether or not the present method is satisfactory. Whether or not there is considered to be a need for standardised methods. METHODS FOR THE ANALYSIS OF WATER THE Analytical Methods Committee would welcome comments from members of the Societjr on the need for revision of the published methods for the analysis of water (“Approved Methods for the Physical and Chemical Examination of Water,’’ Third Edition The Institu- tion of Water Engineers London 1960). Information is particularly sought on any deter- minations not covered by the existing methods and for which there is now a definite need. Communications on both the above subjects should be addressed to- The Secretary Analytical Methods Cominitt ee Society for Analytical Chemistry 14 Belgrave Square London S.W.l.

ISSN:0037-9697    

DOI:10.1039/SA964010129b

出版商:RSC    

年代:1964

数据来源: RSC

摘要:

130 AUTOMATIC METHODS OF ANALYSIS [Proc. SOC. Anal. Chem. Automatic Methods of Analysis The following are summaries of the papers presented at the meeting of the Scottish Section and Microchemical Methods Group held on September 25th and 26th and reported in the November issue of the Proceedings (p. 113). Nomenclature BY T. R. F. W. FENNELL (Royal Aivcvaft Establishment Favnbovough Hunts.) EVERY profession and trade had a language of its own Mr. Fennell said often scarcely intelligible to those outside its ranks. The object of this use of uncommon nomenclature was that by its use one chemist could convey an idea concisely and without ambiguity to another chemist. Unfortunately this was not always as simple as it sounded. In order to overcome this handicap the national and international standardisation bodies not only recommended standards for materials apparatus and test methods but also for nomenclature.In this country we had the British Standards Institution which had issued several glossaries of terms and symbols relating to various scientific and technological disciplines. In the international sphere one of the organisations was the International Union of Pure and Applied Chemistry which periodically published recommendations on for example atomic weights ph ysico-chemical const ants and nomenclature. The objectives of any body desiring to standardise nomenclature were well summed up in the Foreword to B.S. 3527- 1 . To explain to newcomers to the subject the usual meaning of specialised terms. 2. To reduce the number of synonyms or near-synonyms that were in use for the same concept.3. To serve in the elucidation of correct equivalent terms in other languages. Objectives 1 and 3 Mr. Fennell said needed no further elaboration but objective 2 high- lighted one of the difficulties facing the body. Until a process or technique was in common use there was no need to standardise terms and symbols. By the time the process was established numerous terms might be in use for the same operation or apparatus or conversely the same term might be used for different operations or apparatus. R.S. 3527 gave as ijs working guide-“Current usage has been taken as the authority except in a few instances where the usage was likely to cause confusion or to be otherwise inadequate.” This might not be too difficult nationally but internationally it could become tricky.Chemists were no exception. Purely local usage and interpretation developed. December 19641 AUTOMATIC METHODS OF ANALYSIS 131 The second difficulty which was more a question of morale was that the recommendations were not under existing conditions mandatory. The work put in to produce a recommenda- tion might be in vain. How many speakers authors of papers or editors he asked checked whether the term or symbol used was in accordance with the relevant B.S. or I.U.P.A.C. recommendations. R.S. 1991 (1954) had recommended the symbol g for gram but gm. gm and g. were still often seen the last in current issues of the Journal of the Chemical Society. In Pure and Applied Chemistry 1961 recommendations for terminology for scales of working in chemical analysis had been published.I t was seldom however that centigram was seen in place of semi-micro milligram for micro or microgram for ultramicro or submicro. Current usage even if confusing or otherwise inadequate was not easy to overcome. There was always the hope however that recommendations would gradually become more widely used and justify the time and effort spent in producing them. Mr. Fennel1 said that the general theme of the meeting was “Automatic Methods of Analysis,” and it might not appear a t first sight as if there were any problems of nomenclature. In point of fact the Committee of the Micrxhemistry Group had devoted some time to the choice of this title to try to avoid any such difficulty. However a recent survey undertaken on behalf of the Analytical Chemistry Division of I.U.P.A.C.had shown that there was some confusion between the concepts of mechanisation instrumentation and automation. In considering automatic methods of analysis the use of machines mechanisms and instruments was involved. The words listed might be used in discussion on the use of these dei-ices- Machine Instrument Automate Mechanism Instrumentate A4utomatise Mechanise Instrumentalise Automatic Mechanical Instrumental Automata1 Mechanicalise Instrumentation Automatous Mechanicise Automation Mechanicalisation Automatisation Mechanisation Some of these terms were obsolete but all might be found in dictionaries. All from the analytical chemists’ point of view implied the replacement of human endeavour. The first column concerned movement or work and in the analytical context this meant manipulative effort e.g.turning a burette tap lifting a bulb full of mercury or stirring a solution in a beaker. Nowadays t o save effort these jobs were often done by machines or mechanisms. The work was being mechanised by the use of mechanical devices. This replace- ment of human manipulative effort was the process of mechanisation. The other three terms in the list were synonyms for which there was no use. The source of power that replaced the human effort was immaterial. For the chemist an instrument might by defined as a device that refined extended or supplemented human faculties and that was used for observing measuring computing or communicating the present state of a quality. The emphasis was now on the production and relaying of information as distinct from the production of movement.The fact that a device contained mechanisms did not prejudice its description as an instrument if the end product of its function was the production or relaying of information. The adjective instrumental needed no com- ment but the verbs instrumentate (Webster 1961) or instrumentalise (Oxford English Dictionary 1933) did not find general approval. The word instrument itself could serve as a verb as it did in musical and legal parlance and was preferred. The process of replacement of human faculties by the use of instruments was instrumentation. If this use of the term was acceptable instrumentation should not be used as a collective noun for instruments in general but might be used to describe an instrument or group of instruments used for a particular purpose. The above nomenclature might not cause any difficulty but the last column of terms was not so easy to resolve.“Automation” was the current catch-word and was used in all sorts of contexts very often where “mechanisation” or “instrumentation” would do as well if not better. Three of the terms in this list were used on the programme of this meeting the first in the title being “automatic.” This was the oldest word and had been defined (Webster) as “having a self-acting or self-regulating mechanism that performs a required act at a predetermined point in an operation.” Obso- lete synonyms were “automatal” and “automate.” Neither of these terms appeared to have The second column of terms was related to the use of instruments. The idea of control had now been introduced. 132 AUTOMATIC METHODS OF ANALYSIS [Proc.SOC. Anal. Chem. any claim for re-introduction. It was interesting to note in passing that the word “automate” had been originally used as a noun and an adjective and not as a verb as was common now. This use of the word as a verb stemmed from the introduction of the term “automation.” It had been coined in America to describe a process of manufacture that was in effect intensive mechanisation. Later the principle of feedback had been introduced but later still this principle had b:en abandoned as a necessary part of a process described as automation. The result was that the term had now lost any definite meaning that it might at any time have had. This point was illustrated with some current definitions- Automatically controlled operation of an apparatus process or system by mechanical or electronic devices that take the place of human organs of observation effort and decision (Webster 1961).2 . Automatic control of the manufacture of a product through successive stages (Concise Oxford Dictionary 1964). 3. The technique of making an apparatus a process or a system operate automatically (Webster 1961). 4. Use of machinery to save mental and manual labour (Concise Oxford Dictionary 1964). These definitions covered a broad range of degree of control down to no control at all. This range might be slightly contracted by use of some of the terms already discussed. As an example he discussed the performance of an acid - base titration. The operations involved were addition of titrant mixing observation of the effect on the indicator and noting of the titre at the end-point.This term “automation” had had a chequered career. 1 . These human operations might be replaced by- (a) Use of magnetic stirrer (mechanisation). ( b ) Instrumental (photometer or pH meter) detection of the effect of the addition of titrant to the solution (instrumentation). (c) Use of a motor-driven syringe burette (mechanisation). (d) Use of a chart recorder to monitor the response of the indicator system (more advanced instrumentation). The titration could now proceed after the apparatus had been switched on without human attention. The process had been mechanised and instrumented but Mr. Fennel1 asked was it automatic? The apparatus would continue to feed titrant and record the response of the indicator system until the burette jammed and the recorder ran out of paper.It was true that with a knowledge of the rate of addition of titrant and of chart speed the result of this unattended titration could be calculated. Before considering how to classify this stage in development of the titration he suggested further developments- Use of a safety device a stop mechanism to switch off the burette drive motor and recorder when the burette had delivered its maximum volume of titrant. Use of a device that switched off the burette drive motor when the indicator system showed that a pre-set optical density or pH had been reached in the solution. Digital recording of the volume of titrant added. There was no control mechanism. (e) (f) (g) Further developments could be visualised after this stage e.g. washout and refilling systems for the titration vessel a refilling system for the burette and a print-out system for the volumes of titrant added in each titration.At stage ( d ) a titration could be performed without attention but apart from having constant-speed motors fitted to the burette and recorder without control. Stage (e) provided a form of control system to the apparatus but it was “blind” control merely a safety device to stop damage to the apparatus. It switched the apparatus off at a predetermined point in an operation the point when the burette was emptv but was this enough to classify the apparatus as automatic. At stage ( f ) a new principle had been introduced. Indicator response had been linked to the motor drive and this was an example of feedback. The predetermined point was now the end-point of the titration and the titre might be read directly from the burette.Stage (g) was a slight advance on this in that it made the titre easier to read. There was no doubt that the apparatus could This device did perform a desired act. December 19641 AUTOMATIC METHODS OF ANALYSIS 133 be called “automatic” from stage (f) onwards according to the speaker’s earlier definition but there was some doubt about the earlier stages. In order to differentiate between these stages Mr. Fennel1 proposed the nomenclature given below- (;) Up to stage (d) the development of the process should be classified as “mechanisa- (ii) At stage ( e ) the process should still preferably be classed as “mechanised,” but (iii) From stage (f) onwards the process should be classed “automatic.” t ion. ” could be classed “semi-automatic.” These proposals required that the term “automation” should not be used when no control mechanism was incorporated in the system and that it should not be used unqualified until some form of feedback was incorporated.There were still three terms in the last column of the list that had not yet been considered. These were “automatous,” “automatise” and “automatisation.” I t was doubtful whether the use of the adjective “automatous” would help but there was the possibility of introducing the other two terms which had not yet been used to describe analytical operations for the final development of automation i.e. the complete replacement of the analyst when sampling analysis and reporting of the results was done without human attention. I t was a sobering thought to end with that by the time this stage was reached the earlier terms discussed would have become as obsolete as the analytical chemist.Process Gas Chromatography BY C. S. F. PINE DR. PINE said that after the discovery of gas chromatography by A. T. James and A. J. P. Martin (Biochem. J . 1951 vii) in 1951 considerable interest had been shown by the chemical and petroleum industries in the use of fully automatic gas Chromatographs for process-stream analysis. The first process gas chromatographs closely resembled their laboratory counterparts apart from the development of sample-injection valves that could be operated automatically from a repetitive process timer. The first process instruments had been installed early in 1955. Since then an appreciable number of process chromatographs had been installed in plants principally in the chemical and petroleum industries and the number was now growing rapidly.Since 1957-58 instruments had been available commercially and there were now at least 10 manufacturers in this field in the U.K. U.S.A. and Europe. I t had been estimated that some 3000 to 4000 instruments were now installed throughout the world although less than 10 per cent. of these were in the U.K. Considerable developments had taken place over the past 8 years in process chromato- graphy. Present-day instruments were highly accurate and reliable and their use permitted very rapid analyses to be performed; many streams could each be completely analysed in 5 minutes or less. Another common feature today was the use of a single instrument for the automatic analysis in turn of several streams of similar composition.The analysis of up to 10 similar process streams on a single instrument was quite common. Many instruments were also used in automatic control systems particularly in the control of distillation columns. Other common applications included use in reactor optimisation and as monitors to operate alarms in the event of the build up or “breakthrough” of undesirable constituents. Process chromatographs were supplied with katharometer P-ray argon ionisation and flame ionisation detectors. Thus a full range of analyses from those of concentrations (by volume) as parts per million (v.p.m.) to those of percentage concentrations was covered for many organic gases and liquids and for inorganic gases. Analysis of inorganic gases in concentrations of v.p.m.was not however adequately covered at present. The process chromatograph had proved itself to be a highly reliable automatic instrument and its maintenance costs were low. It was applied in those situations in which rapid and frequent analyses were required for control purposes whether performed automatically or manually by a process operator. It was an expensive device; the cost of installation was (Imperial Chemical Industries Limited Heavy Organic Chevnacals DzvLsSioPa Bill) izgham Co. Durham) 134 AUTOMATIC METHODS OF ANALYSIS [Proc. SOC. Anal. Chenz. often in the region of l4000 to E6000 although less expensive instruments were available for simple analyses. However some installations were known to have paid for themselves in under 10 days. Even in those instances in which the “pay-off” period was more likely to be 1 to 2 years the investment could be worthwhile.THE PROCESS CHROMATOGRAPH- A process chromatograph was a complete analytical system that operated automaticallj- apart fron routine maintenance which consisted mainly of checking functional operations once per day and ensuring an adequate supply of carrier gas and sample. A process chromato- graph was composed of four main parts. The analyser section-This comprised a constant-temperature enclosure (or enclosures) containing the sample-injection valve columns and column-switching valves carrier-gas flow controllers detectors etc. This equipment was designed specifically for operation in hazardous areas. Sample handling-The sample was taken from the plant to the analyser by sample- handling equipment.This usually consisted of an arrangement of filters valves etc. to supply the sampling valve in the analyser with a controlled flow of clean sample with the shortest possible delay. The sample was either returned to the process at a convenient point or disposed of in some convenient manner. Automatic sampling was usually one of the most difficult parts in the design of a process-chromatograph system. No single solution was available for all problems. This arose from the sheer diversity of problems encountered. Factors such as temperature pressure dew-point and boiling-point range could all cause difficulties. Programmer-The automatic operation of the analyser was performed by a programmer. This initiated all the necessary functions such as sample injection column switching signal amplification and attenuation automatic zeroing of the recorder and stream switching.These functions were operated on a time-cycle basis by an automatic timer. The programmer was normally located remotely from the analyser and was situated in the plant-control room in conjunction with the recorder. Display of results-Measurements in process gas chromatography were almost invariably of peak height since this was found to be entirely satisfactory in most instances. Integration of areas often used with laboratory chromatographs was regarded as an unnecessary complication. The normal form of display was a Bar-Graph presentation on a strip-chart recorder. With Bar-Graph presentation the chart-drive motor in the recorder was stopped during the emergence of each peak and was energised only to give a constant separation of adjacent peaks and to distinguish successive analyses.If several streams were being analysed on the same chromatograph a marker was added to identify the analyses. When automatic control was involved a continuous record of the values of the peaks concerned was required. The peak heights were “sensed” by a device called a “peak-picker” that automatically read the peak value and inserted it into a suitable storage device (pneumatic or electronic). The store was re-set after each analysis and the output if it was displayed on a recorder appeared as a stepped trace. S-~MPLE INJECTION- The prime need of a process chromatograph was a means for injecting precise volumes of sample into the column by automatic means at regular intervals.Valves had been devehped for this purpose and had been available commercially for at least 5 years. Many were now used in laboratories for sample injection. Their use permitted the injection of liquid or gas samples with a volumetric reproducibility of less than 0.1 per cent. under the most favourable conditions and with volumes down to 1 pl. Working temperatures were as high as 200” C. Various operating principles were used which included piston valves with linear or rotary movement diaphragm valves and flat sliding-face valves again with linear or rotary moving working parts. This had been originally developed and patented by Imperial Chemical Industries Ltd. at Rilling- ham (H. R. Ronnebeck “Improvements in and relating to apparatus for dispensing fluids,” British Patent 800,212 1955) ; it had been very successful and was now available from W.G Pye and Co. Ltd. of Cambridge. Valves working on this principle were also available from process-chromatograph manufacturers in the U.S.A. The cost of these vah-es was in the range Ll00 to ll50. The most successful type was the linear flat sliding-face type of valve. December 19641 AUTOMATIC METHODS OF ANALYSIS 135 COLUMN-SWITCHING TECHNIQUES- The composition of most process streams in the chemical industry was such that it was rarely possible to perform a required analysis with a single chromatograph column in the short times required for process control. Several columns were usually required and it was necessary to insert or remove one or more of these columns in the main carrier stream during the course of an analysis cycle according to some predetermined programme.Valves were required to perform such column-switching operations and those used in practice were the automatically operated sampling valves previously described but suitabl!? adapted. COLUMN TECHNOLOGY- At present the emphasis regarding column technology in process chromatographs was on high speeds of analysis down to 1 to 2 minutes coupled with high long-term stability. Packed columns were used almost exclusively (2- to 4-mm bore) and under isothermal conditions. Temperature programming had not yet had any significant impact in the field. Capillary columns had so far lacked adequate long-term stability i.e. operation for at least 12 months without significant deterioration. CONCLUSION- Process chromatography was expanding rapidly in the field of on-line instrumentation.Many analyses of process streams that were performed previously in laboratories were now made by process chromatographs. This had arisen for various reasons-wider realisation of the existence of such instruments by process management increased reliability of equipment shortages of personnel and possibly the most important reason the sheer economic benefits that could arise. The biggest factor in retarding the use of gas chromatography in process control was the non-continuous nature of the analysis. The present-day generation of process chromato- graphs were almost too slow in chemical process applications although apparently this was not so acute in the oil-refining field. Automatisation in the Field of Clinical Chemistry C.F. M. ROSE (Courtauld Institute of Riochernistvy T h e Middlesex Hospital London W . 1 ) MR. ROSE compared the classical methods of analysis with the Technicon system. He pointed out that in normal methods of analysis the analyst strove to obtain the maximum amount of reaction or yield of the substance subjected to analysis. In the Technicon system a totally different method of approach was used based entirely on comparative analysis. In practice this meant that it was possible to use a reaction which might be unstable in an actual comparison with a standard treated identically in regard to reaction time and condi- tions. This method failed in those instances in which the standard used was not the same or did not react in the same manner as the unknown. The method of estimating calcium in serum was to mix the specimen with a reagent namely Hyamine 2389 that stripped the calcium from the protein.Subsequently the mixture was dialysed into the recipient stream which contained murexide and was controlled at a standard low temperature and a colorimetric determination made. For serum the amount of calcium passing through the membrane was approximately 20 per cent. Considerably more calcium passed through from an aqueous calcium chloride solution and although it was possible to apply a correction factor much better results were obtained if the standard solution was slowed to the same rate of flow as the sample solution by adding a known amount of sodium chloride solution. In most clinical-chemistry laboratories the work pattern followed the same upward trend in the number of analyses required and to quote a specific example at the Middlesex Hospital it had doubled with monotonous regularity every 5 years since 1920.To refer to a particular example was the best way to illustrate these points. 136 AUTOMATIC METHODS OF ANALYSIS [PYOC. SOC. 4 d . CheflZ. Since the amount of space was usually limited it was not possible to increase the number of staff and therefore the introduction of the Technicon system opened a field of investigation. One complete machine had been purchased and most of the recommended methods had been tried. It had soon become obvious that the introduction of this machine had not solved the main problem. In fact at the end of a year only 2 determinations were in routine use. It had been felt however that if a battery of machines was used it should be possible to join together certain common analyses and thereby save considerable time and space.The initial combination of parts to implement this experiment had been expensive but an extremely careful costing carried out over the past 3 years had sh0n.n that the apparatus had paid for itself by the saving in labour cost during this time. A more detailed description of the combinations used and the methods employed was given in the January 1963 issue of the Journal of Laboratory Practice. It could not be too strongly emphasised that the combination chosen and the methods used would vary with each individual laboratory. In fact in the speaker’s laboratory no method was used exactly as published by the manufacturer. Numerous uses had been made of this system in the field of industrial chemistry and apparatus was now available for continuous Kjeldahl determination electrophoretic separation amino-acid analysis ultraviolet-absorption analyses and an 8-channel analyser in the field of clinical chemistry.The system of multiple analyses by a single machine could be the development of the future. A system was in use in Scandinavia whereby 12 different biochemical analyses were carried out on a patient before he entered the hospital. I t was claimed that by this means the length of stay in an expensive hospital bed was considerably shortened and the cost of even unnecessary investigations was more than compensated by the money saved. It was also hoped that by using a punch card or tape the results of these analyses could be fed into a computer and a diagnosis of the particular disease could be made much more quicldy or even sooner than by the usual clinical means.It might be possible by completing a biochemical profile from infancy to old age to predict a disease before it occurred or even the life span of the person concerned. This might even mean that the day of scientific medicine had reached the dawn. Differential Thermal Analysis BY R. D. MITCHELL ( T h e Macnzday Institute foy Sozl Reseavch A bevdeeiz) MR. MITCHELL said that although first developed in 1899 by Roberts-Austen for metal- lurgical studies differential thermal analysis had found most application in mineralogy and particularly in clay mineralogy. The marked increase of interest in the method over the past few years could be related directly to refinements in instrumentation and the high sensitivity of recording and accurate temperature control that could now be obtained permitted the unambiguous detection of extremely small heat effects.The scope of the method had also been greatly increased by the development of controlled-atmosphere techniques which were most valuable in the study of the thermal reactions of organic materials. Thermocouples measured the difference in temperature between a specimen and an inert reference material as both were heated side by side in a suitable block at a constant rate (usually 10” C per minute) from room temperature to the maximum desired. The difference in temperature (AT) between the specimen and the inert material and the temperature ( T ) of either the specimen or the inert materialwere recorded as they were heated.When no reaction occurred on heating the specimen the graph of AT ueYsz.1.s T or t (time) resulted in a straight line parallel to the T-axis but as soon as any reaction commenced the specimen became hotter or cooler than the inert material and a peak developed on the AT/T curve. The maximum of the peak referred to as the “peak tempera- ture” was the point at which the rate of heat input was equal to the rate of absorption of heat by the specimen. Although it did not represent a particular stage of the reaction the “peak temperature” was the most frequently quoted criterion. The area bounded by the peak was related to the energy absorbed or evolved and hence to the amount of reacting material. The method was fundamentally simple. December 19641 AUTOMATIC METHODS OF ANALYSIS 137 APPARATUS AND TECHNIQUE- Since differential thermal analysis was a dynamic method factors associated with apparatus and technique affected the thermal curves.Any apparatus had a limited number of components that had to conform to certain specifications namely a specimen holder to distribute the heat uniformly to the sample and reference material; a temperature controller to heat the specimen holder at a uniform and predetermined rate; a recording instrument to plot AT as a function of T preferably with variable amplification ; and equipment designed to control the atmosphere around the sample. Since some samples might corrode the thermo- couples thereby giving spurious peaks sheathed thermocouples were a desirable feature. Until about 5 years ago most of those interested in using differential thermal analysis had had to construct their own equipment.This had had several disadvantages; indeed much of the criticism of the technique had arisen from those who had attempted to carry out precise work with rather crude apparatus. Fortunately however there were now available commercially several well designed apparatuses and because of this st andardisation of apparatus the main emphasis now rested largely on technique. The most important factors of technique were probably the heating rate and the packing and dilution of the sample. Since dynamic heating was used the temperatures recorded for the various energy changes registered on the curve were not those obtained under static conditions. .i4 slower heating rate resulted in a smaller temperature difference being developed between the sample and the reference material and consequently in broad ill defined peaks on the AT/t curve.A rapid heating rate caused large deviations from thermo- dynamic-equilibrium temperatures the peaks were very sharp but frequently detail was lost. The thermal characteristics of the material to be examined and the objective of the investiga- tion determined to a large extent the heating rate to be adopted. Since a differential thermal curve was a record of the difference in temperature between the specimen and the reference material it was dependent only on those effects that did not occur simultaneously and equally in the two materials. I t was therefore desirable that the thermal properties (e.g. the heat capacity thermal conductivity and thermal diffusivity) of the specimen and the inert material should be compatible and this was particularly necessary when high sensitivities of recording were used.Depending on requirements hard or loose packing might be used but whichever was chosen the packing density of the sample and the inert material had to be the same. The practice of diluting the sample to at least 50 per cent. with inert reference material served to improve compatibility and incidentall). helped to prevent oxidation reactions being controlled by gas diffusion. The particle size of the sample could also affect the thermal curve in that the smaller the particle the more readily was the heat liberated; consequently the peak might be sharper. The effect predominated when the reaction had its rate controlled by the surface of the re- actants or active material as in oxidation reactions.Referring to sample weight it was possible when precision equipment for differential thermal analysis was used and the points of technique outlined above were strictly adhered to to examine samples of the order of 1 mg the method was thus within the semi-micro class. However in the field of clay mineralogy in which the thermal effects tended to be relatively small sample weights of 50 to 100 mg were customary. APPLICATION- Theoretically any change in the sample in differential thermal analysis whether physical or chemical was observable provided it was associated with either the absorption or evolution of heat. The heat-energy changes shown on the differential thermal curve might represent a single reaction or the summation of several simultaneous or even rapidly successive reactions.The endothermic or exothermic effects recorded on a differential thermal curve did not therefore necessarily indicate a specific reaction but simply a change in energy content. In order to interpret a curve a knowledge of possible reactions was required. Nevertheless the relatively simple method of differential thermal analysis provided a great deal of information on the physical and chemical behaviour of the sample under examination information that could be used to provide qualitative and quantitative analyses. The development of differential thermal analysis as mentioned above had been closely associated with mineralogy. The application of the method to inorganic compounds as distinct from minerals had so far been less extensive (except perhaps in the U.S.S.K.) but 138 SOLVENT EXTRACTION [Yroc.SOC. Anal. Chem. could be even more rewarding especially in ascertaining the thermal stabilities of compounds which incidentally required in many instances careful control of the gas atmosphere around the specimen. Identities of compounds might be checked and the technique offered a simple means of distinguishing reactants from reaction products. Solid-phase reactions phase transformations and inversions could be readily detected and the results had contributed to phase-diagram studies and to the interpretation of fusibility diagrams. Precision equipment for differential thermal analysis made obtainable quantitative results that could within limits be used for calorimetric and reaction-kinetic studies.The introduction of controlled-atmosphere techniques to differential thermal analysis had more than any other factor been responsible for the recent wide application of this method to organic materials. It was normal practice to examine organic compounds in either an oxidising atmosphere that enabled the burning characteristics to be determined or an inert atmosphere that suppressed combustion and permitted melting-points boiling-points and phase changes to be observed. The start and course of decomposition of organic materials might be followed by the technique and since changes in heat capacity and the temperature at which these occurred were indicated the method could be used to elucidate changes in structure that influenced the physical properties of a material.The technique was ideally suited for “fingerprinting” polymeric substances. For example the degree of “curve,” which involved polymerisation of unsaturated bonds and the breaking of epoxy rings could be detected as could also phase-transition temperatures in polymers. Mr. Mitchell said in conclusion that it was obvious that differential thermal analysis was finding an increasing use in analytical chemistry and that this was directly due to the high- quality commercial apparatuses that had become available in the past few years and that had resulted in a degree of standardisation hitherto impossible. The potential of the method had by no means been fully exploited and continuous development was envisaged. The latest commercial apparatuses incorporated gas-sampling equipment for identifying and determining the evolved gas associated with a particular energy change. Such a refinement would appear to be the most promising in ascertaining the mechanism of reactions (e.g. those occurring during the pyrolysis of organic materials).

ISSN:0037-9697    

DOI:10.1039/SA9640100130

出版商:RSC    

年代:1964

数据来源: RSC

摘要:

138 SOLVENT EXTRACTION [Yroc. SOC. Anal. Chem. Solvent Extraction The following is a summary of the introduction to the discussion at the Meeting of the Midlands Section held on October lst 1964 and reported in the October issue of the Proceed- ings (p. 106). Solvent Extraction BY D. BETTERIDGE (Department of Chemistry Unzuersity College of Swansea Swaizsen) DR. BETTERIDGE said that there were procedures for extracting most of the elements; the main object of the lecture was to present a few general principles that allowed the practising analyst to select the best procedure and to use it under the optimum conditions. To convert the metal ion in aqueous solution into an extractable species the charge had to be neutralised and waters of hydration had to be displaced. The species could usually be classed as chelate (e.g.8-hydroxyquinolinates and acetylacetonates) or ion-association com- pounds (e.g. (CoCl,,-) (R,NH+) and UO (NO,) (tributyl phosphate),). In principle the underlying theory was similar for both systems although the final equations might be more complex for the ion-association system since the extractable species often consisted of more entities. where D was the distribution ratio K, was the partition coefficient for the species MR, which had an overall formation constant Kf HR was the chelating agent ,8 was the fraction of free metal ion in the aqueous layer and CC,(, was the fraction of the anion R- present in the system (H. A. Laitinen “Chemical Analysis An Advanced Text and Reference,” McGraw-Hill Book Company Inc. New York Toronto and London 1960).Two extreme cases were possible- The basic equation for chelate extraction was- = KDX Kf p cc%D [HRj?ot?l December 19641 PAPERS ACCEPTED FOR PUBLIC-4TION IN T H E ANALYST 139 (1) When p = 1 i.e. the metal ion was not completely complexed then the equation often simplified to D = K*- TH+,n showing that the extraction was dependent on [HRI" L J reagent concentration and pH but independent of metal-ion concentration. When all the metal ion was complexed by the reagent D = KDx and this represented the maximum degree of extraction regardless of changes in reagent concentration or pH. The effect of varying pH and reagent concentration had been demonstrated with 1-(2-pyridylaz0)-2-naphthol and manganeser1. Chelate systems were often unselec- tive and this might sometimes be advantageous.The selectivity might be improl-ed by control of pH and reagent concentration or by the addition of a masking agent. Since equilibrium constants were known for many chelate systems it was comparatively easy to use them sensibly. The amount of metal ion that could be extracted was often less than that extractable by ion-association systems because of the lower solubility of chelates or chelating reagents. Ion-association systems were often selective. Long-chain alkylamines and alkyl phosphates and phosphine oxides had been singled out for attention. They might be super- ficially compared with ion-exchange resins and this had been demonstrated by separating iron and nickel in 4 M hydrochloric acid with di-n-octylmethylamine. The effects of "inert" salts and solvents were mentioned.The improvement in the extraction of a chelate when a solvent that would displace further waters of hydration was added was explicable. The dramatic improvement when cyclohexane was used instead of benzene (T. V. Healey J . Inorg. Nucl. Chem. 1961 19 328) was not so easy to understand. An extractant adsorbed on a suitable polymeric material might be useful in effecting separation by reverse-phase chromatography. Extraction data were useful in predicting feasible separations and suitable conditions. 4-(2-Pyridylazo)- 1 - naphthol had been shown to be a suitable indicator for titrating 0 . 1 ~ copperII with EDTA. The general equation could be used to predict the optimum conditions for use and to calculate the probable indicator error. (2) The scope of the two systems was briefly reviewed. Extractive indicators might be useful for highly coloured solutions.

ISSN:0037-9697    

DOI:10.1039/SA9640100138

出版商:RSC    

年代:1964

数据来源: RSC

摘要:

December 19641 PAPERS ACCEPTED FOR PUBLIC-4TION IN T H E ANALYST 139 Papers Accepted for Publication in The Analyst THE following papers have been accepted for publication in The Agzabsf and are expected to appear in the near future. “Photometric Determination of Titanium in Ores Rocks and Minerals with Dianti- “The Determination of Micro Amounts of N-Isopropyl-N’-phenyl-fi-phenylenediamine,” “An Automatic Method for Determining Nitrate and Nitrite in Fresh and Saline M‘aters,” “The Effect of Nitrilotriacetic Acid Impurity on the Standardisation of Solutions of “A Modified Method for Determining Traces of Xitrilotriacetic Acid in Ethylenediamine- “The Determination of Carbon in Sodium,” by J. A. J. Walker and E. D. France. “The Polarographic Determination of Molybdenum in High-temperature Alloys,” by pyrylmethane,” by P. G. Jeffrey and G. K. E. C. Gregory. by J. R. Davies. by A. Henriksen. Ethylenediaminetetra-acetic Acid,” by R. N. P. Farrow and A. G. Hill. tetra-acetic Acid,” by R. N. P. Farrow and A. G. Hill. J. B. Headridge and D. P. Hubbard. ‘‘L4 Spectrophotometric Method for Determining the Aflatoxins,” by J. Nabnej. and B. I?. Nesbitt. “Colorimetric Determination of Copper in Plants,” by K. R. Middleton. “The Photometric Determination of Zinc in Nickel and Nickel Alloys for Use in Electronic “Determination of Small Amounts of Long-chain Alkylamines in Aqueous Solution,” Devices,” by T. R. Andrew and P. N. R. Nichols. by H. M. N. H. Irving and A. D. Damodaran. 140 CHANGES IN THE REGISTER OF MEMBERS [Proc. SOC. Anal. Clzevz. Changes in the Register of Members DEATH WE record with regret the death of James Laurence Campbell.

ISSN:0037-9697    

DOI:10.1039/SA9640100139

出版商:RSC    

年代:1964

数据来源: RSC

摘要:

140 CHANGES IN THE REGISTER OF MEMBERS [Proc. SOC. Anal. Clzevz. Publications Received The publications listed below have been received by the Editor of The A~zalyst in which journal Book Reviews will continue to appear. INTRODUCTION TO ELECTROANALYSIS. By 1,. L. LEVESON. Pp. viii + 120. London Butter- ANALYSIS OF CALCAREOUS MATERIALS. Pp. viii + 451. London Society of Chemical Industry. Lvorth & Co. (Publishers) Ltd. 1964. Price 15s. 1964. Price 90s. (S.C.I. Monogyaph No. 18) RADIOCHEMICAL ANALYSIS ACTIVATION ANALYSIS INSTRUMENTATION RADIATION TECHNIQUES Edited by JAMES R. DE\'oE. AND RADIOISOTOPE TECHNIQUES JULY 1963 TO JUNE 1964. Pp. xii + 83. Washington D.C. U.S. Government Printing Office. 1964. Price 50 cents. ,\rational Buveau of Standavds Techqaical hTote 248. HANDBOOK OF INDUSTRIAL INFRARED ANALYSIS.By ROBERT G. WHITE. Pp. xiv + 440. Kew 1-ork Plenum Press. 1964. Price $19.50. SYMMETRY IN THE SOLID STATE. Pp. xii + 344. New York and Amsterdam W. A. Benjamin Inc. THEORIE UND PRAXIS DER GRAVIMETRISCHEN ANALYSE. Part 111. BESTIMIMUNG DER NICHT- METALLE. By DR. LASZL~ ERDEY. Pp. 340. Budapest Akadkmiai Kiadb. 1964. Price $13.00; 93s. AUTOMATIC METHODS IN VOLUMETRIC ANALYSIS. By Il. C. M. SQUIRRELL B.Sc. F.R.I.C. Pp s + 201. London Hilger & Watts Ltd. 1964. Price 42s. ROKALL) C. JOHNSON. 1964. London The Royal Institute of Chemistry. 1964. Price 6s. By ROBERT S. KNOX and ALBERT GOLD. 1964. Price (cloth) $11.00; (paper) $6.55. COORDINATION CHEMISTRY THE CHEMISTRY OF METAL COMPLEXES. BY. FRED I~ASOLO and Pp. xii + 180. New Uork and Amsterdam I&-.A. Benjamin Inc. Pp. iv + 47. Price (cloth) $4.35; (paper) $2.15. PRINCIPLES OF ATOMIC ORBITALS. By N. N. GREENWOOD M.Sc. Sc.D. F.R.I.C. (Agonographs for Teachevs No. V I I I ) ANALYTICAL METHODS FOR PESTICIDES PLANT GROWTH REGULATORS AND FOOD ADDITIVES. Volume IV. HERBICIDES. Edited by GUNTER ZWEIG. Pp. xvi + 269. New- York and London Academic Press. MICRO-ANALYSIS IN MEDICAL BIOCHEMISTRY. By I. D. P. WOOTTON Ph.D. M.A. M.B. B.Chir. F.R.I.C. M. C. Path. Fourth Edition. Pp. x + 254. London J. & A. Churchill Ltd. 1964. Price 30s. MANUEL PRATIQUE DE CHROMATOGRAPHIE EN PHASE GAZEUSE. Edited by JEAN TRANCHANT. Pp. ii + 231. Paris Masson et Cie. 1964. Price 36 F. MISES AU POINT DE CHIMIE ANALYTIQUE ORGANIQUE PHARMACEUTIQUE ET BROMATOLOGIQUE. Douzikme Skrie. Edited by J.-A. GAUTIER and P. MALANGEAU. Pp. ii + 239. Paris Masson et Cie. 1964. Price 60 F. BIONEDICAL APPLICATIONS OF GAS CHROMATOGRAPHY. Edited by HERMAN A. SZYMANSKI. Pp. iv + 324. New York Plenum Press. 1964. Price $12.50. DIE ROHSTOFFE DES PFLANZENREICHS. Edited by CONSTANTIN VON REGEL. Part 3. ORGANIC ACIDS. By G. C. \ i 7 ~ ~ ~ ~ ~ ~ . Pp. vi + 194. Weinheim J . Cramer. 1964. Price 68 DM. BRITISH STANDARD 3762 1964. METHODS OF SAMPLING AND TESTING DETERGENTS. Pp. 152. London British Standards Institution. 1964. Price 42s. 1964. Price 86s. ; (subscribers to the series) 80s.

ISSN:0037-9697    

DOI:10.1039/SA9640100140

出版商:RSC    

年代:1964

数据来源: RSC

摘要:

December 19641 NOTICES 141 Notices PURE AND APPLIED CHEMISTRY VOLUME 9 No. 1 1964 THIS issue contains the Special Lectures presented at the Third International Symposium on the Chemistry of Natural Products held in Kyoto Japan April 12th to 15th 1964. A4mong the papers are “High resolution mass spectrometry of natural products,” by K. Biemann (U.S.A.) ; “Isotope labelling and mass spectrometry of natural products,” by C. Djerassi (U.S.A.) ; “Recent advances in X-ray analysis of natural product structures,” by J. Monteath Robinson (U.K.). Pure and AppZied Chemistry is published irregularly four issues per volume at LG( 618) per volume. Reprints may be purchased; all enquiries should be addressed to the publishers Butterworths 4-5 Bell Yard Temple Bar London W.C.2 England. BRITISH STANDARDS INSTITUTION DRAFT SPECIFICATION A FEW copies of the following draft specification issued for comment only are available to members of the Society and can be obtained from the Secretary The Society for Analytical Chemistry 14 Belgrave Square London S.W.1. Draft Specification prepared by Panel TLE/5/3/ 1-Methods of Analysis of Cathode Nickels. D 64/12131-Draft B.S. Methods for The Analysis of Nickel for Use in Electronic Tubes and Valves Part 3 Determination of Carbon (Part 3 of R.S. 3727). THE OFFICAL JOURNAL OF THE INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY THE CHEMICAL SOCIETY LIBRARY SUBSCRIBERS THE Chemical Society has agreed with the approval of the Chemical Council to extend the facilities of its Library to Institutions Firms and other Corporate Bodies in the United Kingdom and the Republic of Ireland.Such subscribers will subject to the regulations for subscribers to the Chemical Society’s Library have the same rights as any individual entitled to use the Library. The Library’s charges are as follows- Loan service postage actual cost ; packing 6d. per parcel. Photocopying service basic charge per article 2s. ; additional charge per page copied Airmail postage (if required) will be charged extra. 6d. All charges for photocopying postage etc. will be dealt with on a credit basis and be settled by means of a periodical statement of account that will be submitted by the Chemical Society. Alternatively individuals attending the Library in person may normally obtain immediate photocopies on a “cash and carry” basis at a cost of 9d. per exposure (one or two pages according to size).Forms of request for enrolment may be obtained from the General Secretary The Chemical Society Burlington House London W. 1. SOCIETY OF CHEMICAL INDUSTRY THE London Section of the Society of Chemical Industry is to hold a Symposium on “Inorganic Single Crystals” on April 12th and 13th 1965 at the School of Pharmacy Univer- sitv of London 29-39 Brunswick Square London W.C. 1. Included in the Afternoon Session for April 13th is a paper entitled “Analysis of Ruby and Sapphire by Spark Source Mass Spectrometry,’’ by H. B. Clarke and L. G. Harvey (Admiralty Materials Laboratory). Further details of the Symposium together with a registration form may be obtained from the Assistant Secretary Society of Chemical Industry 14 Belgrave Square London S.W. 1.142 FORTHCOMING MEETINGS [Pvoc. SOC. Anal. Chem. A.S.T.M. NATIONAL SYMPOSIUM ON HYDROCARBON ANALYSIS-FUTURE DEVELOPMENT AND APPLICATIONS HOUSTON TEXAS JANUARY 22ND AND 2 3 ~ ~ 1965 THE symposium will be introduced by two papers on the theme “Where we are and a look ahead.” Four papers will present potential analytical developments in mass spectrometry nuclear magnetic resonance analysis absorption spectroscopy and applications of gas chroma- tography. The approach to integrated methods will be covered by four papers dealing with petrol and blended fuels kerosene high-boiling aromatic hydrocarbons and heavy petroleum fractions. Methods for determining impurities in hydrocarbons and non-hydrocarbon materials will be discussed in five papers. The symposium will be concluded by a review of the leadership past present and future in this area by the sponsor of the Symposium Research Division IV of Committee D-2.FIRST INTERNATIONAL CONFERENCE ON THERMAL ANALYSIS ABERDEEN 6-~TH SEPTEMBER 1965 THERMO-ANALYTICAL techniques particularly thermogravimetry and differential thermal analysis are becoming increasingly common in research and industry and are now being applied in fields quite distinct from those for which they were developed. The techniques too have developed differently in different countries depending on the outlook of the research workers and the apparatus available. Consequently it has been considered by many interested parties that the time is now ripe for a broadly based international interdisciplinal convention at which problems questions of interpretation and results can be discussed.Moves in this direction have now been made by a small international committee that is currently organising the First International Conference on Thermal Analysis to be held at Aberdeen Scotland on 6-9th September 1965. The main theme of the Conference will be “Thermal Techniques and their Applicability,’’ and circulars giving details are being distri- buted. These together with any further information may be obtained by people in this country from Dr. R. C. Mackenzie The Macaulay Institute for Soil Research Aberdeen Scotland or Dr. J. P. Redfern Department of Chemistry Battersea College of Technology London S.W.ll or for those abroad from any other member of the committee (Prof. Ing. Dr. R. Barta Micurinova 5 Praha 6-Hradcany Czechoslovakia; Prof. I,. G. Berg Khimi- cheskii Fakultet Gosuniversitet Kazan U.S.S.R. ; Prof. Dr. L. Erdey Department of General Chemistry Technical University Budapest Hungary ; Dr. C. B. Murphv Bldg. 5-Rm. 159 General Electric Company 1 River Road Schenectady 5 New York 12305 U.S.A. ; Prof. T. Sudo Geologcical and Mineralogical Institute Faculty of Science Tokyo University of Education 0 tsukakubo-machi Bunkyo-ku Tokyo Japan.) PRINTED BY W. HEFFER 8r SONS LTD.. CAMBRIDGE. ENGLAND.

ISSN:0037-9697    

DOI:10.1039/SA9640100141

出版商:RSC    

年代:1964

数据来源: RSC