ISSN:0003-2654    

DOI:10.1039/AN95479FX025

出版商:RSC    

年代:1954

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN95479BX027

出版商:RSC    

年代:1954

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN95479FP059

出版商:RSC    

年代:1954

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN95479BP067

出版商:RSC    

年代:1954

数据来源: RSC

摘要:

MAY, 1954 THE ANALYST Vol. 79, No. 938 PROCEEDINGS OF THE SOCIETY FOR ANALYTICAL CHEMISTRY ANNUAL GENERAL MEETING THE Eightieth Annual General Meeting of the Society was held at 4.30 p.m. on Wednesday, March 3rd, 1954, in the meeting room of the Royal Society, Burlington House, London, W.l. The Chair was taken by the President, Dr. D. W. Kent-Jones, F.R.I.C. The financial state- ment for 1953 was presented by the Honorary Treasurer and approved, and the Auditors for 1954 were appointed. The Report of the Council for the year ending March, 1954 (see pp. 25&260>, was presented by the Honorary Secretary and adopted. The Scrutineers, Messrs. G. B. Thackray and B. J. Walby, reported that the following had been elected officers for the coming year- President-D. W. Kent- Jones , B.Sc., Ph.D., F.R.1 .C.Past Presidents serving on the Council-Lewis Eynon, G. W. Monier-Williams, J. R. Vice-Presidents-C. A. Adams, A. J. Amos and T. McLachlan. Honorary Treasurer-J. H. Hamence. Honorary Secretary-K. A. Williams. Honorary Assistant Secretary-N. L. Allport. Other Members of CounciZ-The Scrutineers further reported that 366 valid ballot papers had been received and that votes had been cast in the election of Ordinary Members of Council as follows-J. Haslam, 298; C. L. Hinton, 250; R. E. Stuckey, 250; C. Whalley, 248; D. C. M. Adamson, 227; A. G. J. Lipscomb; 223; W. C. Johnson, 222; B. Bagshawe, 186. The President declared the following to have been elected Ordinary Members of Council for the ensuing two years-D. C. M. Adamson, J. Haslam, C. L.Hinton, A. G. J. Lipscomb, R. E. Stuckey and C. Whalley. A. L. Bacharach, R. C. Chirnside, Miss Mary Corner, D. C. Garratt, H. W. Hodgson and H. M. N. H. Irving, having been elected members of the Council in 1953, will, by the Society’s Articles of Association, remain Ordinary Members of Council for 1954. T. W. Lovett (Chairman of the North of England Section), R. S. Watson (Chairman of the Scottish Section), A. M. Ward (Chairman of the Microchemistry Group), A. A. Smales (Chairman of the Physical Methods Group) and L. J. Harris (Chairman of the Biological Methods Group) will be ex-o$icio Members of the Council for 1954. After the business outlined above had been completed, the meeting was opened to visitors, and Dr. E. B. Hughes, F.R.I.C., delivered the Bernard Dyer Memorial Lecture (see pp.261-267). At the close of the meeting the President presented Dr. Hughes with the Bernard Dyer Memorial Medal. Nicholls and George Taylor. ORDINARY MEETING AN Ordinary Meeting of the Society, organised by the Biological Methods Group, was held at 2.30 p.m. on Wednesday, April 7th, 1954, at the Wellcome Research Institution, Euston Road, London, N.W.l. The meeting was in the form of a Symposium on “The Comparison of Chemical and Biological Estimation of Drugs in Quantitative Pharmacology” and, after the Chairman’s introduction, the following papers were presented and discussed : “Digitalis : Chemical Methods,” by J. M. Rowson, Ph.D., M.Sc., Ph.C., F.L.S. ; “Digitalis: Biological Methods,” by G. A. Stewart, B.Sc.; “Vitamin D: Chemical Methods,” by J.Green, Ph.D., A.R.I.C.; “Vitamin D : Biological Methods,” by M. E. Coates, Ph.D. , F.P.S. ; “Chemical and Biological Methods for the Estimation of Adrenaline and Noradrenaline,” by G. B. West, Ph.D., B.Pharm., Ph.C. ; “Routine Methods used in the Quantative Estimation of Adrenaline,” by G. F. Somers, Ph.D., Ph.C. 249 Professor J. H. Burn, M.A., F.R.S., was in the Chair. (A fuller account will be published later.)250 PROCEEDINGS [Vol. 79 NEW MEMBERS Alfred Bacon, Assoc.Met. (Sheff.) ; Ronald Ernest Bailey, B.Sc. (Lond.), A.R.C.S. ; Geoffrey William Barrell, B.Sc. (Melbourne), A.R.A.C.I. ; James Wennington Boyd, B.Sc., A.R.I.C., A.F.Inst.Pet. ; Nathaniel Carmichael, B.Sc. (McGill), M.Sc. (West. Ont.), A.R.I.C. ; Thomas Joseph Leonard Cuthbert, B.Sc.(Manc.), A.M.C.T. ; Harold Ainsworth Harrison, M.Sc., Ph.D. (Manc.), F.R.I.C.; Stephen Claude Jolly, B.Phann., B.Sc. (Lond.), A.R.I.C., Ph.C.; Frank Mercer Lever, B.Sc. (Lond.), A.R.C.S., F.R.I.C., F.I.M. ; Alfred John Maisey, A.R.I.C. ; Frederick Cecil Barron Marshall, B.Sc., Ph.D. (Lond.), D.I.C., F.R.I.C. ; Miss Adele Mittwoch, M.Sc. (Lond.) ; Derek Peter Rowlands, B.Sc. (Sheff.), A.R.I.C.; John Paterson Young, B.Sc., A.R. I.C. Henry Giveen Hamilton Alner, A.R.I.C. ; Thomas Joseph Hayes; Ian Peter Forshaw; Emmanuel St. Clair Fitzgerald Jones; Robert Kerr, B.Sc. (Lond.), A.R.I.C. ; Ernest Arthur Schofield; William Irvine Stephen, B.Sc. (Aber.), Ph.D. (Binn.), A.R.I.C. ; Laurence George Stonhill, B.Sc. (Lond.) ; Mrs. Mary Patricia Taylor, B.Sc.(Liv.) ; Thomas Summers West, BSc. (Aber.), Ph.D. (Birm.). Roy Edward Cockaday, B.Sc. (Leeds) ; David Gideon Colquhoun ; Albert John Nutten, B.Sc. (Aber.), Ph.D. (Birm.), A.R.I.C. ; Richard Pickup, BSc. (Vic.), F.R.I.C. ; Robert Taylor, M.A., Ph.D. (Cantab.). Desmond Ronald Curry, B.Sc. (Dunelm.), A.R.I.C. ; Reginald Roy Muir ; Bernard Stephen Noyes. DEATHS WE regret to record the deaths of ORDINARY MEMBERS ELECTED MARCH 3RD, 1954 JUNIOR MEMBERS ELECTED MARCH 3RD, 1954 ORDINARY MEMBERS ELECTED APRIL 6TH, 1954 JUNIOR MEMBERS ELECTED APRIL 6TH, 1954 Samuel Ernest Melling Thomas Arthur Nightscales Dorothy Elsie Stillwell. SCOTTISH SECTION AN Ordinary Meeting of the Section was held at 7.15 p.m. on Thursday, March l l t h , 1954, in the George Hotel, Edinburgh, 2. A lecture entitled “Applications of Infra-red Spectroscopy” was given by H.A. Willis, B.Sc. (see summary below). APPLICATIONS OF INFRA-RED SPECTROSCOPY MR. H. A. WILLIS traced the development of the study of infra-red spectroscopy from the original discovery by Herschel in 1800 of radiation in sunlight beyond the red region that was capable of refraction and that was detectable by its thermal effects. The science advanced with technical achievements in instrument design, i.e., with the production of light sources, of methods of measuring the radiation and of materials suitable for the manufacture of prisms. The study of the absorption of infra-red light by a variety of compounds led to the discovery that similar materials had similar spectra but that there was dependence in detail on the specific molecular structure. This was illustrated by reference to the spectra of methacrylate polymers that differed in the nature of the esterifying alcohol.All possessed absorptions charac- teristic of the presence of ester groupings, but varied markedly in the regions associated with the hydrocarbon residues. A comparison of the features involved in the design of single-beam and double-beam spectrometers was made, and the advantages of the double-beam instruments, e g . , the ease of compensation for solvent and for water vapour and carbon dioxide in the air, were stressed. The methods of preparing samples of different physical characteristics were indicated. The application of the infra-red method to the determination of the structure of an unknown substance was outlined.The first stage was the determination of the spectrum in the region of 2 to 15 p. The strong absorption bands were used for aMay, 19541 PROCEEDINGS 251 preliminary identification of structural type by reference to correlation tables. The various divisions of these tables were discussed and it was pointed out that, although several interpretations were often possible, many of these could be eliminated by the consideration of such factors as the elementary analysis of the compound. After the various possibilities had been reduced by trial and error methods, the final matching with a spectrum of a substance of known structure led to a complete structural apprecia- tion. The examples were selected from the plastics field and included the identification of a substance, or of substances, used as plasticisers, particularly the alkyl and aryl phosphates and the alkyl phthalates.The lecture concluded with the description of some methods used in the deter- mination of the components of mixtures by infra-red techniques. These included the use of mixtures of standard composition for comparison and, in the example of the determination of monomer in Perspex, the introduction into the beam of the instrument of ‘both a standard sheet of monomer-free Perspex and solutions of the monomer at dfferent concentrations in a transparent solvent. This gave a calibration curve in which the intensity of a particular absorption due to the monomer, relative to the background due to the polymer, was plotted against the concentration of the standard solution introduced.The-concentration of monomer in any sheet of Perspex could then be assessed by examining the intensity of the same absorption peak for that sheet. A JOINT Meeting of the Section with the Aberdeen and District members of the Chemical Society, the Royal Institute of Chemistry and the Society of Chemical Industry was held at 7.30 p.m. on Thursday, April Ist, 1954, in Robert Gordon’s Technical College, Aberdeen. The Chair was taken by Professor R. M. Barrer. A lecture entitled “Some Applications of the Newer Techniques in Analytical Chemistry’’ was given by Dr. J. R. Nicholls, C.B.E., F.R.I.C. (see summary below). SOME APPLICATIONS OF THE NEWER TECHNIQUES IN ANALYTICAL CHEMISTRY DR. J. R. NICHOLLS said that the classical techniques of analytical chemistry were primarily designed for the separation of the material to be determined in a form capable of measurement either gravimetrically or volumetrically.This involved the application of chemical principles to remove interfering substances and to separate the material in a physical state such that a desired measurement of weight or volume could be made. The newer techniques were concerned with separations effected by the application of recently developed chemical principles or by the use of physical processes, and the final determination might involve the measurement of any physical property. There were few new chemical principles that had been applied in such a way as t o warrant description as new techniques; but physical operations had been so widely developed of recent years that there was a danger of them being regarded as tools of the skilled technician rather than as part of the equipment of an analyst.The modern analytical chemist found it essential to be familiar with at least some of them, as by their means he was able to acquire information unobtainable by classical methods. Such techniques were not in place of, but were complementary and supplementary to, classical ones. They were all specialised tools, and as such had their limitations; but the fully qualified craftsman must have them in his tool-chest so that they could be used either singly or in combination to obtain the maximum information and the best results. Examples were given of some of the newer techniques involving- (a) for separation : complexing reagents (chelates, sequestering agents and clathrates) ; extraction with immiscible solvents ; distillation (fractional and mole- cular) ; adsorption (ion exchange and chromatography) ; electrophoresis ; (b) for identification : microscopy (direct and fluorescent) ; crystallography (Barker index and X-ray) ; photography (high-speed) ; (c) for determination : thermogravimetric analysis ; titration of weak acids and bases in non-aqueous solvents ; micro-methods ; instrumentation ; spectrography ; ultra-violet rays ; infra-red rays ; X-rays ; flame photometry ; polarography ; isotopes; radioactivation ; gas analysis (conductance and acoustic) ; mass spectrometry. Reference was made to the use of statistics and to the employment of approximate Some applications of several of these techniques in medical and simplified methods.chemistry, clinical analysis, plastics analysis and forensic work were described.252 PROCEEDINGS [Vol. 79 PHYSICAL METHODS GROUP THE Forty-third Ordinary Meeting of the Group was held at 7 pm. on Tuesday, February gth, 1954, in the Meeting Room of the Chemical Society, Burlington House, London, W.l. The Chair was taken by Mr. A. A. Smales, B.Sc., F.R.I.C. The following papers on “Coulometric Analysis” were presented and discussed : “The Principles of Coulometric Analysis,” by E. Bishop, B.Sc., A.R.T.C., A.R.I.C. (see summary below) ; “An Automatic Coulometric Titrimeter,” by N. Bett, B.Sc., G. Morris, Ph.D., F.Inst.P., and W. Nock, M.A., Grad.1.E.E.; “Some Apparatus and Techniques for Semi- micro Coulometric Analysis,” by G. Packman, M.Sc., A.R.I.C. (see summary below). THE PRINCIPLES OF COULOMETRIC ANALYSIS MR. E. BISHOP said that Faraday’s classical laws related the quantity of electricity to the quantity of ion discharged at an electrode in an electrolytic process. Instead of the amount of substance produced at an electrode being weighed, the weight could be calculated from the amount of electricity (ampere-seconds or coulombs) passed and the chemical equivalent of the substance, provided the process proceeded with 100 per cent. efficiency. On this basis were founded the coulometric methods of analysis, in which the number of coulombs required for a reaction was measured. These methods might be direct, when the test material was plated on to or anodically stripped from an electrode, or oxidised or reduced in solution ; or indirect, when an intermediate material, such as bromine or ferrous ion, was generated at the electrodes and used to produce a chemical reaction. The first type usually made use of constant-voltage electrolysis and the second made use of constant-current electrolysis, Instead, therefore, of a standard solution of acid, base, oxidising, reducing or pre- cipitating agent being added from a burette, as in volumetric titrations, the reagent was generated electrolytically and the amount was measured electrically in coulometric titrations.As the quantity of electricity corresponding to 10-l2 equivalent could be readily measured, the method had a high sensitivity.The principles on which the various methods of electrolysis, reaction and detection of end-point were based were reviewed; and the status of the method was examined. SOME APPARATUS AND TECHNIQUES FOR SEMI-MICRO COULOMETRIC ANALYSIS MR. G. PACKMAN said that several types of coulometer, gas, silver and iodine, had been investigated for use in work on a milligram scale, and the last had been found the most satisfactory. An electrolytic cell of 2.5 ml capacity and an indicator-electrode system had been designed, suitable for both controlled-potential and constant-current operation. A procedure had been devised for when it was necessary to reduce an element before coulometrically oxidising it, and for performing both operations with the same cell and electrodes.Difficulties arose that did not appear in more usual methods in which the sample, already in the lower oxidation state, could be added to a suitable medium (which had been pre-adjusted to end-point conditions) and then oxidised. A combination of controlled-potential reduction and constant-current oxidation had been found satisfactory, and the performance had been tested over the range 5 to 50 micro-equivalents, ferrous ion being used in the first instance as a substitute. THE Forty-fourth Ordinary Meeting of the Group was held at 6.30 p.m. on Tuesday, March 9th, 1954, in the Meeting Room of the Chemical Society, Burlington House, London, W.1. Mr. A. A. Smales, B.Sc., F.R.I.C., was in the Chair. The following papers on “Differential Refractometry” were presented and discussed : “Differential Refractometers: Theory and Construction,” by G.H. F. Seiflow, M.A., A.1nst.P. ; “An Application of Differential Refractometry,” by R. Hill, B.Sc., A.R.I.C. ; “Interferometric Refractometry: A Survey of the Methods,” by H. G. Kuhn, MA., D.Phi1.; “The Use of a Rayleigh Interferometer for Estimating Trichloroethylene,” by R. E. Jahn, M.A. INTERFEROMETRIC REFRACTOMETRY : A SURVEY OF THE METHODS DR. H. G. KUHN said that two types of instrument were used for the measurement of refractive indexes by interference. The Jamin refractometer was b a e d on inter- ference alone and used an extended source, whilst the Rayleigh refractometer wasMay, 19541 ANNUAL REPORT OF THE COUNCIL, MARCH, 1954 253 essentially a diffraction grating with a slit source. The latter type of instrument suffered from an extreme smallness of the fringe spacing; this made the use of a fiduciary fringe system necessary, instead of a cross-wire, which complicated the design. The thick, accurately worked glass plates of the conventional Jamin refractometer gave rise to difficulties that could easily be avoided if pairs of thin plates, with spacers, were used instead. Limitations of interferometric methods making use of compensators and white- light fringes were discussed. The wide range of applications of interferometric refractometry to problems of chemical analysis of gases and liquids was stressed. I t appeared that the method was strangely neglected in this country; this fact might be due to the lack of a sufficiently simple and robust instrument on the home market.

ISSN:0003-2654    

DOI:10.1039/AN9547900249

出版商:RSC    

年代:1954

数据来源: RSC

摘要:

May, 19541 ANNUAL REPORT OF THE COUNCIL, MARCH, 1954 253 Annual Report of the Council: March, 1954 IMPORTANT changes have been made in the constitution of the Society in the past year, and these reflect t.he developments that have taken place over the last decade. The formation of an Association of Public Analysts designed to look after the professional welfare and needs of public analysts was foreshadowed in last year’s Annual Report, and this body has been formed during the year now under review with support from the Society, this support including financial aid on a substantial scale and office help. It is now felt that the Association on the one hand, and the Royal Institute of Chemistry on the other, can satisfactorily deal with the professional life of all analytical chemists, and that the Society can therefore make the furtherance of analytical chemistry its main concern.Reflecting this development, an extraordinary general meeting of the Society approved by an overwhelming majority in December, 1953, the change of name to “The Society for Analytical Chemistry.” At the same time a new grade of junior membership was instituted to encourage younger chemists to join the Society and enjoy its privileges at a lower sub- scription than that of ordinary members. The end of 1953 saw the last issue of British Abstracts C, the analytical abstracts published by the Bureau of Abstracts. The Society gave up the production of abstracts in 1949, and from 1950 to 1953 has supplied its members and subscribers to The Analyst with Abstracts C. Now that these are no longer forthcoming, the Council of the Society has undertaken the production of a journal, to be known as Analytical Abstracts, to replace Abstracts C.The Editorial Committee of this journal sits under the Chairmanship of Mr. R. C. Chirnside; the Editor of the journal is Dr. Norman Evers, and the Assistant Editor is Mr. €3. J. Walby. The roll of the Society now numbers 1646, an increase of 54 over the membership of a year ago. CORONATION OF HER MAJESTY QUEEN ELIZABETH 11-An Humble Address of congratula- tion was presented to Her Majesty on the occasion of her Coronation in June, 1953, and this address was graciously received and acknowledged. HoNouRs-The congratulations and good wishes of the Council have been extended to Professor E.C. Dodds on the honour of knighthood conferred on him by H.M. The Queen. Congratulations are also extended to Dr. J. B. Firth on the award of the C.B.E., Mr. F. R. Ennos on the award of the I.S.O. and Mr. W. C. Johnson on the award of the M.B.E. The Council heard with great satisfaction and delight of the election of Sir Harry Jephcott as President of the Royal Institute of Chemistry during the year. Their congratulations are also extended to- Professor Sir Robert Robinson, O.M., F.R.S., on receiving the Priestley Medal, the Dr. F. H. Carr on his election to an Honorary Fellowship of the Imperial College of Mr. C. H. Manley on his election as President of the Priestley Club, Leeds. Professor H. Burton on his election as Honorary Treasurer of the Royal Institute of Mr.A. Harvey on his election as Honorary Secretary of the International Union of highest honour in American chemistry. Science and Technology. Chemistry. Leather Trades Chemists’ Societies.254 ANNUAL REPORT OF THE COUNCIL, MARCH, 1954 [Vol. 79 Mr. R. C. Chirnside on his election as Vice-president of the Analytical Section of the International Union of Pure and Applied Chemistry. Dr. D. W. Kent- Jones on his election as Honorary Secretary of the newly-formed Foods Division of the Applied Chemistry Section of the International Union of Pure and Applied Chemistry . LONG MEMBERSHIP-The congratulations and good wishes of the Council are extended to A. E. Brown, T. A. Nightscales and W. H. Simmons, who have completed 50 years of membership of the Society, and to S.G. Clifford, R. H. Ellis, W. A. Gibbings, W. R. Hardwick, J. McLaren and W. H. Woodcock, who have completed 40 years of membership. DEATHS-The Council regrets to have to record the deaths of the following members- Mrs. M. B. Craven P. G. T. Hand J. Myers W. Dickson E. 0. Heinrich J. R. Stubbs G. E. Forstner W. C. Hughes W. Thorp Mrs. Craven was educated at Ardwick Higher Grade School and the Faculty of Technology, Victoria University, Manchester, 1905-09, holding a post-graduate scholarship under Professor W. J. Pope. She was chemist to the Pilkington Tile and Pottery Co. Ltd., and later to the Clifton and Kersley Coal Co. In 1916 she returned to the College of Technology and remained there until she retired in 1952, becoming Head of the Inorganic Chemistry Laboratories.She joined the Society in 1944 and was elected an Associate of the Institute of Chemistry in 1920. Dickson was trained a't the Glasgow and West of Scotland Technical College, having spent three years with R. R. Tatlock & Thomson, two years in public works and two years in teaching and analytical work at Edinburgh Central School of Pharmacy. He was later Chief Chemist at the Regent Factory, Linlithgow, of Nobel Explosives Co. Ltd., Research Chemist at Ardeer, and Chief Chemist, Eley Bros. (I.C.I.). After 1925 he was transferred to I.C.I. (Metals Division), Birmingham, remaining there until his retirement in 1940. He joined the Society in 1906 and was elected a Fellow of the Institute of Chemistry in 1938. He died a t the age of 71. Forstner was born in 1901 and educated at the West Bromwich Secondary School and the University of Birmingham, where he obtained the degree of M.Sc.He joined J. Lyons & Co. Ltd. in 1925 and worked with them as an analytical and research chemist until his death. He was elected A.I.C. in 1925 and F.I.C. in 1943. Hand was educated at King's College, London, and was an articled pupil of Messrs. Harrison & Self. After the war of 1914-18 he became research assistant, Chemical Warfare Committee, remaining until 1925. He then joined British Xylonite Ltd. as chemist, and at the time of his death was consultant to B.X. Plastics Ltd. He joined the Society in 1930, and was elected A.I.C. in 1921 and F.I.C. in 1925. Heinrich became B.S. (University of Ca1ifornia)'in 1908, and lived mainly in California, though he worked for a time in Tacoma, Washington, as City Chemist.He was Research Associate in Police Science in his University and a consulting expert in legal chemistry and microscopy. He joined the Society in 1935 and died at the age of about 72. He served in the Special Brigade, Royal Engineers, from 1914 to 1918. After the war he went to Billingham, where from 1922 he was Chief Analyst to I.C.I. (F. & S.P.) Ltd. He joined the Society in 1939 and died at the age of 62. Myers became a Fellow of the Institute of Chemistry in 1920 and was for many years chief metallurgical assistant to G. Rudd Thompson at Newport, later becoming a partner in the practice. He was elected a member of the Society in 1923 and died at the age of 71. Stubbs was born in 1880 and educated at Witton Grammar School and University College, Liverpool, where he obtained the degree of M.Sc. He was assistant to Professor Campbell Brown and W.Collingwood Williams, Public Analysts, Liverpool. During the 1914-18 war he was Captain, R.A.O.C., and afterwards became Public Analyst and Official Agricultural Analyst for Lancashire and Public Analyst for various towns in the county. He became a Fellow of the Institute of Chemistry (Branch E) in 1911. He joined the Society in 1920 and served on the Council in 1929-30 and 1932-39. He was a Vice-president of the Society, 1940-42, and Secretary of the North of England Section, 1932-39, and its Chairman, 1940-42. For three years he was private assistant to J. E. Thorpe He joined the Society in 1936.He died at the age of 58. Hughes joined Brunner, Mond & Co. at Northwich in 1906. Thorp was born in 1866.May, 19541 ANNUAL REPORT OF THE COUSCIL, MARCH, 1954 255 and then worked at Leeds under Smithells and at University College, London, under Ramsay. He became B.Sc. (London and Leeds), and F.I.C. in 1900. He was senior assistant to J. A. Voelcker in the laboratory of the Royal Agricultural Society of England, 1891-92. He lectured on agricultural chemistry and dairying in the next two years and became Public Analyst, Limerick, in 1895. He joined the Society in 1896. ORDINARY MEETINGS-Eight Ordinary Meetings of the Society were held during the year, and the following papers were presented and discussed- April, 1953, in London, on the Determination of Small Amounts of Lead in Foods and “A Reversion Method for the Absorptiometric Determination of Traces of Lead with By H.M. N. H. Irving, M.A., D.Phil., F.R.I.C., L.R.A.M., and E. J. “Preliminary Procedure for the Preparation of Biological Materials for the Micro- “Sample Preparation for Determination of Lead in Foodstuffs.” By D. A. Elvidge, May, 1953, in Glasgow, organised for the Society by the Scottish Section and the Micro- He transferred to Dublin in 1907. Biological Materials : Dithizone.” Butler, B.A., B.Sc., D.Phil., A.R.I.C. determination of Lead.” B.Sc., and D. C. Garratt, B.Sc., Ph.D., F.R.I.C. By R. F. Milton, B.Sc., Ph.D., F.R.I.C. chemistry Group : “Geochemistry and Microchemistry.” By David T. Gibson, D.Sc. “Micro-analysis of Silicate Rocks.Part IV. The Determination of Alumina.” By Christina C. Miller, Ph.D., D.Sc., F.R.S.E., F.H.-W.C., and Robert A. Chalmers, B.Sc. “Microchemical Determination of Sulphur in Organic Compounds.” By William H. Massie, B.Sc., Ph.D., A.R.I.C. This meeting was preceded by a visit to the Clydebridge steel works of Colvilles Ltd. “The Determination of Ergosterol in Yeast. By W. H. C. “The Estimation of Micro Quantities of Calcium.” By G. E. Harrison, Ph.D., F.Inst.P., “The Ultra-violet Spectrophotometric Estimation of the Quality of Mineral Oils Extracted By M. A. Cookson, BSc., A.R.I.C., J. B. M. Coppock, B.Sc., Ph.D., The subject was introduced by G. Roche Lynch, O.B.E., M.B., B.S., D.P.H., F.C.G.I., L.M.S.S.A., F.R.I.C. By May, 1953, in London: Parts I, 11, I11 and IV.” Shaw, Ph.C., F.R.I.C., and J.P. Jefferies, B.Sc., A.R.I.C. and W. H. A. Raymond. from Bread.” F.R.I.C., and R. Schnurmann, M.Sc., Dr.Rer.Nat. October, 1953, in London, on the Destruction of Organic Matter. “The Preparation of Biological Material for the Determination of Trace Metals.” G. Middleton, B.Sc., F.R.I.C., and R. E. Stuckey, B.Sc., Ph.D., F.R.I.C. “Determination of Lead in Foodstuffs.” By H. C. Lockwood, Ph.D., F.R.I.C. October, 1953, in Southampton, organised for the Society by the Physical Methods Group “The Analysis of Inorganic Compounds by Electromigration and Electrochromato- “The Use of Paper Electrophoresis in the Study of Nucleic Acids.” By Roy Markham, “Paper-strip Electrophoresis of Serum Proteins.” By A. L. Latner, M.Sc., M.D. This meeting was preceded by a visit to the Fawley Refinery of Esso Ltd.on the subject of Paper Electrophoresis: graphy.” M.A., Ph.D. F.R.I.C. By F. H. Pollard, B.Sc., Ph.D. November, 1953, in London, on the subject of the Determination of Niobium in Minerals “The Absorptiometric Determination of Niobium in Some African Low-grade Minerals By G. W. C. Milner, B.Sc., F.R.I.C., A.Inst.P., “The Absorptiometric Determination of Niobium in Some African Low-grade Ores. ” and Mineral-dressing Products : and Mineral-dressing Products.” and A. A. Smales, B.Sc., F.R.I.C. By A. E. 0. Marzys, B.Sc., A.R.T.C.256 ANNUAL REPORT OF THE COUNCIL, MARCH, 1954 [Vol. 79 “Spectrographic Determination of Niobium and Tantalum in Sukulu-type Soils.” C. S. Campbell, M.A., and D. Nicholas.“Inorganic Chromatography on Cellulose. Determination of Niobium and Tantalum in Minerals and Ores.” and R. A. Wells, B.Sc., A.R.I.C. Hunt, B.Sc., A.R.I.C., and R. A. Wells, B.Sc., A.R.I.C. mination of Niobium in Low-grade Ores.” R. A. Wells, B.Sc., A.R.I.C. By Part XIV. A Shortened Method for the By R. A. Mercer By E. C. A Rapid Method for the Deter- By E. C. Hunt, B.Sc., A.R.I.C., and “The Colorimetric Estimation of Niobium and Tantalum with Pyrogallol.” “Inorganic Chromatography on Cellulose. Part XV. December, 1953, in London: “Recent Advances in Medical Chemistry.” By Professor C. H. Gray, M.D., D.Sc., M.R.C.P., F.R.I.C. January, 1954, in London, organised by the Microchemistry Group: “Organic Ion Exchange.” “Inorganic Ion Exchange.’’ By G. H. Osborn, A.M.I.M.M., F.R.I.C.An exhibition of microchemical apparatus was held in conjunction with this meeting. JOINT MEETING-A Joint Meeting was held in January, 1954, with the Royal Institute of Chemistry, on the Determination of Alcohol in Blood and Urine, following the presentation of a Report on the subject by a panel of analysts appointed by the Royal Institute of Chemistry t o assist the Alcohol and Road Accidents Committee of the British Medical Association. The Report of the panel was surveyed in a paper by D. W. Kent-Jones, B.Sc., Ph.D., F.R.I.C., and G. Taylor, O.B.E., F.R.I.C. NORTH OF ENGLAND SECTION-Including the Summer Meeting at Llandudno, five meetings have been held during the year-one of which was a joint meeting with the Micro- chemistry Group. By L. Saunders, B.Sc., Ph.D., F.R.I.C. The following papers were read and discussed- “Principles of Chromatography.” By R.L. M. Synge, B.A., Ph.D., F.R.I.C., F.R.S. “Random Reflections on Food Legislation.” By C. A. Adams, C.B.E., B.Sc., F.R.I.C. “The Society for Analytical Chemistry.” By D. W. Kent-Jones, BSc., Ph.D., F.R.I.C. A discussion on “The Analysis of Waters, Sewages and Effluents” was opened by A “Symposium on the Training and Education of Microchemists” included the following W. Gordon Carey, F.R.I.C., and J. G. Sherratt, B.Sc., F.R.I.C. papers- “The Academic Approach.” By C. L. Wilson, D.Sc., Ph.D., F.R.I.C. “Technical Aspects.” “Industrial Requirements. ” By R. Rothwell. By G. Ingram, A.R.I.C. SCOTTISH sEcTroN-In addition to the Annual General Meeting held in Glasgow, four meetings were held during the year, two ordinary meetings in Glasgow and Edinburgh, respectively, the Parent Society meeting in Glasgow, the first in the history of the Section, organised jointly by the Microchemistry Group and the Scottish Section, and including a visit to the Clydebridge Steel Works, and a joint meeting with the Stirlingshire and District Sections of the Royal Institute of Chemistry and Society of Chemical Industry at Falkirk, the first Section meeting held outside Glasgow and Edinburgh.The following papers were presented and discussed, other than those mentioned else- where in this report- Edinburgh, April loth, 1953: “Modern Methods of Analysis in the Training of the Student.” By Christina C. Miller, Ph.D., D.Sc., F.R.S.E., F.H.-W.C.Glasgow, November loth, 1953: “Rapid Determination of Glycerol in Fermentation Solutions.” By K. Sporek, M.A., “Field Analysis in Connection with Water Treatment Problems.” By I. A. Heald, BSc. “Principles of Chromatography.” By R. L. M. Synge, B.A., Ph.D., F.R.I.C., F.R.S. and A. F. Williams, B.Sc., F.R.I.C. Falkirk, December 16th, 1953:May, 19541 ANNUAL REPORT OF THE COUNCIL, MARCH, 1954 257 Following the Council’s recommendation, recorders, specialists in individual subjects, are summarising for publication in The Analyst those papers of a general nature that do not lend themselves to printing in full. The Section has become a member of the Federation of Technical Societies in Glasgow, and a representative has been appointed to the Ramsay Dinner Committee.The membership of the Section has remained stationary at 103. MICROCHEMISTRY GROUP-Three meetings of the Group have been held during 1953: in London, Glasgow and Southport. The Glasgow meeting was an Ordinary Meeting of the Society organised jointly by this Group and the Scottish Section. The Southport Meeting was organised jointly with the North of England Section and the Liverpool and North- Western Section of the Royal Institute of Chemistry. The following papers were read and discussed, other than those mentioned elsewhere in this report- London : Sou t hport : “Microchemistry : An Appraisal.” “Symposium on the Training and Education of Microchemists,” comprising three papers By Cecil L. Wilson, D.Sc., Ph.D., F.R.I.C. as follows- “The Academic Approach.” By Cecil L.Wilson, D.Sc., Ph.D., F.R.I.C. “Technical Aspects,” By Gerald Ingram, A.R.I.C. “Industrial Requirements.’’ By Rudolf Rothwell. Visits were made as follows: Messrs. L. Oertling Ltd., St. Mary Cray, Orpington; Messrs. Colvilles Ltd., Clydebridge Steel Works, Glasgow ; Victoria Colliery, nr. Wigan ; Simpson’s Gold Thread Works, Preston ; North-West Gas Board, Southport Gasworks. The Annual General Meeting in London on January 29th was followed by an Ordinary Meeting of the Society, arranged by the Group. On the same day an Exhibition of Micro- chemical Apparatus was held at the Sir John Cass College. The list of “Reference Substances for Use in Organic Micro-analysis,” which had been drawn up after careful consultation with users and manufacturers, was published in The Analyst for April, 1953.A specially appointed Sub-committee completed the script of the proposed film “How to Use a Microchemical Balance.” As more than 40 per cent. of the Group members reside in the London area, it has been decided to recommend the formation of a London Discussion Group for the purpose of holding informal meetings on microchemical matters. The number of Group members is now 421, an increase of 29 since the last report. PHYSICAL METHODS GROUP-The Physical Methods Group has arranged six meetings in all during the past year, two of which were on behalf of the Parent Society; one in Birmingham on January 31st on the subject of “Chromatography” and the other in Southampton on October 23rd concerning “Paper Electrophoresis.” Three of the Group meetings were held in London, and the remaining one in Ipswich was held jointly with the East Anglian Section of the Royal Institute of Chemistry.The Polarographic Discussion Panel organised one of the Group meetings held in London. The Chairman of the Panel is Dr. A. J. Lindsey, and Mr. G. W. C. Milner is Honorary Secretary. The following papers were read and discussed at meetings of the Group- Annual General Meeting, London, November 25th, 1952. This was followed by an ordinary “The Application of Some Physical Methods in Forensic Science with Particular Reference to the Examination of Materials Relating to Criminal Investigation.” By J. B. Firth, D.Sc., F.R.I.C., M.1.Chem.E. By J. A. C . McClelland, B.Sc., Ph.D., A.R.I.C. meeting on Forensic Science.“The Examination of Questioned Documents.”258 ANNUAL REPORT OF THE COUNCIL, MARCH, 1954 [Vol. 79 Absorptiometry Meeting, London, March 3rd, 1953 : “The Use of High Absorbancy Reference Standards in Absorptiometry.’’ “The Determination of Titanium by High-precision Absorptiometry.” By H. M. N. H. By W. T. L. Irving, M.A., D.Phil., F.R.I.C., L.R.A.M. Neal, M.A., A.R.I.C., and H. G. Short, M.Sc., A.R.I.C. Polarography Meeting, London, April 14th, 1953 : “The Polarographic Determination of Fluoride.” By B. J. McNulty, B.Sc., Ph.D., F.R.I.C., G. F. Reynolds and E. A, Terry. “The Amperometric Titration of Zinc and its Application to the Determination of Zinc in Lubricating Oils.” By D. Pickles, B.Sc., A.R.I.C., and C. C. Washbrook, A.R.I.C. “A Tentative Method for the Determination of Calcium by Means of the Polarograph.” By Mrs.Bertha Lamb, B.Sc. Emission Spectroscopy Meeting, Ipswich, May 8th, 1953.: “Semiquantitative Techniques in Spectrochemical Analysis.” By R. L. Mitchell, B.Sc. , “Some Techniques of Presentation of Sample to the Spectrograph.” By A. H. C. P. “Applications of the Porous Cup Technique.” The number of Group members is now 446. This represents an increase of 28 since the BIOLOGICAL METHODS GROUP-The Group has held four meetings during the year, two On December l l t h , 1952, after the Annual General Meeting, two papers were read and “A Method Identifying the Presence or Absence of Splenin ‘A’ and Splenin ‘B’ in Serum By Raymond Greene, M.A., D.M., M.R.C.P., and Josephine “The Application of Large Plate Methods to Microbiological Assays of Antibiotics and On March l l t h , 1953, a highly successful Symposium on Flavour Assessment was held in collaboration with the Food Group of the Society of Chemical Industry and the Biometric Society (British Region).The Chair was occupied successively by Professor H. D. Kay, Dr. H. 0. J. Collier and Dr. K. Coward, and five papers were presented and discussed- “The Physiological Background of Flavour Assessment.” By E. D. Adrian, O.M. , “Basic Considerations in Regard to Flavour Assessment.” By H. G. Harvey, M.Sc., “The Objective Approach to Sensory Tests.” By A. S. C. Ehrenberg, B.Sc., and J. M. “Sensory Tests and Consumer Acceptance.” By J. M. Harries, B.A. “A Biometrician’s Viewpoint.” By J. 0. Irwin, M.A., Sc.D., D.Sc.The Summer Meeting of the Group took the form of an interesting visit to the Ministry of Agriculture and Fisheries’ Veterinary Laboratory at New Haw, Weybridge. Departments visited included Biochemistry, Manufacture of Vaccines, Tuberculin Production, Poultry Diseases and Manufacture of S.19 Brucella abortus Vaccine. On October Znd, 1953, Organo-phosphorus Insecticides were the subject of a Symposium held jointly with the Crop Protection Panel of the Agriculture Group (Society of Chemical Industry) , the Association of Applied Biologists and the Pharmacological Society. Professor V. B. Wigglesworth, C.B.E., M.D., F.R.S., was in the Chair for the morning session, when two papers were presented and discussed- “Tnsecticidal and Anti-esterase Activity of Organo-phosphorus Compounds. ” By K.A. “Toxic Action of Organo-phosphorus Insecticides in Mammals. ” By J. M. Barnes, Ph.D. , F.R.I.C. Gillieson, B.Sc., Ph.D. By L. G. Young. last Annual Report. of which have been joint Symposia with other societies. discussed- Membership of the Polarographic Discussion Panel is 109. using Guinea Pigs.” Vaughan-Morgan, B. Sc. Vitamin Products.” By K. A. Lees and J. P. R. Tootill, P.R.S. A.R.I.C. Shewan, B.Sc., Ph.D., A.R.I.C. Lord, M.A., Ph.D., and C. Potter, DSc. B.A., M.B., B.Ch.May, 19541 ANNUAL REPORT OF THE COUNCIL, MARCH, 1954 259 The discussion was opened by B. A. Kilby, M.A., Ph.D., F.R.I.C. For the afternoon session the Chair was taken by J. R. Nicholls, C.B.E., D.Sc., F.R.I.C., and three papers were presented and discussed- “The Behaviour of Organo-phosphorus Systemic Insecticides in the Living Plant.” Bv G.S. Hartlev. “Somg Hydrolytic Aspects of Organo-phosphorus Compounds.” By P. R. Carter, B.Sc.. Ph.D., A.R.I.C. “Bio-assay of Organo-phosphorus Insecticides.” By J. F. Newman, B.Sc. Membership of the Group has increased by 13 during the year and now stands at 225. ANALYTICAL METHODS COMMITTEE-A considerable impetus has been given to the work of the Sub-Committees by the holding of more frequent meetings of the Committee, to which Chairmen and Honorary Secretaries of Sub-committees and Panels have been invited, to receive and discuss interim reports. The awaited findings for a standard procedure for determination of lead in foodstuffs have been necessarily delayed. By representation to suppliers of analytical reagents, virtually lead-free reagents have been obtained, thus eliminating one of the most serious sources of error in the determination.However, the Metallic Impurities in Foodstuffs Sub-committee are not yet satisfied with the reproducibility of results when minimal amounts of lead are present. The amount of experimental work done by the Lead Panel has been very con- siderable. The activities of the Vitamin Sub-committee have resulted in the production of a report on a microbiological assay for thiamine that is in the hands of the Publication Committee. Working Panels have been formed under the Chairmanship of Dr. Amos and Mr. Bacharach, respectively, to establish if possible a standard method for the estimation of vitamin B1, and vitamin E.Following publication of the Interim Report on Pure Meat Extracts, the Meat Extracts Sub-committee are now dealing systematically with composite products. STANDARD METHODS COMMITTEE-Dr. Kent- Jones resigned from the Secretaryship of the Committee on his election as President, and Mr. J. B. Attrill has been appointed in his place. Under the Chairmanship of Mr. G. Taylor the Committee is making considerable progress in re-editing the Society’s Standard Methods and in putting together standard methods of analysis for a wide variety of materials. These, after final review, will be published section by section. has met on three occasions during the past year. Amongst matters dealt with were the Rag Flock and other Filling Materials Act, 1951 ; the action taken by certain local authorities with regard to sampling table jellies for the setting test; the freezing point of milk; standards for sausages and the Food and Drugs Amendment Bill.LIAISON COMMITTEE-During the year the following appointments have been made- Mr. L. A. Haddock, Methods for the Examination of Chemical Products. Mr. H. Weatherall, Ubbelohde Apparatus. The President, Mr. R. C. Chirnside and Dr. K. A. Williams, Conference on the Possibility PUBLIC ANALYSTS AND OFFICIAL AGRICULTURAL ANALYSTS COMMITTEE-The Committee B.S.I. Committees: of Making Standards for Analytical Reagents. Joint Library Committee, Chemical Society : Food Manufacturers’ Federation : Dr. J. G. A. Griffiths was again appointed as the Society’s representative. Dr. S. G.Burgess was appointed as the Society’s representative on a Committee dealing with the determination of fat in canned soups. British Iron and Steel Research Association : Dr. J. Haslam and Mr. R. C. Chirnside were appointed as the Society’s representatives at the Seventh Chemists’ Conference of the Methods of Analysis Committee (Metallurgy, General Division).260 ANNUAL REPORT OF THE COUNCIL, MARCH, 1954 [Vol. 79 The Council of the Society thanks all its representatives for the work they have carried out in the various Committees and at the various meetings during the year on behalf of the Society. HONORARY TREASURER’S REPORT-FOr the first time for a number of years the Society’s accounts show a small loss on the year’s working. Such a loss was not anticipated in the Spring when the Society’s yearly budget was considered by the Finance Committee, but two unexpected factors during the year are responsible for this result.In the first place, sales of the bound volumes of the Proceedings of the International Congress on Analytical Chemistry have not come up to earlier expectations, with the result that the loss on the Analyst and Sundry Publications Account is considerably larger than was expected. The sales of this publication are now improving, and this improvement will be reflected in next year’s accounts. Secondly, at the end of the year the Society was called upon to face the cost of setting up an editorial organisation for the publication of AnalyticaZ Abstracts. This necessitated hiring and furnishing an additional office, and engaging additional editorial staff.The accounts for this new departure now appear as a separate item in the balance sheet as the Analytical Abstracts Account and, quite clearly, the expenses incurred during the preparatory work at the end of 1953 must be borne by the Society and are not offset by any financial return in the year under review. The publication of Analytical Abstracts is an expensive undertaking, and one which may involve the Society in a substantial loss. Very careful costings were made before this project was undertaken, and these were based on an estimated figure for sales of Analytical Abstracts to chemists and organisations outside the Society. It is our duty to warn the Society that should the outside sales fall badly short of the predicted figure, the Society may be faced with a loss of anything up to L2,OOO. The Council of the Society, however, have accepted this possibility in view of the importance of analytical abstracts to its members.The experiment with the advertisements in The Analyst, to which reference was made in the last report, has been a success, as will be seen from the increased revenue to the Analyst Account from this source. THE ANALYsT-The 1953 volume contained 740 pages ; the 1952 volume contained 1032 pages, of which 480 pages were the Proceedings of the International Congress on Analytical Chemistry of September, 1952, and 552 pages were usual Analyst matter. The numbers of papers and notes published in 1953 were 96 and 54, respectively (a total of 150)’ against 129 and 28 in 1952 (83 and 28, excluding the Congress papers and lectures). The approximate number of pages of papers and notes was 646, against 970 in 1952, which included the Congress papers and lectures. Nine issues of the Bulletin have been distributed with The Analyst. The printing number of the monthly issues for 1953 was 4800; it is now 4900. ANALYTICAL ABSTRACTS-The new journal of Analytical A bstracts started in January, 1954, and is already enjoying a wide circulation. CHEMICAL couNcIL-During the year the Chemical Council has again distributed large sums of money to assist in the publication of original papers, and the Council acknowledge with thanks the grant of El500 towards the cost of producing The Analyst. DEVELOPMENT OF THE SOCIETY-For the first time in the history of the Society, a Conference of the Honorary Secretaries of the Sections and Groups was held in May in London. The Conference proved extremely successful, and of great use in promoting the integration of the activities of the various departments of the Society. It is hoped to make this an annual event. During the year the Council appointed Mr. N. L. Allport as Honorary Assistant Secretary of the Society to assist the Honorary Secretary, primarily as a link between the Council and the Committees of the Sections and Groups. FOOD LAW INSTITUTE-Advantage was taken of the visit of Mr. c. Wesley Dunn, President of the Food Law Institute of the U.S.A., to this country, by the President to entertain him to an informal dinner at which he could meet members of the Society and discuss problems of food law common to both Great Britain and the United States of America. D. W. KENT- JONES, President. K. A. WILLIAMS, Honorary Secretary.

ISSN:0003-2654    

DOI:10.1039/AN9547900253

出版商:RSC    

年代:1954

数据来源: RSC

摘要:

May, 19541 HUGHES 261 The Third Bernard Dyer Memorial Lecture The Contribution of Public Analysts and Other Analytical Chemists to Public Welfare BY E. B. HUGHES (Delivered after the Annual General Meeting of the Society, March 3rd, 1954) BEFORE giving this Third Memorial Lecture I wish to discharge in a few words my primary duty of paying a tribute to the memory of Dr. Bernard Dyer. His record of lengthy service and of benefit to this Society is unique and will probably remain so. Bernard Shirley Dyer was born in 1856 and died within a fortnight of his 92nd birthday. He was a member of this Society for some 73 years. I do not propose to speak of Dyer’s work, for that, particularly his famous contributions to soil analysis and his work in general for agriculture, was so ably described by Sir John Russell in the First Dyer Memorial Lecture, and a faithful word-picture of the man and his character and career can be found in the obituary written by Mr.George Taylor, his colleague, and Mr. Lewis Eynon. Dyer’s work will live : indeed, his work on soil acidity, for example, has endured the test of over half a century and, despite modern advances, still provides a practical and useful method. What I think we should particularly speak of on these occasions is his personality and character. He was not merely a fine chemist and an excellent analyst, but he had thegift of insight into chemical and analytical problems, for he seemed infallibly to choose the surest and most direct method of attack on a problem, whether of research or of analysis. From his youth he knew what he wished to do and what he could do, and he achieved his objects with seeming ease and happiness.I imagine that his early experience in the laboratory of Dr. Augustus Voelcker must have provided him with a firm foundation of analytical skill and understanding. Nevertheless, it seems almost uncanny that one so young as he was (21 years of age) when he founded his own practice as an analyst and became a member of this Society should have had not only the wisdom and self-confidence that he clearly possessed, but also outstanding ability and foresight. Dyer was modest, courteous and kind, esteemed by all who met him, and generous in his help to the young analyst. He was a great analyst and a stalwart of this Society, and our memory of him is that of a grand and loveable man.THE CONTRIBUTION OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS TO PUBLIC WELFARE When your President and Council honoured me with the invitation t o give this Third Bernard Dyer Memorial Lecture, I accepted with greater readiness than I have since felt was justified, but I did welcome the opportunity to voice some thoughts that have long been in my mind about the importance and status of analysis, and particularly to say something of my friends the pukJic analysts and of the co-operation that exists between them and other food chemists in furthering knowledge of the analysis of food. At that time I did not know that the Society was so soon to change its title, but this event makes what I have to say even more appropriate to the occasion. The title I have chosen for this talk is “The Contribution of Public Analysts and Other Analytical Chemists to Public Welfare,” but obviously it is impossible in the course of this lecture to discuss adequately the contribution made by analytical chemists in all spheres of industry: I therefore shall refer chiefly to those whose work I know best, namely, analysts in the food industry and public analysts.The common factor of our interest in this Society is not merely that we are concerned with analysis and like to hear and’read something of what is being done in it, but that we are analysts: it is the personal factor. The analyst does not drift into his profession, not even on the conclusion of his academic education: he deliberately chooses a career that262 HUGHES: THE CONTRIBUTION OF PUBLIC ANALYSTS [Vol.79 necessitates careful and accurate work, that requires the application of any scientifically controllable means of pursuing an enquiry and that gives him the satisfaction and pleasurable anxiety of pitting his knowledge and skill and ingenuity against the complexities of the problem that confronts him. This, to my mind, pictures the essential character of the analyst, No new progress in chemical knowledge can be allowed to escape his attention, for sooner or later it may provide a useful and probably a common line of attack in analysis. I do not intend to pursue the subject of what the analyst may do-or I think should do-for his own science ; this Society provides by its meetings and its Groups and its Analytical Methods Committee ample opportunities for the zealous analyst-and our journal shows that excellent and valuable work is being done.My chief concern this evening is to give some thought to the service of the analyst to mankind. Sir Robert Robinson, in his foreword to the Proceedings of the International Congress on Analytical Chemistry says- “During the earlier decades of the growth of the modern science of chemistry the importance of analytical theory and practice was well understood and the fundamental technique of many of the pioneers was essentially that of analytical chemistry.” Although analysis for a longish period was not of fundamental importance in chemical progress but rather a useful service, it is now again a factor of prime importance, and the growth of chemical knowledge and of analytical science are mutually essential and mutually dependent. Analysis is not merely the handmaiden of industry-although indeed I fear that it is sometimes, if not often, regarded as the Cinderella of chemistry-it is, and particularly in industry, the sine qua non, not only for control, but for research.If the ordinary individual, the layman from our point of view, were given a simple outline of the various applications of our science, I think his greatest interest would be aroused in its application in biochemistry and the allied sciences-chemical pathology, physiological chemistry and pharmacology-for it is in these that a direct personal appeal would be found: the growing knowledge that is so steadily contributing towards understanding of life, and application that can affect health and bodily welfare and lessen fear of disease.The part that analysis plays in these studies-and certainly when they develop into practice-is an important one. Agriculture and its particularised sciences-pest control, soil analysis, plant nutrition, etc.-also appeal to personal interest and give us faith that they will enable the world for a long time to meet the demands for more and more food. Agricultural chemistry was, in its beginning and growth, chiefly analytical-with a rapid realisation of its benefits. There is now no farmer, nor grower, nor cattle rearer, nor hardly an amateur gardener, to whom such information is not a commonplace of daily life. Dyer, you will remember, made important contributions that are still standard procedures in analysis.Elements in trace amounts in soil and plants have an astonishing effect on plant growth and health, and a deficiency of this or that element may have a serious effect. Diagnosis in many crops can be made from observation of leaves and growth, but the best means, of course, is chemical or spectrographic analysis. One could wish that as much were known about the effects of trace elements on humans-I mean of beneficial elements: the harmful ones are better known-as is known about the effects on plant life. The extensive use of chemical substances as pesticides causes anxiety about the possible effects of their residues on crops. Although there is no evidence that any harm has resulted, it is certainly desirable, indeed essential, that methods of analysis should be available for the detection and determination of trace amounts of these substances-a problem that analysts must resolve.I regard this requirement as even more urgent than the precise specification of known methods of analysis to meet the requirement of standards and limits of contaminants in food. Without it, rule of thumb would be the only guide; erratic results, faulty products and irregular quality would be commonplace instead of rare; progress would be stultified and by chance and intuition only. We analysts occupy a key position-by no means generally recognised- and although we may be the “back-room boys” of industry, we deserve now and then to be considered worthy of a place in the sun.I will not attempt to name industries in which analysts are necessary: I cannot call to mind an exception. The greatest need for our modern industries is to produce more goods of reliable and invariable quality and with a greater output per worker. These are not only matters of Nowadays, in the manufacturing industries, analysis is an essential service.May, 19541 AND OTHER ANALYTICAL CHEMISTS TO PUBLIC WELFARE 263 management, of factory design and engineering, but they call for the services of chemists, often in a high degree. In the food industry, for example, progress would be uncertain and retarded without such help. This need is well recognised by government and by industry, and is evidenced by the number of scientific research associations of various trades and by the magnitude of our Department of Scientific and Industrial Research.Nevertheless, it is recognised that there is need for many more scientists in the service of industry. In the U.S.A. the proportion of scientific and technical staff to other workers is very much greater than it is in this country, and if we are to compete successfully in the world market against such well-served industries, we must increase our application of science. Let me quote to you just a few words from a lecture given by a very wise and far-seeing business man, the late S. M. Gluckstein, before the London Section of the Institute of Chemistry in 1927-27 years ago. “It is said by advertising people that if business is bad you should increase your advertising in order to improve it, while if it is good you should increase your advertising in order to maintain it as well as improve it.Similarly, I saw recently that an American business man of standing said that when trade becomes bad, you should double your laboratory staff. Although no doubt his remark is not intended to be taken quite literally, nor would I go so far as to agree with him completely, there is more than a grain of business sense behind such advice.” This is not to infer that times are now bad, but the paramount need for expansion of trade is an equivalent condition. We in this Society hold our meetings, read papers and make such contributions to our science that our journal is of world-wide high repute, but I think we might also occasionally have a meeting where we can learn what the other fellow does.So I put forward for con- sideration the suggestion of a Symposium on Analysis in Science and Industry-that is on what we do, not how we do it-at which we could learn in some detail what the analyst does in spheres other than our own. (I believe that probably the Society of Chemical Industry would gladly participate with us in a function that would be stimulating and, I am sure, ta the credit of all concerned.) Let us tell industry, and the trade associations, and the economists, and the Government, something of the study and zeal that lie, largely hidden to them, in the analysts’ contribution to the prosperity of industry and of the nation. From this short and far from complete appreciation of what the “other analytical chemist” does to further national and human welfare, I pass on to some special reference to the work of my friends the public analysts, with whom food chemists, of whom I am one, have so much in common.Most of you will know something of the story leading to the establishment of the Food and Drugs Act, as most who speak of food legislation feel impelled to mention it, but in view of what I wish to say I think that just a brief reference here is necessary. An Act introduced to prevent adulteration of food and drugs could be effective only if there were means of detecting and determining the degree of fraud; and so it is that, though one may consider that the first Food and Drugs Act was much overdue, it could hardly have been made truly effective very much earlier, except, of course, against the cruder forms of adulteration.The speedy and striking success of the 1872 Act was due to the fortunate circumstance that there were then in practice a few analysts who had the wisdom and fore- sight to realise that for the successful fulfilment of their duties under the Act they should unite to share their knowledge, and with this object they formed a society which, at their first Annual General Meeting in 1875, was constituted as the Society of Public Analysts. The scientific ability, integrity and astonishing zeal of those pioneers in food analysis rapidly made the Act an effective instrument and gave prestige and dignity to their profession and to the Society they had founded. Theirs was indeed a service to the nation and to analytical chemistry, and we in this Society who have inherited what they so well founded have cause to hold them in esteem and gratitude.I need not here go into details of the development of the Society nor of the great names it has left in the history of analysis, such as Redwood, Allen, Adams, Hehner, Dyer, Stevenson, Wanklyn, Bevan and many others : you will find a charming and modest account of these in “Fifty Years of the Society of Public Analysts,” published in 1932, wherein Bernard Dyer gave an account of the personalities of the period and the events in their term of office, and C. Ainsworth Mitchell gave a succinct record of the main features of progress in the Society.264 HUGHES: THE CONTRIBUTION OF PUBLIC ANALYSTS [Vol. 79 It is common, in referring to the introduction of the Food and Drugs Act of 1872, to refer to harrowing stories of openly fraudulent and sometimes harmful adulteration of food in the early part of the nineteenth century, and to refer to Accum’s book, “A Treatise on Adulteration of Food and Culinary Poisons,” but nevertheless it is pleasing to note that even in those times there were in existence some of the food manufacturing firms whose names are household words to-day and which, I feel sure, were as honourable then as now: there are copies of advertisements of smaller merchants and bakers describing the whole- someness of their wares, and among them, for instance, one of a baker who claimed that his bread was pure and free from alum (1788).We should remember that, although that period was only about a century ago, there was a general callousness in human treatment that in many respects is equally shocking to us.For example- 1837 (17 years after Accum’s book was published): up to then some 200 offences on the penal code were punishable by death; in 1861 this was reduced to something like our present law. In 1825 the tax on salt was repealed: it had been as high as E30 a ton (E30 in those days!) for an essential in food, particularly as it was the only means for preserving meat. In 1851 the window tax was repealed: this had been a tax on health and comfort and no doubt contributed to tuberculosis. In 1842 the employment of women and children underground in mines was forbidden. In 1875 the practice of boys being sent up chimneys for sweeping was abolished.The Food and Drugs Act of 1872 was not introduced as the cure of the one outstanding evil, but was part of the rapid general civic reform of the period. Be that as it may, those days are passed, and public analysts’ work is now the more prosaic-but still important-one of seeking the stray offender or the manufacturer who, generally by mischance, is guilty of a minor infringement of Regulations or of a divergence from the normal not in reality to the prejudice of the purchaser. Thus, taking figures for 1937-38 (the latest I have found available), a total of about 151,370 samples were examined by public analysts and of these more than half (82,357) were milk: the “not genuine” samples amounted to 5.5 per cent., of which nearly 75 per cent. were milk; this shows quite clearly why so much attention is given to the sampling of milk and that, despite the efforts of years, this particularly despicable adulteration is still far too prevalent.These samples taken by public authorities are not all random samples; they represent quite largely a selection of kind and origin in which adulteration might be more suspected, so that, on the whole, the indication is that the occurrence of adulteration of food is slight. From the point of view of the manufacturer, the extent to which testing of his raw materials and products is necessary is much more exigent than is required for compliance with the Food and Drugs Act. He must do all he reasonably can to ensure that his products are genuine and uncontaminated and, so far as possible, leave nothing to chance ; consequently sampling must be more intense.As an indication, I quote a few figures from our o m laboratory: in a year, a total of some 70,000 samples are analysed, some fully, some for specific purposes only; also in one year we make about 3000 determinations of arsenic, 1000 of lead, 1000 of copper and 800 of tin. In industry, as with the public analysts, samples generally prove satisfactory, but the occasional faulty sample must be looked for. A workable, effective and just Food and Drugs Act is a necessity in any civilised com- munity; it not only protects the public but also protects and guides the responsible manu- facturer. From my reading of the new Food and Drugs Amendment Bill, I infer that much more control may be exercised in future by specific Regulations promulgated by the Ministries of Food and Health, which might lead one to fear, perhaps, what we all as individuals dislike in our private lives as well as in business, excessive bureaucratism. I hasten to add that, although I know the existing Act of 1938 requires the Minister “to consult with representative organisations as he thinks fit,’’ my experience as a food chemist has been that this requirement is applied widely and generously, and that the officials responsible do seek and consider evidence from the industry-and inspire its co-operation; and I feel that, if this understanding spirit is maintained, there should be nothing to fear but much to be gained from clearly stated needful and useful Regulations, and I stress needful and useful.Another clause that attracts my attention, as a chemist, is the one stating that methods of analysis may be prescribed and that “evidence of an analysis carried out by the prescribed method shall be preferred to evidence of any other analysis or test.” I trust that such prescribed methods will be such as can be approved, and preferably will be produced, by this Society, and that they may be subject to review as circumstances require.May, 19541 AND OTHER ANALYTICAL CHEMISTS TO PUBLIC WELFARE 265 This occasion gives me the opportunity I have often desired-to pay a tribute to the public analysts, and to express the food chemists’ appreciation of the co-operation between them and us on the scientific work required for establishment of assured methods of analysis, to the advantage of both.I (and many other food chemists) have been associated with public analysts on many committees on methods of analysis of food and the like, and the experience has been a happy one and, I feel sure, to the benefit of the public and the manufacturer alike. That the public analysts have relinquished their claim on the name of this Society and have willingly and generously accepted the change necessitated by the many and expanding interests of the Society is worthy of grateful acknowledgment, of which they have had many assurances but which I wish to emphasise once more. In the new Association of Public Analysts we hope that they will find all the professional status and recognition that are their due, but, above all, we hope that they will still be ardent supporters of this Society and maintain their close scientific contact with chemists of the food industry, which becomes more and more necessary to both as the knowledge of the science of food advances. We are living in an age of manufactured food, and it is futile to pretend that we, or any industrial nation, can revert to the simplicity of, say, even the eighteenth century.What we have to do is to strive to ensure that the food we supply to countryman and townsman alike-for nowadays the countryman is a consumer of manufactured food-shall be wholesome and nutritive as well as attractive and pleasing, and capable of withstanding the exigencies of transport and distribution. This is the objective of the food chemist-and I say this as one who has spent what may be considered as the greater part of a working life as such, Chemists are employed in the food industry for the purposes I have stated, and their most important function-and their first duty to their firm-is to use their knowledge and skill to ensure the purity and quality of their product; the food chemist is paid to maintain- if possible, to enhance-the reputation of his firm’s goods; certainly he would not-and dare not-be the cause of any harm.The food chemist-one of the “other analytical chemists”- is thus as much a contributor to public welfare as is the public analyst: perhaps I could justly say even more so, because his object is not merely to find any evidence of harm or of infringement of law or regulation, but definitely to prevent such mischance.A food chemist’s standard of requirement of purity of a raw material is stringent, for he knows how this or that ingredient or constituent can contribute some desirable or undesirable quality to the manufactured product-and so he works to exacting limits. To him a substance is not necessarily satisfactory solely because it is genuine or pure; it must have certain qualities or characteristics, which are of importance according to the intended use of the substance. You, I think, will realise how this is done; it is by constant application of analysis and micro- biological examination, by tests chosen to give the information required and by specifying all the details of the care required in manufacturing processes; by making tests and inspections to verify the observance of them, and finally advising how the product should be packed and specifying how long it will remain in the condition that the customer rightly expects. It is this sort of work that accounts for the testing of some 70,000 samples that I have previously mentioned.To you, analysts and microbiologists, I need not elaborate this or go into details, but I would emphasise that all this control and checking is a very real part of food manufacture. In the course of such intensive examination, data such as do not come to notice in casual inspection become available, and attention by industrial food chemists results in reduction or elimination of contamination that probably otherwise would have escaped notice. The care that a food manufacturer takes to avoid contamination he naturally requires also of the suppliers of the raw materials, and in this alone there is obviously a public benefit.The sequence of this testing is obvious: it is to see that in the factory there is no contamination, or perhaps more exactly, that there shall be the very minimum, ensured by choice of material for equipment, and that all metals with which the food comes in contact shall be appropriate for the purpose: this applies to plastics as well as to metal-more work for the analyst. Cleanliness is an all-important matter in a food factory and kitchen and must be to a degree well beyond what visual inspection will detect; in fact, to an extent that could hardly be expected in the ordinary household. Cleansing materials are important, and we must know what we use and how they function; also we must know not only their efficacy but their effect on equipment.This necessitates bacterial testing of plant and materials and products, and the formulation of conditions of processing and of cleaning. For this work266 HUGHES: THE CONTRIBUTION OF PUBLIC ANALYSTS [Vol. 79 we prefer chemists who have been trained in the analytical procedures of bacteriology; they have some consideration for the food as well as enmity towards unwanted micro-organisms. This section of the laboratory will also undertake work on fermentation (e.g., enzyme reactions, treatment of trade waste and the like). I have given this sketchy description of science applied in the food factory and kitchen only to indicate the great importance of such work, not to describe in detail how it is carried out, and to show that the able analyst-suitably trained and experienced in the industry- is the best man for the job. In recent years a new name for the food chemist has been used, and seems to be becoming popular, the food technologist.If such a title or grade is to be recognised, and adopted by the food chemist, it must indicate one whose post-graduate scientific training has been con- cerned with food and food manufacture, and not merely the acquisition of enough knowledge to meet the normal requirements for food manufacturing processes. My opinion is that the analyst, suitably experienced, is the ideal food technologist, as I think it important not to lose sight of the fundamentals.We like to have our investigational work and research work in the hands of those who have special knowledge of the products being studied and who have had the experience of the analysis and manufacture of those products. There are exceptions, of course, such as in the physical laboratory, X-ray work and the like, although much of such work is contributory to the work in other sections. There is no reason why the analyst should not know all the technology nor why he should not know something of the functioning of the industrial plant and, when he has special knowledge of the product concerned, consult and work with the engineer and the designer and architect. The analyst should not, in industry, be restricted to the laboratory bench. Knowledge gained in the factory helps him to understand better the object of his work and also to be more useful to the industry.We regard analysis as the backbone of our work. I feel impelled to refer to this because this industry so much affects every individual, in purse as well as in welfare; and this being so, it is an industry particularly liable to be criticised, attacked and even maligned. There is the suggestion that the food manufacturer, for convenience and for profit, makes wide use of “chemicals,” aided and guided by his food technologists, to the consequent detriment of the consumer. How far this is from the truth is obvious from even a cursory scanning of published abstracts of the scientific literature on food, and too, for example, from the subjects discussed at meetings of the Food Group of the Society of Chemical Industry and in particular the exhaustive presentation and discussion of the subject of Chemicals in Food, including Pharmacological Aspects, in September, 1951, all published and available.I would also especially mention the joint request made by the Society of Public Analysts and Other Analytical Chemists and the Food Group to the Ministry of Food to review the Preservative Regulations and to make needed recommendations. To our satisfaction a Committee, on which medical science is well represented, with such terms of reference-including not only preservatives but other chemical additives-was formed and is now actively considering this matter, and I suggest that we all-including those who, being less responsible and less appreciative, are the more ready to criticise-should await that Committee’s recommendations and report.I therefore refrain from any particularisation. Food chemists in this country have assumed that their meetings, discussions, published work and the abundant evidence of their interest in the purity and quality of food would be ample indication of their aims, but in view of recent trends it would be desirable to state the policy as well as carry it out. I have noted such a statement in the 1953 Presidential Address by Professor Bernard E. Proctor to the Institute of Food Technologists (U.S.A.), which Institute is an important body requiring evidence of satisfactory academical and postgraduate training for membership. “It [the Institute] is a respected champion for improvement in food quality and more efficient food processes and equipment. .. . There is no group in this country in whose hands more responsibility is vested concerning the well-being of the public from the standpoint of its food intake.” And, speaking of Chemicals in Food: “The protection of the ultimate food consumer is the first interest of all food technologists.’’ These are sentiments that we can sincerely say represent our views too: they are necessarily the guiding principles of all responsible food chemists. The U.S.A. Food Chemists, in their objective of “the pro- tection of the ultimate consumer,” include as a most important matter the necessity for sound evidence of the harmlessness of any proposed chemical additive to food before its use can be We in our laboratory go further. What of the ethics of the chemist in the food industry? Could we do more? Here are abstracts therefrom-May, 19541 AND OTHER ANALYTICAL CHEMISTS TO PUBLIC WELFARE 267 advocated, and I note with considerable interest-and a certain amount of national satis- faction-that they attach great importance to the work of Professor A. C. Frazer in this country and that his opinions are quoted as “exceptionally able statements of the problem.” A very unsatisfactory aspect of the matter of additives in food-preservatives, colours, emulsifiers and stabilisers-is that there should be such variation in different countries in what is considered suitable and in the amount permitted. There is obviously a lack of knowledge and, equally obviously, I suggest, a lack of frankness in making information available. Committees do not provide information: they can only collect what is available, collate it and make the best possible decisions thereon. One would expect that such matters should be recognised as being for the benefit of all peoples and for simplicity in trade, yet the authorities in each country proceed as if they, and they alone, understand what is right and just. Perhaps one day we shall have some international co-operation; the effort would be worth while because then so many could contribute to the provision of essential knowledge. I know that in what I have said there may be little or nothing new-and no new sentiment or opinion-and if it seems so to you I shall be content, for what I have tried to say was something about ourselves that I believe should be expressed in words and not merely lie dormant in our minds.

ISSN:0003-2654    

DOI:10.1039/AN9547900261

出版商:RSC    

年代:1954

数据来源: RSC

摘要:

May, 19541 AND OTHER ANALYTICAL CHEMISTS TO PUBLIC WELFARE 267 The Polarographic Determination of Fluoride Part 11. The Determination of Fluoride in Bromine, Hydrochloric Acid and Hydrobromic Acid BY MISS J. S. BEVERIDGE, B. J. MACNULTY, G. F. REYNOLDS AND E. A. TERRY (Presented, together with Part I , at a meeting of the Physical Methods Group on Tzcesday, April 14th, 1953) The application of the method described in Part I to the determination of fluoride in bromine, hydrochloric acid and hydrobromic acid is described. In the application discussed, the cathode-ray polarograph appears to be superior to the conventional type of instrument. IN the course of other work1 on the determination of fluoride, it became clear that a method was needed to check the fluoride content of halogen acids used as reagents and in control experiments.Separation of fluoride by the standard technique of distilling it as hydrofluo- silicic acid seemed unlikely to be satisfactory, for, although it might be possible to remove the halogen acid by a low-temperature distillation at less than 120" C before the steam distillation of the fluoride as hydrofluosilicic acid, such a procedure would at best be tedious and time-consuming and might result in erratic losses of fluoride. In these circum- stances a direct method of fluoride determination, more sensitive than those in current use, was required. The polarographic method described in Part I of this series2 has proved satisfactory for this work. Experience in the treatment of hydrobromic acid to remove elements likely to interfere in the determination cf fluoride had indicated the possibility of free bromine being present after treatment.Experiments were therefore made to find methods of determining fluoride in the presence of this element. Although the question of fluoride determination in the presence of free bromine subsequently proved of no importance with hydrobromic acid, a method of determining fluoride in bromine was developed in the course of the work and is presented here. In this paper the experimental development and the final details adopted for each of the three materials concerned are described separately and a general discussion of these applications of the general method is given at the end. EXPERIMENTAL DETERMINATION OF FLUORIDE IN HYDROCHLORIC ACID- The basis of the method was to neutralise as much hydrochloric acid as was compatible with the solubility of the resulting salt and then to add an aluminium - dye complex solution,268 BEVERIDGE, MACNULTY, REYNOLDS AND [Vol.79 prepared as previously described,2 make up to standard volume, heat to 70" C for 5 minutes, cool and record a polarogram. Ammonium hydroxide was used for neutralising the acid, as this base was the least likely to contain fluoride and other impurities, such as iron or aluminium, that would interfere with the method, although there was no reason why other bases of suficient purity should not be used. Preliminary experiments showed that the method could be used in strong salt solution and that no trouble was experienced owing to salting out of the dye, Solochrome Violet R.S.The experiments were carried out in solutions of AnalaR quality ammonium chloride. The ammonium chloride was crystallised twice before use. Double recrystallisation of salts is sufficient to free them from all detectable traces of fluoride except when contamination is heavy ; three recrystallisations may then be required. This was proved in the following way. A saturated solution of ammonium chloride was prepared and the equivalent of 530 pg of fluoride per 50 ml was added as sodium fluoride. The solution was treated in the usual manner and polarograms were made before and after re- crystallisation. The results are shown in Table I, from which it is evident that double recrystallisation is sufficient to remove any normal amount of fluoride.TABLE I REMOVAL OF FLUORIDE FROM AMMONIUM CHLORIDE BY RECRYSTALLISATION Before After 1st After 2nd After 3rd After 4th treatment treatment treatment treatment treatment Fluoride, pg per 50 ml of solution 530 35 9 0 0 A similar experiment was carried out with sodium chloride. With this material re- crystallisation was achieved by addition of 7 M hydrochloric acid ; the precipitated chloride was filtered, washed with a little hydrochloric acid and dried at 150" C. In this experiment fluoride content was reduced from l6pg per 50ml to nil in two recrystallisations. The use of strong salt solutions results in a uniform suppression of the aluminium - dye step-height and some loss of reproducibility. The effect on the fluoride determination is exactly parallel to the effect observed with aluminium alone.Hence, under the new con- ditions, the step-height reduction corresponding to 1 pg of fluoride was of the order of one unit, compared with two units in the absence of salt, i.e., in water; the reproducibility of fluoride concentration was then of the order of $,15 per cent., against &lo per cent. in the absence of salt, for fluoride contents between 0 and 0.5 p.p.m. At these very low levels this was considered satisfactory. METHOD FOR DETERMINING FLUORIDE IN HYDROCHLORIC ACID -AGENTS- The reagents described in Part I2 with the addition of- Ammonium chloride-Purify this by recrystallising AnalaR quality ammonium chloride twice from water. PROCEDURE- Measure 16 ml of the hydrochloric acid into a 50-ml beaker, place it in a bath of ice, and carefully neutralise the sample with concentrated ammonium hydroxide, with methyl red as indicator.Add 5 N perchloric acid dropwise until the pH is 2, as measured with a pH meter, then add 2 ml of 0.1 per cent. v/v acetylacetone and, after stirring well, re-adjust the pH to 7 with ammonium hydroxide. Pour the solution into a 100-ml separating funnel, add 10 ml of redistilled chloroform and shake the funnel vigorously for 2 minutes. Discard the chloroform layer and repeat the extraction three more times. Transfer the water layer to a 50-ml beaker and warm it to remove traces of chloroform. Cool it and add 3ml of a solution containing 10 pg of aluminium per ml, 1 ml of proteose peptone and 2.5 ml of 2 N ammonium acetate. Adjust the pH to 3.9 with perchloric acid and transfer the solution to a 50-ml calibrated flask.Make the solution up to the mark with water, heat it in a water-bath at 70" & 5" C for 5 minutes, and then cool it. Place about 4 ml of the solution in a polarographic cell, deoxygenate it for 10 minutes and record a polarogram at 25" C on "half voltage" from -0.15 to -0.8 volt, using the Add 2 ml of Solochrome Violet R.S. and mix well.May, 19541 TERRY: THE POLAROGRAPHIC DETERMINATION OF FLUORIDE 269 mercury pool as anode. Measure the height, A , of the aluminium - dye complex step, which occurs at -0.32 &- 0.05 volt. Determine the height of the aluminium - dye complex step in the absence of fluoride by dissolving 9.2 g of purified ammonium chloride in about 40 ml of warm water, making the solution just alkaline to methyl red with ammonium hydroxide and proceeding as described above with this solution as the neutralised sample.Measure the step-height, B, of the undepressed aluminium - dye complex step. Then- Calibrate with known amounts of fluoride in a base solution containing 9-2g of ammonium chloride per 50 ml. [F] = K(B - A ) . EXPERIMENTAL DETERMINATION OF FLUORIDE IN HYDROBROMIC ACID- Application of the technique already used for hydrochloric acid necessitated calibration in the presence of ammonium bromide, and preliminary experiments gave results of an unexpectedly erratic nature ; this rendered the method unusable, Examination of the Fig. 1. Calibration for fluoride in ammonium bromide. Curve A, 15 pg of fluoride; curve B, 20 pg of fluoride; curve C, 30 pg of fluoride Fig.2. of cadmium. curve C, 30 pg of fluoride Calibration for fluoride in ammonium bromide in presence Curve A, 15 pg of fluoride; curve B, 20 pg of fluoride; polarographic traces indicated that the erratic results were due to difficulty in measuring the step-height. This arose from the fact that the top of the polarographic wave was curved and that it did not provide a clear line from which to measure. The introduction of a small amount of cadmium ensured that there was a constant point of inflection in the wave from which measurement could conveniently be made, and with this modification results were satisfactory. It is possible in favourable circumstances to obtain good results without the cadmium, but its presence makes the actual measurement much easier.Figs. 1 and 2 illustrate typical waves without and with cadmium.270 BEVERIDGE, MACNULTY, REYNOLDS AND METHOD FOR DETERMINING FLUORIDE IN HYDROBROMIC ACID [Vol. 79 REAGENTS- The reagents described in Part I2 with the addition of- Ammonium bromide-Purify ammonium bromide of AnalaR quality by recrystallising it twice. Some supplies may not need recrystallising, but new supplies should be tested to see that the untreated material gives the same calibration blank as the recrystallised material. Cadmium solution, 1 mg per ml-Dissolve 0.25 g of pure cadmium wire in 5 ml of AnalaR quality 16 N nitric acid. Evaporate the solution just to dryness, dissolve the residue in 5ml of AnalaR quality hydrochloric acid and again evaporate it just to dryness.Repeat this evaporation with hydrochloric acid twice. Finally dissolve the residue in water and make the solution up to 250ml. PROCEDURE- Place 3-0 ml of the hydrobromic acid in a 50-ml beaker and neutralise it with 18 N ammonium hydroxide, with methyl red as indicator. Dilute the solution to 30 ml and treat it as described in the procedure for hydrochloric acid except that the removal of impurities as their acetylacetonates by chloroform extraction may be omitted and 2 drops of cadmium solution must be added before the solution is heated in a water-bath. The aluminium - dye complex step that is to be measured occurs at -0.30 & 0-03 volt and it is followed by that of the cadmium at -0.53 & 0.02 volt. Calibrate the instrument in the presence of known amounts of fluoride, using a 0.2917 g per ml ammonium bromide solution as blank solution.If the cathode-ray polarograph is used for this determination, cadmium should not be added. EXPERIMENTAL DETERMINATION OF FLUORIDE IN BROMINE- An obvious method was to convert the bromine to ammonium bromide with ammonium hydroxide and to proceed as described above. However, it was decided first to try a simpler method, which involved placing a small quantity of bromine under a layer of water con- taining a suitable amount of an aluminium salt, i e . , the amount required in the subsequent polarographic treatment, and carefully evaporating the bromine. It was hoped that by this treatment the fluoride would be trapped in the aluminium solution, which could then be treated in a manner similar to that used for the determination of fluoride in water.This method proved entirely successful. METHOD FOR DETERMINING FLUORIDE IN BROMINE REAGENTS- As previously described.2 PROCEDURE- Place 3 ml of the bromine, 15 ml of water and 3 ml of a dilute solution of an aluminium salt (containing 30 pg of aluminium) in a 50-ml beaker fitted with a lifter and a watch-glass. Heat the beaker gently until the solution becomes colourless and then let it cool. Test the solution for the absence of bromine by placing 1 drop on a tile and adding to it 1 drop of a potassium iodide - starch solution. If a blue colour develops, gently boil the solution for 5 minutes and repeat the test. Wash the watch-glass, the lifter and the sides of the beaker with a little water and dilute the solution to about 30 ml.Determine the fluoride in the solution as described for the determination of fluoride in water in Part I.2 Repeat the heating until the test is negative. RESULTS The results obtained by application of the methods described above are shown in Tables 11, I11 and IV. Both the Cambridge photographic and the cathode-ray polarographs were used in this work.May, 19541 TERRY : THE POLAROGRAPHIC DETERMINATION OF FLUORIDE 27 1 Fluoride added, Pg 0 15 20 25 30 Fluoride added, PLg 0 5 10 15 20 Fluoride added, Pg 0 6 10 20 TABLE I1 RECOVERY OF FLUORIDE FROM HYDROCHLORIC ACID Fluoride found r A With cathode-ray With Cambridge photographic polarograph, polarograph, Pg rg 0.0, 0.0, 0.0, 0.0 0.0, 0.0 14.5, 14.5, 14.5, 16.0 18.0, 18.0, 23.0, 23.0, 20.0, 20.0, 19.0, 18.0, 18.0, 18.0, 21.0, 18.0, 18.0, 17.0 17.0, 18.0, 21.0 25.0, 26.0, 29.0, 27.0, 28.0, 20.0, 20.0 28.0 TABLE I11 RECOVERY OF FLUORIDE FROM HYDROBROMIC ACID Fluoride found A r- With Cambridge photographic polarograph, Pg 3.0, 3.0, 4.0, 1.4, 1.4, 3.0, 5.0, 3.0, 5-0, 2.5, 3.0, 4.0, 4.0, 2.0, 3.0 10.5, 6.8, 6.8, 7.2, 7.0, 6.4, 6.4, 6.4, 14.0, 14-0, 15.0, 10.0, 12.0, 12.0, 8.0, 13.4, 10.6, 12.0, 12.8 22.0, 18.0, 18.0, 20.0, 14.0, 14.2 21.0, 23.0, 22.0 TABLE IV With cathode-ray polarograph, rg 0.0, 0.0 5.0, 5.0 10.0, 10.0 14.0, 14.0 17.0, 20.0 RECOVERY OF FLUORIDE FROM BROMINE Fluoride found -- r- A \ With cathode-ray With Cambridge photographic polarograph, polarograph, Pg rg 0.0 (nine determinations), 1.0, 0.5, 0-3 0.0, 0.0 8.0, 11.0, 10.0, 7.0, 7.0, 13.5, 10.0, 9.0, 9.0 9.0, 11.0, 11.0, 10.0, 10.0, 10.0 6-0, 6.0, 6.0, 5.0, 5.0 5-0, 5.0 19.0, 19.0, 23-0, 20.0, 17.5, 18.0 DISCUSSION OF RESULTS The results are satisfactory, particularly those for hydrochloric acid and for bromine, but for hydrobromic acid there appears to be a factor that causes the spread of results to be rather wide.In general, and particularly with hydrobromic acid, the results with the cathode-ray polarograph appear to be better than those determined with conventional polaro- graphs. Although we have not yet been able to obtain sufficient results with the cathode- ray polarograph to substantiate completely its apparent superiority when these methods are used, it is clear, from practical experience, that the measurement on this instrument of the waves produced is easier and more accurate.It should be noted that different samples of hydrobromic acid were used in the experiments on the photographic and cathode-ray polarographs. It appears that the nature of the hydrobromic acid samples and the shape of the wave produced on the conventional type of polarograph, whichmake it difficult to measure the wave height even in the presence of cadmium, account for most of the rather wide spread of results with this substance.272 MILNER, WOOD AND WOODHEAD : THE SEPARATION [Vol. 79 That the potentialities of this method for the determination of fluoride have as yet only been touched upon must again be emphasised; ideal conditions have not yet been attained. In the work described here, a small depression of a large wave is measured and all errors are thus greatly enhanced. It seems likely that this fault could be overcome by use of a differential (subtractive) circuit3 and this method is now being investigated; only when this project is successfully concluded can the full potentialities of the technique be realised. In conclusion, the authors have to thank the Chief Scientist, Ministry of Supply, for permission to publish this paper, and Mr. A. S. Nickelson for his interest and encouragement. REFERENCES 1. 2. 3. NOTE-Reference 2 is to Part I of this series. Hunter, G. J . , MacNulty, B. J., and Terry, E. A,, Anal. Chim. Acta, 1953, 8, 351. MacNulty, B. J., Reynolds, G. F., and Terry, E. A., AnaZyst, 1954, 79, 190, Semerano, G., and Riccoboni, L., Gazz. Chim. Ital., 1942, 72, 297. CHEMICAL INSPECTORATE MINISTRY OF SUPPLY STATION APPROACH BUILDINGS KIDBROOKE, LONDON, S.E.3 November 2nd, 1953

ISSN:0003-2654    

DOI:10.1039/AN9547900267

出版商:RSC    

年代:1954

数据来源: RSC

摘要:

272 The MILNER, WOOD AND WOODHEAD : THE SEPARATION Separation and Determination of [Vol. 79 Gallium BY G. W. C. MILNER, A. J. WOOD AND J. L. WOODHEAD From a study of the extractability of the halides of gallium from acid solutions with organic solvents, the chloride was found to be more readily extracted than either the bromide or the iodide. In addition, several organic solvents proved to be as efficient as ether for extracting gallium chloride from solution. Diethyl ether was preferred in the analysis of gallium - uranium mixtures. The extracted gallium was then precipitated with camphoric acid after the solution has been buffered with a formic acid - ammonium formate buffer of pH 3.3, this precipitate being separated by filtration through a sintered-glass crucible, washed, dried and finally weighed.The factor for converting the weight of precipitate to weight of gallium proved to be 0.213. The determination of amounts of extracted gallium less than about 3 mg was more satisfactorily accomplished by a potassium ferrocyanide titration with 3 : 3'-dimethylnaphthidine as indicator. GALLIUM readily forms stable complexes that are soluble in organic solvents and can, therefore, be applied to its separation from many other elements. For example, in acid solutions it forms, with cupferron, a complex that is soluble in chloroform. This reaction is not specific, however, as several other elements are also extractable under these conditions, including niobium, titanium, iron, zirconium and so on. The ready solubility of gallium chloride in ether is applicable to the separation of gallium from other constituents in chloride-containing solutions.1 This latter requirement can lead to some difficulty, however, for if gallium metal is directly attacked with hydrochloric acid, some of the gallium may be lost by evaporation.2 It is possible to overcome this difficulty by dissolving the metal in sulphuric acid with the minimum of nitric acid and then adding an excess of ammonium chloride to the resulting solution to form the gallium chloride ions.After the extraction with diethyl ether, it is necessary to recover the gallium from the combined diethyl ether extracts and a t the same time to separate it from any other elements in solution. In early work, Ato3y4 used camphoric acid for precipitating gallium from solution, the precipitate being ignited to the oxide.Various objections have been raised, however, to determining gallium via the oxide owing to the very hygroscopic nature of gallium oxide unless ignition has been carried out at a temperature of 1200" C.2 In developing procedures for the separation of gallium, many organic solvents were investigated and the experiments were extended to include the extraction of gallium bromide and iodide in addition to gallium chloride. These studies were greatly simplified by the useMay, 19541 AND DETERMINATION OF GALLIUM 27 3 of the tracer technique with radioactive gallium. Conditions were also developed for com- pleting the gallium determination without the ignition to the oxide. Full details of these investigations are included in the experimental section.EXPERIMENTAL DEVELOPMENT OF A PROCEDURE FOR SEPARATING THE GALLIUM FROM OTHER CONSTITUENTS- In these investigations suitable gallium solutions were prepared by dissolving weighed quantities of Specpure gallium metal (approximately 100 mg) in a suitable quantity of nitric acid, then adding 20 ml of sulphuric acid, sp.gr. 1-84, and finally evaporating to fumes of this acid to remove the nitric acid completely. After being cooled, each gallium solution was diluted to 100ml with water and a weighed amount of ammonium chloride, bromide or iodide was added. Then after the addition of a suitable amount of radioactive gallium, the gallium halide was extracted with two separate 25-ml portions of a conditioned organic solvent, the conditioning being accomplished by shaking the solvent with 100 ml of 20 per cent.v/v sulphuric acid containing the same amount of ammonium halide as was present in the gallium solution. A measure of the amount of gallium transferred to the organic layer was obtained from the decrease of the activity of the aqueous solution caused by the extraction procedure. Results obtained with 20-g quantities of the ammonium halides and a wide range of organic solvents are summarised in Table I. TABLE I GALLIUM EXTRACTED BY DIFFERENT SOLVENTS I N PRESENCE OF AMMONIUM HALIDES Solvent Diethyl ether .. isoPropy1 ether . . Dibutyl carbitol . . /3/3-Dichlorodiethyl ether Methyl ethyl ketone Methyl isobutyl ketone Methyl propyl ketone Amyl alcohol . . .. Ethyl acetate ..Amyl acetate . . Gallium extracted in presence of Ammonium Ammonium Ammonium chloride, bromide, iodide, 7 A \ 70 70 % .. . . .. > 99 61 2 .. . . .. 90 27 - .. .. .. > 99 . . .. .. 92 . . .. .. > 99 .. .. .. > 99 77 28 . . .. .. > 99 90 38 . . .. .. > 99 1.5 - . . .. .. > 99 18 10 .. .. .. > 99 - - - - - - - - The results in Table I show that gallium chloride is more readily extracted by organic solvents than either the bromide or iodide, and they substantiate Irving and Rossotti’ss earlier findings with diethyl ether. In addition, many other organic solvents are just as efficient for this extraction as diethyl ether, especially the ketones. Subsequent experiments were, therefore, limited to gallium chloride, and the effects of the sulphuric acid content of the solution on the extractability of the gallium were next investigated.These experiments were also limited to only a few of the solvents that from the previous work appeared to be as suitable as diethyl ether. The results are given in Table 11. From Table I1 it is clear that extraction of gallium with diethyl ether is influenced by the final sulphuric acid concentration, whereas the extractions with the ketones are unaffected. The effect of the final concentration of ammonium chloride on the extraction of gallium from 20 per cent. v/v sulphuric acid solutions was next investigated. Again, only a few selected solvents were used and the results in Table I11 show that methyl ethyl ketone is less influenced by a decrease in the ammonium chloride concentration than the other solvents.From the results of the above experiments it is clear that certain ketones are as efficient as diethyl ether for the quantitative extraction of gallium chloride and are less affected by variations in the solution conditions. On the basis of experience with the separation of gallium from solutions containing uranium, however, the ketone extractions are not quite as selective as the diethyl ether extraction. In the analysis of uranium - gallium mixtures, about five times as much uranium contaminated the gallium extracted by ketones as compared with the contamination from the diethyl ether extractions, the amount of uranium co- extracted by the ether being generally less than 1 mg from a 2-g sample. Consequently274 MILNER, WOOD AND WOODHEAD: THE SEPARATION [Vol.79 extractions with diethyl ether were found to be more suitable in the analysis of these particular mixtures. TABLE I1 GALLIUM EXTRACTED FROM 100ml OF SOLUTION CONTAINING 100mg OF GALLIUM, 2Og OF AMMONIUM CHLORIDE AND VARIOUS AMOUNTS OF SULPHURIC ACID, SP.GR. 1.84 Gallium extracted in presence of 20 ml of 15 ml of 10 ml of f A v Solvent Diethyl ether . . .. .. .. .. > 99 Methyl ethyl ketone.. .. .. .. > 99 Methyl propyl ketone . . .. .. > 99 85 > 99 > 99 34 > 99 > 99 TABLE I11 GALLIUM EXTRACTED BY VARIOUS SOLVENTS FROM 100ml OF 20 PER CENT. V/V SULPHURIC VARIOUS AMOUNTS OF AMMONIUM CHLORIDE ACID SOLUTION CONTAINING APPROXIMATELY 100 mg OF GALLIUM AND Gallium extracted in presence of f A -l 15 g of 10 g of 5 g of % % Yo Diethyl ether.... .. .. .. 93 24 - Methyl ethyl ketone . . .. .. .. > 99 > 99 > 99 Methyl propyl ketone . . .. .. > 99 > 99 80 Solvent NH,Cl, NH,Cl , NH,Cl, Methyl isobutyl ketone . . .. .. > 99 98.5 71 METHOD PROCEDURE- Transfer 2 g of the sample to a 650-ml conical beaker, add to it 25 ml of nitric acid, sp.gr. 1-42, and heat the beaker gently to obtain complete solution. Then add 20ml of sulphuric acid, spgr. 1.84, and cautiously evaporate to fumes of this acid. After cooling, transfer this solution to a 100-ml calibrated flask and dilute it to the mark with water. With a pipette, place a suitable aliquot (Note 1) of this solution in a 250-ml beaker, dilute it to 100 ml with 20 per cent. v/v sulphuric acid and dissolve 20 g of ammonium chloride in this solution.Transfer the solution to a 250-ml separating funnel, using not more than 10 ml of water to wash the beaker. Add 50 ml of conditioned diethyl ether (Note 2) , stopper the funnel and shake it well for 30 seconds (Note 3). Transfer the aqueous layer to another 250-ml separating funnel and add a further 50 ml of diethyl ether. Shake well for 30 seconds and transfer the aqueous layer to a third separating funnel. Repeat the extraction with a third 50-ml portion of diethyl ether and then combine all the diethyl ether extracts in the first separating funnel. Wash the combined extracts with 10 ml of the 20 per cent. v/v sulphuric acid - 20 per cent. ammonium chloride solution used for conditioning the diethyl ether and reserve them for the determination of the gallium concentration.NOTES- 1. Take an aliquot of sample solution according to the gallium content- Aliquot taken, ml Gallium 1 to 5 per cent. . . .. .. .. 100 5 t o 10 per cent. .. .. . . .. 50 10 to 20 per cent. . . .. . . . . 25 20 to 80 per cent. . . .. . . . . 10 2. 3. Condition the diethyl ether by shaking 100-ml portions with 100ml of 20 per cent. v/v H2S04 Care must be taken to release the pressure frequently by removing the stopper. containing 20 g of ammonium chloride. EXPERIMENTAL DEVELOPMENT OF SUITABLE PROCEDURES FOR DETERMINING THE EXTRACTED GALLIUM- After the separation of the gallium from the diethyl ether extracts either by evapora- tion or by re-extraction into water, it is necessary to determine the gallium concentration byMay, 19541 AND DETERMINATION OF GALLIUM 275 some convenient procedure. Ato used the insoluble complex, Ga, [C,Hl,(CO,),],, produced from gallium and camphoric acid, for separating the gallium from solution before completing the determination by igniting the precipitate to gallium oxide.This type of procedure is not very satisfactory, however, unless the precipitate is ignited at a temperature of 1200" C, as gallium oxide residues produced by ignitions at lower temperatures are very hygroscopic. The ignition of gallium camphorate to gallium oxide is therefore to be avoided, if possible, and we attempted to complete the determination by weighing the gallium camphorate directly after filtration and drying. In the preliminary experiments some difficulty was encountered in attaining the com- plete precipitation of gallium under Ato's conditions. This discrepancy was traced to lack of control of the pH of the solution at the precipitation stage, and an investigation into the influence of pH by use of buffers prepared from molar solutions of sodium acetate and acetic acid showed that precipitation of gallium camphorate was complete over the pH range from 3.1 to 4.0 (see Fig.1). Attempts to separate the precipitates produced under P" Fig. 1. The effect of pH on the precipita- tion of gallium camphorate from acetic acid - sodium acetate buffers sodium formate buffers Fig. 2. The effect of pH on the precipita- tion of gallium camphorate from formic acid - these conditions by filtration through sintered-glass crucibles failed completely, even No.4 porosity sinters failing to retain the precipitates quantitatively. The replacement of the acetate buffer with a sodium formate - formic acid buffer resulted in better-crystallised gallium camphorate precipitates, which were readily separated by filtration through sintered-glass crucibles. Under these conditions precipitation of the gallium was complete over the pH range from 2.5 to 4.5 (see Fig. 2), and hot water proved to be the most suitable wash solution for this type of precipitate. The gallium camphorate precipitates were always contaminated with sodium salts even after thorough washing. This difficulty was overcome by precipitating the gallium camphorate from a buffer solution of pH 3.3 prepared from molar solutions of formic acid and ammonium formate.Under these conditions the weight of the final camphorate precipitate bore some relation to the weight of the gallium initially taken (see Table IV, columns 1 and 2 ) . As ferric chloride is also extractable by diethyl ether, it is possible for the gallium solutions produced from the diethyl ether extracts to contain ferric iron. The pH of the final formate solution for the precipitation of gallium camphorate is, however, suitable for the reduction of the iron to the ferrous state with hydroxylamine hydrochloride and after this treatment the gallium camphorate precipitates were found to be free from interference by iron. METHOD PROCEDURE- funnels with 25 ml of 20 per cent. v/v sulphuric acid and add it to the beaker. diethyl ether by evaporation on a water-bath. Transfer the diethyl ether extracts to a 400-ml squat-type beaker.Wash the separating Remove the Cool the solution, transfer it to a 50-ml276 MILNER, WOOD AND WOODHEAD : THE SEPARATION [Vol. 79 calibrated flask and dilute it to the mark with water. With a pipette, place a suitable aliquot containing up to about 50 mg of gallium in a 650-ml conical beaker and add 3 drops of thymol blue indicator. Adjust the solution to pH 2.8 by the dropwise addition of approximately 8 N ammonium hydroxide solution, the indicator changing colour from red to yellow. Add 25 ml of a formate buffer solution prepared by mixing 100 ml of M formic acid with 50 ml of M ammonium formate. Also add 1 g of hydroxylamine hydrochloride, 200 ml of water and 50 ml of boiling formate buffer solution containing 1 g of camphoric acid.Boil the result- ing solution for 2 minutes and leave it warm for 1 hour to digest. Filter it through a tared No. 4 sintered-glass crucible and wash the precipitate thoroughly with hot water. Dry at 110" C and weigh the crucible and contents. Use the factor 0.213 for converting gallium camphorate to gallium. RESULTS WITH THIS PROCEDURE- The usual factor for converting gallium camphorate, Ga,[C,H,,(CO,),],, to gallium is 0.189. But, on applying this factor to the weights of camphorate precipitate in column 2 of Table IV, the recoveries for gallium were consistently low (see column 3). These low recoveries were rather inexplicable and the applicability of this factor under these new conditions was therefore checked by igniting weighed amounts of the camphorate precipitate to gallium oxide, Ga203, in platinum dishes at very high temperature and then re-weighing after cooling.The results from three separate experiments are given in Table V and show that the factor under these conditions should be 0.213. When this factor was applied to the results in Table IV, the figures for recovery of the gallium were good (see column 4). TABLE IV RECOVERIES OF GALLIUM AFTER PRECIPITATION AS GALLIUM CAMPHORATE Weight of gallium taken, mg 2.5 5-0 7.5 10.0 20.0 30.0 40.0 50.0 Weight of r camphorate, mg 11.7 23.5 36.1 47.1 95.0 143.5 190.7 235.2 Weight of gallium recovered, mg Factor 0.189 2.2 4.4 6.8 8.9 17.5 27.1 36.1 44-4 -3 Factor 0-213 2.5 5.0 7-7 10.0 20.2 30.6 40.6 50.0 TABLE V DETERMINATION OF THE FACTOR FOR CONVERTING GALLIUM CAMPHORATE TO GALLIUM Weight of gallium Weight of Weight of g g g camphorate, Ga,O,, gallium, Factor 0.2909 0.0834 0.0620 0.214 0-2855 0.0822 0.06 11 0.214 0.2941 0.0840 0.0624 0.212 The factor 0.213 was confirmed by the examination of a thermolysis curve determined for the camphorate precipitate. This curve (Fig.3) also showed that the composition of the camphorate was retained for temperatures up to 135" C and that it was completely converted to Ga,O, at 450" C. The gallium precipitate from the formate solution must therefore have a composition different from that corresponding to the formula Ga, [C8H,,(C0,),j,. The analysis of typical specimens of the camphorate precipitate produced under the above conditions gave the following percentage composition: Ga, 21.3; C, 43.3; H, 5.46; 0, 29.94 (by difference).The empirical formula corresponding to this composition is GaC,,H,,O,, but so far the exact structural formula for this precipitate has not been established.May, 19541 AND DETERMINATION OF GALLIUM 277 Typical results obtained on applying the diethyl ether extraction followed by the camphorate precipitation to the analysis of gallium - uranium mixtures are shown in Table VI. TABLE VI THE ANALYSIS OF GALLIUM - URANIUM MIXTURES Nominal gallium Percentage Composition content, gallium uranium* Impurities Total Yo 75 74.6 24.6 0-03 99-23 60 53.2 46.6 0.01 99.9 99.2 99.8 10 11.45 87.75 t 1 1.23 98.5 0.07 * The uranium was precipitated as ammonium diuranate and ignited to U30,.6 t Not determined.The determination of the smaller amounts of gallium was better accomplished by the potassium f errocy anide titration, with 3 : 3 '-dime t hylnaph thidine as indicator. Belcher6 first used this indicator in the direct determination of small amounts of gallium in organic com- Fig. 3. Thermolysis of gallium camphorate pounds. After the extraction of gallium with diethyl ether, however, the conditions of the resultant gallium solution differed considerably from those recommended by Belcher for the ferrocyanide titration. When known amounts of gallium were taken through such a pro- cedure, the recoveries were always low owing to the difficulty of detecting the end-point of the titration. The titration conditions were therefore investigated.The influence of the pH value on the titration of 1.47 mg of gallium is shown in Fig. 4, the optimum pH range for complete recovery being from pH 2-2 to 2-5. Known amounts of gallium were next taken through the &ethyl ether extraction procedure and the pH values of the resultant aqueous solutions were adjusted to the optimum pH range each time before the ferrocyanide titration. The gallium recoveries were good under these conditions for concentrations from about 0.3 to 3.6 mg of gallium, as shown by the results in Table VII. It was noticed that the titration end-point progressively became more indeterminate for amounts of gallium greater than 2 mg owing to the rapid re-oxidation of the indicator. The addition of a larger volume of absolute ethanol was found to suppress this effect, and the end-point was fairly sharp when 15 ml of ethanol were used, the end-point being reached when the red colour of the indicator did not return for about.5 seconds. No interference was278 MILNER, WOOD AND WOODHEAD : THE SEPARATION [Vol. 79 encountered in the determination of gallium by the complete procedure of ether extraction followed by titration, from similar amounts of uranium, iron, vanadium, copper, zinc, cadmium, lead and aluminium. Details of the titration are as follows. I 2 3 4 pH of solution Fig. 4. The effect of pH on the titration of gallium chloride with potassium ferrocyanide TABLE VII RECOVERY OF KNOWN AMOUNTS OF GALLIUM Gallium taken, mg 0.307 0.735 1.105 1.44 1.83 2.17 2-51 2.87 3.59 Gallium recovered, mg 0.305 0.735 1.108 1.44 1.82 2.20 2.56 2.90 3.57 Error, % - 0.6 nil nil - 0.5 + 1-3 + 2.0 + 1.0 - 1.0 + 0.3 REAGENTS- in 1 litre of distilled water containing 0.2 g of sodium carbonate.against a pure zinc solution with 3 :3’-dimethylnaphthidine as indicator. 1 ml of 0.0075 M K,Fe(CN), = 0.6972 rng of gallium. Potassium ferrocyanide, 0.0075 M-Dissolve 3.1 67 g of AnalaR potassium ferrocyanide Standardise the solution Potassizm ferricyanide, 0.5 per cent. w/v-Dissolve 0.5 g of potassium ferricyanide in Prepare a fresh solution 3 :J’-DimethyZnaphthid~ne-Dissolve 0.200 g of 3 :3’-dimethylnaphthidine in 100 ml of 100ml of distilled water and store the solution in a dark bottle. daily. ethanol. PROCEDURE FOR DETERMINING GALLIUM- Take the aqueous gallium solution (volume about 30ml) obtained from the combined diethyl ether extracts and adjust its pH to a value of 2.3, with the aid of a pH meter, by the addition of ammonium hydroxide.Transfer the solution to a 100-ml titration flask and rinse the beaker with two separate 7 6 m l portions of ethanol. Add 1 drop of the potassium ferricyanide solution, 2 drops of indicator solution and then titrate by adding the standard ferrocyanide solution from a 5-ml burette. Titrate rapidly until the red colour of the indicatorMay, 19541 AND DETERMINATION OF GALLIUM 279 begins to fade and then dropwise until a pale green colour persists for 5 seconds whilst the solution is being shaken. Carry out a blank titration on the reagents. Calculate the gallium concentration in milligrams from the expression (sample titre - blank titre) x 0-6972 x molarity of ferrocyanide/0-0075. PROCEDURE FOR STANDARDISATION OF POTASSIUM FERROCYANIDE SOLUTION- Prepare a standard zinc solution by dissolving 3.269 g of Specpure zinc metal in 15 ml of hydrochloric acid, sp.gr.1-16. Then to it add 100 ml of diluted sulphuric acid (1 + 1) and evaporate to fumes of this acid. Accurately dilute this solution to a volume of 1 litre with water and mix it thoroughly. With a pipette, place 100ml of this solution in a 500-ml calibrated flask and dilute it to the mark with water. Transfer 20 ml of the zinc solution to a titration flask and make it up to 50 ml with water. Add 2.5 ml of 10 per cent. ammonium sulphate solution, 4 drops of 0.5 per cent. potassium ferricyanide and 2 drops of the indicator solution prepared by dissolving 50 mg of 3:3’- dimethylnaphthidine in 10 ml of glacial acetic acid. Rapidly add the potassium ferrocyanide solution to give an excess of about 25 per cent. (normally about 25 ml). Shake the solution and leave it to stand in the dark for not less than 5 minutes. Titrate the excess of ferrocyanide with the standard zinc solution, the end-point being marked by the first permanent pink coloration. total volume of zinc solution (ml) x 0.0006538 x 2000. volume of ferrocyanide solution (ml) x 3 x 65.38 Calculate the molarity of the ferrocyanide solution from the expression- REFERENCES 1. 2. 3. 4. 5. 6. Irving, H. M., and Rossotti, F. J. C., Analyst, 1952, 77, 801. Wilkinson, W. B., Argonne National Laboratory Report No. 4109, Feb. loth, 1948. Ato, S., Sci. Papers Inst. Phys. Chem. Res., Tokyo, 1936, 29, 71; Chem. Abstr., 1936, 30, 8067. - , Sci. Papers Inst. Phys. Chem. Res., Tokyo, 1930, 12, 225; Chem. Abstr., 1930, 24, 2689. Milner, G. W. C . , and Wood, A. J., Atomic Energy Research Establishment Report C/R1041, Belcher, R., Nutten, A. J., and Stephen, W. I., J . Chem. SOC., 1952, 2438. H.M. Stationery Office, 1953. ANALYTICAL CHEMISTRY GROUP ATOMIC ENERGY RESEARCH ESTABLISHMENT HA R WELL NR. DIDCOT, BERKS. October 12th, 1953

ISSN:0003-2654    

DOI:10.1039/AN9547900272

出版商:RSC    

年代:1954

数据来源: RSC

摘要:

280 MITCHELL : THE SPECTROPHOTOMETRIC DETERMINATION [Vol. 79 The Spectrophotometric Determination of Magnesium with Thiazol Yellow Dyes BY T. A. MITCHELL A critical examination of the thiazol yellow method for the colorimetric determination of magnesium has shown the following. (2) The fading of the thiazol yellow - magnesium hydroxide complex is caused by “ageing” of the magnesium hydroxide. This change in the structure of the colloid, which takes place both in the presence and in the absence of thiazol yellow, is inhibited by the addition of glycerol and concentrated sodium hydroxide. (ii) The solubility of magnesium hydroxide and hence of the coloured complex is greatly increased by the colloid protectors, starch and polyvinyl alcohol. Starch, however, is preferable to polyvinyl alcohol for this purpose, because, unlike the alcohol, it does not itself affect the colour of the dye or dye-complex.(iii) Numerous cations and organic compounds interfere, and neither their removal by precipitation nor the use of “compensating solutions” satisfactorily controls this effect. A method is accordingly proposed in which the magnesium is precipitated from solution as magnesium ammonium phosphate, the pre- cipitate is redissolved and the colorimetric determination is carried out on the resulting solution, starch being used as the protective colloid and glycerol as the colour stabiliser. The absorptions of the solutions are measured a t a fixed brief interval after colour development. WHEN sodium hydroxide solution is added to a dilute solution of a magnesium salt in the presence of certain yellow thiazol dyestuffs, a red coloration, related in intensity to the magnesium concentration, is produced. The object of the investigation reported in this paper was to develop a reliable general photometric procedure for determining magnesium by this reaction, and to apply the method t o the estimation of magnesium in plant and soil extracts. Since Kolthoff’s discovery of the reaction in 1927, numerous papers describing its use in the colorimetric estimation of magnesium have appeared in the literature, and the following facts are now well established- (1) Numerous other substances give the same colour change as magnesium under the same c0nditions.l ,2 (2) Certain metal ions and organic compounds in solution alter the intensity of the (3) At concentrations of magnesium above 3 pg per ml a precipitate rapidly settles from the test ~ o l u t i o n .~ , ~ ~ (4) The coloured complex is not stable and a decrease in colour intensity occurs with Many methods for eliminating or standardising these effects have been proposed. Among (a) Their removal from solution by precipitation (calcium as o~alate,~iron and aluminium as phosphates13 or hydroxide^,^,^^,^^ and phosphate as the uranyl salt15), ignition (ammonium ion13 J4) and separation as complexes (iron, aluminium, manganese, copper, titanium and vanadium as acetylacetonatesl6). Standardisation of their effects by the use of “compensating solutions.”5~7~8~10~11 This involves the addition of fixed amounts of the various ions to each test solution ; it is assumed that the effects of these ions are constant when they are present at more than a certain concentration.Suppression of their effects by formation of complexes in the test solution. Thus cyanidel y9 917 reduces interference by copper, cobalt, nickel, zinc, cadmium and mercuric ions, hydroxylamine has been used to prevent manganese interference and sucrose to reduce that of calcium. To prevent the precipitation of the magnesium hydroxide - dye complex, protective colloids, such as st arc he^,^?^ ,12 ,15 dextrins,lS gums,4 agar,18 polyvinyl alcohollo and a number colour due to magnesium.l?3?*,5,6,7,8,Q,10,11 time,3,4,12 those for dealing with interfering substances are- (b) (c)May, 19541 OF MAGNESIUM WITH THIAZOL YELLOW DYES 28 1 of commercial polymers, have been recommended, while additions of hydroxylamine hydro- chloride3 and glycerol14 have been claimed to reduce or prevent fading of the colour. However, in this laboratory, analyses of plant extracts by a variety of the published procedures, which incorporate these refinements, have given results that were generally unreliable.Therefore, the reaction itself, factors affecting the production of stable and reproducible coloured solutions, and methods for eliminating interferences have been investi- gated, and the proposed method is based on the findings from these experiments. METHOD APPARATUS- Coleman model 14 spectrophotometer with matched 13-mm square cuvettes. Capillary tube of 1 mm bore, bent back along its own length by 1 to 2 mm.REAGENTS- to 1 litre. and dilute to 1 litre. ammonium dihydrogen phosphate in distilled water and dilute to 1 litre. Ammonium chloride-Dissolve 50 g of ammonium chloride in distilled water and dilute Ammonium oxaZateDissolve 10 g of crystalline ammonium oxalate in distilled water Citrate - Phosphate reagent-Dissolve 5 g of sodium citrate dihydrate and 25 g of Acetic acid-Dilute 60 ml of glacial acetic acid to 1 litre with distilled water. Ammonium hydroxide-Concentrated and 0.1 N. Sodium hydroxide, 3 N. Thiaxol yeUow (General Aniline Works, Rensselaer, N.Y., or Antara Products, N.Y .)- Dissolve 0.10g of the solid in water and dilute to 100 ml. This stock solution keeps in- definitely if stored away from light. SoZubZe starch-Mix 2-5 g of analytical-reagent grade starch to a paste with water, add 80ml of boiling water, boil for 2 minutes, filter and, when cold, make up to 100 ml.This solution should be prepared every 2 or 3 days. Dye - stabiliser reagent-Mix together 50 ml of glycerol, 50 ml of soluble starch solution and 15 ml of the thiazol yellow solution. This solution must be prepared daily. Magnesium standards-Dissolve 1.230 g of magnesium sulphate, MgS04.7H,0, in water and dilute to 1 litre. This solution contains 120 pg of magnesium per ml, and is diluted to give standards of 90, 60 and 30 pg of magnesium per ml. Dilute to 500 ml. PROCEDURE- Into a 15-ml tapered centrifuge tube put, from a pipette, an aliquot of the solution to be analysed, containing between 15 and 120pg of magnesium. From micro-burettes add 0.1 N ammonium hydroxide to bring the pH to between 4 and 6 and water to make the volume of solution in the tube to a total of 2 ml.(The amount of ammonium hydroxide is determined, for a particular series of samples, by titrating an aliquot of one of them against the 0.1 N ammonium hydroxide, methyl red being used as indicator.) Next add 1 ml of ammonium chloride solution and then 1 ml of ammonium oxalate reagent. Set the tube aside for 10 minutes, then centrifuge it for 5 minutes at 3000 r.p.m. at a radius of 15 cm and take 3 ml of the supernatant liquid by pipette and put it in a second centrifuge tube. To this tube add 2ml of the citrate-phosphate reagent and 2ml of concentrated ammonium hydroxide. Set this aside overnight, then centrifuge it for 5 minutes and, by means of the bent capillary tube, draw off as much of the supernatant liquid as possible without disturbing the magnesium ammonium phosphate precipitate.Without washing it, dissolve the precipitate in 1 ml of 6 per cent. acetic acid, and add 8 ml of the dye-stabiliser reagent and 1 ml of 3 N sodium hydroxide. Mix the solution, set it aside for 1 minute, and then transfer it to a spectrophotometer cuvette and measure the optical density at 520 mp against a reference cell containing distilled water. Construct a calibration graph relating optical density to concentration by using solutions containing 0, 30, 60, 90 and 120 pg of magnesium, prepared by the same method and at the same ti.me as the test samples. A uniform variation in the optical density values of the standards of up to h2.5 per cent.occurs from day to day.282 MITCHELL : THE SPECTROPHOTOMETRIC DETERMINATION [Vol. 79 DISCUSSION OF RESULTS Fading-The rapid decrease in intensity of the red colour of the magnesium hydroxide - dye complex, on standing, was again confirmed. Investigation showed the effect to be associated with an “ageing” of the magnesium hydroxide. The change responsible for fading starts as soon as the magnesium hydroxide is forrned in solution and is independent of the presence or absence of the dye or complex. A number of substances were found to inhibit the fading. They included sodium hydroxide in high concentrations (about 1.25 N in the final solution), polyvinyl alcohol, and calcium ion a t a specific concentration of 125 pg per ml of the final solution.Hydroxylamine3 was without effect, but glycerol1* showed pro- nounced effects. As, however, calcium and polyvinyl alcohol have other undesirable Time c?f standing, minutes Fig. 1. Fading of solutions containing 120 pg of magnesium, 0.0025 per cent. W/V of thia.201 yellow and 0.2 per cent. w/v of starch in addition to the following: curve A, 1.25 N sodium hydroxide; curve B, 8 per Cent. v/v of glycerol and 0.4 N sodium hydroxide; curve C, 0.4 N sodium hydroxide. The solutions were prepared by mixing solutions of the reagents to give the concentrations required properties, their use as colour stabilisers is not recommended. Increased concentrations of sodium hydroxide reduce the range of the optical density measurements, SO that the use of glycerol and moderate concentrations of sodium hydroxide was considered the most practical compromise.In addition, measurement of each solution at a fixed interval (between 1 and 2 minutes) after colour development gave results of improved consistency and accuracy. Protective colloids-As magnesium has been shown to be present in some samples of gum arabic, tragacanth and agar,16 work on protective colloids was confined to analytical-reagent grade soluble starch and polyvinyl alcohol. Both protected the colloidal complex adequately, but starch was preferred because it has no other effect on the coloured solution. Polyvinyl alcohol itself reddened the dye, and though it also increased the ability of magnesium hydroxide to redden it, the resultant effect was a marked reduction in the range of optical density measurements.The soluble starch used (Baker’s C.P. Analysed “Lintner,” 0-2 per cent. w/v) increased the “solubility” of magnesium hydroxide from 7 or 8 pg per ml to 275 to 300 pg per ml. This increased value, measured turbidimetrically on a series of solutions ranging in concentration from 0 to 9OOpg of magnesium hydroxide per ml, was confirmed by estimating the residual magnesium hydroxide left after centrifuging to remove the precipitate formed on the addition of sodium hydroxide to a solution of starch and magnesium ion (600 pg per ml). As the sensitive range of the method described in this paper is 0 to 25 pg of magnesium hydroxide (0 to 10 pg of magnesium) per ml, this starch clearly gives adequate protection.It must be remembered, however, that the protective abilities of starches vary greatly, depending on their original source and subsequent prepara- tion.19 Anomalous results may therefore occur unless a good grade of soluble starch is used. The opalescence that forms in a starch solution after a few hours is no objection to its use, as it is completely dispersed when the concentrated sodium hydroxide is added. Dyestufl-A number of commercial thiazol dyes, Titan Yellow, Clayton Yellow, Thiazol Yellow, Mimosa and Chlorazol Yellow, have been used for the determination of magnesium.May, 19541 OF MAGNESIUM WITH THIAZOL YELLO-vV DYES 283 These vary somewhat in constitution according to the source and the mode of preparation, and show marked differences in sensitivity.20 Interferences-Routine determinations of magnesium are generally required for materials containing substances capable of interfering with the determinations. In the present work the marked effects of small concentrations (25 pg per ml of test solution) of copper, manganese, cobalt, nickel, iron, zinc and especially aluminium were again demonstrated.The effect of calcium was irregular, both intensification and reduction of the magnesium hydroxide - thiazol yellow colour being observed. The effect was dependent on the concentrations of magnesium and calcium in solution and varied with temperature. Where calcium caused a reduction in intensity, it was followed, when the solution was set aside, by a gradual increase. For all the elements examined the effects increased markedly with concentration, and no maximum was ever observed.It was considered, therefore, that “compensating solutions” could effect no practical control of interferences. In addition to the effects of metal cations, Wavelength, mp Fig. 2. Absorption spectra of solutions containing 0.0025 per cent. w/v of thiazol yellow, 0.2 per cent. w/v of starch and 0.25 N sodium hydroxide in addition to the following: curve A, 10 per cent. v/v of ethanol; curve B, 0.2 per cent. w/v of polyvinyl alcohol; curve C, 120 pg of magnesium; curve D, no additional reagent the interference by many organic compounds was studied, and it was confirmed that small amounts of citrate ion (10 to 50 pg per ml of test solution) and tartrate ion suppress colour formation. An examination, by the method of Natelson, Pincus and Lugovoy,21 of the citrate content of extracts of fresh plant tissue in 2 per cent.acetic acid showed it to be appreciable in many instances, and sufficient to cause large errors (50 per cent. and greater) in the magnesium determination. Absorption curves plotted for solutions containing 0.2 per cent. w/v of starch, 0-0025 per cent. w/v of thiazol yellow, 0.25N sodium hydroxide and various alcohols showed that alcohols also redden the dye (see Fig. 2 ) . The use of ethanol as a dye ~ o l v e n t ~ ~ ~ ~ ~ ~ ~ is therefore inadvisable. Because the dye and complex are so sensitive to the presence of other compounds, it was considered essential to separate the magnesium from all interfering substances before proceeding with the colorimetric determina- tion.Earlier methods involving purification by precipitation of these substances are fre- quently time-consuming, only specific substances are removed, and magnesium may be lost in the precipitate. Precipitation of the magnesium itself, as magnesium ammonium phosphate, was therefore tried. Preliminary trials showed that large amounts of phosphate and ammonium ion (100 and 200 pg, respectively, per in1 of the final solution) did not affect the colorimetric determinations, nor was there any effect when these amounts were combined in one solution. Calcium, ferric iron, aluminium and manganese also give precipitates with phosphate and concentrated ammonium hydroxide. Calcium was therefore removed as oxalate, and iron and aluminium were held in solution with citrate.No simple convenient control for manganese was found, but a minimum amount of 50 pg in the aliquot of solution taken is necessary to cause appreciable interference.284 MITCHELL THE SPECTROPHOTOMETRIC DETERMINATION [Vol. 79 ACCURACY The addition, individually, of 2500 pg of calcium or 1000 pg each of aluminium, copper, cobalt, nickel, zinc or ferric iron to standards containing 0, 30,60,90 and 120 pg of magnesium gave results which did not differ significantly from those with the pure standards. Up to 50 pg of manganese did not interfere, but above that level considerable increases in colour intensity occurred. From a bulk plant-ash extract, in 0.1 N hydrochloric acid, containing 116 pg of magnesium per ml (determined gravimetrically as pyrophosphate) , ten solutions were prepared, ranging in strength from 0.1 to the full strength of the original solution.Ma@esium was determined in each of these ten solutions 10 times, and the results are shown in Table I. Spectrographic analysis showed the following major elements to be present also : calcium, 633 pg per ml; potassium, 1280 pg per ml; manganese, 3.0 pg per ml; sodium, 117 pg per ml; magnesium determined spectrographically was 111 pg per ml. At all levels there was good agreement with the gravimetric figure. TABLE I RESULTS OF REPLICATE DETERMINATIONS OF TEN SOLUTIONS PREPARED BY DILUTING A SOLUTION OF KNOWN STRENGTH Dilution . . i Magnesium found, tcg Per ml Mean .. Concentration found for original solution, pg per ml . . Standard deviation .. 0.1 12-0 11.5 11.0 11.0 13.0 11-5 12.0 12.0 11.5 12.0 11.8 118 1.2 0.2 25 26 26 21 22 22 21 21 22 23 23 115 3.5 0.3 35 34 34 35 35 34 37 35 36 35 35 117 1.6 0-4 47 47 49 47 50 47 47 47 48 48 48 119 1.9 0.5 59 61 59 59 60 61 60 61 63 60 60 120 2.3 0.6 68 74 70 69 69 72 72 72 69 67 70 117 3.8 0.7 83 82 83 78 80 78 79 79 81 80 80 115 3.3 0.8 0.9 90 104 87 108 87 105 97 107 94 104 97 104 95 104 95 108 89 107 89 107 92 106 115 118 6.9 3.0 1.0 117 120 112 119 114 116 117 117 117 118 117 117 4.0 A series of extracts of fresh plant tissue in 2 per cent. w/v acetic acid were analysed with and without additions of known amounts of magnesium, with the results shown in Table 11. Recoveries ranged from 93 to 107 per cent. and averaged 101 per cent. TABLE I1 RECOVERIES OF MAGNESIUM ADDED TO PLANT EXTRACTS Material Tomato petiole Cauliflower leaf .. Cauliflower leaf . . Cauliflower petiole Cauliflower petiole Cauliflower petiole Cabbage petiole Cabbage petiole Cabbage petiole Ryegrass leaf . . Ryegrass leaf . . Ryegrass leaf . . Clover petiole . . Clover petiole . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . .. .. .. Magnesium originally found, PLg 63 30 57 55 51 63 73 43 45 61 51 57 44 48 Magnesium added, Clg 30 30 45 30 45 60 45 60 60 60 60 60 45 60 Tota! magnesium found, Clg 95 61 102 85 96 123 115 105 105 122 112 120 89 108 Difference, pg 32 31 45 30 45 60 42 62 60 61 61 63 46 60 Recovery, 107 103 100 100 100 100 93 103 100 102 102 105 100 100 % The author wishes to thank Mr. J.E. Allan for the spectrographic analysis.May, 19541 OF MAGNESIUM WITH THIAZOL YELLOW DYES 285 REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. Welcher, F. J., “Organic Analytical Reagents,” Van Nostrand Co. Inc., New York, 1948, Vol. IV, Eilers, H., Chem. Weekblad, 1927, 24, 448; Chem. Abstr., 1928, 22, 103. Gillam, W. S., I n d . Eng. Chem., Anal. Ed., 1941, 13, 499. Garner, R. J., Biochem. J . , 1946, 40, 828. Ludwig, E. E., and Johnson, C. R., Ind. Eng. Chem., Anal. Ed., 1942, 14, 895. Muller-Ncugluck, H. H., Gluckauf, 1941, 77, 34; Chem. Abstr., 1941, 35, 6709. Peech, M., and English, L., Soil Sci., 1944, 57, 167. Drosdoff, M., and Nearpass, D. C., Anal. Chem., 1948, 20, 673. Willson, A. E., and Wander, 1. W., Ibid., 1950, 22, 195. Young, H. Y., and Gill, R. F., Ibid., 1951, 23, 751. Hunter, J . G., Analyst, 1950, 75, 91. Stross, W., Ibid., 1942, 67, 317. Kidson, E. B., N.Z. J . Sci. Tech., 1946, 27A, 411. Hanssen, W. J., Pieters, H. A. J., and Geurts, J. J., Anal. Chim. Acta, 1948, 2, 241. Hirschfelder, A. D., and Serles, E. R., J . Biol. Chem., 1934, 104, 635. Abrahamczik, E., Mikrochemie. 1947, 33, 209. Mellan, I . , “Organic Reagents in Inorganic Analysis,” Blakiston Co., Philadelphia, 1941, pp. 212, Becka, J., Biochem. Z., 1931, 233, 118; Chem. Abstr., 1931, 25, 3680. Alexander, J ., “Colloid Chemistry : Principles and Applications,” Chapman & Hall Ltd., London, Mikkelsen, D. S., and Toth, S. J., J . Aozer. Soc. Agron., 1947, 39, 165. Natelson, S., Pincus, J. B., and Lugovoy, J. K., J . Biol. Chem., 1948, 175, 745. p. 391. 417 and 661. 1945, p. 321. RUKUHIA SOIL RESEARCH STATION HAMILTON, NEW ZEALAND DEPARTMENT OF AGRICULTURE June 15th, 1953

ISSN:0003-2654    

DOI:10.1039/AN9547900280

出版商:RSC    

年代:1954

数据来源: RSC