ISSN:0003-2654    

DOI:10.1039/AN94772FX033

出版商:RSC    

年代:1947

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN94772BX035

出版商:RSC    

年代:1947

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN94772FP041

出版商:RSC    

年代:1947

数据来源: RSC

摘要:

426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively.Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE.By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time.The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice.Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction SEPTEMBER, 1947 Vol. 72, No. 858 THE ANALYST PROCEEDINGS OF THE SOCIETY OF PUBLIC ANALYSTS AND OTHER ANALYTICAL CHEMISTS Fluorimetric Analysis The following four papers were read at a meeting of the Physical Methods Group in London, on February llth, 1947.Fluorimeter Design BY E. J. BOWEN THE first consideration relating to fluorimeter design is whether the measurements should be by eye or by photo-cell. Visual measurements suffer from all the weaknesses of the human observer, while photo-electric methods can be carried out more accurately and rapidly, and with less fatigue. There are occasions, however, when visual methods may be preferred, if the solution contains unextracted impurities themselves fluorescing with a different colour. Changes of tint of the fluorescence then give warning that there is something unsatisfactory about the solutions. Instruments for visual work are the Pulfrich Photometer or adapted plunger- type colorime ters . In photo-cell instruments the lamp, solution cell, and yhoto-cell may all be arranged in line, or the photo-cell may be arranged to collect the fluorescent light emerging at right angles to the exciting light beam.The latter arrangement seems preferable, as for very weak fluorescences it may not be possible to remove by filters all traces of the direct exciting light beam. In the right-angled arrangement up to four photo-cells could be used round the solution cell, though in practice two would probably be the optimum. For very accurate work it is desirable to eliminate the effects of fluctuations in the intensity of the exciting-light source. This is most conveniently done by using a double apparatus to allow of balancing. Light Such an arrangement is illustrated in Fig.1. P 0 9 P Fig. 1. See Umberger and Lamer, J . Awtev. Chem. SOC., 1945, 67, 11. from a central lamy L sends out two beams in opposite directions; these are made parallel by lenses and of appropriate wavelength by light-filters Fl. After passing diaphragms D, the beams traverse solution cells C . One cell contains a standard and the other the solution to be measured. These need not be solutions of the same substance if standards more stable than the solutions to be measured are better. The fluorescent light passes diaphragms D, and filters F, to reach photo-cells P. The photo-cell outputs are connected in opposition to a measuring device balanced to zero when identical solutions are placed in the cells C. 377 Fluoriineter viewed from above.378 BOWEN : FLUORIMETER DESIGN [Vol.72 The following considerations relate to the various components. Lamp-For most work the small high-pressure 125-watt mercury lamp is the best, since high-intensity monochromatic light, and long-wave ultra-violet light, are easily obtained from it. To avoid inconstancy of output the lamp should be provided with a stabilised voltage and guarded against irregular ventilation, since of the three lamp variables, voltage, current and temperature, only two are independent. It may happen that the absorption band of a fluorescent solution, as of rubrene in hexane, lies in a region where the mercury lamp provides no line. A concentrated filament projection- type tungsten-filament lamp must then be used. This needs a copper sulphate solution filter to remove heat from the light beam and some care in design to dissipate the great heat in the lamp housing.Filters F,-For measurements at low concentrations the filters Fl should transmit a spectral region more or less coincident with a high or a maximum value of the absorption band of the solution. Using the mercury lamp it is roughly true that colourless solutions (even when concentrated) need the 3650 A. line, and yellow solutions the 4358 A. line. The presence of nitrites, sulphites, and other light-absorbing substances in the solution may render the use of the 3650 A. line impossible even though it may fit best the absorption band of the fluorescent substance. In some circumstances the mercury line 4047 A. might be very useful, but it is not easy to isolate at high intensity.Gelatin-film (between glass) filters are commonly used because they can be obtained in a greater range than coloured glass filters. When exposed to the full radiation of the mercury lamp, however, they may show rapid deterioration. It is very desirable to interpose an ultra-violet absorbing glass filter such as Chance OY9 or 10 to minimise this trouble. SoZution cells-Given sufficiently sensitive detecting inst rumen ts, the ultimate sensi tivi ty of fluorimetry is set by five factors: (a) Rayleigh and Raman scattering from the liquid. (b) Scattering from dust particles. (c) Scattered light from reflections from the cell walls. (a) Fluorescence of the solvent. (e) Fluorescence of the cell walls. Present-day sensitivities are so far from the limit set by (a) that this may be left out of consideration. Factors (b) and (d) can be minimised by careful purification and technique. Factor (c) is a matter of careful choice of material.Glass fluoresces owing to the presence of traces of certain elements such as manganese, cerium, samarium or europium, and the production of “non-fluorescent ” glass needs the co-operation of the glass manufacturers. Scattered light from the cell walls is probably the largest source of error in most instruments. The following devices would reduce this trouble. (a) The use of a cell shaped like a cross as shown in Fig. 2, constructed of opaque material with four clear plane faces. (b) Scrupulous care in avoiding surface contamination and scratches in the conventional type of rectangular cell.(c) Careful adjustment of lenses and of diaphragms D, to limit the path of the light- beam to the centre part of cell C. (a) The use of very thick glass ends to the cell C on the exciting light axis, or, alter- natively, impersion of C in a larger rectangular trough containing a liquid, so that the light-scattering planes where the exciting light enters and leaves the solution are kept well away from being “viewed” by the photo-cell at P. Balancing of @zoto-ceZZs-There are various ways of balancing the photo-cells and of obtaining a measure of the fluorescence. The reading may be taken either directly from the opposed photo-cell outputs when unknown and standard solutions are placed one in each of the cells C, or the detecting instrument in the photo-cell circuit may be brought to zero by adjusting (a) a variable calibrated diaphragm in a D, position, or (b) a variable and graduated resistance or potentiometer in the electrical circuit.The relative merits of these methods have never been fully assessed. Filters F,--These may be gelatin-film filters chosen to transmit the fluorescent light while removing the exciting wavelengths. Were these 100 per cent. efficient, errors due to scattered exciting light would disappear. There is usually need to off-set loss of light by using not very dense filters.Sept., 19471 BOWEN : FLUORESCENCE QUENCHING IN SOLUTIONS 379 Photo-cells-The barrier-layer type of photo-cells has the advantage of not needing an external source of electrical supply. They are not sensitive enough, however, for work with ieebly fluorescent solutions. Vacuum-type alkali-metal cells, chosen for the wavelength range of the fluorescence to be studied (Le., potassium for blue and green, rubidium for orange, and caesium for red) are then necessary. Their outputs are amplified, either by the D.C. method with an electrometer valve (preferably enclosed with photo-cell and high resistance TO PHOTO- 1 CELL Fig. 2. in an evacuated glass envelope) or by A.C. methods with light-choppers interposed in the light beam. A new development, however, is now on the way. Nine-stage photo-electron multipliers, such as the American R.C.A. tube 931 A, provide exceedingly high sensitivities to light over the whole spectral range, and are capable of measuring to 10-7 foot-candles or less. Used with a spectrometer they permit the direct measurement of Raman lines from liquids which need quite.long exposures of a photographic plate. As it is very desirable to cut down the intensity of the exciting light beam to avoid photochemical changes in unstable solutions, these new detectors will provide greater sensitivity with lessened risk of destruction of fluorescent material. One may even forecast a fluorimeter of the future with a spectrometer interposed between the solution and the multiplier cell, whereby both the intensity and the wavelength distribution of a feeble fluorescence may be simultaneously determined. PHYSICAL CHEMISTRY LABORATORY OXFORD

ISSN:0003-2654    

DOI:10.1039/AN9477200377

出版商:RSC    

年代:1947

数据来源: RSC

摘要:

426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively.Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE.By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time.The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice.Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years.The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion.The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on.Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp.15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction Sept., 19471 BOWEN : FLUORESCENCE QUENCHING IN SOLUTIONS 379 Fluorescence Quenching in Solutions BY E. J. BOWEN THE mechanism of fluorescence is given the following interpretation on present-day theory. When a molecule absorbs a quantum of light it receives a large accession of energy, and “jumps” in the very short time interval of 10-l6 seconds to an electronically excited state, one of its electrons having assumed a new wave-pattern or orbital. If undisturbed, this excited state persists for a time interval of about seconds on the average and then re- radiates all or almost all of the absorbed light energy.In a liquid, molecules collide in time intervals of about 10-l2 seconds. Excited molecules of most substances lose all their energy as heat before they have lived long enough to radiate, either because of energy transformations caused by collisions or because of internal energy changes. Such substances do not show the phenomenon of fluorescence. Only molecules having peculiarly stable excited states380 BOWEN : FLUORESCENCE QUENCHING IN SOLUTIONS [Vol. 72 can resist deactivating effects for long. These are usually either ions such as rare-earths or UO,”, where the excited electron is one from an inner shell relatively protected from outside influences, or “conjugated” organic substances with systems of “non-localised’ ’ electrons where the excitation is “spread” and “thinned out” over a large number of linkages.The intensity of fluorescence is strictly proportional to the amount of light absorbed. “Saturation” could be produced only at light intensities many thousand times greater than at present can be used. For analytical work dilute solutions are employed, where the fraction of light absorbed, and hence the fluorescence, is sensibly directly proportional to the con- centration of fluorescent substance, or should be. When two solutions with concentrations in the ratio of 2 : 1 are compared, however, often the fluorescent intensity ratios are less than 2 : 1. For very dilute solutions this error may arise from fluorescence of the glass cells, unwanted scattering, etc.In stronger solutions there may be a real deviation from the 2 : 1 ratio of intensities, owing to the effects described below. The term “quenching” has been used to cover all these effects; it seems better however to restrict its meaning to cases where a real non-proportionality of fluorescence to concentration in dilute solutions exists. In an ideal case of unquenched fluorescence, each absorbed light quantum should lead to the emission of a quantum of fluorescent light, and the “fluorescence efficiency”, (emitted quanta) /(absorbed quanta), should be unity. Although the absolute values of fluorescence efficiencies are not easy to measure, it puts matters on a sounder basis to define “quenching” as any effect reducing a fluorescence efficiency below unity.On this view all non-fluorescent coloured substances are 100 per cent. quenched. With this definition the molecular picture of the quenching process can be classified into a number of types: 1. Intramolecular effects. 2. Intermolecular effects: (a) Bimolecular collisions, (i) with solvent molecules, (ii) with solute molecules, i.e., with added “quenchers” or with other molecules of the fluorescent substance. (b) Compound-formation in solution, (i) with solvent molecules, (ii) with solute molecules, i.e., with added substances or with other molecules of the fluorescent substance. 3. Inner filter action of solvent or added substances. The term “quenching” is narrowed by some workers to effects under 2; sometimes to 2 (a) only.Inner filter action, 3, is merely the diminution of fluorescence of a substance in solution through the presence of a “coloured” solvent or other solute whereby part either of the absorbed or of the fluorescent light is wasted, almost as if an absorbing screen were inter- posed in the light beam. It occurs only when the absorption by the “coloured” substance is not small, and could be recognised by detectable changes in the light absorption. Compound-formation in solution, 2 (b), refers to chemical equilibria established in the solution before the fluorescence is examined, and must carefully be distinguished from photo- chemical action, which causes fluorescence to diminish with time but is not a true quenching effect. Many fluorescent dyes in aqueous solution, e.g., uranin, are less fluorescent in con- centrated solutions.This is associated with a change of absorption spectrum due to dimer (or polymer) formation by a thermal equilibrium. The h e r molecules are not fluorescent and act as inner filters. The effect is much more marked in aqueous than in alcoholic solutions, i.e., in the liquid of higher dielectric constant, and therefore the forces holding the dimer together cannot be “dipole” forces ; wave-mechanical “dispersion” forces or “hydrogen bonding” are probably the cause. In some cases, e.g., the quenching of the fluorescence of anthracene in benzene solution by added bromobenzene, the “compound-formation’’ is not apparent from very noticeable changes in the absorption spectrum, but the effect can be shown to be 2 (b) (ii) and not 2 (a) (ii) because the quenching effect diminishes with rise of temperature.This is due to the break-up of the “compounds” at higher temperatures so that a greater fraction of the absorbed light is available for free anthracene molecules. By applying the Van t’Hoff isochore the heat of formation of the compound is obtainable from the temperature coefficient of quenching, and values of 0.5 to 2.0 k. cal./mole are obtained for different systems.Sept., 1947) BOWEN FLUORESCENCE QUENCHING IN SOLUTIONS 381 Experimentally, collisional quenching, 2 (a), is dbtinguishable from 2 (b) because it increases with rise of temperature. Both 2 (a) (ii) and2 (b) (ii) obey the equation (Fo - F)/F = k [Q], where Fo and F are the fluorescence intensities without and with added quencher, and [Q] is the quencher concentration; k is called the “quenching constant.” In gaseous systems k is the product of collisional frequency and probability of quenching on one collision, but in liquids the collisional must be replaced by the Wcuunter frequency.In all measurable examples of collisional quenching by added substances in solution the probability of quenching on one collision is high. Collisions in liquids differ from those in gases in that neighbouring molecules make many “repeated” collisions before separating; such a group of collisions is called an “encounter.” If quenching occurs early in the course of an encounter the quenching constant will be determined by the encounter and not the collisional rate, and the former is a function of the viscosity of the liquid.It has been shown that +R k = 7 x 1021PR8 approximately, where P = probability of quenching during one encounter, R = sum of radii of fluorescent and quenching molecules, = about 7 x cm., t = half-life of fluorescent molecule = sec. approximately, and D = diffusional constant of solute molecules, proportional to (absolute temperature) /(viscosity). The second term of the equation becomes important only in viscous liquids. This “collisional” type of quenching is shown by dissolved oxygen in solutions of fluorescent aromatic hydrocarbons; the quenching is strong in fluid hexane solutions and small in viscous paraffin solutions. For ordinary values of the molecular constants the maximum value of k is about 160, i.e., such quenching becomes inappreciable a t a quencher concentration below 10-2 g./litre.Quenching processes 2 (a) and 2 (b) appear to be markedly distinct from each other; (a) depends on encounter rate and therefore on viscosity, (6) depends on mass-action constants of compound-formation and on inner filter action, and they have opposite temperature effects. In spite of this one cannot attribute fundamentally important differences to the two classes. For solutions of anthracene, carbon tetrachloride bromoform and acetylene tetrabromide are “co@isional” quenchers, while bromobenzene, isopropyl bromide and tri- methylene dibromide are “compound” quenchers. The difference seems to arise solely from the life-time of the “compound” and its relation to the half-life of the fluorescent molecule. Nitrobenzene behaves as a “compound” quencher for solutions of rubrene; m-dinitro- and s-trinitrobenzenes, though usually forming more stable compounds with aromatic hydro- carbons here act as “collisional” quenchers, evidently because of stereochemical interference effects of the phenyl groups of the rubrene with the nitro groups of the two latter substances.Here the excitation energy is supposed to be degraded to heat by some internal rearrangement of energy within the molecule. The temperature coefficient might be expected to be small, but no clear experimental test has yet been applied to recognise this class. In both classes the polarity or dielectric constant of the solvent might in some instances be an important factor through its influence on the “transition probability” of the passage of the molecule from its excited potential energy surface to the ground one.A polar solvent might (compared to a non-polar one) increase or decrease quenching effects (a) by raising or lowering the “crossing points” of such surfaces, or (b) by changing the “transition strength” between the upper and lower states. Here again little quantitative application is available for fluorescent solutions. Sharply to be distinguished from the quenching effects discussed above are Photochemical reactions occurring between molecules in solution, where the changes increase with time. Such reactions may or may not be observed as subsequent effects to intermolecular quenching processes of group 2, and should not themselves be referred to as “quenching.” A great many of the photochemical effects observed in solutions of fluorescent substances are electron- transfer reactions, e.g., in solutions of thionine to which ferrous ions have been added.Fluorescence quenching occurs accompanied by a photochemical reaction whereby the thionine molecules (T) excited by light receive an electron from a ferrous ion, changing to T’ + Fe”’. The leuco-form of the dye is then produced by the reactions: T‘ + H + TH (semi-quinone) Intramolecular effects grouped under 1 are difficult to distinguish from 2 (a) (i). and 2TH -+ TH, + T382 SIMPSON : APPLICATIONS OF FLUORIMETRIC ANALYSIS pol. 72 Electron-accepting ions or molecules may also quench with photo-reaction to give positive dye ions. In different examples of fluorescent solutions reversible or irreversible destruction of the fluorescent substance may be observed, and photosensitisation often occurs, Le., a permanent change in some added substance in the solution is brought about while the con- centration of fluorescent material remains unchanged. These effects can all be explained by variations in the secondary changes following on the initial electron-transfer reaction associated with the fluorescence quenching. The term “fatigue” has sometimes been used to cover examples of fluorescence weakening with exposure to light and recovering in the dark. Occasionally it has been applied to irreversible effects, but it seems anyhow a poor term to employ when ordinary photochemical nomenclature is available, and is better left to describe effects in solid phosphors, where the actual processes taking place are much more obscure. Dissolved oxygen quenches the fluorescence of some solutions, particularly of aromatic hydrocarbons. Continued exposure may lead to irreversible oxidation effects. If easily oxidisable substances are simultaneously present, photosensitised oxidation of the latter may occur, the fluorescent substance remaining unchanged. In these circumstances an increase of fluorescence may be observed with time of exposure, owing to the consumption of the oxygen and the consequent elimination of its effect as a collisional quencher. PHYSICAL CAE MISTRY LABORATORY OXFORD

ISSN:0003-2654    

DOI:10.1039/AN9477200379

出版商:RSC    

年代:1947

数据来源: RSC

摘要:

426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively.Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE.By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time.The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice.Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years.The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion.The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on.Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp.15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction 382 SIMPSON : APPLICATIONS OF FLUORIMETRIC ANALYSIS pol. 72 Applications of Fluorime tric Analysis to the Study of Pterins BY (MISS) D. M. SIMPSON DURING the last few years interest in the study of the pterins has increased enormously as it has become apparent that this group of substances is widely distributed in living matter. Interest has been further stimulated by the recognition that pterins may be used to treat certain anaemias in animals and that the molecule of folk acid contains xanthopterin.1 The study of the pterins began with the work of HopkinsJz who in 1895 isolated materials, later shown to be leucopterin and xanthopterin, from the wings of butterflies.During the years 1925 to 1944, workers in the schools of Wieland, Purrmann, Schopf and Koschara succeeded in isolating a number of pterins from natural sources, in determining their structural formulae and in achieving their synthesis. (For a summary of this work, see 3.) The most important and widely distributed pterins are leucopterin, xanthopterin (9-deoxyleucopterin, uropterin) and anhydroleucopterin (8-deoxyleucopterin, isoxanthopterin) . OH OH OH Anhydroleucopterin Leucopterin Xanthopterin Various derivatives of these substances have been prepared, such as carboxylic acids and thiopterins with sulphur at the 2-carbon atom.* One of the most characteristic properties of the pterins is that, unlike the purines, they show a pronounced fluorescence in solution, even at high dilutions; some pterins also fluoresce in the solid state.This suggests that the fluorescence spectra could conveniently be used as a means of identifying pterins in mixtures; further the intensity of fluorescence might, with suitable precautions, be employed to determine the concentration of pterin present. The earlier workers, for example Schopf and Becker,6 contented themselves with describing the colour of the fluorescence as observed visually. This procedure has its limita- tions as the apparent tint is considerably affected by the colour of the solution. Hiittel and Sprenglinge determined roughly the region over which fluorescence was observed for ichthyo- pterin, a material isolated from the skin of members of Cyprinidae, with which the fluorescyanine of Polonovski and his co-workers is probably identical.’ It is clear that if fluorescence spectra are to be used as a means of identifying pterins, the first requirement is that these spectra should be accurately determined.Since theSept., 19471 TO THE STUDY OF PTERINS 383 fluotescence spectrum of a pterin differs according to whether it is solid or in solution, and varies with the pH of the solution, standard spectra must be obtained for a suitable range of conditions. It is also desirable to use light of a definite wavelength, for example Hg 3650 A, to excite the fluorescence. Standard spectra are at present available only for leucopterin and xant h~pterin.~ The meagre data on pure pterins do not allow any generalisation to be made on the question of the relationship between fluorescence spectrum and chemical constitution.It may, however, be pointed out that the fluorescence spectra of leucopterin and xanthopterin in solution are of the same family type, both showing two strong bands between 4358 and 5461 A. These bands do not appear to be markedly changed even when there is evidence that the molecules are present in a combined state, though they show slight variations, presumably owing to salt formation, if the pH of the solution is altered. The ichthyopterin of Huttel and Sprengling,6 a derivative of anhydroleucopterin, shows in solution at pH 4 to 8, bands at 4500 to 4700 A.(strong, maximum 4316 to 4323 A.') and 6900 A. (weak). A pterin from the eyes of the minnow (Phoxinus phoxinus), kindly provided by Mrs. Pirie (Nuffield Institute of Ophthalmology, Oxford), shows a different type of spectrum, with bands at 4200 to 4600 A. (strong, maximum 4400 A.) and 5250 A. (weak) in neutral solution. There is thus no reason to expect that the fluorescence spectra of all pterins should be similar. Polonovski and his co-workers4 suggest that fluorescence is associated with the grouping =N-C--N= in the first ring. If this structure is absent, as in some of the thiopterins, the fluorescence disappears. It is probably unwise to identify pterins solely by means of their fluorescence spectra. These spectra consist of broad bands; it is difficult to determine the positions of the maxima with very great precision, and the absolute intensities are not known.On the other hand there is comparatively little interference from other substances. The ultra-violet absorption spectra of pterins, as of most complicated molecules, also consist of broad bands, but they may be obtained quantitatively and with much greater accuracy ; most substances, however, show some absorption in the region 2000 to 7 0 0 0 ~ . The identification of a pterin in a mixture should be made, not only by means of the fluorescence spectrum, but also by using the ultra-violet absorption spectrum and the chemical properties of the material; if all three lines of evidence are in agreement then the identification may be considered reliable.Most biological materials show some fluorescence under ultra-violet light. This is frequently confined to the blue parts of the spectrum well away from the strong characteristic pterin bands, so that little interference i s experienced. Thus it was possible on the basis of the chemical evidence and the ultra-violet and fluorescence spectra to conclude that the argentaffine cells of the stomach and intestine contain xanthopterin, probably as a complex.3 In this connection it should be noted that the dry preparations show fluorescence, although solid synthetic xanthopterin does not fluoresce. In the investigation of the fluorescent material in liver extracts other difficulties are encountered.8 The riboflavine present produces an intense band in the same region 5200 to 5 8 0 0 ~ (maximum 5 3 0 0 ~ ) as that of one of the xanthopterin and leucopterin bands.Happily the shape of this band is very characteristic, and it can be effectively suppressed by working in normal acid solution. Examination of a large number of liver extracts showed that the position and relative intensity of those bands of their fluorescence spectra not due to riboflavine were remarkably constant. This suggested that the same fluorescent material was responsible in every instance. These bands correspond most closely to those of leucopterin, though they appear over a pH range greater than that of its solubility. This makes it probable that the leucopterin, if present, is in the form of a complex. In this case it would not, however, be justifiable to identify the fluorescent material definitely as leucopterin, until it has been obtained in a much higher state of purity, so that confirmatory evidence may be derived from its chemical properties and ultra-violet absorption spectrum. On the other hand the fluorescent material isolated from the eye of the dog fish (Sqzcalus ucanthias) was successfully shown to consist mainly of xanthopterin, on the basis of its fluorescence and ultra-violet spectra and its chemical behaviour.9 An interesting problem in this connection is the constitution of the so-called uric acid pigment.* This curious red material, which is readily soluble in water and in acid and I _ _ _ _ _ ~ ~~~~~~~~~ * The work on the spectra of this material, which has not been previously published, was carried out in collaboration with Dr.W. Jacobson (Strangeways Research Laboratory, Cambridge).384 SIMPSON : APPLICATIONS OF FLUORIMETRIC ANALYSIS [Vol. 72 alkaline media, is obtained by heating uric acid with water in sealed tubes at 200" C. for some hours. HopkinseJo, from an examination of its chemical properties suggested that it contains a pterin, probably xanthopterin. The ultra-violet absorption spectrum of a specimen kindly provided by Dr. Quibell (Manchester University) is very similar to that of xanthopterin. The fluorescence spectra in solution show bands at : 4650 A. (ms), 5300 A. (s), 5680 A. (ms), 5900 A. (ms), 6200 A. (w); N / 2 NaOH; 4560 A. (s), 5170 A. (Ins); neutral; 4590 A. (s), 5200 A. (ms), 5920 A. (w) ; 20% H,SO,.(s) = strong; (MS) = moderately strong; (w) = weak The material certainly contained uric acid as an impurity, which would not, however, have appreciably affected its fluorescence spectra, as the latter substance shows a very faint blue fluorescence in alkaline media only. The positions of the bands of the uric acid pigment in neutral and acid solution correspond to those of xanthopterin, in agreement with the con- clusions of Hopkins. The relative intensity of the bands is different; this is to be expected as the solutions are red, indicating absorption in the blue and yellow which would lead to self-absorption of the fluorescent light. This inner filter effect has also been observed with impure dark coloured specimens of xanthopterin. The fluorescence spectrum of the uric acid pigment in alkaline solution does not correspond to that of xanthopterin.It shows a remarkable increase in intensity in the region 5100 to 6000 A., indicating that some other material fluorescent at pH > 7 must be present. It is impossible to suggest what this may be, though it can be stated with some certainty that it is not leucopterin. The quantitative analysis of solutions containing pterins by means of fluorescence spectra is a much more difficult problem. Use of fluorescence for quantitative purposes implies that the exciting light must not be so strongly absorbed that the fluorescence is confined to a thin layer at the side of the cell nearest to the exciting beam. This difficulty is encountered particularly in dealing with dark coloured solutions such as some commercial liver extracts8 The dilution required to ensure that there is no appreciable drop in fluorescence intensity across the cell is so-large that the resultant errors in calculating concentrations may be considerable.High dilutions are also required to eliminate self-quenching and the absorption of fluorescent light by the solution itself. This last effect was very pronounced in the solutions of impure xanthopterin and uric acid pigment. A rough calculation for leucopterin, based on its observed molecular extinction coefficient (E'L 1P at 3600 A . ~ ) and molecular weight (195), suggests that if Hg 3650 A. is used as exciting radiation the concentration to be employed is of the order of milligrams per litre, if the fluorescent light is observed over the full width of a 1-cm.cell. Not many attempts have been made to determine pterin concentrations by means of fluorescence spectra. The work of Koschara, von der Seipen, and Aldred,ll who found the combined concentration of xanthopterin and riboflavine in urine from the intensity of fluorescence, is probably unreliable, as one would not expect the total intensity to benecessarily proportional to the total concentration if more than one fluorescent material were present. The work of Decker,12 who used the total intensity of fluorescence to measure the con- centration of leucopterin in various natural materials, is typical of the case in which the true chemical nature of the fluorescent substance is known. He determined calibration curves for intensity of fluorescence plotted against leucopterin concentration for synthetic material in solutions of known fiH, and compared the fluorescence of his unknown preparations with that of the standard solutions.This method could be improved if, instead of the total intensity of fluorescence, the intensity at a particular wavelength (preferably that of the maximum of one of the characteristic bands) were used to compare standard and unknown solutions. This would seem to be the only really reliable method to employ. It is sometimes possible to use fluorescence spectra to determine relative concentrations even if the exact chemical nature of the fluorescent material is not known, when it is of course impossible to obtain standard spectra for comparison. * Such a procedure is only justifiable if it is clear that interfering fluorescence is absent.In the case of the liver extracts previously discussed, the intensity of fluorescence observed, when that due to the riboflavine is suitably suppressed, runs parallel to the haemopoetic activity of these preparations, which strongly suggests that both fluorescence and activity are due to one and the same substance. The intensity of fluorescence of these materials may thus be used as a measure of their clinical activity.8 This is a very valuable conclusion, as the intensity of fluorescence may be rapidlySept., 19471 TO THE STUDY OF PTERINS 386 found, whereas previously only complicated clinical and biological methods have been available for the assessment of clinical activity. The determination of the absolute con- centration of active substance in such preparations cannot be carried out until the exact chemical nature and molecular weight of the fluorescent material have been established, and until pure specimens are available to provide comparison spectra.SUMMARY Fluorescence spectra alone are insufficient to identify pterins in complex mixtures; ultra-violet absorption spectra and chemical tests should also be employed. Standard fluorescence spectra of synthetic pterins are at present available only for xanthopterin and leucopterin. Using the complementory methods listed above, it has been possible to demonstrate the presence of pterins in such diverse materials as the argentaffine cells of the stomach and intestine, the fluorescent substance obtained from the eye of the dog fish (SquaZ~s acanthias) and the so-called uric acid pigment. To date, few quantitative determinations of the concentrations of pterins have been made by means of fluorescence spectra. Provided that suitable precautions are employed to avoid quenching and inner filter effects, this should be feasible if synthetic material is available for comparison. Examination of a large number of liver extracts suggests that the intensity of fluorescence might be used as a measure of the clinical activity of these preparations. REFERENCES 1. 2. 3. 4. Angier, R. B., ef al., Science, 1946, 103, 667. Hopkins, F. G., Phil. Trans. Roy. SOC., B, 1895, 186, 861. Jacobson, W., and Simpson, D. M., Biochem. J., 1946, 40, 3. Polonovski, M., Vieillefosse, R., and Pesson, M., Compt. vend., 1944, 218, 796; Bull. SOC. Chim., Polonovski, M., Guinard, S., Pesson, M., and Vieillefosse, R., BuU. SOC. Chins., SchtSpf, C., and Becker, E., Annalen, 1936, 524, 49. Huttel, R., and Sprengling, G., Ibid., 1943, 554, 69. Polonovski, M., Busnel, R., and Pesson, M., Helv. Chim. Acta, 1946, 29, 1328. Jacobson, W., and Simpson, D. M., Biochem. J., 1946, 4-0, 9. Pirie, A., and Simpson, D. M., Ibid., 1946, 40, 14. Hopkins, F. G., Proc. Roy. SOC., B., 1941-42, 130, 359. Koschara, W., von der Seipen, S., and Aldred, P. A., Hoppe-Seyler's 2. physiol. Ckepn., 1939, 262, ' 158. Decker, P., Ibid., 1942, 274, 223. CAMBRIDGE 1945, 12, 78. 1945, 12, 924. 5. 6. 7. 8. 9. 10. 11. 12. LABORATORY OF PHYSICAL CHEMISTRY

ISSN:0003-2654    

DOI:10.1039/AN9477200382

出版商:RSC    

年代:1947

数据来源: RSC

摘要:

426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively.Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE.By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time.The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice.Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years.The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion.The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on.Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp.15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice.Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C.Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner.He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively.Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice.Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE.By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time.The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years.The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions.After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on.Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175).Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction Sept., 19471 TO THE STUDY OF PTERINS 386 Some Applications of Fluorimetry in Vitamin Analysis BY E. KODICEK IT is well known that a number of vitamins or their derivatives fluoresce. This fluorescence has been used in several instances for their quantitative estimation. Table I gives a list of vitamins or related compounds that show a fluorescence or develop it on appropriate treatment. TABLE I FLUORESCENCE OF VITAMINS AND RELATED COMPOUNDS Fluorescence Fluorescent compounds (under specified conditions) Vitamin B, .. Riboflavine.. .. Pyridoxal .. .. Nicotinamide .. N-Methylnicotinamide Co-zymase . . .. Folic acid . . .. Vitamin A .. .. .. Thiochrome .. * . Riboflavine .. .. Pyridoxal .. . . CNBr complex .. .. F, .. .. Fc .. .. Folic acid .. .. Vitamin A Blue Yellowish-green Blue Blue Blue Blue Blue Yellow I propose to deal principally with vitamin B,, riboflavine, N-methylnicotinamide (“N-MN”) and nicotinamide-with short references to N-methylnicotinuric acid betaine and co-zymase,386 KODICEK : SOME APPLICATIONS OF FLUORIMETRY [Vol. 12 which we have also studied at Cambridge. For the estimation of these we have worked out methods which in our experience over several years have proved satisfactory for a considerable variety of materials. Without going into details of procedure, I propose to concentrate on the principles involved and to point out the advantages and disadvantages of the methods we use.(1) RELIABILITY AND ACCURACY- deviation. The requirements that should be fulfilled in an ideal method are as follows. (a) The results should be repeatable with small error, say, f 5 per cent. standard (b) Recovery of added vitamin should be complete. (c) The method should be specific, and should agree with at least one other method, preferably biological. Treatment of extracts should ensure that only the vitamin is present in solution or that other fluorescent substances that may interfere are as far as possible removed. These interfering substances may be either quite unrelated to the vitamin, or structurally related but biologically inactive. The blank, treated as far as possible in the same way as the unknown, should correct the error due to any unspecific fluorescence remaining in the extract.( d ) The extract should contain all the vitamin in its fluorescent form. (e) The extract should be clear, colourless and free from the so-called “quenching” effect. (f) Internal standards should be used in order to eliminate changes of fluorescence for reasons outside our control. By this I mean the standard solution should be estimated in presence of the unknown. (2) EASE AND RAPIDITY- (a) As few steps as possible should be employed and the simplest treatment adopted (b) Techniques that may involve losses outside our control should be omitted. For example, in the use of adsorption procedures, variations in the properties of the adsorbing material or in the nature of the extract may result in ineffective adsorption by, or incomplete elution from, the adsorbent.Having indicated the requirements of an ideal fluorimetric method, we will now consider our procedures. VITAMIN B, We use the method of Harris and Wang,1~2~3~4~6 the well-known principle of which consist. in conversion of vitamin B, to thiochrome (Jansens) by oxidation with alkaline ferricyanides The steps are as follows. (1) Extraction of the material at acid pH on the water-bath, and digestion with takadiastase and papain to break up the bound vitamin. B, which may be present as co-carboxylase. (2) Preliminary washing with isobutanol to remove interfering substances. (3) Rapid oxidation by alkaline ferricyanide in presence of methanol, followed by treatment with 30 per cent.hydrogen peroxide. (4) Extraction of the formed thiochrome with isobutanol and clarification of the isobutanol layer with absolute ethanol. (6) Use of an extract treated similarly but without oxidation, as the “blank.” (6) Finally, matching of the isobutanol layer for its fluorescence, either visually or photometrically. The standard deviation for determinations on numerous samples by this method has been found to be of the order of f 5 per cent. The vitamin-B, potency of numerous samples of foodstuffs estimated by this method has agreed well with that found by the biological bradycardia method, and also by growth and con- vulsions.2 The preliminary washing with isobutanol was found to be essential; it removes most of the interfering material.Rapid oxidation by adding sodium hydroxide followed by ferricyanide is necessary to obtain reliable results. The presence of methanol stabilises the conversion of vitamin B, to thiochrome. With regard to the blank, the use of hydrogen peroxide eliminates a great part of the undesired fluorescence and renders matching much easier. Nevertheless, there are one or two materials that give a fluorescence of a different tint from that of the thiochrome standard, rendering the results unreliable. For such materials Vitamin B, can be recovered completely.Sept., 19471 IN VITAMIN ANALYSIS 381 it is best to use a visual method, as the difficulties are at once obvious and can nearly always be overcome by suitable procedures, e.g., washing with light petroleum or excess of hydrogen peroxide.A photo-cell, on the other hand, will record the total fluorescence, limited of course by the filters used, but the result will not accurately represent the vitamin B, content of the extract . It has been reported that N-methylnicotinamide can seriously interfere with the assay of vitamin B,. It will be seen from Table I1 that 4 pg. of N-MN per ml., a concentration likely to occur in normal urine, does not alter the fluorimetric readings of vitamin B, found by the method of Harris and Wang. TABLE I1 FLUORIWETER READINGS OF VITAMIN B, SOLUTIONS WITH AND WITHOUT N-METHYLNICOTINAMIDE (N-MN) (Filters Wratten 49A + 2A) However, the interference is not very serious. Treatment 1 ml. of water . . .. .. .. .. Blank + 4 rg. of N-MN . . ... . . . Blank Blank H - 11 .. .. .. . . Oxidised n + 0.4 pg. of vitamin B, . . . . .. n * n Oxidised 99 I9 n Oxidised n 19 i ' 4 pg.;f N-MN Blank Flnorirneter readings mm. 1 1.6 1.6 2 13 1 12 With regard to the extraction, no hard and fast ruIe can be laid down as to how to extract efficiently every possible material. The best procedure has to be worked out for each separately. The final extracts obtained by this method are clear. Internal standards are always used. The method is comparatively simple and quick. It does not rely on adsorption procedures. There are one or two materials, for example blood, for which the method has so far not proved satisfactory. Blood seems to contain substances that either destroy the vitamin B, during the preparation of extracts or else quench the fluorescence. Good recoveries could not be obtained.RIBOFLAVINE The method we have worked out (Kodicek and Wang') uses the yellow-green fluorescence of riboflavine excited by blue light. (1) Extraction on the water-bath with 0.1 N hydrochloric acid. Precipitation of proteins by metaphosphoric acid and/or digestion with takadiastase when starchy materials are assayed. (2) Washing of the extract with chloroform at acid $H and oxidation with saturated potassium permanganate solution followed by treatment with hydrogen peroxide to decolorise the remaining permanganate. (3) The extracts are adjusted to pH 6; methanol is added to clarify them if necessary. (4) Fluori-photometric readings are taken, with blue filters for the incident light and yellow filters between the solution and photo-cell.A sensitive photo-cell galvanometer circuit is used. (5) In the blank, the riboflavine is reduced to a non-fluorescent compound with a neutralised solution of sodium hyposulphite (Na2S204). For a great number of materials the results are reproducible with a standard error of about f 6 per cent. With foods of low riboflavine content, for instance white flour, the error is greater but does not exceed 10 per cent. Added riboflavine can be recovered completely. The method is satisfactorily specific. The results agree well with those of microbiological assays. Washing with chloroform removes most of the interfering fluorescence. The oxidation with permanganate and hydrogen peroxide decolorises the extract almost com- pletely.Nevertheless, a certain amount of residual unspecific fluorescence remains in some extracts. Allowance is made for it by the blank procedures. It is important to point out that when hyposulphite (Na2S,04) is used as the reducing agent in the blank, blue light is essential for obtaining correct readings. We have observed that under ultra-violet light sodium hyposulphite diminishes very strongly, or extinguishes The principle of the procedure is as follows.388 KODICEK: SOME APPLICATIONS OF FLUORIMETRY jyol. 72 almost completely, the total fluorescence of the extract. When a cell containing this reducing agent is placed in a beam of ultra-violet light in front of a cell containing riboflavine, for instance, the solution does not fluoresce. But when blue light is used as the exciting source the fluorescence is almost unaltered.The extraction of riboflavine, when combined with enzymic digestion, seems to be com- plete. The resulting extract is clear and almost colourless. Quenching is observed in many instances and is allowed for by use of an internal standard. The method is quick and easily carried out. Adsorption procedures were found to be unnecessary when a sensitive galvano- meter circuit was used. We employ a direct-reading fluorimeter of the Cohen type, giving a deflection of about 100 mm. for 0.05 pg. of riboflavine per ml. of final extract. N-METHYLNICOTINAMIDE (N-MN) We have modified (see Kodicek and Carpenter8) the ketone procedure recommended for urine by Huff, Perlzweig, and Tilden,9 for the estimation of N-MN, which has been shown to be an important metabolite of nicotinic acid.The principle of the method is asfollows. N-Methylnicotinamide in aqueous alkaline solution reacts with ketones to produce a greenish- blue fluorescence. On acidification the fluorescence changes to blue, and is intensified by heating. We use methyl ethyl ketone instead of acetone because it gives greater fluorimeter readings and is less volatile, and have modified the procedure for the blank* (see below). The specificity of the method was tried by testing a number of compounds, of which only co-zymase and N-methyl-nicotinuric acid betaine were converted into fluorescent com- pounds. They can be eliminated by deducting the residual fluorescence of a filtrate passed through a Decalso column, as, unlike N-MN, they are not adsorbed.For urine, with which we could find little or no fluorescence in Decalso filtrates, another simpler blank has been adopted ; the addition of sodium hydroxide is omitted and the reaction conducted throughout at an acid fiH at which N-MN does not develop a fluorescence. Internal standards are used for reference. Recovery of added N-MN is complete. The advantages of the method are that it is quick and easily performed. The one-phase procedure reduces the possible errors. We have tested extracts obtained from liver and found that by far the greater portion of the fluorescence remains in the Decalso filtrates and therefore cannot be due to N-MN. The fluorescent compound in these extracts behaves like the samples of co-zymase we have tested.Measurement of this fluorescence might form the basis of a method for estimating co-enzymes. NICOTIN AMIDE ScudilO has observed that nicotinamide when treated with cyanogen bromide, and then extracted at an alkaline pH with isobutanol, fluoresces like F,, the compound formed from N-methylnicotinamide. We have applied the ketone method mentioned above to the estimation of nicotinamide. Pure nicotinamide can be estimated readily when the reaction is allowed to proceed at an alkaline $I-€ and the fluorescence is measured at this pH. Procedwe-Take 10 ml. of M/15 phosphate solution ($H 6.8) containing 50 to 100 pg. of nicotinamide and add 4 ml. of freshly prepared cyanogen bromide solution (see Wang and Kodicekll). Cool for 5 minutes and make up to 15ml.with water. Take 5 ml. of this solution, add 2 ml. of methyl ethyl ketone and 1 ml. of 5 N sodium hydroxide and make up to 30 ml. with water. Keep the solution in the dark for 3-5 hours. Then read on a photo-electric fluorimeter with Wood's filter for the incident light and Wratten No. 47 and Calorex filters between solution and photo-cell. The fluorescence under these conditions reaches its maximum after 3.5 hours and declines slowly within the next 2 hours. The intensity of the fluorescence is proportional to the concentration of nicotinamide (Fig. 1). Banks and s$eciJicity-Two types of blanks were investigated : (1) omitting cyanogen bromide-"No CNBr" blank, and (2) omitting 5 N sodium hydroxide-"No NaOH" blank. Nicotinamide does not fluoresce under the conditions of either of the blank procedures.To test the specificity of the method and of both blanks, a number of miscellaneous compounds were investigated. The following compounds, at a concentration of 1 pg. per ml. of final solution, gave no fluorescence : nicotinic acid, coramine, trigonelline, a-picolinic acid, amino- pyridine, nipecotic acid , pyridine, nicotine, sulphapyridine , nucleic acid , adenylic acid, indole-3-acetic acid, 1-methyl-indole-3-acetic acid, glucose, urea, uric acid, choline , inositol, pantothenic acid and P-aminobenzoic acid. Heat for 4 minutes in a water-bath at 56" C.Sept., 19473 IN VITAMIN ANALYSIS 389 Other compounds tested showed a fluorescence (Table 111). The most intense fluorescence was produced by vitamin B,, but it could be differentiated from that due to nicotinamide by its development in the “No NaOH” blank.Folic acid and pyridoxal gave a fluorescence which increased when sodium hydroxide was omitted (“ No NaOH ” blank). t I 1 I 1 I 0.2 0 4 06 0% 10 l a N icot inamide, pg./rnf. Fig. 1. Standard curve of fluorescence of nicotinamide. N-Methylnicotinamide chloride and co-zymase showed a slight fluorescence which- unlike that of nicotinamide-persisted even when the cyanogen bromide treatment had been omitted (“No CNBr” blank). TABLE 111 Fluorimeter readings, 111111. Material r A * 1 pg./ml. of final solution Full procedure “No CNBr” blank “No NaOH” blank Nicotinamide . . .. .. 62 2 2 N-Methylnicotinamide . . . . 10 10 2.6 Co-zymase (48 per cent. purity) 6.6 6.6 2 Quinolinic acid .. . . . . 6.6 1.6 1.5 Vitamin €5, .. . . . . 108 16 109 Pyridoxal .. . . . . 8 3.6 19 Folic acid . . . . .. 8.6; 4.6 9-6 The procedure has not yet been fully developed for the estimation of nicotinamide in biological material. For analytical purposes where a differentiation between nicotinic acid and its amide is needed, the method may be found useful. SUMMARY A critical survey of some fluorimetric methods for the estimation of vitamin B,, riboflavine, N-methylnicotinamide and nicotinamide has been presented. REFERENCES 1. Wang, Y. L., and Harris, L. J., Biochem. J., 1939, 33, 1366. 2. Harris, L. J., and Wang, Y. L., Ibid., 1941, 35, 1060. 3. - - Ibid., 1068. 4. Wag, Y . L., and Harris, L. J., Chemistry and Isdustry, 1942, 61, 27. 6. - - Brit. Med. J., 1943, 11, 461.6. Jansen, B. C. P., Rec. truu. chim. Pays-Bas, 1936, 55, 1046. 7. Kodicek, E., and Wang, Y. L., 1947, in the press. 8. Kodicek, E., and Carpenter, K. J., 1947, in the press. 9. Huff, J. W., Perlzweig, W. A., and Tilden, M., Fcd. PYOC., 1945, 4, 92. 10. Scudi, J. V., Science, 1946, 103, 667. 11. Wang, Y. L., and Kodicek, E., Biochem. J., 1943, 37, 630. DUNN NUTRITIONAL LABORATORY CAMBRIDGE390 FLUORIMETRIC ANALYSIS : DISCUSSION [Vol. 72 DISCUSSION ON THE PRECEDING PAPERS The CHAIRMAN, Mr. R. C. CHIRNSIDE, said that the Group had been very fortunate in persuading experts to come and deal with this subject. Mr. Bowen had dealt with fluorescence in general, and Dr. Kodicek and Dr. Simpson had described two spxial applications. The subject was of considerable interest at the moment, especially, he understood, for those people who had to test for vitamins under the new Orders of the Ministry of Food, and no doubt there were members present who were interested in other applications of the subject.The four papers would be discussed together. Mr. WINCH said that he felt rather an intruder at the gathering and had not expected to be called upon to open the discussion. He was very interested, however, in the possibility of applying his knowledge of photo-electric photometric techniques to problems of fluorimetric measurement. He had developed for photometric, spectro-photometric and colorimetric purposes a photometer unit consisting of an emissive- type photo-electric cell together with an electrometer triode and associated grid leak resistance, all mounted in one evacuated tubular bulb.This was operated in a valve bridge D.C. amplifier circuit, the controls of which were in a separate cabinet connected to a mains-operated power unit and precision voltage stabiliser. The whole equipment, described as a Universal Photo-electric Photometer, had now been commercialised, and in this form had a limiting sensitivity of 10-8 lumens. Under laboratory conditions considerably higher sensitivity had been achieved. This instrument had proved a useful tool in a large number of applications to special photometric problems, and he thought that it might prove very helpful in fluorimetric investigations. Mr. Bowen’c proposed optical system for a photo-electric fluorimeter appeared in general to be sound, provided stray light was prevented from reaching the photo-electric cells.Mr. Winch saw no real difficulty in providing effective screening that would achieve this latter requirement. Mr. B. S. Cooper, a colleague of his, had recently collaborated with him in some interesting experimental fluorescence measurements utilising a Universal Photo-electric Photometer, and he suggested that Mr. Cooper might like to give details of what had been done. Mr. B. S. COOPER said that although his experience was confined to one day’s work in practical fluori- metry, he had felt that with Mr. Winch’s expert photometric knowledge something might be done to increase the sensitivity and accuracy of fluorimetric estimation. A preliminary trial had been carried out a t Kings Langley in collaboration with Dr.Wokes, and i t was clear that the Universal Photo-electric Photometer had sufficient sensitivity to cover the requirements. A limit, however, is imposed by certain inadequacies in the design of most commercial fluorimeters and by certain unexplained fluorescence a t the lowest con- centrations. Later, some tests were carried out at Wembley to determine the useful range of sensitivity obtainable in an experimental fluorimeter incorporating a Universal Photo-electric Photometer. The apparatus, as arranged, used a 125-watt high-pressure mercury lamp, a Corning filter (No. 6860, 5 mm. thick) to isolate the 365-mp. radiation and a large liquid cell, 10-cm. cube. The fluorescent radiation emerged through a Chance OY12 filter (a non-fluorescent chromium glass, opaque to near U.V. and violet radiation) and was received by the most sensitive photometer unit (100,000 megohms) that Mr.Winch could provide. The geometry of the apparatus and the photometric screening was such that the photo-cell could receive only the fluorescent light from the liquid. Using quinine sulphate supplied by Dr. Wokes, it was easy to obtain a reading (2.0) with a concentration as low as -1 millimicrogram per ml., but it was important to note that distilled water alone gave a reading almost as high, via., 1.7. At these very low concentrations therefore they were trying to measure something that gave effects very little different from those of distilled water. Another matter worth noting was that the Chance filters OY9 and OYlO which had been mentioned were both fluorescent, probably owing to the presence of cadmium sulphide.The exit filter in a fluorimeter system should be non-fluorescent, such as the Chance OY12 already mentioned, although this filter was rather dense for the purpose. From a recent informal conversation he had the impression that Chance Bros. would be prepared to make filters suitable for fluorimetry i f enough people were interested. In connection with double-beam instruments, although in certain circumstances they were the most satisfactory, it should not be forgotten that the double-beam principle did not correct for every possible fluctuation of the light source. With a discharge lamp, particularly of the high pressure type such as was used to get high beam intensity, the fluctuation might be a movement of the luminous column rather than a change in its intensity, in which case the double-beam principle would not give perfect compensation.Dr. F. WOKES admitted his responsibility for introducing to THE ANALYST the term “quenching” as applied to various deviations from linearity in fluorescence calibrations. He asked Mr. Bowen to suggest an alternative title to describe such deviations when they did not comply with the latter’s precise definition of “quenching.” Mr. Bowen had referred to the temperature effect. Some figures for the magnitude of this under different working conditions would be of great value to those who were trying to improve the accuracy of fluorimetric assays. The various instrumental errors described by Mr.Bowen could be best explored by calibration curves. It was regrettable that in many publications on fluorimetric analysis calibration data were lacking. Could this be more precisely described. The blank used by Dr. Kodicek did not appear to allow for interfering substances produced by the oxidation of ferricyanide. In his second slide the reading of 1 mm. for the Dr. Kodicek had referred to the use of an internal standard in different fluorimetric assays.Sept., 19471 FLUORIMETRIC ANALYSIS : DISCUSSION 391 water blank seemed rather high in comparison with the reading of 13 mm. given by the 0-4 pg. of aneurine. This would suggest a possible error of 7 or 8 per cent. and also a low sensitivity for the fluorimeter. Dr. Simpson should be congratulated on the excellent series of fluorescence spectra shown.Had she observed in her absorption spectra the usual mirror image relationship with the corresponding fluorescence spectra ? Mr. BOWEN, in reply to Mr. Cooper, said that he would like to suggest that the residual factor might still be the effect from the cell or it might be the Raman radiation from the water. Presumably with a very dense filter all radiation scatter would be cut out; the Raman radiation would pass the filter. Mr. COOPER said that although he was not certain, he thought that the residual fluorescence was con- tinuous radiation and not a line spectrum. This was based on visual observation through a series of narrow band colour filters. Mr. BOWEN said that some years ago some French investigators worked on very feeble effects from alkalis.They shone a light into a cell and made a very long exposure a t right angles and got what they called fluorescence, but what amount, if any, was Raman radiation he did not know. Raman radiation was polarised. Except in highly viscous media, the molecule turned round in several rotations before it emitted fluorescence, which was therefore unpolarised. If nicol prisms were inserted i t was possible to distinguish between Raman radiation and fluorescence. No design was free from zero error. The error might be due to impurities or to the glass, or a number of things might cause the curve to deviate from linearity. He could not conceive any better term than “instrumental error. ” As for temperature effect, one got a big temperature effect only with inter-molecular quenching.In a solution like that of fluorescein, for example, there was not a very big temperature effect, but with a quenched solution, if it was of the bimolecular collision type, the temperature effect was quite high, though generally smaller if it was of the bond type-of the order of 10 per cent. for 20” C. Therefore there could be considerable errors, but they occurred only in solutions. Concerning the glass filters, he suggested that OY9 and 10 filters could be used in the main light beam. Mr. COOPER said that a fluorescent filter might be objectionable even in the incident beam, since the fluorescent radiation could get into the liquid cell. In any event Chance OY9 and OYlO could not be used in the incident beam if near ultra-violet radiation were required, By this he had meant the addition of standards to the unknown.The method they were using for thiochrome was the Harris-Wang method, which meant a visual method; therefore, in his Table 11, which represented the experiments done visually, he had wanted to show actual numbers and figures. The absorbent filters Wratten 49 were used, and thus the sensitivity was low. It was distinct enough to obtain what he wanted in order to show the difference. It was in the range that he had mentioned. Dr. SIMPSON, in reply to the question asked of her by Dr. Wokes, said that she did not think the absorp- tion curves had been investigated at sufficiently low optical densities. The pterins had strong bands in the ultra-violet, and the spectra had not been observed at wavelengths as great as 4000 A.Mr. H. N. RIDYARD emphasised the importance of Mr. Bowen’s remarks on the use of the term “quenching.” This is used in very many papers in a loose manner to cover losses in fluorescence due to a variety of quite different causes, whereas photo-chemists have always used it in the restricted sense defined by Mr. Bowen. As a result, different effects have been confused and attempts to overcome or allow for these frustrated in consequence. For the same reason he would object to the alternative general term “instm- mental error,” suggested by Mr. Bowen, since this suggests difficulties lying in the apparatus. He would prefer some term such as “fluorescence inefficiency” which left to more precise terms the description of where the losses occurred.This had a connection also with the method of using internal standards advocated by Dr. Kodicek and widely used: this is not always as strictly accurate as it is sometimes assumed to be, and the rigorous of external and internal standards would help to an appreciation of the sources of error. Mi-. Cooper had called attention to the wandering beam of a discharge lamp in relation to the use of photo-cells placed on opposite sides of the light sources. He (the speaker) had always disliked this arrange- ment, and some years ago he employed in photochemical work a thin glass or quartz plate placed a t 45” to the light beam to obtain a measure of the beam actually used. He had been interested to note that this arrangement has been employed in at least one recently described fluorimeter.Dr. WHITE said that he was in the position of being faced with a number of fluorimetric problems in the near future, and he had been particularly interested in two that Mr. Bowen had mentioned, one concerning quenching. and the other, particularly, his analysis. He thought that his method of looking at the various phenomena might be of some value, particularly in laboratories where the advantage of spectrographic methods was available, in distinguishing the fluoroscopic portions of different materials. He would like to suggest that Mr. Bowen should pursue this matter perhaps a little more deeply in the form of a communication of some sort to one of the journals, in which the ideas could be put forward for other people to develop on a practical basis.He thought that Mr. Bowen had got something there of real value to some of those concerned in fluorimetric work. He agreed, however, that it might possibly be Raman radiation. He fully agreed with what had been said about instrumental error. That was a common feature. Dr. KODICEK said that Dr. Wokes had asked him about an internal standard. He had not had time to go into details.392 FLUORIMETRIC ANALYSIS : DISCUSSION pol. 72 Dr. J. G. A. GRIFFITHS asked if there were any substances that exhibited a fluorescence efficiency of unity. Where the fluorescence efficiency was less than unity was there not a probability that there would be a serious decrease in concentration of the substance under examination, as a result of photochemical reaction, in the course of the fluorescence measurements ? The geometry was awkward, and, secondly, it was necessary to compare very feeble quantities of light of different wave- lengths.He thought the fluorescence efficiency of rhodamjne was 0.4 and those of certain of the yellow dyes were of the order of 0.8. With regard to the photo-chemical changes that occurred, it was necessary to be clear in one's mind about the different possibilities of fluorescence quenching, There were some dyes-alizarin for example- completely non-fluorescent under any conditions, and that presumably was an intramolecular effect occurring in 10-usec. It was practically inconceivable that this activated molecule could react with dissolved oxygen.The collisions between molecules and solvents were about lO-'a sec., but the fluorescent molecule had a period of 10-6 sec., a relatively long period compared with collisions of a solvent molecule. There were thus a large number of possibilities of quenching. There could be quenching with and without photochemical action. The change could be reversible or non-reversible. All this could be explained in terms of suitable chemical equations which had been put forward by a number of people. Dr. A. H. GILLIESON mentioned the use of the American R.C.A. I.P.21, 22 or 28 electron multiplier tubes with electronically stabilised high-tension source, with which linearity over a range of 100,000-fold could be achieved. That type of instrument had been used for measurements of inorganic fluorescences in solid solutions down to an absolute amount of 10-ls g.of fluorescent substance, and was relatively easy to construct. Three laboratories were developing this type of instrument in this country-at the moment for fluorescence in solid solutions but fluorescence in liquid solutions would be undertaken. Dr. P. ELLINGER said he would like to make the following comments on Mr. Bowen's first paper. (1) He did not agree that photo-cells should be arranged a t right angles to the incident beam. If the primary source of light was not extremely powerful and a considerable proportion of the primary beam was absorbed by the solution to be tested, the secondary beam might shift to the proximal side and reach only one end of the photo-cell, the conditions being uncontrollable.With an arrangement of the photo-cell in line with the primary, and sets of satisfactory filters as those made by Corning or Kodak, rays of the primary beam reaching the photo-cell were of very low, constant and measurable intensity, and the values could be deducted from those from the secondary light source. (2) With highly sensitive selenium rectifier cells, sufficient sensitivity could be obtained to measure very minute amounts of fluorescent material, e.g., thiochrome in isobutanol down to 0.26 pg. can be measured with an accuracy of about f 6 per cent. The advantage of the rectifier cell is that it can be brought much nearer to the source of the secondary light than the vacuum cell. An increase of sensitivity of the photo-cell or the galvanometer was undesirable because it increased simultaneously the instrument errors which were the greatest source of difficulties and inaccuracies.(3) As to whether photo-electric or visual fluorimetry was preferable one should keep in mind that the human eye was at least as sensitive as the best photo-cell, particularly in the green and yellow. With good sets of standards very good results could be obtained with visual measurement. (4) The question how the currents of the two photo-cells should be balanced for measurement had not been mentioned. The most reliable way was by electrical balancing which did not interfere with the optical arrangement; unfortunately this was not the usual method of balancing in the instruments sold commercially. Most photo-cells were not evenly sensitive over the whole area and altered their resistance when the size of the exposed area was altered.Methods of balancing that interfere with the aperture of the beam should, therefore, be avoided. (5) The question should be discussed under which circumstances fluorimetry or ordinary absorptiometry should be used. Fluorimetry was preferable only if absorption was in a spectral region where the sensitivity of eye or photo-cell was nil or very low and the emission spectrum was in a region of high sensitivity of the analysers. In all other circumstances ordinary absorptiometry was preferable. Mr. BOWEN, in answer .to the last point, said that he had always imagined, perhaps wrongly, that absorption photometry was used for rather higher concentrations and fluorimetry below those concentrations. Fluorimetry could be used right down to the limits of instrumental error. In his earlier remarks he was envisaging that work was always done in fluorimetry with such dilute solutions as he had been speaking of; he did not think it should ever be used for cases of fluorescence confined to the cell wall. Dr. S. Y. THOMPSON said that in attempts to increase the sensitivity of fluorimeters used by him for riboflavine work he had found the limiting factor to be the fluorescence of practically all the glass or gelatin colour filters available in this country, particularly when the blue mercury line 4 3 5 8 ~ was used. Mr. COOPER said that by using filters in the manner he had described fluorescence of the filters them- selves was eliminated. The last filter in the optical path was not fluorescing and also had the proper characteristics for absorbing unwanted radiation, hence all that was measured was the fluorescence of the liquid itself. Mr. E. C. SLATER said that for the past five years he had used an American instrument similar in design to that described by Mr. Bowen. Its sensitivity, expressed as the concentration that would give a galvano- meter deflection of 1 mm., was 0.002 pg. per ml. for quinine sulphate in 0.1 N sulphuric acid (Corning 597 Mr. BOWEN,. in reply, spoke of the difficulty of measuring fluorescence efficiency. It had been done in a number of instances with the brilliant fluorescent dyes.Spt., 19471 PRINGLE: A RAPID QUALITATIVE TEST FOR ADDED IRON IN FLOUR 393 lamp filter, Corning 038 + Wratton 47 photo-cell filters) and 0.0002 g. per ml. for fluorescein (Corning 664 lamp filter, Coming 038 + 361 photo-cell filters). This sensitivity was found sufficient for vitamin work. He had found that with this instrument the readings were quite critically dependent on the volume of the solution in the cell (capacity 26 ml.), being maximum with 20 ml. Although there was an obvious exphna- tion of the rise to the maximum he could not see why there should be a subsequent fall. Could Mr. Bowen suggest an explanation ? Mr. BOWEN suggested that it was an effect due to reflection either of the incident light or of some of the fluorescent light, depending on the level of the liquid surface. Dr. S. JUDD LEWIS suggested that it should be very helpful to refer fluonmetric comparisons to standard substances as controls on the optical methods using the photo-electric cell. For example, mannitol always exhibits the same fluorimetric values, whether it is purified by three or four recrystdlisations from alcohol or water; the latter medium is perhaps the safer (see J. Soc. Chem. I&., 1944, 168). References to such a standard substance may be more reliable than those made by physical measurements. The two systems should be studied in relation to each other.

ISSN:0003-2654    

DOI:10.1039/AN9477200385

出版商:RSC    

年代:1947

数据来源: RSC

摘要:

426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively.Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction Sept., 19471 PRINGLE: A RAPID QUALITATIVE TEST FOR ADDED IRON IN FLOUR 393 A Rapid Qualitative Test for Added Iron in Flour BY W.J. S. PRINGLE QUALITATIVE tests for the presence of added. nicotinic acid1 and vitamin BI2 have been published and a test for added iron is now described. It has been found sufficiently sensitive to detect also accidental contamination of flour with iron from the rolls and other machinery in the mill.3 The test depends upon the formation of a mauve iron lake with alizarin (1 : 2-dihydroxy- anthraquinone). In analytical chemistry alizarin is mainly used as a reagent for aluminium, with which it forms a red lake, but this element is not likely to be a source of interference in the present test as it is added to flour only to a limited extent, in Ameiica as a self-raising agent, in the form of sodium aluminium sulphate'.Manganese also forms a lake with the reagent, but the natural manganese, iron and aluminium contents of the flour either do not react with the alizarin under the conditions of the test or only react to a limited degree, so that the effect of these natural flour constituents is negligible. PROCEDURE- Soak acid-washed filter papers in a filtered saturated alcoholic solution of alizarin, remove them from the solution and allow them to drain for a few moments; then place them on glass plates and dry them over a hot plate or in an oven. After cooling, moisten the dried paper (which should now have a uniform brownish-yellow colour) on the glass plate with just enough N hydrochloric acid to wet it thoroughly. .For a 9-cm. Whatman No. 30 paper 1.25 ml. is sufficient. Place 2 or 3 g. of the flour to be tested on a small sieve (14 in. diameter) covered with silk bolting cloth, and distribute it evenly over the filter paper by tapping the sieve while moving it about over the paper. When sufficient flour has been added to absorb all the acid (this is shown by the flour covering the surface of the paper remaining dry) blow off the excess flour and wipe the glass plate clean up to the edge of the paper. After waiting 5 to 10 minutes to allow the iron to be dissolved by the acid, invert the glass plate and hold it over the mouth of an open bottle of concentrated ammonia solution.Move the plate about to allow the ammonia vapour to come in contact with all parts of the filter paper. After a few moments the adhering side of the filter paper as seen through the glass plate begins to turn a violet colour owing to the formation of ammonium alizarinate. When all the acid has been neutralised the filter paper has a uniform violet colour all over and is ready for drying. The drying may be carried out over a hot plate or in an oven (preferably with a glass door). It is important that the heating should be stopped as soon as the paper is dry, as over-heating causes the formation of a brown coloration which obscures the test. The heating should be stopped when the filter paper starts to buckle and leave the surface of the glass plate.The violet colour of the ammonium alizarinate is discharged on drying, leaving the coloured iron compound unchanged against the original brownish-yellow background. The form which the coloured areas take is dependent on the nature of the source of the iron that has been added to the flour. If the iron has been added in powder form (either as reduced iron or sodium iron pyrophosphate) the coloured areas will appear as spots with intensely qoloured centre and a paler coloured surrounding circle. The size of the spot depends upon the length of time allowed to elapse between the addition of the flour to the acid-soaked394 NOTE [Vol. 72 paper and the neutralisation of the acid with the ammonia vapour. Each spot indicates the locus of an individual particle of added iron or iron salt.If, on the other hand, an iron solution has been sprayed on to the flour, coloured spots will still be formed, but they will be considerably larger in area and of approximately even intensity throughout. THIOCYANATE TEST- A simple test for iron-enriched flour that has recently been described4 depends upon the use of 5 per cent. potassium thiocyanate solution in h7 hydrochloric acid. In this method the enriched flour and a control (unenriched) flour are slicked side by side in the manner used for the Pekar test6 and the reagent is added with a dropper at the junction of the two flours, in amounts sufficient to wet an area approximately 1 in. in diameter. Allow to stand for at least 10 minutes. “In the event that added iron compounds are present, a deeper red colour will be found than in the case of the unenriched flour.Small local areas of intense red show up after 20 minutes, indicating the location of individual particles of iron.” The need to wait 20 minutes for the full result of the test is due to the fact that usually the iron is added in the ferrous condition and is only slowly changed to the ferric state after being brought into solution by the acid component of the reagent. Thiocyanate reacts only with ferric iron, and we have found that the test may be speeded up and made much more sensitive if an oxidising agent is added to the acid thiocyanate reagent. If equal quantities of a 2 per cent. solution of ammonium persulphate and the acid thiocyanate reagent are mixed and this new reagent is used for the test the full result is apparent after two minutes. An additional improvement to the test is the substitution of the technique of the Pekar test for wetting the surface of the flour, instead of the addition of the reagent from a dropper.The slicked flours are carefully slid into the new reagent solution and then removed and the excess of reagent is wiped away. This ensures more even wetting of the flours and prevents the break-up of the smooth surface which often occurs when a dropper is used. The thiocyanate test may also be carried out in the manner described above for the alizarin test. A dry filter paper is wetted with 1.25ml. of the new reagent and the flour to be tested is sprinkled on by means of the sieve. This method has the advantage that smaller quantities of sample and of reagent are required. SUMMARY- Two methods have been described for the detection of added iron or its salts in flour. REFERENCES 1. 2. 3. 4. 6 . Kent, N. L., “Milling,” October 27th, 1945. @inton, J. J. C., Chemistry and Industry, 1946, 62, 94. Jones, C. R., and Moran, T., Cereal Chem., 1946, 23, 248. “Consolidated Grain Milling Catalogues,” p. 418, Chicago; “American Miller and Processor,” 1946. “Cereal Laboratovy Methods,” p. 48, Belleville, N. J., American Association of Cereal Chemists, 1936. THE RESEARCH ASSOCIATION OF BRITISH FLOUR MILLERS CEREALS RESEARCH STATION ST. ALBANS, HERTS. Mavch, 1947

ISSN:0003-2654    

DOI:10.1039/AN9477200393

出版商:RSC    

年代:1947

数据来源: RSC

摘要:

426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international.The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively.Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited.The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE.By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time.The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice.Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years.The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr. Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion.The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies. Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on.Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents. It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation.Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate. There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp.15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction 394 NOTE [Vol. 72 Note A SIMPLE DIRECT-READING SEMI-MICRO BALANCE IN a recent investigation involving numerous preparations on a semi-micro scale, weighings were considerably facilitated by the construction of the simple direct-reading balance shown in Fig. 1. This has a capacity of about 0 to 80 mg., but for other purposes the sensitivity may be increased or decreased. The essential parts of the apparatus are of glass. A self-locating fulcrum system centres the pointer with respect to the scale. No arrestment is thus necessary; when the weighing spoon is removed, the counterpoise end of the beam comes to rest upon the glass-covered surface of the wooden upright.To prevent interference by draughts the balance is enclosed in a small wooden box, the front of which is glazed and opens outwards in the manner of a door. The beam, weighing spoon support, pointer and damping device are constructed from a single piece of 3-mm. diameter glass rod, as shown in Fig. 2. The pointer is formed by drawing down the rod to about 0.8 mm. diameter and bending as shown. To construct the fulcrumSept., 19471 NOTE 395 or “knife edge” a piece of 3 mm. rod is drawn out at both ends and bent twice at right angles, as shown at a. The extremities of the fulcrum are then fused until hemispherical, care being taken that the “legs” are of the same length.Sealing wax is used to cement the finished fulcrum to the beam. Fig. 1. A small glass trough cemented in a groove cut across the top of the wooden upright serves as a bearing surface for the fulcrum. Stages in construction of this trough are shown in Fig. 3. A hole about 3 to 4 mm. in diameter is first blown in the wall of a length of 8-mm. outside-diameter glass tubing, as shown at a. The tubing is then heated in the region of the hole and the ends are pulled apart, as shown at b. When cold, about 3 cm. of the narrow central portion, which has a cross-section shown at c, is cut out, and, by heating carefully in the blowpipe flame, the ends are closed to form a small “boat” about 25 mm. long and about 2.6mm.wide. The finished component is depicted at d. - - - 6 8 1 0 I : ! . - ! 2 ! : ! .r (CM. Fig. 2. Weighing is carried out on small glass spoons, which are very convenient for picking up the material to be weighed and for transferring it to the reaction vessel when the weighing is complete. Details of construction are shown in Fig. 4. U-section glass, prepared in a similar manner to that described above, but of larger size, is employed. If soft glass is not objected to, a batswing burner is preferable to a blowpipe in the fabrication of these larger sections. Handles consisting of 2-cm. lengths of 1.5 mm. diameter glass rod are attached to the rear ends of the spoons. By cutting small pieces from the ends of the handles, the spoons are adjusted-to be equal in weight; when the adjustment is complete, the ends of the handles are rounded in the blowpipe flame.396 NOTE Wol.72 A paper scale graduated in 2-mg. divisions and covered with sheet celluloid is mounted on the wooden base (Fig. 1) so that the pointer moves close to its surface but does not touch. To enable the zero to be adjusted, a tilting device A is fitted to the base. This consists of a short length of 2-B.A. brass screw rod which may be rotated by means of the knob. The rod passes through the base and then through a nut soldered to a piece of sheet brass secured wa L J C 0 l a a m . Fig. 4. e--d Fig. 3. to the underside of the base. The end of the rod then makes contact with the bottom of the balance case. Rotation of the knob tilts the base as required; the method of adjustment is thus similar to levelling up an ordinary balance equipped with a plummet.Counterweight 8 consists of a 2-cm. length of rubber pressure tubing which is split longi- tudinally. It is sprung into position on the upper part of the pointer and may be slid up or down, thus allowing the sensitivity of the balance to be adjusted. I 2 3 4 5 6 7 8 TIME FROM START,S€C. Fig. L 0 1 0 2 0 3 0 4 0 5 0 M > K ) 8 0 LOAD, MG. Fig. 6. Preliminary experiments with the balance showed that readings were dficult to obtain rapidly owing to the large oscillations necessarily set up on applying the load. This difficulty was overcome by the use of artificial damping, accomplished by causing the looped end of the pointer (b, Fig. 2) to dip into thin machine oil contained in the oilbath C.This may be constructed from thin tinplate; alternatively a 10-cm. porcelain boat may be used. The oilbath is filled to about one-half with oil. As is clear from Fig. 6, the use of damping permits weighings to be completed in a few seconds. Calibration of the scale is carried out by using short pieces of 22 S.W.G. copper wire which have been previously weighed on a balance of nonnal form. A typical calibration curve is shown in Fig. 6. In practice, the accuracy of the instrument is limited by variations in the distribution of the material in the weighing spoon. If the material is packed against the side of the spoon remote from the fulcrum, it will obviously exert a greater turning moment than if packed against the opposite side of the spoon.This effect is shown in Table I. Each result was obtained by placing a predetermined load in a weighing spoon and repeatedly observing the apparent weight. After each observation, the spoon was gently tapped to redistiibute its contents and then replaced on the balance.Sept., 19473 Material Sucrose powder . . U e . * n s9 .. Copperwire .. n r , .. a n .a OFFICIAL APPOINTMENTS TABLE I REPRODUCIBILITY OF BALANCE mg. mg. I3*O 32*2 61*6 True weight Observed weight 13.9, 13.3, 13.1, 12.8, 14.1, { 13-3, 13.6, 12.8, 13-9, 13.1 } 32.6, 31.8, 32.0, 31.8, 32.6. (32-8, 31.6, 33.6, 33.1, 32.6 ) 50.7, 62.6, 61-3, 62.1, 51.6, { 52.1, 50.7, 61-8, 61.3, 52.4 } 21.4, 21.4, 20.8, 21.4, 21.6, 40.1, 41.1, 41-3, 41.1, 41.1, 82.8, 82.8, 83.4, 83.8, 83.0. 40.5 (41.1 83*0 { 83-0 397 Max. error mg. 1.1 1.4 1.0 0.6 0.8 0.8 The general performance of the balance is shown by the results in Table 11, obtained by picking up by shovelling action various amounts of powdered sucrose in a weighing spoon, observing the apparent weight and then determining the true weight on a balance of con- ventional pattern. TABLE I1 TYPICAL RESULTS I N THE WEIGHING OF True weight Observed weight mg* mg* 6.0 4.6 13.0 13-4 22.7 24.0 30-2 304 51.6 61.6 77.0 76.6 POWDERS Error mg. - 0.6 + 0-4 + 1.3 + 0.2 0.0 - 1.4 Though the balance in its present form is not a highly accurate instrument, it is useful for the rapid weighing of reagents for semi-micro preparations, qualitative analysis, etc. Its cost is negligible and its construction involves glass-working of but a rudimentary character. Perhaps the least satisfactory constructional feature is the oilbath method of damping, which hampers the portability of the instrument. This could be overcome by employing a slightly more complicated design, or in all probability by employing electro- magnetic means of damping. CHEMISTRY DEPARTMENT L.C.C. NORWOOD TECHNICAL INSTITUTE KNIGHT’S HILL, LONDON, S.E.27 J. T. STOCK M. A. FILL December, 1946

ISSN:0003-2654    

DOI:10.1039/AN9477200394

出版商:RSC    

年代:1947

数据来源: RSC

摘要:

426 REVIEWS INKS : THEIR COMPOSITION AND MANUFACTURE. By C. AINSWORTH MITCHELL, D.Sc., F.I.C. Fourth Edition. Pp. xi + 408. London: Charles Grihn tt Co., Ltd. 1937. Price 12s. 6d. net. This, the fourth edition of the standard and, indeed, so far as the reviewer’s knowledge goes, the only text-book on the subject in the language, bridges L gap of 13 years. The author, pre-eminent in his particular sphere, needs little more introduction to the world of technical industry than he does in his official capicity to readers of THE ANALYST, while his reputation in forensic science in all that appertains to handwriting is international. The chemistry of ink, difficult as it is and at times not a little obscure, hcl- riot developed markedly in the interval since 1924; but what progress has been made is covered by Dr.Mitchell in this edition in a very thorough manner. He has found it necessary to enlarge his work to the extent of some 20 per cent. and, in addition, to rewrite a large portion. The arrangement of the book follows the lines of previous editions. After a comprehensive historical introduction, the work is divided into three sections dealing with writing inks, printing inks, and inks for miscellaneous purposes, respectively. Under Section 1 are considered the chemical nature and treatment of the various raw materials used for writing inks from lcmp black to galls, the composition of finished iron-gall, logwood, vanadium, aniline black, and coloured inks, as well as a comprehensive scheme €or the tech~ical examination of inks, handwriting specimens and the identification of forge:-ies.Section 2 deals with the manufacture and examination of printing inks. ,tnd Section 3 with the miscellaneous materials entering into the compositilxx of copying, marking, safety, sympathetic, typewriter inks and so on. Amongst new matter may be noted references to the use of lignone sulphni--,ites in connection with writing ink, a scheme for the identification of individual con- stituents in inks in the form of writing, and the application of filtered ultra-.& if )let light and of infra-red photography in the elucidation of those problems to which such methods are suited. The British Government Standard Specificatior:s for Writing Inks, revised in 1928, are included for the first time. The avaihble evidence upon the constitution of gallotannin is brought up to date and <tbly reviewed, and there is a Comprehensive list of British patents.It is as difficult to withhold admiration of the encyclopaedic scope cjf the matter and references in this book as it is of the erudition and industry displiiyed in its compilation. Practically nothing that comes to mind has escaped atterition, and it is with rather impish glee that the reviewer, after careful search, asserts that he finds no specific reference to the type of alkaline (ammoniacal) gallotannate- iron ink, said t o find favour in the United States, although the di-ammonium hydroxyferrigallate compound of Silbermann and Ozorovitz receives notice. Nor is there mention of that class of quick-drying writing fluids which depend for their efficiency upon partial destruction of the paper sizing by caustic alk 1.5 or sodium silicate.There is no evidence that lignone sulphonate inks have proved se-rious competitors to iron-gall writing inks (pp. 15 and 175). Apart from the unkttmwn quantity of permanence, the principal failing of this type lies in their liability to contain traces of free sulphurous acid to which suspicion attaches in connt-ction Sept., 19473 OFFICIAL APPOINTMENTS 397 Official Appoin trnents PUBLIC ANALYST APPOINTMENTS NOTIFICATION of the following appointments of Public Analysts has been received from the Ministry of Health since the last record in THE ANALYST (1947, 72, 263). Public Analysts - APPointrttents DIXON, Frederick (Deputy) . . City of Manchester. HERON, Neil (Deputy) . . . . Borough of Gosport. PEDEN, Miss J. D. (Deputy) . . County of Staffordshire. WILLIAMS, Albert Lester . . . . Borough of Gosport. Mr. H. Dedicoat did not take up his appointment as deputy Public Analyst for the County Borough of Leeds (cf. Zoc. cit.). OFFICIAL AGRICULTURAL ANALYST APPOINTMENTS NOTIFICATION of the following appointments of Official Agricultural Analysts has been received from the Ministry of Agriculture and Fisheries since the last record in THE ANALYST (1947, 72, 254). Oficial Agricultural Analysts Appointments HERON, Neil (Deputy) . . . . County Borough of Liverpool. WILLIAMS, Albert Lester . . . . County Borough of Portsmouth.

ISSN:0003-2654    

DOI:10.1039/AN9477200397

出版商:RSC    

年代:1947

数据来源: RSC