摘要:

466 ALLAN : ATOMIC-ABSORPTION SiPECTROPHOTOMETRY WITH [Vol. 83 Atomic-absorption Spectrophotometry with Special Reference to the Determination of Magnesium BY J. E. ,4LLAN (Department of Agriculture, Rukuhia Reseavch Station, Hamilton, New Zealand) The determination of magnesium by atomic absorption is examined in detail. The apparatus and method are described, and the results are discussed with regard to reproducibility, accuracy and sensitivity. It is shown that, by this method, reliable magnesium determinations can be made with the same ease and rapidity as flame-photometric determinations of sodium and potassium. THE possible use of atomic-absorption spectra for general analytical purposes was first realised by Walsh, who, in 1955,l considered the theoretical and experimental problems involved and concluded that the method showed considerable promise and could have several advantages over emission methods.In a later paper,2 an experimental atomic-absorption spectrophotometer was described and results were given for a number of elements. In this laboratory, the determination of elements of @cultural interest by the method is being studied and the results obtained for magnesium are presented here. In the analysis of plant material, soil extracts and so on, magnesium, of the four major cations present, is the most difficult to determine. The other three, sodium, potassium and calcium, can be readily determined with speed and accuracy by flame-photometric methods, and for some years in this laboratory a simple triple-beam filter flame photometer has been used for this purpose.As magnesium emission is weak compared with the flame background, the method cannot be applied to the determination of this element. Reasonable results can be obtained by using a monochromator to iso1,ite the magnesium line, but, even when this is done, the necessity of backing off a large backgi-ound reading and the fact that the emission - concentration curve is flattened by self-absorption reduce the sensitivity and precision. The fact that magnesium emits weakly and shows strong self-absorption made it appear that the atomic-absorption method would be particularly suitable for its determination. That this is so has been fully confirmed by the results reported later. EXPERIMENTAL Briefly, the basis of the method is the measurement of the light absorbed a t the wave- length of the resonance line by the unexcited atoms of the element.This measurement is made by spraying the sample into a flame to provide a reproducible and clearly defined cloud of atoms and by using as the light source a lamp that emits the line spectra of the element to be determined. LIGHT SOURCE- Emission from the light source should be steady, to avoid the necessity for double-beam operation, and should be intense in relation to the emission from the flame, to avoid having to eliminate the latter. Further, the lines should be sharp and narrower than the absorption line in the flame so that the peak absorption can be measured. For magnesium, these requirements are met by the magnesium - aluminium hollow-cathode lamp manufactured by Hilger and Watts.This lamp, which has a cathode of duralumin, operates at currents up to 70 mil, with a voltage drop across the lamp of about 260 volts. About 500 volts are required to start the discharge and usually a power supply that delivers a somewhat greater voltage is used with a series resistor to control the current. A full description of the operation of a hollow- cathode lamp with an iron cathode has been published by Crosswhite, Dieke and Legagneur.3 The magnesium - aluminium lamp, however, difers from the iron lamp in that the emission does not reach maximum intensity immediately after the lamp is switched on, but requires a warming-up period of at least 30 minutes. During this time, the intensity of the aluminium spectrum is reasonably constant, but that of the magnesium spectrum increases greatly.Similarly, when the current through the lamp is changed, the same interval should be allowed for the intensity to reach a steady value. The apparatus used is shown in Fig. 1.466 ALLAN : ATOMIC-ABSORPTION SiPECTROPHOTOMETRY WITH [Vol. 83 Atomic-absorption Spectrophotometry with Special Reference to the Determination of Magnesium BY J. E. ,4LLAN (Department of Agriculture, Rukuhia Reseavch Station, Hamilton, New Zealand) The determination of magnesium by atomic absorption is examined in detail. The apparatus and method are described, and the results are discussed with regard to reproducibility, accuracy and sensitivity. It is shown that, by this method, reliable magnesium determinations can be made with the same ease and rapidity as flame-photometric determinations of sodium and potassium. THE possible use of atomic-absorption spectra for general analytical purposes was first realised by Walsh, who, in 1955,l considered the theoretical and experimental problems involved and concluded that the method showed considerable promise and could have several advantages over emission methods.In a later paper,2 an experimental atomic-absorption spectrophotometer was described and results were given for a number of elements. In this laboratory, the determination of elements of @cultural interest by the method is being studied and the results obtained for magnesium are presented here. In the analysis of plant material, soil extracts and so on, magnesium, of the four major cations present, is the most difficult to determine.The other three, sodium, potassium and calcium, can be readily determined with speed and accuracy by flame-photometric methods, and for some years in this laboratory a simple triple-beam filter flame photometer has been used for this purpose. As magnesium emission is weak compared with the flame background, the method cannot be applied to the determination of this element. Reasonable results can be obtained by using a monochromator to iso1,ite the magnesium line, but, even when this is done, the necessity of backing off a large backgi-ound reading and the fact that the emission - concentration curve is flattened by self-absorption reduce the sensitivity and precision. The fact that magnesium emits weakly and shows strong self-absorption made it appear that the atomic-absorption method would be particularly suitable for its determination.That this is so has been fully confirmed by the results reported later. EXPERIMENTAL Briefly, the basis of the method is the measurement of the light absorbed a t the wave- length of the resonance line by the unexcited atoms of the element. This measurement is made by spraying the sample into a flame to provide a reproducible and clearly defined cloud of atoms and by using as the light source a lamp that emits the line spectra of the element to be determined. LIGHT SOURCE- Emission from the light source should be steady, to avoid the necessity for double-beam operation, and should be intense in relation to the emission from the flame, to avoid having to eliminate the latter.Further, the lines should be sharp and narrower than the absorption line in the flame so that the peak absorption can be measured. For magnesium, these requirements are met by the magnesium - aluminium hollow-cathode lamp manufactured by Hilger and Watts. This lamp, which has a cathode of duralumin, operates at currents up to 70 mil, with a voltage drop across the lamp of about 260 volts. About 500 volts are required to start the discharge and usually a power supply that delivers a somewhat greater voltage is used with a series resistor to control the current. A full description of the operation of a hollow- cathode lamp with an iron cathode has been published by Crosswhite, Dieke and Legagneur.3 The magnesium - aluminium lamp, however, difers from the iron lamp in that the emission does not reach maximum intensity immediately after the lamp is switched on, but requires a warming-up period of at least 30 minutes. During this time, the intensity of the aluminium spectrum is reasonably constant, but that of the magnesium spectrum increases greatly.Similarly, when the current through the lamp is changed, the same interval should be allowed for the intensity to reach a steady value. The apparatus used is shown in Fig. 1.August, 19581 SPECIAL REFERENCE TO THE DETERMINATION OF MAGNESIUM 467 Both the intensity of emission and the width of the emitted line vary with the current. The intensities of a number of lines as a function of the current are shown in Fig.2. The curves in Fig. 2 show that the intensities of both the aluminium and magnesium lines increase more rapidly than the current, and, to keep the intensity of the magnesium line at 2 8 5 2 ~ to within 21 per cent. of the value at 60 mA, the current must be controlled to within +O-1 mA. The effect on the calibration curve of the widening of the magnesium line at 2852~, which occurs as the current is increased, is shown by curves A, B, C and D in Fig. 4, p. 468, and will be referred to later. On this account also, close control of the current is necessary. It was found to be convenient to operate the lamp from an electronically regulated power supply of conventional design, which delivered a regulated voltage of 1150 volts. This voltage, which is also used to operate the photomultiplier tube referred to later, is applied to the hollow-cathode lamp as shown in Fig.3. In this circuit, the 807 valve tends to maintain a constant anode current, which compensates changes in the resistance of the hollow-cathode lamp. The current through the lamp can be set to any desired value between 35 and 70 mA by means of resistor R,. l o o 0 l Current, rnA Fig. 2. Intensity of the hollow-cathode spec- trum as a function of the current: curve A, A1 I 3093 A line; curve B, Mg I 2 8 5 2 ~ line; curve C, Mg I1 2796 A line Q. regulated H = Hollow-cathode lamp M = 0 to 100 mA milliameter R, = 9500-ohm 50-watt wire-wound re- R, = 200-ohm 2-watt wire-wound resistor R, = 500-ohm 5-watt wire-wound resistor V = 807 valve hollow-cathode lamp sistor Fig.3. Current-control circuit for BURNER AND ATOMISER- The burner shown in Fig. 1 is the standard LundegHrdh type, which burns an air - acety- lene mixture supplied at the rate of 1.1 litres of acetylene and 8 litres of air per minute. The atomiser (not shown in Fig. 1) is basically a LundegHrdh atomiser, but has been modified to suck the solution up from a beaker to avoid the usual procedure of dismantling the spray chamber when solutions are changed. About 7.0 ml of solution are used per minute, of which about 0.12 ml enters the flame. Other burners have been used with the same atomiser and will be discussed later. After the burner, a diaphragm with a )-inch diameter opening prevents entry into the spectrograph of light from the blue cone of the flame.468 ALLAN ATOMIC-ABSORPTION SPECTROPHOTOMETRY WITH [Vol.83 The height of the burner is adjusted so that the beam of light from the hollow-cathode lamp, which reaches the spectrograph through the diaphragm, passes through the flame about Q inch above the top of the burner. The hollow-cathode lamp and the burner are placed reasonably close together and about 18 inches from the slit of the spectrograph. This is not at all critical, but the light that enters the spectrograph from the flame is; reduced in relation to that from the lamp as the distance from the spectrograph is increased. SPECTROGRAPH- The spectrograph used is a Hilger medium-quartz instrument with an exit slit and a photomultiplier (R.C.A. IP28), positioned t o intercept the magnesium line at 2852 A, mounted on a spare plate holder.As the spectrum of the lamp is practically free from background and as there are no lines close to the magnesium line at 2852 A except a very weak line at 2856 A, reasonably wide entrance and exit slits can be used (about 0.5 mm), thus per- mitting the plate holder carrying the exit slit <and the photomultiplier to be removed and replaced without fine adjustment. The anode current of the IP28 is measured by a Cambridge galvanometer (450 ohms), which is provided with a variable shunt to control its sensitivity. By means of a 1.5-volt battery and a variable resistor, a small direct current can be applied to the galvanometer in opposition to the current from the photomultiplier in order to back off the dark current and the current due to emission from the flame.GENERAL OPERATION- The emission of light from the flame at the wavelength measured is weak compared with that from the hollow-cathode lamp. It consists of radiation from OH radicles and is un- affected either by the presence of cations or anions sprayed into the flame or by magnesium in the amounts considered. Its removal, e g . , by chopping the hollow-cathode light and amplifying the photomultiplier output at chopping frequency, is therefore not necessary, and it is sufficient to back off electrically the current due to this emission. Magnesium concentration. p p m Fig. 4. Calibration curves for magnesium a t different current supplies t o the hollow-cathode lamp and different flame widths: curve A, 70 mA, 2.1 cm; curve B, 60mA, 2.1 cm; curve C, 50 mA, 2.1 cm; curve D, 40mA, 2.1 cm; curve E, 60mA, 4.8 cm; curve F, 60 mA, 7.5 cm The procedure for measuring the absorption is therefore as follows.After at least 30 minutes for the hollow-cathode lamp to attain a steady emission and for the photomulti- plier to fatigue, distilled water is sprayed into the flame and, with a shutter in front of theAugust, 19581 SPECIAL REFERENCE TO THE DETERMINATION OF MAGNESIUM 469 lamp, the small galvanometer reading, about 5 divisions, due to the photomultiplier dark current and flame emission is backed off electrically. The shutter is then opened and the galvanometer adjusted to the full-scale reading with the variable shunt. Distilled water is then replaced by the solution to be analysed and the galvanometer reading is taken.After ten or twelve solutions have been analysed, the zero and full-scale readings are again checked with distilled water in the flame. The zero reading rarely alters, but the full-scale reading may change slightly, owing to photomultiplier fatigue. SENSITIVITY- The extent to which the measured absorption approaches the peak value will depend on (a) the ability of the monochromator to resolve the line being measured from the other radiation of the lamp, and (b) the width of this line in relation to that of the absorption line in the flame. As the spectrum emitted by the lamp is practically free from background, the resolution of the monochromator is not of great importance in the present instance, provided that the magnesium line at 2 8 5 2 ~ is separated from other lines. The effect of reducing the width of the hollow-cathode line by decreasing the current is shown in Fig.4, from which it can be seen that, down to 50 mA, an increase in absorption is obtained. At the same time, of course, the intensity of the lamp is reduced, and it was found to be con- venient to operate the lamp at 60 mA for routine analytical work. An improvement in linearity also results from the narrower line, although some curvature always remains, caused, no doubt, by the finite width of the hollow-cathode line. The greatly increased curvature at 40 mA is difficult to explain. When pressure broadening in the flame is ignored and the shape of the absorption line is considered as being due to the Doppler broadening only, then the relationship between the peak absorption and concentration is given b y e RESULTS AND DISCUSSION 2 ~ 2 JE .. Nf Kmax. = - DA 7T mc2 where K,,,. = the absorption coefficient at the centre of the line, DA N f = the Doppler width of the line, = the number of atoms capable of absorbing at wavelength A, and = the oscillator strength of the line. In this equation, only DA and N are subject to experimental conditions. DA for a particular element line alters only with temperature and is proportional to Tt. The effect of this on K,,,. is, however, unimportant in practice, as it is overshadowed by the dependence of N on temperature. N , the number of atoms capable of absorbing, is proportional to the product of the concentration of these atoms in the flame and the length of the light path through the flame.Fig. 4 shows curves obtained by using three burners of different length. When the two larger burners, which were of the fish-tail type, were used, the length of the flame appeared to be equal to the length of the burner opening. The smallest burner was the usual Lunde- gdrdh type, and the flame path was somewhat longer than the burner opening (about 2.4 cm). The sensitivities obtained can be seen to be approximately proportional to the length of flame. There is, of course, a limit to the increase in sensitivity that can be obtained in this way. The burner opening cannot be decreased in width unduly or it will become blocked by salt deposits, As the length increases, therefore, the area of the opening increases and eventually the flame will become unstable and flash back.A5 the number of excited atoms is always a very small fraction of the total, the number of unexcited atoms is virtually equal to the total number of atoms, and the concentration of these in the flame will depend on two factors. The first is the efficiency of the atomiser as judged by the amount of spray, sufficiently finely divided to be completely volatile, that is introduced into the flame per unit volume of air. It is of interest to note that, in emission flame photometry, if the sensitivity is expressed as the concentration required to give the full-scale reading, it is possible to camouflage a poor atomiser by using an optical system of greater light-gathering power or a more sensitive galvanometer or photocell.Such devices are, however, of no avail in the measurement of absorption, which therefore provides a direct test of atomiser efficiency.470 ALLAN : ATOMIC-ABSORPTION SPECTROPHOTOMETRY WITH [vol. 83 The second factor on which the concentration of atoms in the flame depends is obviously the dissociation of the magnesium compounds and this will depend on the flame temperature. From the work of Huldt and Lagerquist,6 who determined the concentration of free magnesium atoms in a flame similar to that used in this instance, with a temperature of 2410" K, it appears that only a small proportion of the total magnesium (about 1.5 per cent.) is dissociated into atoms, the rest presumably existing as magnesium oxide. If this is so, the measured absorp- tion will depend markedly on the flame temperature and the use of a hotter flame should, by increasing the dissociation of the magnesium oxide, lead to increased sensitivity.A small increase can be obtained by using an excess of acetylene in the flame, which presumably increases the dissociation of magnesium oxide by decreasing the free oxygen concentration. With the 7-5-cm burner, an acetylene flow of 1-56 litres per minute (sufficient to render the lower 1 inch of the flame luminous) increased .;he absorption by about 25 per cent. The results obtained with the 2-1-cm burner are about six times as sensitive as those reported by Russell, Shelton and Walsh,2 who used a coal gas flame and a 2-cm Meker burner. This greater sensitivity is, no doubt, caused by a combination of the factors discussed above, In general, the sensitivities reported here are adequate for most magnesium analyses-at least for agricultural materials.REPRODUCIBILITY- Provided that the air and acetylene pressures, the photomultiplier voltage and the hollow-cathode current are adequately controlled, duplicate readings agree to better than 1 per cent., as in emission flame photometry. In order to test the possibility of calibrating the galvanometer directly in magnesium concentration instead of using standard solutions to plot a calibration curve for each set of samples, five solutions containing 0.3, 1.0, 3.0, 6.0 and 10.0 p.p.m. of magnesium were analysed twenty times over a period of 1 week, the 4.8-cm burner being used. During this period, the apparatus was dismantled several times to allow the spectrograph to be used for other purposes.The coefficients of variation of the apparent magnesium concentration were 1.7 per cent. for solutions in the middle of the range, 3.0 per cent. for the solution containing 10 p.p.m. and 6.0 per cent. for the solution containing 0.3 p.p.m. When this experiment was carried out, the power supply for the hollow-cathode lamp was not fully stabilised and the known variations in the current would account for about half the variation in the measured absorption. I have since found, however, over a morle extended period, that the nature of the emission from the hollow-cathode lamp does c'hange, a decrease in intensity of the mag- nesium emission being accompanied by a sharpening of the magnesium line.The result of this is that now, after several months' use on routine analyses, calibration curves are about 30 per cent. more sensitive than those reported here. My experience has been confined to one lamp only and, of course, it may not be typical. ACCURACY- As the number of excited atoms is always a small fraction of the total number of atoms present in the flame, variations in their number, and hence in their emission, caused by the presence of other elements in the flame, will have no effect on the number of unexcited atoms and hence on the measured abs0rption.l Potassium and calcium, both at a concentration of 200 p.p.m., did not affect the absorption of a series of solutions containing from 0.3 to 10.0 p.p.m. of magnesium. In the first place, other elements could interfere by emitting light sufficiently close to the magnesium wavelength to be passed by the monochromator and sufficiently intense, in comparison with the hollow- cathode lamp, to be detected.The only likely element is sodium, which emits a weak line at 2853 A. Under the experimental conditions described, exactly the same absorption was obtained from 2.0 p.p.m. of magnesium in 0.1 N hydrochloric acid as from the same concen- tration of magnesium in 10 per cent. w/v sodium acetate solution (a commonly used soil extractant containing approximately 17,000 p.p.m. of sodium). Had interference by the sodium emission occurred, it could, of course, have been overcome by the use of a chopper and tuned amplifier as suggested by Wa1sh.l This lack of interference is in marked contrast to the situation that occurs in the determination of magnesium by flame-emission methods, where the degree of interference by sodium is considerable and depends on the resolution Inaccurate results could, however, arise from two causes.August, 19581 SPECIAL REFERENCE TO THE DETERMINATION OF MAGNESIUM 47 1 of the monochromator.In the usual LundegArdh method, in which a medium spectrograph with an entrance slit of 0-04 mm is used, interference by sodium is detectable when the sodium is present at a concentration ten times that of the magnesium, and the analysis of sodium acetate extracts of soil for magnesium is impractiable. The second way in which inaccurate results could arise is by an alteration in the concen- tration of magnesium atoms.This would affect the emission and absorption equally and could be caused either by the solution being sufficiently different, in surface tension, viscosity and so on, from the standard solution to affect the atomisation or by the presence in the solution of elements that combine chemically with magnesium in the flame. The magnitude of the first effect depends on the type of atomiser used. With the LundegArdh atomiser used in this work, it is found that, in the analysis of N ammonium acetate solutions, results are obtained that are about 5 per cent. low when standard solutions in 0.1 N hydrochloric acid are used. This same depression occurs in emission flame photo- metry for potassium, sodium and calcium and can, of course, be readily overcome by using standards that are sufficiently similar in physical characteristics to the samples.Depression of magnesium emission by sulphate, phosphate and aluminium has been reported by various workers. If, as seems likely, this is caused by formation in the flame of compounds less readily volatilised and dissociated than the magnesium salt used to prepare the standard solutions, then the magnitude of the effect will depend on the flame temperature and also on the fineness of the spray introduced into the flame by the atomiser. In the present instance, no depression in either emission or absorption has been caused by sulphate (up to 0.1 N sulphuric acid) or by phosphate (up to a concentration of phosphorus equal to sixty times the magnesium concentration). Aluminium causes a depression both in absorption and emission and must be removed if present in the samples at a concentration comparable with that of the magnesium.This depression is shown by the following results- Aluminium concentration, p.p.m. .. .. 0 2 4 10 20 40 Apparent magnesium concentration, p.p.m. . . 2.50 2.40 2.33 2.18 2.03 1.83 APPLICATION- Provided that sufficient regard is paid to physical properties, which could influence the atomisation, and to the presence of chemical constituents, which could combine with magnesium in the flame, this method should be applicable to any solution that contains ~- magnesium. Work in this laboratory is mainly concerned with the determination of magnesium in agricultural materials, and” the methbd has been successfully applied to the analysis of plant-ash solutions, soil extracts, lysimeter and drainage waters, blood sera and milks. The sensitivity of the method is such that soil extracts and water samples can be analysed without the prior concentration necessary for analysis by emission methods For blood serum, the normal range of magnesium concentration can be covered by using a solution obtained by dissolving the ash from 1 ml of serum in 25 ml of 0.1 N hydrochloric acid. CONCLUSIONS The atomic-absorption method for the determination of magnesium has proved to be rapid, accurate and sufficiently sensitive for most purposes. By its use, magnesium deter- minations can be performed with the same ease as, and probably with greater reliability than, flame-photometric determinations of sodium, potassium and calcium. I gratefully acknowledge the assistance of Miss L. Wood and IVIr. 0. E. Clinton with this work and thank Mr. D. F. Waters for his constant interest and encouragement. REFERENCES 1. 2. 3. 4. 6. Walsh, A., Sflectrochim. Acta, 1955, 7, 108. Russell, Barbara J., Shelton, J. P., and Walsh, A., Ibid., 1957, 8, 317. Crosswhite, H. M., Dieke, G. H., and Legagneur, C. S., J . Ofit. SOL. Anzer., 1955, 45, 270. Mitchell, A. C. G., and Zemansky, M. W., “Resonance Radiation and Excited Atoms,” Cambridge Huldt, L., and Lagerquist, A., Arkiv. Fysik, 1950, 2 , 333. University Press, 1934. Received November 15th, 1957

ISSN:0003-2654    

DOI:10.1039/AN9588300466

出版商:RSC    

年代:1958

数据来源: RSC

摘要:

472 CARSON : THE POLAROGRAPHIC 1)ETERMINATION OF THALLIUM, [Vol. 83 The Polarographic Determination of Thallium, Iron and Copper in High-purity Cadmium Metal BY R. CARSON (Rhoanglo Mine Services Limited, Research and Development Division, Kitwe, Northern Rhodesia) A polarographic technique is described by which traces of thallium and iron can be co-determined, after extraction of the trichlorides, in essentially the same base electrolyte. Copper does not interfere at the concentrations under consideration and is separately determined by an extraction procedure with sodium diethyldithiocarbamate. An alternative polarographic procedure is described for the determination (sf copper, in which an ammonium chloride - ammonium hydroxide base electrolyte is used. THE methods decribed in this paper were devised to provide a rapid and accurate procedure for the determination of traces of thallium in high-purity commercial cadmium. Pure cadmium might contain, in addition to traces of thallium, comparable traces, i.e., from 0.0002 to 0.0010 per cent., of iron, copper, lead, zinc, tin, nickel and silver, with possibly smaller amounts of antimony, arsenic, tellurium and indium, Spectrochemical solution methods in current routine use in these laboratories do not permit the accurate determination of concentrations of thallium below about 0.001 per cent.Consideration of the nature and concentrations of the other trace constituents suggested an extraction - concentration approach for thallium. The possibility was therefore indicated of including iron in a scheme for thallium by utilising the solubilities of the trichlorides in diethyl ether.A further advantage would consequently result, since the recommended non-spectrographic method for iron determination is tedious and necessitates a preliminary extraction of the thiocyanate compound with a mixture of pentanol and diethyl ether. Interference by copper might be anticipated in a diethyl ether extraction of the trichlorides of iron and thallium, but this apparently does not occur at the concentrations involved. Preliminary experiments on the removal of interference by copper indicated that an extraction method for its determination was satisfactory. Since the original investigations by Noyes et al. on the relative solubilities of thallic and thallous salts,l extensive use has been made of the solubility of thallic chloride in diethyl ether as a preliminary step in the determination of traces of the metal.In consequence, detailed accounts exist of the applications of this method in various fields.2 Two publication^^^^ and the Hudson Ba:y Company’s Methods of Analysis describe successful polarographic methods for the determination of thallium ; these methods depend on the cathodic reduction of the thallous ion. The fact that the half-wave potential of this reduction remains remarkably constant when diferent base electrolytes are used has extended its application in defining potential ranges in polarographic analysis. None of the base electrolytes described was found to be a satisfactory medium for the determination of thallium and iron.Considerable promise was shown, however, by polarography in a sodium chloride - ammonium acetate buffered base electrolyte, similar to the type proposed by Semerano and Gagliardis for the determination of greater amounts of lead, zinc and iron. This base elec- trolyte has frequently been used in these laboratories for the determination of small amounts of lead and iron in tailings from lead and zinc flotation - concentration processes. It is, in our experience, the only base electrolyte that permits satisfactory polarography of iron in concentrations from 0.1 to 40 per cent. EXPERIMENTAL POLAROGRAPHIC DETERMINATION OF THALLIUM.- A base electrolyte solution, buffer solution ;and standard thallium solution were prepared Four 10-ml portions of base electrolyte solution were placed by pipette in 50-ml squat Standard thallium solution was added to give 25, 50, 75 and 100 pg of thallium, as described on p.475. beakers.August, 19581 IRON AND COPPER IN HIGH-PURITY CADMIUM METAL 473 respectively, in the beakers. These solutions were warmed on a hot-plate until crystallisation of sodium chloride occurred. One millilitre of buffer solution was added to each beaker and the volume of each solution was adjusted to 10.0 ml in a calibrated flask. These solutions, without further treatment, were polarographed on a Tinsley 158 instrument with a static mercury anode and a cathodic drop-rate of 3.0 seconds. The diffusion currents were measured at a half-wave potential of 0.5 volt; the results were as follows- Thallium added, p g .. .. .. .. 26 50 75 100 Diffusion current, pA x lo2 . . .. 3.5 8.0 12.6 16.5 A linear relationship can be observed between the thallium content and the diffusion current. EXTRACTION OF THALLIUM FROM CADMIUM METAL- A 50-g sample of Specpure cadmium was dissolved in a mixture of nitric and hydro- chloric acids and the solution was evaporated to dryness on a hot-plate. Twenty millilitres of hydrochloric acid were added to the residue and the evaporation was repeated. The resulting cadmium chloride was dissolved in water and the solution divided into five equal aliquots. To each of these aliquots was added, respectively, 0, 25, 50, 75 and 100 pg of thallium in the form of a standard solution. These solutions were made 8 N with respect to hydrochloric acid, and sufficient bromine water was added, dropwise, to give each a distinct yellow colour.Each of the solutions was then extracted with five 10-ml portions of pure diethyl ether. The extracts were combined and washed with three 20-ml portions of dis- tilled water. The washed extracts were evaporated to dryness in a water bath and 10 ml of base electrolyte solution were added to each. Heating in the water bath was continued until crystallisation of sodium chloride occurred. The solutions were cooled to room tem- perature and to each was added 1.0ml of ammonium acetate buffer solution, after which the volume was adjusted to 10.0 ml. These solutions were then polarographed as before, the diffusion currents again being measured at a half-wave potential of 0.5 volt; the results were as follows- Thallium added, pg .. . . . . 0 25 50 75 100 Diffusion current, pA x lo2 . . .. Nil 4.0 7.5 12.0 16.0 Comparison of these results with those obtained by the polarographic determination of thallium alone indicates that the combined extraction and polarographic method is completely satisfactory. EXTRACTIOK OF THALLIUM FROM CADMIUM SOLUTIONS CONTAINING COPPER AND IRON- Standard solutions were again prepared as in the previous experiments, each containing, in addition to the same fixed amount of thallium, 200 pg each of copper and iron. Spot tests with sodium diethyldithiocarbamate solution, carried out on the dried residue from the evaporation of the ether extract, indicated the complete absence of copper, and tests carried out on the residual solution after extraction of thallium indicated the absence of iron.The presence of iron in the ethereal solution was confirmed by testing with ammonium thiocyanate solution. From the results of these observations it was apparent that thallium and iron could be quantitatively removed by extraction of their chlorides from 8 N hydrochloric acid with diethyl ether, copper, to the maximum concentration expected in high-purity cadmium, being left in the aqueous solut2oa. EXTRACTION OF THALLIUM FROM HIGH-PURITY COMMERCIAL CADMIUM METAL- Several samples of high-purity cadmium containing traces of copper, iron, thallium, silver, nickel, lead, zinc, tin, antimony, indium and tellurium, which had previously been spectrographically analysed in these laboratories, were dissolved, extracted and polarographed as previously described.To the solutions of the samples were then added small amounts of thallium corresponding to approximately 50 per cent. of the expected thallium contents. These spiked solutions were treated in the same way, their thallium contents being finally assessed by the polarographic method. The results of four determinations are shown in Table I.474 CARSON : THE POLAROGRAPHIC DETERMINATION OF THALLIUM, TABLE I [Vol. 83 POLAROGRAPHIC DETERMINATION OF THALLIUM IN HIGH-PURITY CADMIUM The initial thallium content of each sample, determined spectrographically, was < 0.001 pter cent. Original diffusion Final diffusion Diffusion current Calculated amount of current due to Amount of current due to due to added thallium in original thallium, thallium added, thalliuni, thallium, sample, 0 * 0 0 0 9 2 13.0 50 19.5 6.5 7-5 50 14.0 6.5 0.00055 12.0 50 19.0 7.0 0 * 0 0 0 8 6 12.5 50 19.0 6.5 0 * 0 0 0 8 9 pA x lo* PLg p A x 1'08 pA x lo* % From a comparison of the results in Table I with the results for the determinations of thallium alone and in the presence of Specpure cadmium, it is apparent that the method is sufficiently accurate to permit the determination of thallium in a 10-g sample to within 2 0.0002 per cent.POLAROGRAPHIC DETERMINATION OF IRON- The polarography of iron has been extensively examined in these laboratories, and it has been shown that a method enunciated by Semerano and Gagliardi5 could, in principle, be accurately applied to the determination of the low iron contents of zinc and lead con- centrates and tailings. A feature of even the purest obtainable sodium chloride used in this type of base electrolyte is its high blank contribution.Commercial sodium chloride of allegedly high purity has been found often to contain as much as 0.002 per cent. of iron, and, although corrections can be made for this figure in routine analyses involving several milligrams of iron, its presence cannot be tolerated in the microgram range. Extraction of the base electrolyte with diethyl ether has been shown effectively to decrease the blank value to nearly one-tenth of its initial value, but the low inherent acidity of the base electrolyte makes extraction impossible beyond this point. The method adopted for the purification of the base electrolyte was as follows- The base electrolyte solution was prepared only as required, and addition of the gelatin was omitted until after the extraction.Twenty-millilitre aliquots were extracted, after the addition of bromine water, with six successive 10-ml portions of diethyl ether. The extracted solution was exposed to the atmosphere in an open beaker for 30 minutes to permit the evaporation of the small amount of ether that gravitational separation did not remove. The requisite amount of gelatin solution was then added and the solution was stored ready for use. A blank determination of its purity was carried out before each series of determinations. To 10.0-g samples of Specpure cadmium metal, treated as described for the extraction experiments for thallium, were added 25, 50, 75 and 100 pg, respectively, of iron in the form of a standard solution.The solutions were extracted and polarographed in the same way as for thallium, but with omission of the ammonium acetate buffer solution, the diffusion currents being measured a t a half-wave potential of -0.15 volt ; the results were as follows- Iron added, p g . . . . .. . . 25 50 75 100 Diffusion current, pA x lo2 . . . . 1.3 2.5 3.7 6.0 These results confirmed that the sodium chloride base electrolyte provides satisfactory polarography for iron down to microgram amounts. EXTRACTION OF COPPER- The generally applied method for the determination of traces of copper is colorimetric, involving complex formation with sodium diethyldithiocarbamate.The yellow colour pro- duced by the complex obeys Beer's law and can be quantitatively measured in aqueous or carbon tetrachloride solutions. Interference has not been experienced when this reaction has been applied to solutions prepared from high-pusity cadmium and containing only those elements previously listed, provided that sufficient citric acid has been added before develop- ment of the colour. Originally, it was expected that copper would interfere with the thalliumAugust, 19581 IRON AND COPPER IN HIGH-PURITY CADMIUM METAL 475 determination by exhibiting a slight chloride solubility in diethyl ether, and, for this reason, its removal by an extraction method was proposed, However, after copper had been shown to have no effect on the accuracy of the thallium determination, the method was retained, as it was rapid and accurate for determining copper. The use of spectrophotometric instru- ments and standard graphs is replaced by a simple titration that offers almost as high a degree of accuracy.The extraction method for copper can be replaced by the well established polarographic procedure in an ammoniacal base solution after extraction as the diethyl- dithiocarbamate complex. METHOD REAGENTS- All reagents must be of recognised analytical grade. Citric acid solution, 20 per cent. aqueous. Sodium diethyldithiocarbamate solution, 0-05 per cent. aqueous-This solution must be Carbon tetrachloride. Ammonium chloride - ammonium hydroxide base electrolyte solution-Mix equal volumes Gelatin solution, 1.0 per cent.aqueous. Hydrochloric acid solution, 8 N. Bromine water. Diethyl ether. Sodium chloride - hydrochloric acid base electrolyte solution-Dissolve 250 g of sodium chloride and 10 ml of a 0.5 per cent. aqueous solution of gelatin in 0.1 N hydrochloric acid, and dilute to 1 litre with 0.1 N hydrochloric acid. Ammonium acetate buffer solution-Dissolve 386 g of ammonium acetate and 286 ml of glacial acetic acid in water, and dilute the solution to 1 litre. Standard copper solution-Dissolve 0.01 g of Specpure copper powder in concentrated nitric acid, add concentrated sulphuric acid and evaporate the solution until fumes are evolved. Standard iron solution-Dissolve 0.01 g of Specpure iron wire in the minimum amount of concentrated hydrochloric acid, and dilute the solution to 1 litre.Standard thallium solution-Dissolve 0.01 g of Specpure thallium wire in the minimum amount of diluted nitric acid (1 + l ) , and dilute the solution to 1 litre. EXTRACTION PROCEDURE FOR DETERMINING COPPER- Dissolve a 10-g sample of metal in concentrated nitric acid, with the addition of small amounts of water to moderate the vigorous reaction. Evaporate the solution to incipient dryness on a hot-plate. Add 20 ml of concentrated hydrochloric acid and again evaporate to dryness. Repeat this procedure, the dried salts thus obtained being nitrate-free chlorides. Add 50 ml of water and warm to dissolve the salts. Cool the solution, add 10 ml of 20 per cent. citric acid and transfer to a 100-ml conical separating funnel. Add sodium diethyl- dithiocarbamate solution, accurately, 0.5 ml at a time, shaking thoroughly after each addition.After each addition, extract the solution with 5-ml portions of carbon tetrachloride until the yellow colour of the copper complex is no longer visible in the organic layer. Record the end of the titration as that point at which the further addition of 0.5 ml of reagent no longer forms a visible yellow colour in the solvent layer. In this way a titre is measured to the nearest 0.5 ml. Since 0.5 ml is approximately equivalent to 10 pg of copper, the method gives a result to the nearest 0.0001 per cent. It is not recommended that the reagent be further diluted for a greater accuracy of titre, but, rather, that if greater accuracy is required, a larger original sample be taken. Standardise the reagent against a solution containing 100 pg of copper and to which citric acid has been added as in the sample analysis. POLAROGRAPHIC PROCEDURE FOR DETERMINING COPPER- Transfer the combined carbon tetrachloride extracts to a 100-ml squat beaker and evaporate to dryness in a water bath.To the dried residue add 5 ml of concentrated nitric acid and continue heating on the water bath to destroy the organic matter. Add 5 ml of concentrated hydrochloric acid and heat on a hot-plate until the volume has been reduced to about 2 ml. Add 2 ml of 50 per cent. v/v sulphuric acid and evaporate the solution until freshly prepared. of 4 M ammonium chloride and 4 M ammonium hydroxide. Dilute the solution to 1 litre.476 CARSON [Vol. 83 fumes are evolved. Carefully add successive small amounts of nitric acid until all organic matter has been completely destroyed.Evaporate the resulting clear solution almost to dryness. Add 3 ml of water and neutralise the excess of acid by the dropwise addition of ammonia solution, sp.gr. 0.880, use being made of an indicator paper if necessary. Add 2.5 ml of ammonium chloride - ammonium hydroxide base electrolyte solution and 0.5 ml of gelatin solution, and dilute to exactly lO.Orr11. Filter the solution through a Whatman No. 31 filter-paper into a polarographic cell and polarograph as follows- Range-Apply -0.2 to -0.6 volt against the static mercury anode. Sensitivity-A full-scale deflection at 4 PA, with counter-current as required and Half-wave potential-Approximately --0.40 volt.slight damping. Compare the wave height thus obtained with a graph prepared in the same way from the standard copper solution. PROCEDURE FOR DETERMINING IRON- Treat a 10-g sample of metal in the way described under “Extraction Procedure for Determining Copper,” as far as the production of a dried chloride residue. Add 50 ml of 8 N hydrochloric acid and heat to obtain a clear solution of salts. Add sufficient bromine water, dropwise, to render the solution distinctly yellow, and transfer it to a 100-ml separating funnel, Extract the solution with five 10-ml portions of diethyl ether, combine the extracts and wash them with three 20-ml portions of water. Transfer the washed extract to a 50-ml squat beaker and evaporate to dryness in a water bath. Add 3 ml of concentrated hydrochloric acid to the dried residue and again evaporate .to dryness in the water bath.Add 10 ml of sodium chloride - hydrochloric acid base electrolyte solution to the residue and warm to effect dissolution of the salts. Polarograph this solution for iron by applying the necessary counter-current in the range 0.0 to -0.30 volt against the static mercury electrode. Compare the wave height thus obtained with a standard graph prepared in the same way from solutions of Specpure iron wire. If non-routine or very :infrequent samples are being analysed, it will probably be better to use the standard-additio:n comparison technique. By this technique, two solutions are polarographed, the second being identical with the first, but containing a known amount of added reducible ion. The difference between the wave heights thus obtained is proportional to the amount of added ion. PROCEDURE FOR DETERMINING THALLIUM- squat beaker and warm on a hot-plate until crystallisation of sodium chloride occurs. the solution, add 1 ml of ammonium acetate bufler solution and dilute to 10 ml. this solution for thallium as follows- Transfer the polarographic solution, after the iron has been determined, to a 50-ml Cool Polarograph Range-Apply -0.3 to -0.8 volt against the static mercury anode. Sensitivity-A full-scale deflection at 0.5 pA with maximum counter-current. Compare the wave height thus obtained with a standard graph prepared in the same I thank Mr. Chapman, Consulting Metallurgist for Anglo American Corporation of way, or use the standard-addition technique. South Africa Ltd., for permission to publish this paper. REFERENCES 1. 2. 3. 4. 5. Noyes, A. A,, Bray, W. C., and Spear, E. B., J . Amer. Chem. SOC., 1908, 30, 515. Snell, F. D., and Snell, C. T., “Colorimetric Methods of Analysis,” Second Edition, D. Van Nostrand Lingane, J. J., J . Amer. Chem. SOC., 1939, 61, 2099. Kolthoff, I. M., and Lingane, J. J., “Polarography,” First Edition, Interscience Publishers Inc., Semerano, G., and Gagliardi, E., Anal. Chim. Acta, 1950, 4, 422. Co. Inc., New York, 1939, p. 207. New York and London, 1946, p. 266. Received December 9th, 1967

ISSN:0003-2654    

DOI:10.1039/AN9588300472

出版商:RSC    

年代:1958

数据来源: RSC

摘要:

August, 19581 WOOLLEY 477 Tin - Cadmium Alloys The Colorimetric Determination of Thallium in BY J. F. WOOLLEY (Standard Telephones 6. Cables Ltd., Reclijer Division, Edinburgh Way, Harlow, Essex) A colorimetric method is described for the determination of thallium in Microgram amounts over the range 5 to 80 p.p.m. can tin - cadmium alloys. be determined with an error of &2 p.p.m. VARIOUS methods1 to for determining microgram amounts of thallium were examined during a search for a rapid method of controlling the thallium content of tin - cadmium alloys. None of these methods was found to be satisfactory, mainly because of interference by the large amounts of tin and cadmium present or the lengthy procedures required for the separation of thallium from these elements. The method described by Pohl,s although suitable, has the disadvantage of requiring an ultra-violet spectrophotometer for measuring the absorption of the thallium - sodium diethyldithiocarbamate complex at 315 mp.Papers9J0 describing the use of methyl violet as a reagent for the colorimetric deter- mination of thallium have recently been published. Since the development of the method described, fuller details for the use of this reagent have become available, but experiments indicate that it has no particular advantage over rhodamine B when applied to the determination of thallium in tin - cadmium alloys. The use of rhodamine B was described by Feigl, Gentil and Goldstein11 for the detection of thallium. Onishi12 gave details of a colorimetric method for the determination of thallium, in which the thallic - rhodamine B complex was extracted with benzene.This work has been confirmed by using pure thallous sulphate solutions, but direct application to the determination of thallium in tin - cadmium alloys was not possible, owing t o interference from tin and cadmium, which also form complexes with rhodamine B. Separation of thallium was therefore necessary. Wada and Ishii13 stated that thallium and gold could be separated from all other elements by extraction with diisopropyl ether from 0.1 N hydrobromic acid. Preliminary experiments showed that thallium was extracted from 0.1 N hydrobromic acid with diiso- propyl ether and that no co-extraction of tin or cadmium took place. Further experiments showed that the thallic - rhodamine B complex was soluble in diisopropyl ether.Tin - cadmium alloy was readily soluble in hydrobromic acid containing 10 per cent. v/v of bromine. These preliminary experiments indicated that a rapid colorimetric method for the deter- mination of thallium was available and the method was developed for use with tin - cadmium alloys containing 5 to 80 p.p.m. of thallium. DEVELOPMENT OF THE METHOD EXTRACTION OF THALLIUM FROM HYDROBROMIC ACID SOLUTION- The time required for complete extraction of thallic bromide from hydrobromic acid with diisopropyl ether was determined by shaking solutions prepared as for the calibration curve (see p. 478) with 25-ml portions of diisopropyl ether for increasing periods of time, after which the thallic-rhodamine B complex was formed and the optical density of the extract was measured.Three extracts were measured after being shaken for 1, 3 and 5 minutes, respectively; the optical densities were 0.612, 0.590 and 0.567, from which it can be seen that maximum extraction is attained after 1 minute. The distribution coefficient was shown to be 1.0 by repeated extraction of a solution of thallic bromide in hydrobromic acid with fresh 25-ml portions of diisopropyl ether for 1-minute periods, after which the thallic - rhodamine B complex was formed and the optical density of the extract was measured. The optical densities of the first extracts of two samples were 0.613 and 0.608, and in both, after a second extraction, the optical density was zero. FORMATION OF THALLIC - RHODAMINE B COMPLEX IN DI~SOPROPYL ETHER- the time required for formation of the complex was determined.By variation of the shaking time of the diisopropyl ether extract - rhodamine B mixture, After they had been shaken478 WOOLLEY: THE COLORIMETRIC DETERMINATION OF [Vol. 83 for 1, 3 and 5 minutes, respectively, the opticxl densities of three samples were 0.608, 0.604 and 0.590, from which it can be seen that the complex solution reached maximum optical density after 1 minute. The decrease in optical density with increased shaking time is considered to be caused by the slow mutual dissolution of the diisopropyl ether - hydrochloric acid mixtures, which results in a slight shift of the distribution coefficient as observed at 1 minute. COLOUR STABILITY OF THE THALLIC - RHODAM [NE B COMPLEX- The stability of the complex in diisopropyl ether was determined by measuring the optical density of the coloured solution after known periods of time.After 0, 1 and 15 hours, the optical densities of two solutions were 0.610 and 0.615, 0.610 and 0.613 and 0.605 and 0.609, respectively. These figures show that the complex is stable for at least 1 hour and that the decrease in optical density after 15 hours is only slight. APPARATUS- Any type of spectrophotometer or absorptiometer is suitable ; the work described was carried out in 2-cm cells with a Spekker H760 absorptiometer, Kodak No. 5 green filters being used. REAGENTS- Hydrobromic acid - bromine mixture-Add 25 ml of bromine to 225 ml of hydrobromic acid, sp.gr. 1-46 to 1.49. Use analytical-reagent grade materials and mix well, Rhodamine B solution-Dissolve 0.2 g of rhodamine B in 1 litre of N hydrochloric acid. Diisopropyl ether-Analytical-reagent grade.Into a 100-ml beaker weigh accurately 0.25 g of sample. METHOD The maximum absorption of the thallic - rhodamine B complex occurs at 550 mp. PROCEDURE- Add 5 ml of hydrobromic acid - bromine mixture, immediately cover the beaker with a watch-glass to prevent losses by spitting, and heat to approximately 40” C to effect complete dissolution of the alloy. Rinse the watch-glass and beaker walls with 5 ml of distilled water, heat the solution at a temperature just below its boiling-point until excess of bromine has been expelled and then cool to room temperature. Transfer the solution to a 100-ml stoppered separating funnel, graduated at 25 ml, and dilute to 25 ml with distilled water.Add 25 ml of diisopropyl ether and shake for exactly 1 minute. Allow the phases to separate, and discard the aqueous layer. Add 20 ml of rhodamine B solution to the ethereal solution and shake for exactly 1 minute. Allow the phases to separate, discard the aqueous layer and transfer the ethereal extract to a dry stoppered cylinder. Note that transfer of the ethereal extract to the dry cylinder prevents the introduction of droplets of the aqueous phase into the absorptiometer cells. Carry out a reagent blank determination simultaneously with the sample. Measure the optical density of the sample extract in 2-cm cells against the blank solution with a spectrophotometer or absorptiometer.From the calibration curve, determine the number of micrograms of thallium in the ether extract. PREPARATION OF CALIBRATION CURVE- Measure 5 ml of hydrobromic acid - bromine mixture into each of six 100-ml beakers. Add, by pipette, 0.0, 0-2, 0.5, 1-0, 1.5 and 2.0 ml, respectively, of thallous nitrate solution containing 1Opg of thallium per ml to the beakers. Add 5ml of distilled water to each beaker, heat gently until excess of bromine has been expelled and cool to room temperature. Continue as described under “Procedure” from “Transfer the solution to a 100-ml stoppered separating funnel. . . .” Measure the optical densities of the ether extracts in 2-cm cells with a spectrophotometer or absorptiometer. Construct a calibration curve of micrograms of thallium against optical density.A linear relationship is obtained with a sensitivity of 0.3 pg of thallium per 0.01 unit of optical density. RESULTS Recovery experiments were carried out by adding known amounts of thallium, as thallous nitrate solution, to 0.25-g portions of thallium-free tin - cadmium alloy dissolvedAugust, 19581 THALLIUM I N TIN - CADMIUM ALLOYS 479 in 5 ml of hydrobromic acid - bromine mixture. The recoveries, which are considered to be satisfactory, were as follows- Thallium added, pg . . . . 5.0 5-0 10.0 10.0 15.0 15.0 Thallium found, pg . . . . 5.2 5-2 10.1 10-3 14.7 14.8 Recovery, % .. .. .. 104 104 101 103 98 99 The reproducibility of results was determined by applying the method to a batch of tin - cadmium alloy containing a nominal 40 p.p.m.of thallium. The results were as follows- Weight of sample, g . . 0.2484 0.2678 0.2527 0.2399 0.2470 0.2504 Thallium found, p.p.m. . . 43 43 45 44 44 46 (mean, 44) Mean deviation, p.p.m. . . -1 -1 $1 0 0 $2 CONCLUSION It is considered that the method is adaptable to the determination of thallium in the presence of a large number of interfering elements by virtue of the selectivity of the extraction procedure. I thank Standard Telephones and Cables Ltd. for permission to publish this paper. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. REFERENCES Moeller, T., and Cohen, A. J., Anal. Chem., 1950, 22, 686. Haddock, L. A., Analyst, 1935, 60, 394. Cinerman, C., and Selzer, G., Anal. Chim. Acta, 1956, 15, 213. Berg, R., and Roebling, W., 2. angew. Chem., 1935, 48, 430 and 597. Lederer, M., Anal. Chim. Acta, 1951, 5, 185. Schoeller, W. R., and Powell, A. R., “Analysis of Minerals and Ores of the Rarer Elements,’’ Third Edition, C. Griffin & Co. Ltd., London, 1955, p. 91. Pavelka, T., and Morth, H., Mikrochemie, 1932, 11, 30. Pohl, H., Erzmetall, 1956, 9, 530. Gur’ev, S. D., Sbornik Nauch. Trudy, Gos. Nauch. Inst. Tsvet. Met., 1955, 10, 371. Blyum, I. A., and Ul’yanova, I. A., Zavod. Lab., 1957, 23, 283. Feigl, F., Gentil, V., and Goldstein, D., Anal. Chim. Acta, 1953, 9, 393. Onishi, H., Bull. Chim. SOC. Japan, 1956, 29, 945. Wada, R., and Ishii, R., Bull. Inst. Phys. Chem. Res. Tokyo, 1934, 13, 264. Received February 21st, 1958

ISSN:0003-2654    

DOI:10.1039/AN9588300477

出版商:RSC    

年代:1958

数据来源: RSC

摘要:

August, 19581 THALLIUM IN TIN - CADMIUM ALLOYS 479 Notes VITAMIN CONTENTS OF ANIMAL FEEDINGSTUFFS PROGRESS in animal nutrition has led to the widespread use of vitamins of the B complex as supplements to animal rations. The proportion in which any one of these vitamins needs to be TABLE I MILLIGRAMS OF NUTRIENT PER KILOGRAM OF FEEDINGSTUFF* Pro- Nico- Panto- vitamin Ribo- tinic thenic Pyri- Vitamin Feedingstuff At flavin acid acid doxin Choline B,, Wheat .. .. .. - 1-1 59.4 13.0 4.4 999 - Oats . . .. .. .. - 1.1 8.8 5.7 2.2 1496 - Yellow maize .. . . 0.8 1.1 2-2 3.3 4.6 550 - Lucerne meal .. .. 107 14.1 70.4 26.0 8.8 1896 0.02 Grass meal . . .. .. 137 12-5 55.0 33.9 6-6 1346 - Dried peas . . .. . * - 2.9 26.4 13.0 6-4 1298 - Locust bean .. .. . . 3.2 0.4 17-6 0.7 4.6 51 - Linseed .... .. _. 2.2 41-8 8.4 9.0 1547 - Ground nut . . .. .. - 2-2 299.2 31.0 9.9 1797 0.01 Palm kernel cake . . .. - 0.9 11.0 2.2 2.0 229 0.02 Palm kernel meal . . .. - 1.1 11-0 2.2 3.5 319 - Undecorticated cottonseed . . - 1.5 22.0 7.9 3.3 1098 0.02 Decorticated cottonseed . . - 2.6 26-4 4.0 6.6 2594 0.01 Barley .. .. .. - 1.1 70.4 3.5 4.2 1797 - Copra meal . . .. * . - 1.1 28.6 4.8 3-1 51 - Dried brewers' yeast. . .. - 42.9 378.4 17.8 15.2 5588 0.02 * The figures shown can be converted to milligrams per pound, a form of expression commonly t The amount of vitamin A (in international units per kilogram) approximately equivalent used in Britain, by multiplying by 0-45. biologically to a pro-vitamin A figure is obtained by multiplying the latter by 1667.480 NOTES [Vol.83 incorporated in a ration depends upon the amount of it naturally present in the ingredients of the ration. Unfortunately, published information 0x1 the vitamin contents of common feedingstuffs is very meagre, and we have, therefore, extended existing data by determining the amounts of a number of water-soluble vitamins in a series of common feedingstuffs, and the pro-vitamin A (,%carotene) content of four of them. Compariso:? of our figures (see Table I) with those collected from the literature and recorded by Kent- Jones and Amos’ reveals differences that emphasise the need to extend even further the figures for the vitamin contents of feedingstuffs in order more readily to decide the influence of the composition of the ration upon the minimum levels of supplementation for satisfactory nutrition of various types of livestock.The microbiological assay procedure used foi- the determination of nicotinic acid, riboflavin, pantothenic acid, pyridoxin and vitamin B1, and the chemical method for the determination of choline were those described by Kent-Jones and Am0s.l Carotene was determined by the method of Booth,g which excludes other carotenoids : in most animal feedingstuffs this can be assumed to be 8-carotene. We thank Mr. E. C. Apling and Mrs. J. Whitten for undertaking many of the determinations, REFERENCES 1. 2. Kent-Jones, D. W., and Amos, A. J., “Modern Cereal Chemistry,” Fifth Edition, The Northern Booth, V. H., “Carotene: Its Determination in Biological Materials,” W. Heffer & Sons Ltd., Publishing Co.Ltd., Liverpool, 1957. Cambridge, 1957. THE LABORATORIES D. W. KEKT-JONES DUDDEN HILL LANE A. J. AMOS WILLESDEK, LONDON, N.W.10 G. B. THACKRAY Received March 20th. 1958 FUNCTION OF THE SULPHYDRYL GROUP IN THE DETERMINATION OF THIAMINE WITH 6-AMINOTHYMOL THE yellow colour produced when thiamine is t:reated with 6-aminothymol in alkaline solution has been used recently in a method for determining the vitamin in amounts of the order of 10 to t / Arnounli of thiol. pg Fig. 1. Reaction of aminothymol with thiols: curve A, thio-p-cresol ; curve B, thiosalicylic acid ; curve C, thiamine; curve D, cysteine; curve E, thioglycollic acid 60 pg.lv2 The results of an investigation of the reactions involved in this method indicate that the sulphydryl group is the main functional grou:? in the formation of the colour, and that other sulphydryl compounds can be determined in a siinilar manner.August, 19581 NOTES 48 1 FUNCTION OF THE SULPHYDRYL GROUP- It has been reported that certain substances other than thiamine, notably those of a phenolic character, form coloured products with alkaline solutions of aminothymol.Only one of these, cysteine, formed a yellow colour in a similar concentration range to that of thiamine. On the assumption that the colour was attributable to the presence of a sulphydryl group, the test was applied to a number of different thiols. Fig. 1 shows the response of the reagent to these sub- stances under the conditions described for the determination of thiamine.2 Thio-p-cresol formed a turbid solution, and the product was extracted into toluene - butanol mixture (9 $- 1) from acid solution before optical-density measurements mere made.The orange-yellow colours produced with aromatic sulphydryl compounds are very intense and more stable than the greenish yellow colours of the non-aromatic series, but none of the compounds examined gave any measurable colour after treatment with iodine in acid solution. From these results i t was concluded that fission of the thiazole ring of the thiamine molecule occurs under the influence of alkali, and the thiol so formed reacts with aminothymol. According to Williams and Ruehle,8.4 quaternary thiazolium salts are split at the C-S linkage by an excess of alkali with the formation of a thiol-aldehyde. In order to apply the aminothymol test, a sample of 4-methyl-5- ( p-hydroxyethyl) thiazole was prepared by sulphite cleavage of thiamine ; neither this nor the pyrimidine portion of the thiamine molecule showed any positive reaction with aminothymol, but, on conversion to its ethiodide, the thiazole portion formed a colour practically identical with that formed by thiamine itself.The reactivity of this compound was also destroyed by treatment with iodine. Downes and Sykess have prepared a disulphide by treating 3-benzyl- 2 : 4-dimethylthiazolium bromide with alkali and iodine. FUNCTION OF AMINOTHYMOL- For the reaction between aminothymol and a thiol to proceed quantitatively, the presence of free oxygen is essential. This is not evident a t low concentrations unless the solutions are de-gassed before mixing, but, at higher levels, vigorous aeration is necessary.Since oxidised thiols do not respond to the test, it is clear that aminothymol requires at least partial oxidation before the reaction can take place. This is borne out by the observation that preliminary aeration of alkaline solutions of aminothymol greatly accelerates colour development when a thiol is added. The most probable oxidation product of 6-aminothymol in the early stages of the reaction is thymoquinoneimine (I). Undoubtedly this reaction does not reach completion, ammonia being slowly liberated, and, after standing for about 1 hour, the solution no longer reacts with thiamine. McAllisterE has assigned the structure 11 to the yellow product obtained in alkaline solution from 2 : 6-dichloroquinonechloroimide and mercaptoglyoxalines, and it is suggested that thymoquinoneimine reacts similarly under mildly oxidising conditions to form the compound 111.I CH, A CH, c1 I O=C?=N-S-R I c1 I CH d€, CH, \ A (1) (11) (111) Although McAllister formulates the structure I1 on the basis of Gibbs’s reaction for phenols,’ certain experimental observations suggest a reaction that involves the imino group rather than the ketonic group. For example, it has been found that replacement of the imino hydrogen by an alkyl group destroys completely the reactivity of the quinoneimine towards thiols. Further, although 4-amino-2 : 6-xylenol is as sensitive to thiols as aminothymol, 4-amino-3 : 5-xylenol is devoid of activity. Saunders and Watsons have pointed out that, owing to steric effects, the reactivity of quinones is inhibited by the presence of o-methyl groups.A more detailed investigation of the yellow products of the reaction between aminothymol and sulphydryl compounds is made difficult by their extreme instability. The action of mineral acids, warming or even standing in neutral solution for a few hours causes rapid decomposition, which leads to the formation of disulphides and coloured phenolic oxidation products. The data presented are in agreement with the N-mercaptoquinoneimine structure proposed by hkhllister, and indicate that the reaction may be applicable generally as a method for the photometric determination of free or derived thiols.482 NOTES I thank the Directors of Novadel Ltd.for permission to publish this Note. REFERENCES [Vol. 83 1. 2. 3. 4. 5. 6. 7. 8. ST. ANN'S CRESCENT Hayden, K. J., Analyst, 1957, 82, 61. Hayden, K. J , , and Elkington, R. H., Ibid., 1957, 82, 650. Williams, R. R., J . Amer. Claem. Soc., 1935, 57, 1865.. Williams, R. R., and Ruehle, A. E., Ibid., 1936, 58, 1063. Downes, J. E., and Sykes, P., Chent. 6- Ind., 1957, 1095. McAllister, R. A,, J . Pharm. Pharnzacol., 195C1, 7, 135. Gibbs, H. D., J. Biol. Ckem., 1927, 72, 649. Saunders, B. C., and Watson, G. H. R., Biochem. J . , 1950, 46, 629. XOVADEL LIMITED WANDSWORTH K. J. HAYDEN LONDON, S.W.18 Received January 24th, 1958 VOLUMETRIC DETERMINATION OF SOME ORGANOCHLOROSILANES WITH AMMONIUM: THIOCYANATE THE observation by Gingold and Rochow' that ammonium thiocyanate will undergo double decomposition with dimethyldichlorosilane to precipitate ammonium chloride prompted the direct determination of some organochlorosilanes in organic solvents with ammonium thiocyanate.Details of the procedure and the results of the experiments carried out to establish a new simple technique for determining the concentration of some organochlorosilane solutions directly by means of precipitation with a solution of ammonium thiocyanate in acetone in presence of ferric chloride solution as indicator are given. Although it is fairly simple to determine th8:se chlorosilanes by titration of the acidity, or chloride ion, after hydrolysis with water, the proposed method has the advantage that it is carried out entirely in organic solvents and no precautions are needed against possible loss of hydro- chloric acid, which might occur if adequate preczutions were not taken in the aqueous hydrolysis method.METHOD REAGENTS- Ammonium thiocyanate solution, 0.3 M in acetone-Dissolve 224 g of ammonium thiocyanate (dried in a vacuum-desiccator after recrystallisation from methanol) in 100 ml of warm anhydrous acetone, and dilute with more anhydrous acetone to 1 litre. Standardise the solution against a 0.05 N aqueous solution of silver nitrate. Ferric chloride solution, 1 per cent. in diethyl ether-Dissolve 1 g of anhydrous ferric chloride in 10ml of absolute ethanol, and dilute to 100ml with anhydrous diethyl ether. PROCEDURE- With use of a pipette calibrated by means of mercury, place exactly 1 ml of the chlorosilane sample solution in a 100-ml conical flask, and add 10 to 30 ml of anhydrous diethyl ether.Add 2 or 3 drops of 0.3 M ammonium thiocyanate i n acetone from a 5-ml microburette graduated in 0.01 ml; the solution should now assume a white turbidity owing to the formation of ammonium chloride. Shake the solution and add 1 drop of 1 per cent. ferric chloride solution in diethyl ether. Continue the titration to the appearance of a persistent red colour owing to the formation of ferric thiocyanate. I t is necessary t o shake the flask vigorously during the titration and t o keep the contents below 5 O C by using iced water. Practice is, i5t first, required for accurate detection of the end-point, but reproducible results should soon be achieved. Calculate the concentration of chlorosilane in the sample solution (C) from the following equation- A x I.' x 35447 B - per cent.w/v, C = where A = v = B = the molar concentration of the ammonium thiocyanate solution, the volume, in ml, of ammonium Chiocyanate solution used (mean of at least five titrations), and the chlorine content, in per cent. w/w, of the chlorosilane.August, 19581 NOTES 483 RESULTS AND DISCUSSION The proposed procedure was applied to solutions of twelve different chlorosilanes. The results, together with the calculated values, are shown in Table I. Methylchlorosilane and phenyl- chlorosilane were supplied by the Shin-etsu Chemical Industrial Company in purified grades. Ethylchlorosilanez and isopropylchlorosilane8 were prepared by Grignard synthesis and then purified by careful single distillation.The sample solutions were prepared by dissolving the weighed chlorosilane in either anhydrous benzene or ethyl acetate. The results in Table I show that the proposed method is useful and convenient for rapidly determining chlorosilanes in organic solvents, especially when the solvent mixture is of unknown composition so that the usual techniques, e g . , refractometric or gravimetric, cannot be applied effectively. Throughout the preliminary investigations it was found that addition of a large amount of dry diethyl ether to chlorosilane samples was most effective for the production of a suitably sharp end-point ; dilution with diethyl ether, especially when methylchlorosilane or ethylchorosilane was used, made the precipitation of ammonium chloride so complete and the colour owing to the formation of ferric thiocyanate so distinct that 1 drop of ammonium thiocyanate solution in excess was sufficient t o make the end-point easily recognisable.I thank the Shin-etsu Chemical Industrial Company for the supply of some pure chlorosilanes. TABLE I DETERMIXATIOX OF SONE CHLOROSILANES IN BENZENE AND IN ETHYL ACETATE Concentration Concentration found, calculated, Chlorosilane Solvent % w/v % w/v Benzene 6-10 6.72 Ethyl acetate 11.26 11.26 Benzene 5.08 5-10 Meth yltrichlorosilane* Dimethyldichlorosilane* Ethyl acetate 9.90 9.91 Ethyltrichlorosilane . . . . Diethyldichlorosilane . . . . Benzene 17.32 17-37 Ethyl acetate 4.45 4.52 Benzene 61.70 61.74 Ethyl acetate 30.37 30.42 Benzene 20.20 20.32 Ethyl acetate 12.24 12.37 Benzene 70.88 71.01 Ethyl acetate 21.11 21-30 isoPropyltrichlorosilane Phenyltrichlorosilane .. * Some results obtained by the author with these chlorosilanes will soon be published in J . Chew Soc. Japan (Ind. Chew. Sect.). REFERENCES 1. 2. 3. FACULTY OF TECHNOLOGY Gingold, K., and Rochow, E. G., J . Anzer. Chem. SOC., 1952, 74, 6306. Rochow, E. G., U.S. Patent No. 2,258,220, 1941. Booth, H. S., and Spessard, D. R., J . Amer. Chem. Soc., 1946, 68, 2660. DEPARTXENT OF APPLIED CHEMISTRY GUMMA UXIVERSITY TOSHIO TAKIGUCHI KIRYU, JAPAX Received February 12th, 1958 INCREASING THE PRECISION OF FREEZING-POINT DETERMINATIONS THE freezing or crystallising-point of a material is often used as a criterion of its purity or com- position. Determination of the freezing-point by conventional methods, however, is hampered by the tendency of many substances to supercool. To overcome this difficulty, either elaborate arrangements are used to add external seed or else cooling curves are drawn and extrapolated to what is hoped is the true freezing-point of the material.Supercooling can be almost completely avoided in the majority of determinations by a simple addition to the usual apparatus specified in Appendix B of British Standard 1998 : 1953. This can be adapted to a form suitable for freezing-point determination by attaching to the wire a small brass cup containing a cooling agent. The wire is passed through the cork of the tube containing the sample The use of a cooled wire to induce crystallisation is fairly well known.'484 BOOK REVIEWS [Vol. 83 so that the cup is just above the cork.The end of the wire dips 5 to 10 mrn into the liquid and is positioned to make contact with the stirrer at each oscillation. During the determination, the brass cup is kept full of a substance, such as ice, solid carbon dioxide or liquid air, which serves as a heat sink some 50" C or so below the freezing-point of the sample. As the sample approaches its freezing-point, the intense cooling at the point of entry of the wire into the liquid causes crystallisation in a small volume of the liquid. The crystals so formed are detached by the stirrer and dispersed throughout the bulk of the sample, thereby ensuring adequate seed at the critical point. Supercooling is usually undetectable, and, if temperature readings are made at suitable intervals of time, the freezing-point is sufficiently marked to obviate the preparation of cooling curves.The rate of heat abstraction by the device can be varied within wide limits by changing the diameter of the wire and the temperature of the heat sink. The method is thus adaptable in principle to the majority of freezing-point determinations, in particular those that have to be conducted below room temperature. As an example, the following conditions gave good results with mixtures of ethylene glycol and water, which readily supercool in the absence of seed. A piece of 18 s.w.g. (0.048-inch diameter) copper wire was used, attached to a cup 15 mm in diameter and 20 mm tall, which was filled with small pieces of solid carbon dioxide. The outer bath temperature was maintained between 8" and 14" C below that of the sample in order to achieve a. uniform rate of temperature decrease of approxi- mately 0-2" C per minute. The sample was pre-cooled on solid carbon dioxide to obtain an approximate freezing-point value, after which its temperature was allowed to increase by 1" or 2" C before insertion in the apparatus. The temperature was read every 30 seconds, and the first temperature to be followed by four more readings that differed by less than 0.05" C was taken as being the true freezing-point. Acknowledgment is made to the Engineer-in-Chief of the Post Office and to the Controller I thank Mr. R. A. Fraser of Duplicate determinations usually agreed to within 0.05" C. of H.M. Stationery Office for permission to publish this Note. Benzole Distillers Ltd. for valuable suggestions. REFERENCE 1. Findlay, A., "A Practical Physical Chemistry," Eighth Edition, Longmans, Green & Co. Ltd., London and New York, 1954, p. 109. LONDON MATERIALS SECTION TEST & INSPECTION BRANCH POST OFFICE ENGINEERING DEPARTMENT STUDD STREET, LONDON, N.l J. C. HARRISON Received Januavy 30th, 1958

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DOI:10.1039/AN9588300479

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年代:1958

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484 BOOK REVIEWS [Vol. 83 Book Reviews ORGANISCHE FALLUNGSMITTEL IN DER QUANTITATIVEN ANALYSE. By Dr. WILHELM PRODINGER. Fourth Edition. Pp. xvi + 246. Stuttgart: Ferdinand Enke Verlag. 1957. Price (paper) DM.33; (cloth boards) DM.35.60. Prodinger’s “Organic Precipitants in Quantitative Analysis” has won its place on the analyst’s bookshelf already, but the author has again been at great pains to summarise all the important advances in this field since the publication of the successful third edition. The coverage is best indicated for new readers by the following list, in which figures in brackets give the number of pages of text devoted to each topic : dipicrylamine ( 5 ) , sodium tetraphenylborate (lo), picrolonic acid (8), anthranilic acid (lo), quinaldinic acid (1 1).cupferron (17), neocupferron (1), N-benzoyl- phenylhydroxylamine ( 1), dimethylglyoxime (3), benzoinoxime (6), salicylaldoxime (6), mercapto- benzthiazole (7), oxine (22), oc-nitroso-/)-naphthol { 6), pyrogallol (1), thionalide (16), sulphosalicylic acid (8), guadinium carbonate (3), tannin (14), ai-sonic acids (lo), mandelic acids (2), nz-cresoxy- acetic acid (3), 9-amino-acetophenone (1), “naphthin” (1 (or 4)-azaphenanthrene) (4), ethylene- diamine (4), propylenediamine (2), pyridine (1 0), tolidine and benzidine (2), thiourea (6), tetra- phenyl- and triphenylmethyl-arsonium salts (6), nitron (4) and triphenyltin chloride (2). Certain reagents recently advocated, viz., violuric acid, bismuthiol 11, phenarsazinic acid and l-nitroso-2-hydroxy-3-naphthoic acid have not been included, because nothing apart from the original papers has been written about them, and as yet the author has had no personal ex- perience of their potentialities or limitations.This may be the reason for omitting dithiol, phenylselenic acid and some reagents developed by Russian chemists.August, 19581 BOOK REVIEWS 485 This book follows the pattern of its predecessors in giving detailed descriptions of particular separations and quantitative determinations. It is thoroughly practical in outlook and there are repeated indications of the possibility and reasons for errors in certain of the published pro- cedures. The author comments on discrepancies between the optimum drying temperatures for precipitates reported by Duval from studies with his thermobalance and those recommended by other workers who used conventional drying ovens or furnaces of different designs.This book is well printed, strongly bound and remarkably free from misprints and errors, although the formulae for the complexes of scandium and thorium with 8-hydroxyquinoline (pp. 122 and 123) should have been Sc(Ox),.HOx and Th(Ox),.HOx. No reference is made to Hollingshead’s four-volume monograph on “Oxine,” and the author has little space to spare for the reagents nioxime, heptoxime or niccolox-and none for furil-dioxime. Although it has long been demonstrated that the correct formula for the complex of thiourea and lead nitrate is Pb(NO,),.6CS(NH2), (Haworth and Mann, J . Chem. Soc., 1943, 66l), Mahr’s erroneous and improbable formula BPb(NO,),.11CS(NH2), has not been corrected in this edition. H. IRVING PURITY CONTROL BY THERMAL ANALYSIS. Proceedings of the International Symposium on Purity Control by Thermal Analysis, Amsterdam, 1957. Sponsored by the I.U.P.A.C. and organised by the Committee on Physico-Chemical Data and Standards. Edited by W. M. SMIT. Pp. xii + 182. Amsterdam: Elsevier Publishing Co.; London: Cleaver- Hume Press Ltd.; New York: D. Van Nostrand Co. Inc. 1957. Price 24s.; $4.85. Chemical compounds of high purity are required not only for research purposes and as standards for the calibration of instruments, but certain of them are used industrially, for example, titanium tetrachloride and dimethyl terephthalate. Hence, methods of determining purity of substances are of great importance and the development of new methods becomes necessary as standards of purity are raised.During the past 15 years or so, much effort has been directed to the use of thermal properties for measuring the purity of substances. The present state of knowledge of this subject was reviewed a t an International Symposium in Amsterdam in 1957 organised by the Committee on Physico-Chemical Data and Standards of I.U.P.A.C. This volume contains the proceedings of the Symposium: sixteen papers, the text of the Chairman’s opening address and a summary of the discussion. The papers have previously been published as Volume 17, No. 1, of Aizalytica Chimica Acta. The papers deal with the theory, applications and techniques of the thermometric method for obtaining melting and freezing curves and of the calorimetric method for measuring temperature - heat-content curves.The analyst will be particularly interested in the papers dealing with generai methods, for example, the comparison between thermometric and calorimetric techniques, a critical survey of the calorimetric method and the theory and practice of thermometric methods. Precise measurements in this field require a large number of observations and i t is desirable to use automatic control as far as possible. Three papers describe apparatus for the automatic or partly automatic control and recording of thermal analyses. Several of the papers consider the interpretation of experimental results to obtain a figure for the purity of the sample. Three papers are concerned with special applications of the methods.The discussions at the Symposium are suminarised in the last eight pages of the book. I t is probable that the melting (or freezing) curve method for purity determination will be much more widely used in the future and i t is of interest to note that the Symposium recommended that the reliability of this method be tested by the comparison of the results on standard samples by several interested laboratories. The volume is well produced and the price is very reasonable. J. F. MARTIN FLAME PHOTOMETRY. By F. BURRIEL-MARTf and J. R.4Mf~EZ-hfuZoz. Pp. xii -/- 531. Amster- dam: Elsevier Publishing Co.; London: Cleaver-Hume Press Ltd.; New York: D. Van Xostrand Co. Inc. 1957. Price 65s. The authors have previously published in Spanish a review of flame-photometry methods and the very great interest shown in that work led them to write the present book designed for English-speaking workers.They set themselves the task of producing a manual that will serve both as a textbook for those who have never used the technique and as a work of reference for those already using flame photometry. One of the great difficulties in writing a book on this subject is the tremendous variety of instruments available and the almost impossible task of correlating data obtained from them.486 BOOK F.EVIEWS [Vol. 83 In addition, there are in existence large numbers of laboratory-built flame photometers. The authors of the book have coped with this difficu:ty very well in that they have not gone into too much detail on those problems, particularly interference problems, which depend so largely on instrumental details.They have also pointed c u t carefully that the analytical procedures that can be undertaken must depend on the type arid versatility of the available equipment. For instance, although anyone who IS particularly interested in instrumentation will delight in the ten pages devoted to detailed comparison of all the known commercial instruments and many of the laboratory instru- ments that have been described in the literature, many readers may consider the section too detailed. The book is divided into 6 major divisions plus an appendix, 25 chapters and 117 sections, with further headed sub-divisions within many of the sections and this results sometimes in a somewhat discontinuous text that may not be easily readable to someone new to the subject.To counteract this there is an extremely good subject index, which makes the finding of any particular piece of information quite easy. Although there has been no attempt to provide a complete bibliography, this having been made unnecessary by previous publications by another author, 909 references are given. The translation by W. C. Darwell is very good indeed; there are few passages that reveal that the book was written originally in Spanish. On its own merit the book is extremely useful, but, in addition, it is the first work on this subject in English, and so i t cannot fail to be a most important addition to the library of any modeIn laboratory. The subject has been treated very fully, in places almost too fully.L. BREALEY A MANUAL O F PAPER CHROMATOGRAPHY AND PAPER ELECTROPHORESIS. By RICHARD J. BLOCK, EMMETT L. DURRUM and GUNTER ZWEIG. Second Edition. Pp. xii + 710. New York and London: Academic Press Inc. 1958. Price $12.80; 91s. 6d. So rapid have been the advances in this branch of analytical chemistry that the first edition of this book, published in 1955, has had to be largely re-written. Part I, comprising two-thirds of the whole, is concerned with paper chromatography and is the work of R. J. Block and G. Zweig; the remainder, written by E. L. Durrum, is devoted to paper electrophoresis. In the introduction the reader is reminded t h i t R. Consden, A. H. Gordon and A. J. P. Martin (Biochem. J . , 1944, 38, 224) were the first to use paper as the inert support in place of the silica gel originally proposed by A.J. P. Martin and R. L. M. Synge (Biochem. J., 1941, 35, 1358). Following on this pioneer work, numerous investigators have employed the principle of paper partition chromatography to separations of all kinds of closely related substances with striking success, and the purpose of this treatise is to present some of the results, so that the reader may have a knowledge of past studies sufficient to guide him in planning procedures to deal with his own requirements in this field, without recourse to an extensive search of the literature. After a chapter devoted to an exposition of theoretical principles, there is a useful illus- trated account, extending to more than 60 pages, of the methods of paper chromatography.This section is the foundation of the discourse and has been most carefully written. The next chapter, comprising an account of the various methods of quantitative assessment, makes interest- ing reading and, although naturally including decailed explanations of the senior author’s Total Colour Density and Maximum Colour Density methods, the Elution principle, as well as the Area of Spot proposal of R. B. Fisher et al. (Nature, 1948, 161, 764), are equally well described. From this point on, for 333 pages, the work is devoted to detailed descriptions of paper-chromatographic methods as applied to various classes of compounds, the titles of the ten chapters being: Amino Acids, Amines and Proteins ; Carbohydrates; Aliphatic Acids; Steroids, Bile Acids and Cardiac Glycosides ; Purines, Pyrimidines and Related Substances ; Phenols, Aromatic Acids and Indole Compounds ; Naturally Occurring Pigments; Miscellaneous Organic Substances ; Antibiotics and Vitamins; Inorganic Separations.There are some 67 Tables of R, values, and the work is docu- mented throughout. Part I of the book concludes with a list of approximately 1800 references, a few of these belonging to the year 1957. At the end of the volume there is also an index of about 1180 substances showing the page where the R, value is quoted. As stated in the Preface, the authors have not attempted to discuss all the published work on paper chromatography, their object having been to write a practical manual in which tried and proved procedures are summarised.I t would appear that most of the substances to which paper chromatography has been applied are mentioned in the text, although, necessarily, in many instances it has only been possible to quote the more important references.August, 19581 BOOK REVIEWS 487 After a chapter on theoretical considerations, the author of Part I1 skilfully introduces the practical aspects of paper electrophoresis by illustrated descriptions of his own early arrangements of apparatus, and hence readers without previous acquaintance with the technique are able to follow its later developments with ease. An Appendix giving the formulae of the commonly used electrolytes, with notes on them, is particularly useful. There are then 88 pages of biblio- graphy comprising over 1700 references on paper electrophoresis and closely allied topics, and the value of these is enhanced by the appended subject classification.The index at the end of the volume covers Parts I and 11. This book bears the stamp of authority and is certain to stimulate further research in the development of a most valuable, and essentially simple, analytical technique. DIE METHODEN DER MIKROMASSANALYSE. By Professor Dr. JOSEF MIKA. Second Edition. Pp. xvi + 375. Stuttgart: Ferdinand Enke Verlag. 1958. Price (paper) DM 63; (cloth boards) DM 66. The first edition of Mika’s textbook was published in 1939, and many developments in volu- metric analysis have taken place in the interval. Mika, in this new edition, has re-cast the original work and widened its scope considerably. It must be emphasised, however, that this publication is not just a handbook that describes all the known methods of micro-titration.On the contrary, it is really a guide to the whole subject and is likely to be of great help to analysts of all kinds who have to carry out volumetric titrations on the macro, micro or ultra-micro scale. In the general part, Mika deals with the purpose of micro-volumetric analysis, the purity of chemicals that are used and methods of end-point detection, including colorimetric, photometric, potentio- metric, amperometric, conductometric and high-frequency procedures. He pays particular attention to the various methods available for the delivery of known weights or volumes of volumetric solutions, whether by conventional burette, weight burette, flask burette or capillary or coulometrically.The preparation of volumetric solutions is described, and observations are made on the most desirable working concentrations, as well as on the subdivisions of solutions. In the special part, volumetric methods of neutralisation analysis in aqueous and non-aqueous media, oxidation and reduction procedures, titrations involving complex formation and methods involving precipitation are dealt with most thoroughly; examples are given of the applications of the tests. Naturally, the bias in this type of book is towards the inorganic side. Nevertheless, it is the kind of publication that must appeal to all analysts who are interested in principle rather than scale and who wish to place the volumetric work of their particular laboratories on a rather firmer basis.TECHNIQUE OF ORGANICHEMISTRY. Volume X : FUNDA- MENTALS OF CHROMATOGRAPHY. By HAROLD GOMES CASSIDY. Pp. xviii + 447. New York and London: Interscience Publishers Inc. 1957. Rice $9.75; 78s. This book represents one of the first attempts at a fundamental treatment of all the chromato- graphic techniques. It covers the following types of chromatogram : liquid - solid (adsorption chromatography), liquid - liquid (miscalled “partition” chromatography), both on columns and paper, and gas - liquid. Curiously enough, no treatment is given of the gas - solid chromatogram. The subjects dealt with in the fifteen sections are: Introduction; The nature of chromato- graphy; The molecular interactions on which chromatographic separation rest ; General theory ; Gas - liquid partition chromatography: Column partition chromatography; Paper partition chromatography; Adsorption chromatography; Ion exchange ; Electron-exchange polymers; Foam and emulsion fractionation; On recognising and evaluating zones; On the relation of R or R, to molecular structure; On choosing mobile and stationary phases ; On using chromatography; and, finally, an Appendix that gives lists of manufacturers supplying apparatus.The Subject and Cumulative Indexes are adequate. Nevertheless, all the basic information for each technique is present. Where information from published papers is dealt with, the relevant sections of original works are quoted in full, so that no author can complain of heim misremesented. NOEL L. ALLPORT The book is divided into two parts, one of which is general and the other special. This book is really first class. J. HASLAM Edited by ARNOLD WEISSBERGER. In a book of this size no subject can be treated comprehensively.48 8 PUBLICATIONS RECEIVED British workers in the field might quibble over Dr. Cassidy’s arrangement and classification scheme, but, on the whole, the book does deal fairly adequately with the fundamentals of the chromatographic technique. Wisely, no attempt has been made to cover all the published work on the subject, since a list of the references alone would fill a book of similar size. Dr. Cassidy’s book is a good addition to the literature on the subject and can be recommended to those facing separation problems not already solved, and to those interested in the basic phenomena involved in chromatographic techniques. A. T. JAMES

ISSN:0003-2654    

DOI:10.1039/AN9588300484

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年代:1958

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48 8 PUBLICATIONS RECEIVED Publications Received SOUTH AFRICAN JOURNAL OF AGRICULTURAL SCIENCE. Edited by V. E. DE KOCK. Volume 1, No. 1, March, 1958. Pp. 108. Pretoria: Department of Agriculture. Single copies 7s. 6d. ACADEMY). Chief Editor: Dr. SATYA PRAKASH, D.Sc. Volume 1, No. 1. Pp. 78. Allahabad, India : Vijnana Parishad. Annual Subscription: Rs. 8.00; 12s. ; Single copies Rs. 2.00; 3s. Edited by J.-A. GAUTIER. Sixihme Sbrie. Pp. iv + 171. Paris: Masson et Cie. 1958. Price 2600 fr. By L. C. MARTIN, D.Sc., A.R.C.S., D.I.C., and B. K. JOHNSON, D.I.C. Third Edition. Pp. xii + 138. London and Glasgow: Blackie & Son Ltd. 1958. Price 12s. 6d. Edited by KENNETH A. KOBE and JOHN J . MCKETTA, jun. Volume I. Pp. xvi + 641. New York and London: Interscience Publishers Inc. 1958.Price $13.50; 103s. By LESLIE YOUNG, D.Sc., Ph.D., F.R.I.C., and GEORGE A. MAW, Ph.D., F.R.I.C. Pp. 1180. London: Methuen & Co. Ltd.; New York: John Wiley & Sons Inc. 1958. Price 16s. BIG MOLECULES. By SIR HARRY MELVILLE, KC.B., Ph.D., D.Sc., F.R.S. Pp. 180. London: G. Bell & Sons Ltd. 1958. Price 15s. VIJNANA PARISHAD ANUSANDHAN PATRIKA (THE RESEARCH JOURNAL O F THE HINDI SCIENCE MISES AU POINT DE CHIMIE ANALYTIQUE PURE ET APPLIQUBE ET D’ANALYSE BROMATOLOGIQUE. PRACTICAL MICROSCOPY. ADVANCES IN PETROLEUM CHEMISTRY AND REFINING. THE METABOLISM OF SULPHUR COMPOUNDS. Based on the Royal Institution Christmas Lectures. RECOMMENDED METHODS FOR THE ANALYSIS OF TRADEFFLUENTS. Prepared by a Joint Commit- tee of the Association of British Chemical Manufacturers and The Society for Analytical Chemistry.Pp. xii + 124. Cambridge: W. Heffer & Sons Ltd., for The Society for Analytical Chemistry. 1958. Price 42s. A SELECT INTERNATIONAL BIBLIOGRAPHY OF NUTRITION, FOOD AND BEVERAGE TECHNOLOGY AND DISTRIBUTION 1936-56. By E. ALAN BAKER, A.L.A., and D. J. FOSKETT, M.A., F.L.A. London: Butterworths Scientific Publica- tions; New York: Academic Press Inc. Price 63s.; $11.00. MODERN ELECTROANALYTICAL METHODS. Edited by G. CHARLOT. Pp. xii + 186. Amsterdam: Elsevier Publishkg Co. ; London : Cleaver-Hume Press Ltd. ; New York and Toronto : D. Van Nostrand Co Inc. 1958. Price 24s.; $4.85; Dfl. 12.50. Reprint of JanuarylFebruary issue of Aivlalytica Chimica Ada, 1958, 18, pp. 1-182, with By WILLIAM C. WAKE, M.Sc., Ph.D., F.R.I.C., F.I.R.I. Pp. x + 237. London: Maclaren & Sons Ltd. 1958. Price 50s. ; $8.00. CONTAMINANTS. By the Committee on Recommended Analytical Methods, American Conference of Government Industrial Hygienists. Loocc leaf, viii + 50 pages (11 Methods). Cincinnati, Ohio : American Conference of Government Industrial Hygienists. 1958. Price $5.00. Orders OY enquiries should be addressed to The Secretary-Treasurer, A .C.G.I.H., 1014 Broadway, Cincinnati 2, Ohio, U.S.A. By F. D. GUNSTONE, Ph.D., BIBLIOGRAPHY OF FOOD. Pp. xii + 331. Introduction and Index. THE ANALYSIS OF RUBBER AND RUBBER-LIKE POLYMERS. MANUAL O F ANALYTICAL METHODS RECOMMENDED FOR SAMPLING AND ANALYSIS OF ATMOSPHERIC The price includes also the next nine methods that receive Committee approval. AN INTRODUCTION TO THE CHEMISTRY OF FATS AND FATTY ACIDS. A.R.I.C. Pp. x + 161. London: Chapman & Hall Ltd. 1958. Price 32s.

ISSN:0003-2654    

DOI:10.1039/AN9588300488

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年代:1958

数据来源: RSC