摘要:

400 Analyst, June, 1968, Vol. 93, pp. 400-402 Determination of Gypsum in Solonetzic Soils by an X-ray Technique BY S. U. KHAN AND G. R. WEBSTER (De$artment of Soil Science, University of Alberta, Edmontm, Canada) Gypsum in soils containing large amounts of sodium sulphate has been determined satisfactorily by an X-ray technique. Potassium chloride is used as an internal standard. Ratios of counts on diffraction peaks of maximum intensity for gypsum and potassium chloride are used for the quantitative determination of gypsum in soil. THE precise determination of gypsum in soils is difficult because of the inherent errors involved in the extraction of this mineral by water.l Several methods reported in the literaturelv2J appear unsatisfactory for solonetzic soils containing large amounts of sodium sulphate.Thus there is a reason for developing a satisfactory method for the quantitative determination of gypsum in such soils. In the technique described here, use is made of the principle that each salt in soils should produce its own characteristic diffraction pattern, independently of others, and that the relative intensities of the peaks are related to the proportion of the salt present. In practice, the average recorded height of one prominent reflection from each salt is usually sufficient for model determinations, provided the instrument has been calibrated with standard samples to agree with established intensity - concentration curves, no significant superimposition by peaks of other constituents is encountered, and correction is made for background intensity.EXPERIMENTAL All of the work was carried out with a Norelco Geiger counter, X-ray diffraction spectro- meter, in which copper radiation was used, a nickel filter and a scanning speed of 1" change in 28 per 2 minutes. The tube was set at 35 kV and 15 mA. A scale factor of 8 and time constant of 4 were used on the recorder. Two soils, a Black Solonetz and a geographically associated Eluviated Black Chernozem, were used in this study. The chemical characteristics of these soils have been described el~ewhere.~ The two soils contained essentially the same clay minerals,s but the Black Solonetz contained appreciable amounts of sodium and magnesium sulphates. The procedure for preparing powder samples (300 mesh) was essentially the same as that outlined by Tatlock,6 and they were mounted in rectangular aluminium holders.In preliminary experiments, the following powdered samples were scanned at 29 from 2" to 52" : solonetzic soil, chernozemic soil, chernozemic soil plus gypsum, chernozemic soil plus gypsum and sodium and magnesium sulphates, and gypsum plus sodium and magnesium sulphates. Potassium chloride (2 per cent. w/w) was added to each sample as an internal standard. This salt was not present in either of the two soils. The results of these experiments indicated that gypsum was not present in any horizon of the chernozemic soil. Consequently, the Bt, horizon of this soil was used as matrix material in preparing standard samples for the subsequent study. It was also found that the X-ray diffraction peaks of gypsum and potassium chloride were not significantly superimposed on those of other salts or clay minerals 0 SAC and the authors.KHAN AND WEBSTER 401 present in either soil.The most intense diffraction peaks of gypsum and potassium chloride were at 29 values of about 11.70" and 28*41", respectively (Fig. 1). These peaks were con- sidered best for the quantitative determination of gypsum. Degree 29 Cu Ka Diffraction pattern of the Eluviated Black Cherno- zem Bt, horizon containing gypsum and potassium chloride ( I background intensity positions) Fig. 1. Standard samples were prepared, each containing 2 per cent. w/w of potassium chloride and varying proportions (0 to 4.0 per cent. w/w) of gypsum, to cover the expected range in the soil.The selected diffraction peaks for gypsum and potassium chloride were scanned (Fig. l), the instrument was set on the peaks of maximum intensity and the time required to register a certain fixed number of counts recorded. The background intensity for each peak was taken as the average of four measurements, two on each side of the peaks (Fig. 1). 22 - 2.1 - 20 19 - 1.8 - 1.7 - 1% 1-5 - 1.4 - 1.3 - - - 0 050 10 1.5 2'0 2 5 3 0 3.5 4'0 Gypsum In soil, per cent w/w Fig. 2. Calibration graph for gypsum determination in soil The ratios of counts per minute for gypsum and potassium chloride, after being corrected for background, were plotted against gypsum concentration (Fig. 2). For the determination of gypsum in the solonetzic soil, the same procedure was adopted and the concentration read from the calibration graph (Fig.2). The results are shown in Table I.402 KHAN AND WEBSTER TABLE I CONCENTRATION OF GYPSUM IN BLACK SOLONETZ SOIL Depth, Gypsum, Soil horizon* inches per cent. w/w 2 t Csa C 0 to 4 - 4 to 16 0.22 16 to 23 2.79 23 3-42 * Soil description is according to the Canadian Soil In all of the determinations four different mounts for each powder sample were used and each mount was read three times. Thus the average of all of these measurements repre- sented one value. The technique appears satisfactory, as 91 per cent. w/w of added gypsum in solonetzic soil was obtained in recovery tests. The presence of sodium or magnesium sulphate, or other salts normally found in solonetzic soils, will not interfere. The authors thank Dr. R. D. Morton, Mineralogist, Department of Geology, University of Alberta, who advised in this study. Acknowledgment is also extended to the National Research Council of Canada for financial assistance. Classification System. REFERENCES 1. 2. 3. 4. 5. 6. Tatlock, D. B., Bull. U.S. Geol. SUYV., 1966, No. 1209. 7. Richards, L. A., Editor, “Diagnosis and Improvement of Saline and Alkali Soils,” Agriculture Bower, C. A., and Huss, R. B., Soil Sci., 1948, 66, 199. Lagerwerff, J. V., Akin, G. W., and Moses, S. W., Proc. Soil Sci. SOC. Amer., 1965, 29, 535. Cairns, R. R., Can. J. Soil Sci., 1961, 41, 24. Arshad, M. A., and Pawluk, S., J. Soil Sci., 1966, 17, 48. Sixth Meeting of the National Soil Survey Committee of Canada, 1965, Research Branch, Canada Received September 26t12, 1967 Handbook 60, US. Department of Agriculture, Washington, 1954. Department of Agriculture, Ottawa, p. 16.

ISSN:0003-2654    

DOI:10.1039/AN9689300400

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

Analyst, June, 1968, Vol. 93, ++. 403405 403 Rapid Determination of Uranium Dioxide in Uranium Phosphides BY J. L. DRISCOLL" AND P. E. EVANS (Department of Metallurgy, University of Manchester Institute of Science and Technology, Manchester 1) A rapid gravimetric method for the determination of uranium dioxide in uranium monophosphide and triuranium tetraphosphide is described. The phosphide compounds are dissolved in an ethyl acetate - hydrochloric acid solution and the remaining uranium dioxide oxidised in air to triuranium octoxide. A precision of &0.2 per cent. w/v is claimed for each determination. DURING studies1 on uranium phosphides it was necessary to make rapid determinations of the oxygen content (occurring as uranium dioxide) of an appreciable number of samples.Facilities for a limited number of oxygen determinations by a vacuum-fusion method, were available, and the results were used for comparison with those obtained with the wet chemical method described in this paper. Larsen3 showed that in metal - metal oxide mixtures it is possible to dissolve uranium selectively with a solvent of hydrogen chloride in ethyl acetate. The reaction was milder than with hydrochloric acid and complete dissolution took place whereas, with the aqueous acid, insoluble uranium compounds were formed. Ashbrook4 further developed the method by using a solution of hydrochloric acid and ethyl acetate to separate uranium dioxide from triuranium octoxide , uranium monocarbide, uranium and uranium trioxide. The solubility of uranium oxides was shown to be dependent on the oxygen-to-uranium ratio, increasing linearly from 0 per cent.at an oxygen-to-uranium ratio of 2 (uranium dioxide) to 100 per cent. at an oxygen-to-uranium ratio of 2.667 (triuranium octoxide). It is known that uranium phosphides are soluble in hydrochloric acid,5 and that triuranium tetraphosphide (U3P,) is more soluble than uranium monophosphide (UP), which is more soluble than uranium diphosphide (UP,) ; it was, therefore, expected that the hydrochloric acid - ethyl acetate method could be developed for the determination of uranium dioxide in uranium phosphides. METHOD APPARATUS- nected by a B24 joint to a vertical, water-cooled condenser (about 50 cm long). arm for evacuation by a water-pump. temperature control. Dissolution unit-This consists of a 250-rn1, short-necked, round-bottomed flask, con- Filtering apj6aratus-A conical filter funnel fitting into a conical filter flask, with a side- Furnace-An open-ended tube furnace capable of operating up to 1000" C, with accurate Ethyl acetate-Analytical-reagent grade.Hydrochloric acid, 36 per cent. w/w-Analytical-reagent grade. Hydrochloric acid - ethyl acetate solution-Mix 25 volumes of 36 per cent. w/w hydro- chloric acid with 75 volumes of ethyl acetate. Prepare freshly for each determination. PROCEDURE- Weigh accurately 0.5 to 1.0 g (depending on expected uranium dioxide content) of sample in powder form into the round-bottomed flask. Add 150 ml of cold ethyl acetate hydro- chloric acid (75 + 25 per cent. v/v) - and fit the condenser.Reflux gently for 1 hour at a solvent temperature of 75" to 80" C. Dissolution must be camed out in a fume cupboard * Present address : Electricity Council Research Centre, Capenhurst, Chester. 0 SAC and the authors.404 DRISCOLL AND EVANS: RAPID DETERMINATION OF [AndJ6t, VOl. 93 because of evolution of phosphine. Allow to cool until the flask can be handled, then filter the solution by suction through a Whatman No. 50 filter-paper. Wash the uranium dioxide residue several times with cold solvent. Transfer the filter-paper and residue to a tared platinum crucible and heat to 230" C at 100" C per hour in a tube furnace open to air. Heat from 230" to 250" C at 10" C per hour, then rapidly to 1000" C. Cool in a desiccator before weighing. The amount of uranium dioxide is then determined from the weight of triuranium octoxide produced.RESULTS AND DISCUSSION The method described above required considerable investigation to arrive at the correct conditions. The completion of dissolution of the phosphide phases was determined by taking X-ray diffraction patterns of the residue at various stages of the reaction. No phosphides were detected after about 1 hour of dissolution, although the lower limit of detection was about 2 per cent. w/w. However, as visible signs of reaction had ceased well within 1 hour it was considered that all of the phosphide phases had been dissolved. Conversion of uranium dioxide into uranium octoxide required careful control of the heating rate, especially in the temperature range 230" to 250" C.A fast rate of heating through this critical range resulted in ignition of the filter-paper; a rate of not more than 10" C per hour was necessary to char the paper without burning. The first weighing of the ignited residue was made after 1 hour at 1000" C; further periods of heating at this temperature did not usually produce any change in weight. An X-ray diffraction pattern of the ignited residue showed it to be triuranium octoxide when compared with the pattern from a standard triuranium octoxide sample. The residue also dissolved in the hydrochloric acid - ethyl acetate solvent, thus confirming Ashbrook's4 observations on the solubilities of uranium oxides. The lattice parameter of the uranium dioxide residue showed the material to be stoicheio- metric, as is to be expected, as analysis of these residues has always shown values* between UO,O to UO,.,,.Agreement was also found between the lattice parameters of uranium loxide in the uranium phosphides - uranium dioxide mixture and "extracted" uranium dioxide after dissolution of the phosphides. TABLE I URANIUM DIOXIDE CONTENTS OF URANIUM PHOSPHIDES DETERMINED BY DIFFERENT METHODS Powder Uranium dioxide, per cent. w/w Uranium dioxide, per cent. w/w (per cent. w/w of oxygen converted into uranium dioxide by conversion factor of 8.45) Batch Wet chemical method Fusion analysis 1 8.5; 8.6; 8.6 7-8 2 6-8; 6.7; 6.7; 6.4 6.2; 6.7; 6.0 Comparison of oxygen-fusion analyses and wet chemical analyses on samples from the same batch of powder (Table I) shows reasonable agreement and suggests that all of the oxygen impurity in uranium phosphides occurs as second-phase uranium dioxide.The pre- cision of each determination was estimated as k0.2 per cent. w/w. The accuracy was more difficult to assess, as the use of vacuum and inert-gas fusion methods are reporteds to give inconsistent results for oxygen in uranium phosphides ; values for oxygen content of identical samples were found to differ by 50 per cent. Smaller variations were found in this work (Table I) (and several additional powder batches that were not analysed by the wet chemical method), but these were still considerably larger than the variations in multiple wet chemical analyses on the same batch. No conclusion can, therefore, be drawn on the absolute accuracy of the method, but it is thought that a good indication of the uranium dioxide content is obtained over a wide range of uranium monophosphide - uranium dioxide compositions.The method was found to be satisfactory for uranium dioxide in uranium monophosphide and triuranium tetraphosphides, and determinations of 3 to 50 per cent. w/w of uranium dioxide were made. As-prepared powders, cold-pressed and sintered, and hot-pressed speci- mens (after crushing to powder) could be analysed. No study of uranium dioxide in uranium diphosphide was made, and it is expected that this will be more difficult because of the lower solubility of uranium diphosphide than uranium monophosphide and triuranium tetraphos- phides in hydrochloric acid.June, 19681 URANIUM DIOXIDE IN URANIUM PHOSPHIDES 405 It is, perhaps, fortunate that the oxygen impurity in uranium phosphides occurs as a second-phase uranium dioxide. The method described in this paper, therefore, allows rapid determination of the main impurity in these compounds. The authors thank Professor K. M. Entwistle for the provision of facilities, and U.K. Atomic Energy Authority (Hanvell) for carrying out oxygen-fusion analyses and for financial assistance for one of them (J.L.D.). REFERENCES 1. 2. 3. 4. 5. 6. Driscoll, J. L., and Evans, P. E., J . Amer. Ceram. Soc., in the press. Parker, A., U.K. Atomic Energy Authority Report, AERE-AM61, H.M. Stationery Office, London, Larsen, R. P., Analyt. Chem., 1959, 31, 545. Ashbrook, A. W., Analyst, 1962, 82, 595. Heimbrecht, M., Zumbusch, M.. and Biltz, W., 2. anorg. allg. Chem., 1941, 245, 391. Allbutt, M., Junkinson, A. R., and Carney, R. G-, U.K. Atomic Energy Authority Report AERE- Received December 14th, 1967 1960. R4903, H.M. Stationery Office, London, 1965.

ISSN:0003-2654    

DOI:10.1039/AN9689300403

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

406 Analyst, June, 1968, Vol. 93, ?$ 406-408 Determination of Ammonia by the Nessler Method in Waters Containing Hydrazine BY N. T. CROSBY (Laboratory of the Government Chemist, Ministry of Technology, Cornwall House, Stamford Street, London, S.E. 1) Hydrazine is known to interfere in the determination of ammonia with Nessler’s reagent. A method is described in which this interference is prevented by prior oxidation with potassium iodate in acidic solution. The method can be used directly for trace amounts of ammonia, or following distillation when other interfering substances are present. THE trend in recent years towards increased pressures and ratings of steam boilers has been made possible by parallel advances in water-treatment practice to reduce scale and minimise corrosion problems.Hydrazine is now widely used to remove dissolved oxygen, as the reaction products are volatile and therefore do not increase the dissolved solids content of the boiler water. Under normal operating conditions, however, some decomposition of hydrazine to ammonia may occur in the boiler, and both substances may also be present in the feed-water, steam and condensate. Methods of analyses are therefore required to determine both hydrazine and ammonia in the presence of each other. The reaction between ammonia and Nessler’s reagent is the established basis of most laboratory methods1 for the determination of small amounts of ammonia in water and it can be conveniently adapted as a field test. Unfortunately, hydrazine and certain other compounds containing nitrogen interfere, producing a coloured or opalescent solution with the reagent. Many of these compounds, including hydrazine, are volatile so that a preliminary distillation does not remove the interference.An alternative method involving the con- version of ammonia into indophenol blue has been described2 and no interference from hydrazine at the 2 p.p.m. level was observed. This method is sensitive but a spectrophoto- meter or absorptiometer is required, and one of the reagents is slightly unstable. Previous attempts to remove hydrazine interference have been concerned with rather higher concentrations than are likely to be encountered in normal boiler-water practice. Pugh and H e y n ~ , ~ after reviewing several authors’ work on the destruction of hydrazine by a wide variety of oxidising agents, concluded that only iodic acid, bromine, alkaline perman- ganate, iodine, hypochlorous acid and ferricyanides will oxidise hydrazine without the concomitant production of ammonia.They showed that the first three were satisfactory. Distillation and removal of excess of halogen with tin(I1) chloride were required. Other workers have shown that hydrazine can be precipitated with Fehling’s solution* or with ben~aldehyde.~ Penneman and Audrieth6 showed that iodine can be used to determine hydrazine titrimetrically, but that the pH value of the solution is critical. None of the available procedures seemed to be particularly suitable for the routine on-site testing of boiler-water samples containing extremely small amounts of ammonia and hydrazine. The proposed method makes use of the reaction between hydrazine and potassium iodate in acidic solution.The reaction is quantitative, and the resulting solution can then be used for the determination of ammonia by the Nessler method1 directly. If, however, other substances are present, which normally interfere with the Nessler method, the solution should first be distilled. 0 SAC; Crown Copyright Reserved.CROSBY EXPERIMENTAL 407 The method of preparation of Nessler’s reagent and its use in the determination of ammonia in water have been fully described e1sewhere.l Samples of water containing less than 0.05 mg of hydrazine per litre gave no reaction with Nessler’s reagent. Above this concentration coloured opalescent solutions were produced.Thus, if a sample contains more than 0.05 mg of hydrazine per litre, a false figure for the ammonia content will be obtained. The error increases as the hydrazine concentration increases and is particularly serious when the concentration of ammonia in the sample is low. The proposed methods were tested by determining the percentage recovery of ammonia from a series of waters that contained 0 to 5 mg of ammonia per litre as NH,. Each sample contained 20mg of hydrazine per litre. Recoveries of ammonia in each determination agreed with the theoretical value +5 per cent. This is essentially the uncertainty involved in reading the disc. The range of each disc used, with its accuracy, is given below- Disc Range of NH,, Accuracy of NH,, Clg Clg NAA .. .... 1 to 10 1 NAB .. .. . . 10to26 2 NAC .. .. . . 28 to 60 4 INTERFERENCES- Compounds such as cyclohexylamine , morpholine and octadecylamine are sometimes added to feed-water or steam to produce a non-corrosive condensate. These chemicals react with Nessler’s reagent and are steam-volatile and will not, therefore, be removed by prior distillation. The maximum allowable concentration of each compound in the test solution, which will not interfere in either of the proposed methods, is shown below- Cyclohexylamine . . . . 1 mgper 50ml i.e., 20p.p.m. Morpholine .. .. . . 10 mg per 50 ml i.e., 200 p.p.m. Octadecylamine . . .. 400 pgper 50ml i.e., 8p.p.m. Finally, the methods were tested on a series of fortified samples taken from medium- pressure hot-water and steam systems.The results are shown in Table I, and the charac- teristics of the various waters used are given in Table 11. TABLE I DETERMINATION OF AMMONIA IN BOILER WATERS AND CONDENSATES Sample NO. 5781 609 610 674 678 700 Free ammonia, after addition of 20 mg per Free ammonia, Free ammonia, after litre of hydrazine Description mg per litre addition of 20 mg per + 0.5 mg per litre of sample (as nitrogen) litre of hydrazine of ammonia Boiler water* . . .. 0.40 0.44 Boiler feed . . .. .. Nil Nil Condensate .. .. Nil Nil Condensate .. .. 0.20 0.18 Boiler feed . . .. .. 0.16 0.16 Circulating water, medium- pressure system .. Nil Nil * Procedure (A) not applicable. TABLE I1 CHARACTERISTICS OF BOILER WATERS AND CONDENSATES Chemical analysis (mg per litre) Sample number 0-95 0.50 0-50 0-70 0.64 0.50 Total dissolved solids at 180’ C .. Alkalinity as CaCO, . . . . Total hardness as CaCO, . . Chloride as C1 . . .. .. Sulphate as SO, . . .. .. Phosphate as PeO, .. .. Silicate as SiO, . . .. .. Copper asCu .. .. .. pH . . .. .. .. .. .. Iron as Fe . . .. . . .. 5;s 5025 1000 5 600 1730 3.2 131 Absent 0.1 11.6 609 86 50 15 10 20 1.1 2.0 0-6 0.1 8.0 610 8 15 5 1 3 0.2 0.1 0.1 2.2 6.1 674 17 10 2 Absent 0.8 Absent Absent 0.1 0.9 6-0 678 1005 320 340 286 130 0.9 20.5 0.2 Absent 7.5 700 415 140 100 60 125 0-5 9.8 Absent Absent 7-9408 CROSBY METHOD REAGENTS- Use a recognised analytical grade. Potassium iodate. Sodium carbonate-Freshly prepared. Ignite sodium hydrogen carbonate in a platinum dish for 20 minutes, with occasional stirring.Sodium thiosulphate. Dilute hydrochloric acid (1 + 1 v/v). B.D.H. Lovibond Nessleriser with standard 50-ml Nessleriser glasses. B.D.H. Lovibond Nessleriser with standard ammonia discs. APPARATUS- PROCEDURE (A) DIRECT DETERMINATION- Fill a 50-ml Nessler cylinder to the mark with the sample and add a few crystals of potassium iodate. Add 005ml of the dilute hydrochloric acid and stir vigorously. Check that the solution gives an acidic reaction with litmus paper, and then leave to stand for at least 10 minutes. Add 2 ml of Nessler’s reagent and allow to stand for a further 10 minutes. Match the colour produced against a suitable disc in the Nessleriser apparatus. (B) DISTILLATION PROCEDURE- Add 500 ml of sample to the distillation flask and add dilute hydrochloric acid, drop- wise, until the solution is just acid to litmus. Then add 0.5 ml of dilute hydrochloric acid in excess.Add a few crystals of potassium iodate, mix well and leave to stand for at least 10 minutes. Then add sodium carbonate until the water is alkaline and remove any remaining colour caused by iodine with a crystal or two of sodium thiosulphate. Distil as in the standard procedure and add 2 ml of Nessler’s reagent to 50-ml portions of the distillate. Leave to stand for 10 minutes and match the colour produced against the disc in the Nessleriser apparatus. Permission to publish this paper has been given by the Government Chemist, Ministry of Technology. REFERENCES 1. “Standard Methods for the Examination of Water and Wastewater,” Twelfth Edition, American Public Health Association, American Water Works Association and the Water Pollution Control Federation, New York, 1965. 2. 3. 4. 5. 6. Tetlow, J. A., and Wilson, A. L., Analyst, 1964, 89, 453. Pugh, W., and Heyns, W. K., Ibid., 1953, 78, 177. Wiebke, E. F., Analyt. Chem., 1951, 23, 922. Mellor, J. W. , “A Comprehensive Treatise on Inorganic and Theoretical Chemistry,” Volume VIII, Longmans, Green & Co., London, 1928, p. 370. Penneman, A., and Audrieth, C. F., Analyt. Chem., 1948, 20, 1058. Received November lst, 1967

ISSN:0003-2654    

DOI:10.1039/AN9689300406

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

Analyst, June, 1968, Vol. 93, p p . 409412 409 A Titrimetric Method for the Determination of Phosphate BY B. C . SINHA, S. DAS GUPTA AND S. KUMAR (Central Glass and Ceramic Research Institute, Calcutta 32, India) Phosphate has been determined by precipitating it as zirconium phosphate with a known excess of zirconium, and back-titrating the excess with EDTA. Iron(III), titanium(IV), thorium(1V) and bismuth(II1) do not interfere. Fluorine forms a strong complex with zirconium(1V) and its prior elimination is necessary when present in excess of 1.4 mg. The method has been applied to the rapid determination of phosphorus pentoxide in phosphatic fertilisers, and the time taken is less than 90 minutes. The ratio of zirconium to phosphorus in the precipitate was found to be 1 : 1 and the compound is probably zirconyl phosphate, ZrO(HPO,), as distinct from the usual compound, zirconium phosphate, Zr (HPO,),, obtained by the addition of an excess of phosphate to a zirconium(1V) solution.X-ray diffraction patterns of the two compounds were also found to be different. PHOSPHATE is usually determined as ammonium or quinoline molybdophosphatel s2 by lengthy procedures. Methods3s4s5 have also been reported in which the phosphate was precipitated as ammonium magnesium phosphate; it was then dissolved in acid and magnesium(I1) titrated with EDTA. The disadvantage of this method is that the precipitate reaches a constant composition rather slowly. Slumper and Metlelockc recommended a gravimetric method in which phosphate was precipitated as zirconium phosphate in 6 N hydrochloric acid, and the precipitate was ignited and weighed as (221-0,) P,O,.Budavsky, Pencheva, Russinova and Russeva7 reported an indirect complexometric method based on the precipitation of zirconium phosphate with a known excess of zirconium(1V) in 15 to 20 per cent. sulphuric acid and back-titrating the excess of zirconium(1V) with EDTA, with xylenol orange indicator. The ratio of zirconium to phosphorus in the precipitate was stated to be 1:2, which is also obtained when zir- conium(1V) is precipitated by a large excess of phosphate ions. Apparently the observation of Budavsky, Pencheva, Russinova and Russeva' is not in agreement with that of Slumper and Metlelock.6 Another limitation of the indirect complexometric determination of phosphate is that a solution of zirconium(1V) in sulphuric acid was reported to be unsuitable for direct EDTA titration.8 Sinha and Das Guptas confirmed that when zirconium(1V) was titrated with EDTA in sulphuric or hydrochloric acid medium, low results were obtained because of the complex polymerisation behaviour of zirconium(1V). It was, however, shown that in 1 to 1.25 N nitric acid, direct EDTA titration could be satisfactorily carried out at, or above, 90" C with xylenol orange indicator.With this background, the present investigations were undertaken with a view firstly to ascertaining the stoicheiometry of the precipitate obtained by adding an excess of zirconium( IV) to a phosphate solution, and secondly to working out a rapid method for the determination of phosphate. EXPERIMENTAL REAGENTS- Zirconium solution-A 0.05 M solution was prepared by dissolving 13-5 g of analytical- reagent grade zirconyl nitrate, ZrO(N0,),.2H20, in 140 ml of 8 N nitric acid.The solution was then boiled for 5 minutes to de-polymerise any polymerised zirconyl ion and diluted to 1 litre. The final acid strength was 1 to 1.25 N. The molarity of the zirconium solution was checked by the direct complexometric m e t h ~ d , ~ based on titration of zirconium( IV) with standard EDTA in the hot (90' C) N nitric acid solution, with xylenol orange indicator. Potassium dihydrogen phosphate solution-A 0.05 M solution was prepared by dissolving 3.40 g of analytical-reagent grade potassium dihydrogen phosphate in 500 ml of distilled water. A 0.01 M solution was prepared by diluting 50 ml of 0.05 M solution to 250 ml in a calibrated flask.8 SAC and the authors.410 SINHA, DAS GUPTA AND KUMAR: A TITRIMETRIC METHOD [Analyst, VOl. 93 EDTA solution-A 0.05 M solution was prepared by dissolving 18.61 g of the disodium salt of EDTA in distilled water and diluting to 1 litre. The final molarity was then found by titrating it with a standard zinc solution in acetate buffer (pH &2), with xylenol orange indicator. A 0.02 M EDTA solution was prepared from the standard 0.05 M EDTA solution by appropriate dilution. Iron(II1) nitrate solution-This was 0-05 M in N nitric acid. Titanium solzction-This was 0.05 M in 2 N nitric acid. PROCEDURE- A solution containing 0.71 to 88 mg of phosphorus pentoxide was placed in a 250-ml calibrated flask.A 125-ml volume of 4 N nitric acid was added, and the solution diluted to nearly 200ml. Zirconium phosphate was then precipitated by adding a known excess of 0-05 M zirconyl nitrate solution (10 to 30 ml). The solution was then heated on a steam-bath for about 30 minutes, then cooled, and the volume made up to 250ml with N nitric acid. The precipitate was filtered off on to a dry filter, and, after discarding the first portion of the filtrate, 100 ml were transferred to a 500-ml conical flask and diluted to 200 ml with water. The solution was heated to boiling for 1 minute to expel oxides of nitrogen, then the zirconium( IV) was titrated slowly with standard EDTA solution, with xylenol orange indi- cator. The temperature of the solution during titration should be 90" C , or more, and the addition of EDTA near the end-point should be at the rate of 1 drop per second.The end-point was indicated by a sharp colour change from pink - red to lemon yellow. RESULTS AND DISCUSSION During the precipitation of phosphate from N nitric acid by adding an excess of zir- conium(IV), the precipitate was found to be colloidal in nature, and did not settle rapidly. By precipitation from 2 to 3 . 5 ~ nitric acid, however, this difficulty could be overcome. The excess of zirconium was titrated in 1 to 1-25 N nitric acid in order to avoid any poly- merisation while heating the solution to, or above, 90" C, which is necessary to ensure complete reaction of zirconium(1V) with EDTA. TABLE I EFFECTS OF DIFFERENT METAL IONS ON THE DETERMINATION OF Actual phosphorus pentoxide content 17.75 mg PHOSPHORUS PENTOXIDE Phosphorus mg mg m g Titanium .. .. 12 17.66 -0.19 24 17.79 + 0-04 Amounts added, pentoxide found, Deviation, Iron . . .. .. 14 28 Thorium . . .. 23 46 Bismuth . . .. 21 42 Aluminium . . .. 27 56 18-00 17.60 17-68 17-86 18-02 17-95 17.74 17.65 + 0-25 - 0.20 - 0.07 + 0.1 1 + 0.27 + 0.20 - 0.01 - 0.10 Most of the elements, including titanium(1V) , bismuth(II1) , iron(II1) and thorium(IV), did not interfere with the determination of phosphorus pentoxide (Table I). This is in accordance with the earlier observations of Sinha and Das Gupta,g who showed that most of the elements did not form a complex with EDTA in N acid. It also appears that these elements do not precipitate as phosphate during the precipitation of zirconium phosphate in 2 to 3-5 N nitric acid.In the presence of fluorine, however, low titre values were obtained, probably because of the formation of a strong complex with zirconium(IV), and the final results were high. The effect of fluorine on the determination of low and high phosphorus pentoxide content is shown in Table 11. Fluorine has little effect when present in amounts of less than 1.425 mg; however, when the fluorine content is more, the sample taken should be treated with perchloric and boric acids to remove it.June, 19681 FOR THE DETERMINATION OF PHOSPHATE 41 1 TABLE I1 EFFECT OF FLUORINE ON THE DETERMINATION OF PHOSPHORUS PENTOXIDE Fluorine added, mg 0.475 0.475 1.425 1.425 1.90 1.90 2*85* 2*85* 340* 3*80* Phosphorus pentoxide present, mg 17.75 7 1.00 17-76 71.00 17.76 71-00 17-75 71.00 17-75 71-00 Phosphorus pentoxide found, mg 17.76 70-95 17.93 71-22 18.36 7 1.68 19.25 72.27 20.19 73.54 Deviation, mg nil - 0.05 +O.lS + 0.22 + 0.61 + 0.68 + 1-60 + 1-27 + 2-44 + 2.54 * End-point was not sharp.In order to ascertain the ratio of zirconium to phosphorus in the precipitate, zirconium phosphate was precipitated from 1 to 25-ml solutions of 0.5 M potassium dihydrogen phos- phate by adding a varying excess of de-polymerised 0.05 M zirconium(1V) solution, and the excess of zirconium was titrated with EDTA. From the amounts of zirconium(1V) used for the precipitation of known amounts of phosphate, the ratio of zirconium to phosphorus was found, as can be seen from Table 111, to be 1 : 1 compared with 1 : 2 reported by Budavsky, Pencheva, Russinova and Russeva.7 The observed stoicheiometry suggests that the compound present in the precipitate is ZrO (HPO,).TABLE I11 DETERMINATION OF THE RATIO OF ZIRCONIUM TO PHOSPHORUS IN ZIRCONIUM PHOSPHATE 0.05 M KH,PO, taken, ml 25 20 10 5 2 1 0.05 M zhCOIlhlm(IV added, ml 30-66 30.66 19-92 10.55 6-33 2.11 0.05 M EDTA 0.05 M zirconium(1V) required to titrate consumed by excess of zirconium(IV), phosphate, ml ml 5.69 24.97 10.62 20.04 9.79 10.13 5-68 4.97 4.32 2.01 1-12 0.99 Zirconium-to- phosphorus ratio 1 : 1.00 1 : 1.00 1 : 0-98 1 : 1-01 1 : 1.00 1 : 1.01 The X-ray diffraction pattern of the compound is found to be different from that of the zirconium phosphate, Zr(HPO,),, obtained by the addition of a large excess of phosphate to zirconium( IV) .TABLE IV THE CONCENTRATION RANGE OF PHOSPHORUS PENTOXIDE IN WHICH DETERMINATIONS WERE CARRIED OUT Phosphorus pentoxide taken, mg 0.7 1 3.53 7-10 14-20 17.75 36-50 71.00 88.75 Phosphorus pentoxide found by the present method, mg 0-68 3-51 7.13 14-30 17.64 35-64 71.12 88-62 Deviation, mg - 0.03 - 0.04 + 0.03 +0.10 -0.11 +Om14 +0-12 -0.13 The phosphate content of a series of solutions was determined by following the present procedure, and the results are shown in Table IV. It appears that the method can be used for the determination of a wide range of phosphorus pentoxide contents (0.71 to 88 mg com- pared with the range of 45 to 55 mg claimed by Budavsky, Pencheva, Russinova and Russeva).'412 SINHA, DAS GUPTA AND KUMAR Attempts were then made to determine phosphorus pentoxide in phosphatic fertilisers.A weighed amount of between 0.1 to 0-5 g of finely powdered and dried (1 hour at 105” C) sample containing 10 to 80 mg of phosphorus pentoxide was refluxed in a 500-ml conical flask with 65 to 70 ml of 8 N nitric acid for 10 to 15 minutes. It was then transferred quantitatively to a 500-ml flask and diluted to almost 200ml. When the sample contained more than 1.425 mg of fluorine, it was decomposed with 5 ml of 60 per cent. perchloric acid and 10 ml of concentrated nitric acid in a platinum basin. When fumes of perchloric acid appeared, the basin was cooled and 0.1 g of boric acid added. The contents were then evaporated almost to dryness. The residue was dissolved in a few drops of nitric acid and water, then the solution was transferred to a 250-ml beaker, 35ml of nitric acid were added, and the solution boiled before transferring to a 250-ml calibrated flask and diluting to 200ml with water.Phosphate was then precipitated with a known excess of zirconium(1V) and deter- mined by the procedure described earlier. The results of replicate determinations, together with those obtained with the ammonium molybdophosphate method, are shown in Table V. The results compare favourably. The time taken for determination is well within 90 minutes, compared with the few days required when the magnesium pyrophosphate method, gravi- metric or titrimetric method is used. TABLE V DETERMINATION OF PHOSPHORUS PENTOXIDE IN PHOSPHATIC FERTILISERS Phosphorus pentoxide Phosphorus pentoxide determined determined by the by the molybdophosphate Materials present method, per cent. Average method, per cent. Ammonium phosphate 53.12 53.39 53.33 53.52 53.38 53.55 19.21 19-5 1 19.32 Superphosphate of lime 19.52 19.39 19.22 The authors thank Shri K. D. Sharma, Scientist-in-Charge, Central Glass and Ceramic Research Institute, for his permission to publish this paper. 1. 2. 3. 4. 5. 6. 7. 8. 9. REFERENCES Scott, W. W., and Furman, N. H., “Standard Methods of Chemical Analysis,” Fifth Edition, D. Van Nostrand Company Inc., Princeton, New York, Toronto and London, 1939, p. 694. Wilson, H. N., Analyst, 1951, 76, 65. Huditz, F., and Maschka, H., 2. analyt. Chem., 1952, 136, 185. Pribil, R., and Jelinkova, Vi, Chemickd Listy, 1952, 46, 400; Chem. Abstv., 1952, 46, 11,032. Eschmann, H., and Brochon, R., Chemist Analyst, 1956, 45, 38. Slumper, R., and Metlelock, P., C . R. Hebd., Sdanc. Acad. Sci., Paris, 1947,224, 122; Chem. Abstv., Budavsky, O., Pencheva, L., Russinova, R., and Russeva, E., Talanta, 1964, 11, 1225. Pzibil, R., and Vesely, V., 2. analyt. Chem., 1964, 200, 332. Sinha, B. C., and Das Gupta, S., Analyst, 1967, 92, 558. 1947, 41, 4061. First received March 30th, 1967 Amended January 16th, 1968

ISSN:0003-2654    

DOI:10.1039/AN9689300409

出版商:RSC    

年代:1968

数据来源: RSC

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Analyst, June, 1968, Vol. 93,fi. 413 413 The R6le of Nucleation in Precipitation 1 from Homogeneous Solution BY A. TOWNSHEND (Chemistry Department, The University, P.O. Box 363, Birmingham 15) THE important benefit of precipitation from homogeneous solution for the analytical chemist is the production of relatively large, easily manipulable precipitate crystals. The size of the crystals is a direct consequence of the rate and duration of the nucleation process. Although the effect of nucleation on precipitation from homogeneous solution has recently been reviewed,l s2 the following comments may clarify the r81e of nucleation with regard to the analytical efficacy of precipitation from homogeneous solution. The nuclei of precipitates may be built entirely of the ions involved in the subsequent precipitate (homogeneous nucleation) or may include minute impurity particles as part of their structure (heterogeneous nucleation). Heterogeneous nucleation requires less energy than homogeneous nucleation and thus can occur at lower reactant concentrations.For instance, heterogeneous nucleation of barium sulphate is initiated by initial reactant concen- trations of 20 to 30 times the solubility of that salt, whereas homogeneous nucleation requires concentrations of 1000 times the ~olubility.~ Moreover, as heterogeneous nucleation occurs on impurity particles, which are found in the water from which the solutions are prepared, the number of nuclei formed in this way (and hence the number of precipitate crystals) is more or less independent of reactant concentrations.The number produced by homogeneous nucleation, however, increases rapidly with increasing reactant concentration^.^ An important effect of precipitation from homogeneous solution, therefore, is to minimise the concentration of precipitant so that homogeneous nucleation is eliminated, as with barium sulphate or calcium oxalate, or is appreciably reduced, as with iron(II1) hydroxide. In this way, the number of nuclei formed is reduced, and relatively few large crystals are eventually produced. If homogeneous nucleation is eliminated, the nzcmber of particles produced by precipitation from homogeneous solution is little different from that produced by direct mixing of suitably dilute solutions.5 The relatively small differences that do occur arise because several heterogeneous nucleation processes of varying efficiency are p~ssible,~,~ so that, at low con- centrations, only the more efficient processes operate, and there is a reduction in the concen- tration of nuclei produced, e.g., from 3 x lo6 per ml for solutions 2 x lo4 M in barium and 1 0 - 2 ~ in sulphate to 1 x 106 per ml Tor a similar barium solution and 1 0 - 3 ~ ~ulphate.~ However, even when homogeneous nucleation would not have occurred by direct mixing of reactants, precipitation from homogeneous solution remains advantageous because it reduces the rate of growth of precipitate particles, so that co-precipitation is likewise reduced.REFERENCES 1. Walton, A. G., “The Formation and Properties of Precipitates,” Interscience Publishers, New 2. Cartwright, P. F. S., Newman, E. J., and Wilson, D. W., Analyst, 1967, 92, 663. 3. Nielsen, A. E., Acta Chem. Scand., 1961, 15, 441. 4. Mealor, D., and Townshend, A., Talanta, 1966, 13, 1069. 5. - - , Ibid., 1966, 13, 1191. 6. me&, D. H., and Driy. J. A., Ibid., 1966, 13, 289. York, London and Sydney, 1967. Received January 30th, 1968 0 SAC and the author.

ISSN:0003-2654    

DOI:10.1039/AN9689300413

出版商:RSC    

年代:1968

数据来源: RSC

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414 Analyst, June, 1968, Vol. 93, j5p. 414416 Analytical Methods Committee REPORT PREPARED BY THE METALLIC IMPURITIES IN ORGANIC MATTER SUB-COMMITTEE The Determination of Small Amounts of Tin in Organic Matter Part II*: Amounts of Tin from 30 to 150 pg THE Analytical Methods Committee has received the following Report from its Metallic Impurities in Organic Matter Sub-committee. The Report has been approved by the Analytical Methods Committee and its publication has been authorised by the Council. REPORT The constitution of the Sub-committee responsible for the preparation of this Report was: Mr. W. C. Johnson (Chairman), Dr. J. C. Gage, Dr. T. T. Gorsuch (resigned November, 1966), Dr. R. A. Hoodless, Miss E. M. Johnson, Mr. D. A. Lambie (appointed January, 1967), Dr. H.Liebmann, Dr. R. F. Milton, Dr. E. J. Newman and Mr. G. B. Thackray, with Mr. P. W. Shallis as Secretary. INTRODUCTION The Sub-committee has previously recommended a method for determining up to 30 pg of tin in organic matter.l As tin can be present in organic matter, particularly foodstuffs, over a fairly wide range of concentrations, a method for determining amountslarger than 30 pg was required. In consequence, the Sub-committee has investigated a colorimetric method involving the use of the zinc complex of toluene-3,4-dithiol. This method has been found to be satisfactory, and is recommended for the determination of tin from 15 p.p.m. upwards. Full details of the method are given in the Appendix to this Report. METHOD B: FOR AMOUNTS OF TIN FROM 30 TO 150 pg The method recommended is based on the modification of Clark’s method2p3 proposed Sodium lauryl sulphate is used as dispersing.agent for by Ovenston and Kenyon.486 preventing coagulation of the red tin - dithiol complex. EXPERIMENTAL- The Sub-committee decided to test the method by carrying out a collaborative exercise with a sample of dried carrots as the organic matter. Each laboratory carried out a series of recovery experiments by adding known amounts of tin to the sample before wet oxidation. The tin was added as aliquots of a standard tin solution. The results obtained are shown in Table I. Laboratory B also carried out some recovery experiments in which fruit pulp was used as the organic matter. The results obtained are shown in Table 11. It was found that erratic results were obtained if the acid concentration in the final colorimetric solution varied appreciably from the equivalent of 1 ml of concentrated sulphuric acid in 20ml of solution.Variable results were also obtained unless the amount of nitric acid used for the digestion was kept to a minimum, and all the nitric acid was removed from the final sulphuric acid residue. *For details of Part I of this series, see reference list, p. 416.DETERMINATION OF SMALL AMOUNTS OF TIN IN ORGANIC MATTER. PART 11 415 B C TABLE I RECOVERY OF TIN FROM 10-g PORTIONS OF DRIED CARROTS Laboratory Tin added, p.p.m. Tin recovered, p.p.m. A 15*0C 15.2 15.0c 16.6 15.0c 16.2 30.0c 30.4 30.0C 3 0 4 30.0C 31.0 150& 19.0 15.08 18.5 15-08 16.3 30.0” 33.5 30.0& 33.0 30.08 31.3 10- Ob 9.5 15.0C 14.5 15-0c 14.5 30-0C 28-0 30-0C 30.0 30.0C 29.0 Samples marked “a*’ were wet oxidised with nitric, perchloric and sulphuric acids.Samples marked “b” were wet oxidised with nitric and sulphuric acids. Samples marked “c” were wet oxidised with 50 per cent. w/v hydrogen peroxide and sulphuric acid. TABLE I1 RECOVERY OF TIN FROM 10-g PORTIONS OF FRUIT PULP Tin added, p.p.m. Tin recovered, p.p.m. 15.0 12.7 15.0 13.5 30-0 28.7 30.0 29.5 Appendix RECOMMENDED METHOD FOR THE DETERMINATION IN ORGANIC MATTER OF AMOUNTS OF TIN FROM 30 TO 150pg PRINCIPLE OF METHOD- The organic matter in the sample is destroyed by wet oxidation with nitric and sulphuric acids, with nitric, perchloric and sulphuric acids,s or with 50 per cent. w/v hydrogen peroxide (tin free) and sulphuric acid.’ The residue is diluted with water and extracted with a solution of dithizone in carbon tetrachloride to remove any copper present.The aqueous solution is then allowed to react with zinc dithiol in the presence of thioglycollic acid, and sodium lauryl sulphate, which acts as a dispersing agent for the tin - dithiol complex. The extinction of the red-coloured suspension is measured at 535 mp. RANGE- The aliquot of the sample solution taken should contain between 30 and 150pg of tin. All reagents should be of analytical-reagent quality unless stated otherwise. Dithizone solution-Prepare a 0.02 per cent. w/v solution in carbon tetrachloride. This solution should be recently prepared or stored in a refrigerator. Sodium ZauryZ suZ@ate solutiort--Prepare a 1 per cent.w/v aqueous solution using sodium lauryl sulphate of B.P. quality. Sulphuric acid, 20 @er cent. v/v-To 50 ml of water cautiously add 20 ml of concentrated sulphuric acid (sp.gr. 1-84). Cool and dilute to 100ml. Tin stock solution-Dissolve 0.100 g of pure granulated tin in 20 ml of sulphuric acid (sp.gr. 1-84) by heating until fumes appear. Cool, cautiously dilute with 150ml of water, and cool again. Add 65 ml of sulphuric acid (sp.gr. 1.84), again cool, and transfer to a 500-ml calibrated flask. Dilute to the mark with water. REAGENTS-416 ANALYTICAL METHODS COMMITTEE Tin standard solution-Dilute 10 ml of tin stock solution to 100 ml with water. Prepare freshly each day. Zinc dithiod-Dissolve 0-2 g of zinc dithiol in 1 per cent.sodium hydroxide solution containing a few drops of ethanol. Add 1 ml of thioglycollic acid and dilute to 100 ml with 1 per cent. sodium hydroxide solution. Prepare immediately before use. PROCEDURE- Destroy the organic matter in an appropriate amount of the sample by wet oxidation with sulphuric and nitric acids; sulphuric, perchloric and nitric acids; or sulphuric acid and 50 per cent. w/v hydrogen peroxide. When oxidation is complete, dilute the solution with 10 ml of water and boil gently to fuming. Allow the solution to cool, add a further 10 ml of water and boil gently to fuming. Transfer the final clear solution to a calibrated flask of such volume that the diluted solution contains no more than the equivalent of 4ml of concentrated sulphuric acid per 100 ml.Transfer, by pipette, 10ml of this solution containing between 30 and 150pg of tin into a separating funnel, add 5 ml of dithizone solution, and shake the funnel. Allow the layers to separate, and discard the lower dithizone layer. Continue the extraction with successive 5-ml portions of dithizone solution until the extracts remain green. Wash the aqueous solution with two successive 5-ml portions of carbon tetrachloride, and discard the washings. Transfer the aqueous phase to a 20-ml calibrated flask and add 20 per cent. sulphuric acid, so that the final solution contains the equivalent of between 0.7 and 1 ml of concen- trated sulphuric acid. Add 1 ml of sodium lauryl sulphate solution, mix, and then add 1 ml of zinc dithiol reagent. Dilute to the mark with water, mix thoroughly, and immerse in a boiling water bath for exactly 1 minute.Allow the solution to cool at room temperature for 20 to 30 minutes, and then measure the extinction of the solution at a wavelength of 535 mp, by using l-cm cells with a reagent blank solution in the comparison cell. Read the number of micrograms of tin equivalent to the observed extinction from a previously prepared calibration graph, and calculate the tin content of the sample. PREPARATION OF CALIBRATION GRAPH- Transfer aliquots of standard tin solution to cover the range 30 to 150pg of tin to a series of 20-ml calibrated flasks. Add 5 ml of 20 per cent. sulphuric acid, mix, and proceed as described above beginning a t “Add 1 ml of sodium lauryl sulphate solution. . . .” Measure the extinctions of the solutions, and construct a graph relating the extinctions to the number of micrograms of tin. (1 ml of solution = 20 pg of tin). REFERENCES 1. Analytical Methods Committee, Analyst, 1967, 92, 320. 2. 3. - , Ibid., 1937, 62, 661. 4. 5. 6. 7. NOTE-Reference 1 is to Part I of this series. Clark, R. E. D., Ibid., 1936, 61, 242. Kenyon, C., and Ovenston, T. C. J., Nature, 1951, 167, 727. Ovenston, T. C. J., and Kenyon, C., Analyst, 1955, 80, 566. Analytical Methods Committee, Ibid., 1960, 85, 643. - , Ibid., 1967, 92, 403.

ISSN:0003-2654    

DOI:10.1039/AN9689300414

出版商:RSC    

年代:1968

数据来源: RSC

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Analyst, June, 1968, Vol. 93, $9. 417-420 417 Analytical Methods Committee REPORT PREPARED BY THE PROPHYLACTICS IN ANIMAL FEEDS SUB-COMMITTEE The Determination of Furazolidone in Feeds THE Analytical Methods Committee has received the following Report from its Prophylactics in Animal Feeds Sub-committee. The Report has been approved by the Analytical Methods Committee and its publication has been authorised by the Council. REPORT The constitution of the Prophylactics in Animal Feeds Sub-committee responsible for the preparation of this Report was: Mr. S. G. E. Stevens (Chairman), Mr. R. J. Anderson (appointed January, 1967), Dr. P. Casapieri (resigned December, 1966), Mr. P. J. Cooper (resigned May, 1967), Mr. G. Drewery, Mr. A. W. Hartley, Mr. R. S. Hatfull, Mr. D. H. Mitchell, Mr.J. A. Stubbles, Mr. C. B. Stuffins (appointed August, 1966) and Mr. D. C. Thomas, with Mr. P. W. Shallis as Secretary. INTRODUCTION Furazolidone is an anti-blackhead drug normally used at a level of about 0.0125 per cent. in poultry feeds. Although frequently used alone, it is sometimes used in conjunction with nitrofurazone and, in consequence, the Sub-committee required a method in which the presence of nitrofurazone did not interfere. The Sub-Committee’s attention was drawn to an unpublished method (private communi- cation from Smith, Kline & French Laboratories Ltd., Welwyn Garden City) that had been used successfully for some years. In this method the feed sample is extracted with light petroleum to remove fats and some other interfering substances, and the drug is then extracted into acetone.The acetone extract is passed through a column of alumina, on which any nitrofurazone present remains as a strongly absorbed band near the top of the column,lS2 and the eluate is evaporated to dryness. The residue is dissolved in pentyl alcohol, from which the drug is extracted into aqueous urea solution, and the optical density of the coloured product is measured spectrophotometrically at 375 mp. EXPERIMENTAL A preliminary collaborative investigation of this method was carried out in seven labora- tories. Two samples of feeds from different manufacturers were used and medication of the feed was carried out within each laboratory. The results of this preliminary investigation were disappointing, the range of recoveries for thirty determinations being 52 to 101 per cent., with a mean of 77 per cent. In general, members taking part were dissatisfied with the lack of detail given in the method for the pre-treatment of the alumina and the preparation of the column.It was also found that insufficient emphasis had been given to the need to protect solutions of furazolidone from the light at all times. A further collaborative investigation was carried out after the procedure for the pre- treatment of the alumina had been more rigorously specified. Seven laboratories took part and three samples of feeds from different manufacturers were used; medication of the blank feed was again carried out within the participating laboratories. The results obtained on this occasion were considered to be particularly good, only four out of the sixty-two deter- minations giving recoveries outside the range 83 to 108 per cent.The full results are shown in Table I. 0 SAC.418 111 ANALYTICAL METHODS COMMITTEE TABLE I DETERMINATION OF FURAZOLIDONE IN POULTRY FEEDS BY THE [Analyst, VOl. 93 RECOMMENDED METHOD C D 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 - Weight of Furazolidone feed taken, added, Feed Laboratory g m g I A - 1-30 2.10 5-50 B 10.0 0-94 1.04 0.98 C 10.0 0.886 0-850 1.192 1.008 D 10.0 1.00 1-00 1.00 1.00 1.00 1.00 0.96 0-93 1.00 0.90 1.10 1.04 1-142 0.757 1-217 1.200 1.00 1-00 1.00 1.00 1.00 1.00 1.00 1.00 1.55 1-46 1.00 1.40 3.00 4.30 0.91 1.10 0.827 1.255 0.824 0.900 1.0 1.0 1.0 1.0 1.0 E 10.0 1.0 1.0 F 10.0 1.01 1-13 G 10.0 1.0 B C D 10.0 10.0 10.0 Furazolidone found, mg 1-29 2.08 5-38 0.90 0.71 0.83 0.90 1 0.911 1.126 1.053 1-050 1.002 1.040 0.963 0.92, 0.97 0.93, 0.95 1.18 0-94 1.00 0.87 0.74 0.94 1.067 0.714 1.195 1-174 0.998 0.987 1.043 0.997 1-048 1.020 0.88, 0.92 0.92, 0.89 1-61 1-49 0-94 1.39 2-92 4.25 0.97 1-12 0.810 1.300 0.866 0.964 0.969 0.978 1.005 0-972 1.045 1.01, 0.89 0-93, 1-06 1.30 1.22 0.94 Recovery, per cent.99 99 98 96 68 83 102 107 95 105 105 100 104 96 92, 97 93,95 123 101 100 97 67 91 93 ' 94 98 98 100 99 104 100 105 102 88,92 92, 89 104 102 94 100 97 99 107 102 98 104 105 107 97 98 101 97 105 101, 89 93, 106 128 108 94 The total variation between the sixty-two individual determinations was analysed statistically into two components-between laboratories and feeds and within laboratories and feeds. The ratio of the two mean squares was si@cantly high (p = O-OOl), indicating the presence of relative biases between laboratories and feeds.The arithmetic mean of allJune, 19681 DETERMINATION OF FURAZOLIDONE IN FEEDS 419 sixty-two determinations was, however, 98.4 & 0.84 per cent., i.e., within two standard deviations of 100 per cent., which suggests that there is little inherent bias in the method and that the average differences between laboratories and feeds tend to be random. The estimated standard deviation for a single determination and a randomly chosen laboratory and feed was k9-2. During the collaborative work some members experienced difficulty owing to the de- position of crystals of urea from the saturated aqueous solution used for extracting the drug from pentyl alcohol.It was found that a solution containing 90 g of urea in 100 ml of water was a satisfactory alternative and avoided the difficulty mentioned above; this modification has therefore been included in the recommended method. In the method as examined the preliminary extraction was carried out with light petroleum, boiling-range 40" to 60" C. The Sub-Committee's attention has subsequently been drawn to the fact that a cleaner extract can be obtained more quickly by using light petroleum, boiling-range 60" to 80" C, and the Sub-committee has concluded that both grades are satisfactory. The method recommended by the Sub-committee for determining furazolidone in poultry feeds is given in the Appendix. The permission of Smith, Kline & French Laboratories Ltd.to publish details of this method is gratefully acknowledged. Appendix RECOMMENDED METHOD FOR THE DETERMINATION OF FURAZOLIDONE IN POULTRY FEEDS PRINCIPLE OF METHOD- After preliminary extraction with light petroleum to remove fat the feed sample is extracted with acetone in a Soxhlet extractor. The acetone extract is passed through a column of alumina, on which any nitrofurazone present is retained. The acetone eluate is evaporated to dryness and the residue dissolved in pentyl alcohol. Furazolidone is then extracted from the pentyl alcohol with aqueous urea solution and the optical density of this solution is measured at 375mp. REAGENTS AND MATERIALS- Light petroleum, boilingrange 40" to 60" C OY 60" to 80" C.Acetone. Pentyl alcohol. Pentyl acetate. Alumina-Neutral alumina; Brockmann activity 1; 100 to 240 mesh. Aqueous urea solution-Dissolve 9Og of urea in 100ml of water. PREPARATION OF CHROMATOGRAPHIC COLUMN- Slurry 500 g of the alumina with 1 litre of hot distilled water, and then decant off the supernatant liquid. Dry the alumina at 105°C to constant weight before use. Fill a column (30 cm long by 1 cm diameter) to a height of 20 cm by adding a slurry of the prepared alumina in acetone. Allow the excess of acetone to drain off to the top of the alumina. Repeat this procedure twice more. PROCEDURE- Weigh sufficient of the feed sample expected to contain between 0.9 and 1.1 mg of furazolidone into a 25-mm x 80-mm Soxhlet thimble, and place it in a Soxhlet extractor.Extract with light petroleum for half an hour. (There should be 13 to 17 cycles of solvent through the extractor during the half-hour period of extraction.) Remove the thimble from the apparatus, drain off the residual solvent, and dry the thimble containing the extracted feed in a current of warm air. Transfer the dried thimble to a clean Soxhlet extractor, and extract with acetone for 1 hour; use a steam-bath for heating and protect the apparatus from light. (There should be at least 25 cycles of solvent through the extractor during the hour.)420 ANALYTICAL METHODS COMMITTEE Evaporate the acetone extract to a volume of 5 to 10 ml on a steam-bath, and then cool to room temperature. Transfer the acetone extract to a prepared chromatographic column, and elute with acetone until the furazolidone band has passed through. Evaporate the acetone eluate just to dryness on a steam-bath. Dissolve the residue in 10 ml of pentyl alcohol, and transfer the solution to an amber-glass 125-ml separating funnel; wash in with 10 ml of pentyl acetate. Extract the solution with five separate 10-ml portions of aqueous urea solution, and transfer each separated aqueous extract to an amber-glass 100-ml calibrated flask. Dilute to the mark with saturated aqueous urea solution, and mix. Measure the optical density of the solution at 375mp against aqueous urea solution as a blank. NOTE-solutions of ftkazolidone should be protected from light at all times. E:& of furazolidone in aqueous urea solution = 643. REFERENCES 1. 2. Luhman, A., J . Ass. Off. Agric. Chem., 1958, 41, 333. Stone, L. R., Ibid., 1964, 47, 662.

ISSN:0003-2654    

DOI:10.1039/AN9689300417

出版商:RSC    

年代:1968

数据来源: RSC

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Artdyst, June, 1968, Vol. 93, PP. 421-424 421 Book Reviews PROGRESS IN CHEMICAL TOXICOLOGY. Edited by ABRAHAM STOLMAN. Volume 3. Pp. xvi + 413. All of the authors are recognised international authorities, and their chapters are authoritatively and, as important, critically written. Harger and Forney write on “Aliphatic Alcohols” and report particularly on ethanol; they deal with many of the discrepancies noted in publications prior to early 1966. Maehly’s chapter on “Volatile Toxic Compounds” discusses the toxicology and analytical methodology of halogenated hydrocarbons, aromatic hydrocarbons, inorganic and organic acids. The emphasis is on colour tests, although gas-chromatographic techniques are covered. Feldstein on “Carbon Monoxide” pinpoints many of the problems and basic methods in a short twenty pages.One of the most important chapters is by Mannering and Anders on the “Application of Gas Chromatography to Toxicology.” This is a 92-page chapter and is most comprehensive dealing not only in review form, but with practical experimental details. These latter are of the greatest value and reflect the authors’ great experience in this field. A very wide range of compounds is covered, from gases to pesticides, via the barbiturates, anaesthetics, glycosides, etc., as well as ancillary techniques, such as trapping procedures. Dal Cortivo, Matnsiak and Cejola report on “Developments in Spectroscopy: Spectrochemical Methods” ; they give a critical account and include a table on the frequency and distribution of metals in human tissue. Mutschke and Pribilla write on a topic very much ignored to date by forensic toxicologists, namely, “Detection of Radionuclides of Biological Interest in Human Bones and Tissues.” This extensive chapter is highly practical, giving full experimental details for such elements as strontium-90 and strontium-89, caesium-137, iodine-131, radium-226, thorium, uranium and plutonium-239.The editor contributes a chapter on the “Combined Action of Drugs with Toxicological Implica- tions,” which combines a discussion of pharmacological actions in experimental animals, as well as analytical results of some cases in man. This is a useful, well referenced, review chapter. Rehling reports from the Registry of Human Toxicology of the Toxicology Section of the American Academy of Forensic Sciences on “Poison Residues in Human Tissues.” All forensic toxicologists will be grateful for this publication.Where else can one find results on over 150 fatal barbiturate poisonings, 90 barbiturate - alcohol combinations, 17 cases of chloral hydrate, 28 paraldehyde deaths, 42 cyanide deaths, 11 involving strychnine, 4 boric acid, 52 arsenic, 20 lead, 18 mercury and 3 thallium, as well as a host of tranquillisers? This chapter alone makes this book a sine qua non for all analysts involved in human-tissue analyses. The additional chapters are of such a standard that it is difficult to think of another publication that ranks so highly in this specialised field of analysis. At 128s. it may be considered expensive. This reviewer thinks it will be money well spent.A. S. CURRY New York and London: Academic Press. 1967. Price 128s. This is undoubtedly the best in this series of Volumes on Chemical Toxicology. THE ANALYTICAL TOXICOLOGY OF INDUSTRIAL INORGANIC POISONS. By MORRIS B. JACOBS, Ph.D. New York, London and Sydney: Interscience Publishers, a division of To anyone however remotely connected with toxic substances, analylxally or toxicologically, the name Jacobs, and what it implies, is almost certain to have been mentioned. Over the 27 years since the first edition of “The Analytical Chemistry of Industrial Poisons, Hazards and Solvents” appeared, Dr. Jacobs’ publications have become increasingly recognised throughout the world for the wealth of reliable information they contain, and today they are accepted as standard textbooks of analytical methods in the field of industrial hygiene.The second edition of Jacobs’ book appeared in 1949, and now we have an up-to-date version of that publication under a new title. This latest book is really a revision of the earlier publication, but, with so much new informa- tion available, it is not surprising that an entirely new book has emerged. It is inevitable, therefore, that some information contained in the earlier publications does not appear in this book, but these omissions have only been made after careful consideration, and, indeed, valid and acceptable explanations. Pp. xxvi + 943. John Wiley & Sons Inc. 1967. Price 200s.422 BOOK REVIEWS [Analyst, Vol. 93 Compared with its predecessor, this book includes methods for the detection of newly recog- nised poisons, and new sections on radioactive nuclides, detector tubes and methods for evaluating the absorption of industrial poisons in blood or urine.The chapter on war gases included in the first edition of Jacobs’ book, but not in the second, now appears as a revised and expanded contribution based on recent knowledge. A random selection of chapter titles includes Industrial Hygiene and Industrial Poisons ; Sampling ; Absorbers, Absorbents, and Adsorbents ; The Characteristics and Sampling of Dust; The Chemical and Microscopic Estimation of Silica, Lead, Mercury and Arsenic; Other Harmful Metals ; Sulfur Compounds ; Phosphorus and Phosphorus Compounds ; Common Poisonous Com- pounds of the Halogens, Carbon Monoxide, Carbon Dioxide, Cyanides, and Nitriles ; and Clinical Chemistry and Industrial Toxicology.The 50-page appendix, consisting of eighteen tables with, for example, data on safe concen- tration levels of various poisons, is literally packed with useful information, under such headings as Limits of Inflammability and Explosive Range ; Threshold Limit Values for 1964 ; Probable Safe Concentration Limits of Exposure for Gases, Probable Safe Limits of Exposure for Certain Industrial Dusts, Concentrations of Common Air Pollutants in the Average Urban Area ; Abnormal Values in Urine Caused by Occupational Poisons; and Abnormal Values in Blood Caused by Occupational Poisons. As with so many books with “household” names, it can be reasonably assumed that the author started on this publication almost before the ink was dry on the last, Indeed, a provisional Preface was prepared by Dr.Jacobs, and most of the manuscript was available before he died. His death in 1965 must have placed a heavy burden on those members of his family, and others, who have so ably succeeded in bringing this latest contribution into print. Similar recognition is also due to many others referred to in the text, who have made contributions based on their own expertise, thus ensuring the book’s continued pride of place in the laboratory, and elsewhere. An up-to-date and internationally recognised book such as this hardly needs a review, a “mention” here would almost suffice, because the progressive analyst or toxicologist, in the field, needs no convincing that he must have access to whatever “Jacobs” has to say on the present state of the science.W. T. ELWELL INORGANIC CHEMISTRY. By R. T. SANDERSON. Pp. xii + 430. New York, Amsterdam and This is a further addition to the Reinhold’s Chemistry Textbook Series, but the book was originally intended as a second edition of the author’s “Chemical Periodicity,” which was published in 1960. However, during this period, the revisions needed became so extensive, and the additions so important, that the necessity for a new book became obvious. In these days of turmoil and change in chemical education at all levels, one matter has become very clear; during this period we have witnessed a move away from descriptive chemistry towards the physical, mathematical and theoretical viewpoint of the topic.Often this has led to what amounts to a drastic neglect of descriptive chemistry. In no field has the trend been more obvious than in inorganic chemistry, and because, in most educational institutions, the people who held responsibility for inorganic teaching also taught analytical chemistry, we have a neglect of this subject at almost every level. The direction of inorganic chemistry has been towards a deeper and fundamental understanding of the bonding, reactions and structure of inorganic compounds. However, in these days when one has been asked “Of what technological importance is your work ? ” then this trend probably does need re-assessment. The theoretical aspects of inorganic and organometallic chemistry do indeed provide stimulating intellectual exercises.But an adequate supply of experimental chemical observations on actual compounds is needed for inter- pretation. If this supply is not available, then of how much use are the theories and explanations ? Thus we can also ask how a true appreciation of chemical theory can be acquired if an aware- ness of its applications, etc., is lacking ? Professor Sanderson has tried to rectify the imbalance, by writing this book. Naturally, as the book is a sequel to “Chemical Periodicity,” it gives a wider and more comprehensive coverage of the whole field. Also, one of the book’s main themes is the use of the concept of partial charge as an aid in interpreting inorganic chemistry. The author feels that although chemists have found this idea interesting, full appreciation of the potential of the method has yet to be accepted, although no facts have appeared in the last 15 years to dispute these ideas. London : Reinhold Publishing Corporation.1967. Price 102s.June, 19681 BOOK REVIEWS 423 The book is a lengthy one, 430 full size pages, with 24 chapters, a supplement and an index. The level of the book is for very good scholarship candidates and, obviously, first and second year university students. At the end of each chapter there are review questions, and questions for discussion. These latter questions should help to improve the staff - student relationship, which is often criticised in a variety of ways today. In the reviewer’s opinion, this book should be available in all libraries for students and staff, but its relatively high cost will probably prevent its large-scale purchase by students.G. NICKLESS ADVANCES IN CHROMATOGRAPHY. Volume 4. By J . CALVIN GIDDINGS and ROY A. KELLER. Pp. xiv + 380. London: Edward Arnold; New York: Marcel Dekker. 1967. Price 130s. As the title suggests this is the fourth book in the series “Advances in Chromatography.” The object of the series is to try to present, in a series of volumes, the significant and real advances’ in some particular facet or branch of chromatography, that have occurred or are occurring at that time. Naturally, in each volume there are several authors, each contributing a chapter and each acknowledged to be an expert in that field. To this extent this volume follows the layout of the previous three volumes, and is divided into two main sections on general chromatography and gas chromatography. In the section on general chromatography, the correlation and prediction of I?, values in thin-layer chromatography on alumina and silica, steroid separation and analysis, and the funda- mentals of ion-exchange cellulose design and their use in biochemistry are discussed.The section on gas chromatography contains discussions on adsorbents in gas chromatography, packed capillary columns, mass-spectrometric analysis of gas-chromatographic eluents and the polarity of stationary liquid phases. All of these chapters are extremely fine contributions to the literature on chromatography, but special mention should be made of chapters by Snyder and Kiselev. In view of the topicality of the subject matters covered by these chapters their appearance is most timely.Synder’s chapter describes a general theory for the correlation and prediction of R, values in thin-layer chromato- graphy, and the application of the theory to certain literature R, data. A major problem in the application of the theory to practical separation problems is the complexity of some of the correla- tion equations. Unfortunately, this mathematical complexity also reflects the complex nature of most absorption systems. However, it is hoped that extensive tabulations of I?F values will include the precautions that have been taken to maintain adsorbent activity constant between elutions. The chapter by Professor Kiselev is very useful, since it presents the results of investigations of non-specific and specific molecular interactions occurring during the adsorption and chromato- graphy of molecules of different geometric and electronic structures on surfaces of different com- positions.From this, it appears that this method should become an important analytical and preparative method, with several advantages over the gas - liquid chromatographic method, especially for the analyses of gases and mixtures at high temperatures. The chapter is a lengthy one, but repays for careful reading, especially the large number of Russian and basic physico- chemical background references that are listed. The chapter, in which the coupling of mass-spectrometric analyses and gas-chromatographic eluents are described, explains the instrumental considerations and the introduction of eluents to the mass spectrometer’ and gives specific applications of gas-chromatographic - mass-spectro- metric analysis.One extremely interesting feature is the inclusion of a discussion of the pitfalls that occur in the interpretation of mass spectra. In the reviewer’s opinion this volume is the best of the series to the present, and should be available wherever chromatography is used or studied. G. NICKLESS PUBLICATIONS OF THE NATIONAL BUREAU OF STANDARDS. By BETTY L. OBERHOLTZER. Pp. xviii + 740. National Bureau of Standards Supplement to Miscellaneous Publication 240. Washington 25, D.C. : Superintendent of Documents, US. Government Printing Office. 1967. Price $4.00. This book is a comprehensive catalogue of all publications by the National Bureau of Standards from July, 1960, to June, 1966, and also includes a list of papers published elsewhere by members of the staff of the Bureau from 1960 to 1965.It is the fourth in a series of catalogues, which, taken together, provides a complete list of all the Bureau’s publications since it was formed in 1901.424 BOOK REVIEWS [Analyst, Vol. 93 Abstracts of papers published in the Journal of Research of the N.B.S. prepared by their authors occupy 272 pages, and 124 pages are given to the list of papers by N.B.S. staff published elsewhere. An author and subject index occupying 332 pages completes the book. Information on how to obtain N.B.S. publications and on their prices and availability is also given. In all, nearly 7000 titles are listed covering all aspects of chemical, physical, mathematical and engineering sciences of interest to the Bureau, and the book will be of undoubted value to technical libraries and information departments.Intending purchasers outside the U.S.A. should, however, note that remittances should be in US. exchange and include an additional one quarter of the publication price to cover postage. P. W. SHALLIS ABSORPTION SPECTRA IN THE ULTRAVIOLET AND VISIBLE REGION. Edited by DR. L. LANG. This is a further collection of data sheets for nearly 200 compounds, assembled on the loose-leaf principle. Each sheet has the absorption curve on one side and full numerical data on the other, showing log I,/I for stated wavelengths, solvents , concentrations and cell thicknesses.This volume has information on many pyrimidine and pyridine derivatives, on di- and tri-substituted benzenes, acetophenones and benzophenones and chalcones. I t includes data on groups of arseni- cals, salicylates, sulphylimines, sterols and some quinoline and triazole derivatives. Most of the absorption curves appear to be new, but no other selection principle is evident. When a substance exhibits only continuous end absorption, the need for a diagram as well as numerical data is not obvious. As in the previous volumes of the series, the production is excellent. Volume VII. Pp. vi + 7-412. Budapest: Alcademia Kiado. 1967. Price 115s. R. A. MORTON ISOTOPES IN CHEMISTRY. By J . F. DUNCAN and G. B. COOK. Pp. xvi + 258. Oxford: Clarendon This is a stimulating book that could be read with profit by undergraduate and postgraduate students who are interested in the ways in which isotopes have increased our fundamental under- standing of chemistry.It covers a wide range of topics, including reaction kinetics, isotope effects, the Mossbauer effect, the chemistry of radioactive elements and isotopic methods of analysis. The latter chapter is a short but comprehensive introduction to the subject, with useful references for any analyst entering the field of isotopic techniques, but it is not a practical manual of instruc- tion. I was particularly impressed by the useful reviews of applications of isotopes in the study of diffusion processes and exchange reactions. The Clarendon Press has maintained its high reputation for clear typography and there is a useful index. Most of the figures are quite clear, although I failed to follow Fig. 2.2, and the conclusion drawn from Fig. 9.7 seemed doubtful. In a single reading I located eleven misprints, including the erroneous spelling “Prometheum” three times on p. 223. Somewhat more serious defects are the mis-statements scattered throughout the book. For example, alpha particles do not “appear as thick black lines when viewed under a microscope’’ as stated on p. 39, nor can a gamma ray “be converted into a mono-energetic electron” (p. 20). The phrase “to behave rare-earth-like” (p. 247) could have been better expressed. My final criticism concerns the references. While the text is up-to-date, most of the references are at least ten years old and even for the Mossbauer effect no literature later than 1962 is quoted. In a sense, the authors are correct when they say that the neutrino has only been detected “very recently” (1953; p. 17), but, according to de Solla Price, science has doubled in the intervening fifteen years. Developments in isotopic science are doubling at a much faster rate. Press. 1968. Price (hard cover) 55s.; (paperback) 27s. 6d. H. J.M.BowEN

ISSN:0003-2654    

DOI:10.1039/AN9689300421

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

424 BOOK REVIEWS [Analyst, Vol. 93 APRIL (1968) ISSUE, p. 207, 27th line. IBID., p. 207, 28th line. IBID., p. 209, 5th line. Ism., p. 209, 25th line under FUTURE DEVELOPMENTS. IBID., p. 223. For “Lockyer’saa~37” read “Lo~kyer’s23~~~.” For “determinati~n~~” read “determinations*." For “0.1” read “0.01.” For “calcium43 and magnesium” read Insert after reference 11 “12. Gajan, R. J., in Gunther, F. A., Editor, “Residue “ca1c:ium~ and aluminium.” Reviews,” Springer-Verlag, Berlin, Gottingen and Heidelberg, Volume 6, 1964, p. 75.

ISSN:0003-2654    

DOI:10.1039/AN9689300424

出版商:RSC    

年代:1968

数据来源: RSC