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Analyst, July, 1968, Vol. 93, pj5. 461468 461 Observations on the Distribution and Determination of Fluorine Compounds in Biological Materials, Including Soils BY R. J. HALL (Ministry of Agriculture, Fisheries and Food, National Agricultural Advisory Service, Kenton Bar, Newcastle upon Tyne NEI 2YA) The distribution of fluorine compounds found in biological materials, including soils, is outlined. Several improvements are proposed for the sampling and ashing of animal and plant tissues, and soil, including the use of finely ground suspensions in dilute agar solution. Some modifications are suggested in the separation of fluorine by diffusion as hydrofluoric acid and its subsequent determination with alizarin complexan. The effect of silica in the analysis of plants and soils for fluorine is discussed.IN recent years, the determination of small amounts of fluorine in biological materials has been facilitated by the increasing adoption of diffusion procedures for the separation of fluoride from interfering ~ubstances,~ , 2 9 3 ~ ~ and by the introduction of alizarin complexan for the direct determination of the fluoride ion.39596 In applying these methods to the deter- mination of fluorine in a variety of materials, including plant tissues and soils, difficulties have been experienced, and it is thought that the following observations may be useful to other workers interested in this subject. THE DISTRIBUTION OF FLUORINE COMPOUNDS IN BIOLOGICAL MATERIALS- It has now been established that, in addition to the main fluoro minerals, cryolite (3NaF.A1F3), fluorspar (CaF,), fluorapatite [CaF,.3Ca,(P04) J and sellaite (MgF,), which are present in soils and geological structures, and, in respect of fluorapatite, in animal tissues such as bone and teeth, fluorine is present in several tropical plants as w-mono-fluorinated carbon compounds.Marais' was the first to report that the toxic principle of DichapetaZum cymosum (a poisonous South African plant) is a fluoroacetate, which has now been isolated from two Australian plants, Acacia georginaes and Gastrolobium g~andiJEorztm.~ Longer-chain fluorocarboxylic acids have also been identified in a few other Dichapetalum species.lOJ1 There is an extensive literature on the r6le of fluorine in the structure of bone, teeth and soft animal tissues and, with the advent of drugs and pesticides containing organofluorine compounds, there is increasing interest in the distribution of the forms of fluorine in soil and other biological specimens.In Table I, an attempt is made to group, in a somewhat arbitrary manner, the fluorine-containing compounds found in biological materials. TABLE I DISTRIBUTION OF FLUORINE IN BIOLOGICAL MATERIALS Animal tissues and body fluids Plants Soils Ionised fluorine in blood, Water and dilute acid- Water and dilute acid- Perchloric acid diffu- F-. Fluoro minerals sible F-, possibly with aluminium, cal- fluorophosphates cium, magnesium, silicon and phosphorus; diffusible after fusion with potassium hydroxide urine, and soft tissues. extractable F-, prob- extractable F-. Per- Fluorapatite in bone ably simple fluorides.chloric acid diffusible and teeth Fluorine-containing e g s in blood and unne. Protein-bound F-, probably acid- labile Organic 0 SAC; Crown Copyright Reserved. Alkali-labile, short and long-chain carbon - fluorine compounds soluble in organic solvents None so far identified462 HALL: DISTRIBUTION AND DETERMINATION OF FLUORINE [Analyst, Vol. 93 In these studies, the water-extractable fluorine in soils is considered to be that which is extracted after shaking 10 g of finely ground soil with 50 ml of distilled water for 30 minutes at room temperature on a reciprocating shaker. The fluoride that is liberated by treatment with 47 per cent. w/w perchloric acid at 60" C for a t least 24 hours has been called the acid- labile or diffusible fluoride and, in soils, it is suggested that it can be regarded as the fluoride potentially available to the plant.It will include fluorapatite, as well as simpler fluorides, but, in all probability, will exclude organically combined fluorine and complex minerals containing fluorine and silica. To determine total fluorine in soils the material must be fused with strong alkali. With most plant tissues, observations in this laboratory indicate that the total fluorine is also the diffusible or acid-labile fluorine, but in some tropical species,ll in addition to in- organic fluoride, there are two groups of organically bound fluorine that are not degraded by strong perchloric acid. One group contains alkali-labile compounds, and the other, fluorine derivatives soluble in organic solvents, such as light petroleum and carbon tetrachloride.The alkali-labile group consists of short-chain compounds, such as fluoroacetates, from which the fluorine can readily be removed by treatment with strong alkalilo It is possible that some of the fluorine present in these plants is conjugated with protein. Little seems to be known about the inorganic fluorine compounds in plant tissues. That some plants contain high levels suggests that the fluorine is in a comparatively inactive forrn, perhaps combined with calcium or magnesium, or even as fluorophosphates, and stored in various tissue cells of the plant. While several techniques, such as infrared spectroscopy and gas chromatography, need to be used for the actual identification of specific components, the final evaluation of results may well depend on the ability to determine accurately extremely small amounts of fluorine.ANALYTICAL PROCEDURES PREPARATION OF SAMPLES- Plant specimens-Surface contamination is best removed by placing the fresh material in a polythene or polypropylene domestic colander, and immersing it in distilled water. The sample should then be dried between sheets of clean white filter-paper. Small amounts should be air-dried at about 25 to 30" C by spreading the sample on filter-paper and placing it in a warm room or cupboard; oven-drying at 60" C overnight is also suitable. It is unwise to dry at 100" C, because of the possibility of loss of volatile fluorine compounds. Conven- tional determinations for dry-matter content can be carried out on suitable sub-samples at 105" C.Soils-About 500 g of soil, spread evenly in a tray, 10 x 8 inches, should be air-dried at 80" to 90" F for 48 hours. Soft animal tissues-These should be chopped into small pieces and dried at 60" C for 48 hours. Bone-The marrow should be removed, the bone sawn into small pieces, then finely ground in a hammer-mill and de-fatted by extraction with light petroleum. It is customary to express the fluorine content as a percentage of the bone ash or de-fatted bone. GRINDING OF SAMPLES- Soft animal and plant tissues-After first grinding the dried tissue in a hammer-mill, further grinding in a metal ball-mill for 18 to 24 hours will usually reduce the material to a suitably fine powder. In this laboratory, a special steel ball-mill is used, the interior of which is chromium-plated, with beaters of chromium-plated steel rod.A Casella grain-mill has also proved useful for the preliminary grinding of small or difficult plant samples. The mechanism of this apparatus consists of four stainless-steel knives that rotate at several thousand r.p.m. against four similar, but stationary, knives within a stainless-steel chamber, the fine plant particles falling through a sieve into a glass container. Conventional hammer- mills do not always reduce the dried tissue to a sufficiently fine powder. After grinding, the material is passed successively through stainless-steel or nylon sieves of 8-inch diameter, and of B.S.S. 100 and 300 mesh, which have mesh apertures of 150 and 53 p , respectively; these are supplied by Messrs.Endecotts Ltd. If the material is ground long enough, it is possible to pass all of it through the 300-mesh sieve, thus producing particles that are even smaller than those of the standard kale described by Bowen.12July, 19681 COMPOUNDS I N BIOLOGICAL MATERIALS, INCLUDING SOILS 463 Soils-Grinding in the ball-mill to pass the 300-mesh sieve has been found to be the most satisfactory procedure. SAMPLING FOR ASHING OR DIRECT DIFFUSION OF ACID-LABILE FLUORIDE- Considerable difficulty was experienced in obtaining good replication of results when 10 to 100mg of finely ground preparations were weighed directly into the diffusion bottles or platinum crucibles. In the diffusion procedure, there was a tendency for plant powder to form into small lumps that would not disintegrate, even after contact with strong perchloric acid for 24 hours.The problem was overcome by preparing suspensions of the finely ground specimens in 0.1 per cent. agar, which remain stable for at least 24 hours. To test the reproducibility of sampling, ten replicate l-ml volumes of two plant and three soil suspensions containing 10 to 50 mg of sample per ml were transferred, by pipette, into small aluminium dishes and dried at 100" C for 18 hours. The weights of the dried aliquots are shown below. Plant suspension, mg per ml (a) 61.0 to 51.9; mean 61.4 f 0-5 (b) 22.6 to 23.0; mean 22.8 f 0.2 Soil suspension, mg per ml (a) 48.9 to 49.7; mean 49-4 f 0.5 (b) 20.6 to 22.2; mean 21.3 f 0.9 (c) 11.6 to 12.0; mean 11.8 f 0.2 The results indicate that the weight error involved in measuring such suspensions by volume is little more than that of a balance with a sensitivity of +_0-2mg.Even with soil (b), which had a high sand content, the error did not exceed 1 4 per cent. Preparation of susfiensions in agar-Prepare a 0.1 1 per cent. w/v solution of good quality agar (Difco agar or Oxoid agar No. 3 is suitable, but not Oxoid Ionagar No. 2). Preserve it with a crystal of thymol. The solution keeps for 3 to 4 weeks. Plant tissues-Weigh 1.0 g of finely ground plant powder into a 50-ml calibrated flask, add 5 ml of M lithium hydroxide and 2 drops of s-octyl alcohol to prevent the formation of froth. Shake it until the particles are dispersed; the plant material is partially soluble. Make up to volume with agar solution.Mix thoroughly. Soils-Weigh suitable amounts to give 20mg of soil per ml and suspend them in the agar solution alone. In practice, suspensions of 20mg of sample per ml have given the most reproducible results, but suspensions containing 50 mg of sample per ml can be used. When the agar is freshly prepared, the suspensions remain stable for a long period but, after a few days, the ability of the agar solution to hold the soil in suspension tends to deteriorate. Ashing-Experience during the past few years has shown that some muffle furnaces cause serious contamination of ashed specimens.3J3 Attempts to overcome this extremely difficult problem have included the use of tightly closed containers within the muffle furnace for the platinum crucibles, a silica-lined muffle furnace, a Simon-Meuller crucible furnace and high temperature hot-plates.In every instance, serious and variable extraneous con- tamination resulted when the temperature rose above 400" C. As it is generally considered necessary to ash some materials, e.g., soils, at temperatures of about 600" C, it was essential to examine carefully the ashing procedures. Simple ashing over a small, glass spirit burner was found to eliminate contamination and give the most reliable results; it is not as tedious as may be supposed. REAGENTS- METHOD OF ASHING FOR SOILS AND TISSUES Lithium hydroxide, M-This was prepared by the method of Hall.3 Magnesium succinate, 0.2 M-This was prepared by the method of HalL3 Cellulose suspension in 0.1 per cent.agar-Suspend 50 g of Whatman cellulose powder in 500 ml of hot 0.2 M hydrochloric acid and leave it to stand for 30 minutes. Filter on a Buchner or sintered-glass funnel, and wash it with hot water until free from acid. Dry at 100" C. Prepare a suspension of 20 mg per ml in 0.1 per cent. agar alone, as for soil. Preserve it with a crystal of thymol. PROCEDURE- capacity. With a pipette, introduce 1 ml of the sample suspension into a platinum crucible of 15-ml Add 0.3 ml of M lithium hydroxide and 0.6 ml of 0.2 M magnesium succinate,464 HALL : DISTRIBUTION AND DETERMINATION OF FLUORINE [Analyst, VOl. 93 and mix with a small nickel spatula, washing the spatula with a few drops of distilled water and collecting them in the crucible. For soil, add 1 ml of cellulose suspension in addition.Evaporate to dryness in a stainless-steel-lined oven at 100" C. By using a pair of platinum- tipped tongs and an ordinary glass laboratory spirit burner with a brass or porcelain wick holder, and filled with methanol, carefully heat the upper half of the crucible until the sample has completely carbonised. Although no evidence has been obtained to show that losses of fluorides occur in the smoke, it seems advisable to avoid heating the sample directly at first because of the formation of smoke; continue the ashing by holding the crucible in the conventional manner over the flame. When most of the carbonaceous material has been burnt off, leaving a grey ash, allow the crucible to cool, and add a few drops of distilled water. With a micro spatula, break up the ash and gently rub any carbon particles down the wall of the crucible.Wash the spatula with a little water, collecting this in the crucible, and replace the crucible in the oven to dry. When dry, re-heat the crucible carefully over the spirit burner, starting by heating the wall, as before. During this second stage the remaining traces of carbon are removed, thus leaving a clean ash. The whole procedure for each sample should take only 2 to 4 minutes. FUSION OF SILICEOUS MATERIAL- Soils and plant samples rich in silica need to be fused with alkali to convert fluorosilicates into fluorides. Several workers have reported on the relative merits of sodium and potassium hydroxide when used for this purpose.14 In this work, various reagents were tried, but only with potassium hydroxide were quantitative recoveries obtained.The results of these tests are shown in Table 11. Test No. 1 2 3 4 5 6 7 TABLE I1 RECOVERY OF FLUORIDE FROM SOIL AFTER FUSION WITH ALKALIS Fusion reagent* Lithium hydroxide . . .. Potassium hydroxide . . .. Sodium carbonate .. .. Sodium hydroxide. . .. .. Sodium peroxide . . .. .. Potassium hydroxide . . .. Potassium hydroxide . . .. Fluoride determined, pg 1 Origmal soil + 1 pg of F- 3.60 3.60 4.56 5-47 2.30 2.50 - 2.50 - 3.00 1.66 2.28 1.06 1.27 1.98 3-95 4.27 6.24 + 2 pg of F- Difference, as percentage of added fluoride Nil 91 20 20 70 72 21 98.5 98.5 * 0.5 g of solid reagent was added in each test. Tests 1 to 5 were done with 20mg of the same soil. Except for sodium carbonate, the reproducibility of triplicate fusions was good.The sodium carbonate fusions needed to be heated over a micro bunsen burner at a temperature of about 800" C for melting to occur. Two different soil suspensions were used for tests 6 and 7 when 2 pg of fluoride were added. In each instance the fluoride was added with the soil suspension at the beginning of the analytical procedure. METHOD OF FUSION- After ashing in the manner described above, add 0.5 g of solid potassium hydroxide and heat very gently, with continual swirling of the crucible over the spirit burner, until the potassium hydroxide has liquefied and all of the water has evaporated off. Continue heating until as much of the ash as possible has dissolved in the molten potassium hydroxide; this takes about 1 minute.Do not heat to such an extent as to cause the potassium hydroxide to volatilise. Some soils, particularly those of a sandy nature, do not completely dissolve. Cool, add 1 ml of water and transfer the mixture quantitatively into a 10-ml graduated tube or flask containing 3 or 4ml of water. Wash out the crucible with four successive l-ml volumes of 10 per cent. v/v sulphuric acid using a dropping pipette with a rubber teat. Make the volume up to 10 ml with water. The resulting solution, which is usually colourless butJuly, 19681 COMPOUNDS IN BIOLOGICAL MATERIALS, INCLUDING SOILS 465 contains a small amount of residue according to the type of sample, can now be used for the direct diffusion of hydrofluoric acid. Blanks on 20 mg of cellulose, with all of the reagents, must be taken through the whole ashing and fusion procedures.The fusions of soil samples and other fluorine-rich materials can be conveniently made up to 10ml of solution, or appropriately greater volume, from which 1 ml is a maximum aliquot to remove for the diffusion of hydrofluoric acid. Samples of especially low fluorine content may be transferred directly into the diffusion bottle; in this event, dissolve the ash in 0.5 ml of 10 per cent. v/v sulphuric acid, transfer the solution into the diffusion bottle and wash out the crucible with two 0 6 m l volumes of ice-cold 70 per cent. w/w perchloric acid containing silver ~ulphate.~ This procedure, however, is not suitable for ashes fused with potassium hydroxide. DIFFUSION OF HYDROFLUORIC ACID- Some minor modifications have been introduced into the method originally publi~hed.~ The papers absorbing the diffused hydrofluoric acid are now treated with 1 drop of 0.5 M sodium hydroxide containing 50 per cent.v/v of propylene glycol; this reagent has greater absorbing efficiency than 0.2 M magnesium succinate. The propylene glycol delays drying out of the papers. It is essential to wipe the inside of the neck of the bottle with a filter-paper to ensure that no traces of acid are left that could interfere with the absorption of hydrofluoric acid and the subsequent reaction with the alizarin complexan. Carnauba wax, which is hard and effects a better seal, is now used alone instead of the original mixed wax for sealing the caps, The cap is sealed by holding the bottle horizontally with the neck and cap over the container of hot wax and then applying the wax from a dropping pipette.The volume of liquid in the diffusion bottle should not exceed 3 ml, and maximum diffusion of fluoride is achieved by using 0.5 ml of plant or soil suspension with 1 ml of the silver - perchloric acid reagent. THE DETERMINATION OF FLUORIDE WITH ALIZARIN COMPLEXAN- The adoption of alizarin c0mplexan~1~ as a direct colour reagent for inorganic fluoride has become widespread and, in the author’s experience, has removed much of the uncertainty inherent in the use of reagents that are bleached by the fluoride ion. For concentrations above 0.2 p.p.m. of fluoride in the reaction mixture, the blue fluorochelate can be measured directly at 615 nm with little error, but for lower levels, and for precise values, extraction into isobutyl alcohol containing an amine is necessary.Here again, experience has shown the need for several small changes to be made in the original m e t h ~ d . ~ 1. The alizarin complexan, as now supplied by Messrs. Hopkin and Williams Ltd., does not need to be purified. 2. Some batches of t-butyl alcohol have been found to contain acidic impurities that either prevent the formation of the lanthanum - alizarin chelate or interfere with the extraction of the fluorochelate into isobutyl alcohol; it is therefore advisable to re-distil the reagent. 3. The composite lanthanum - alizarin reagent can be prepared more conveniently as follows. Transfer 0.4724 g of succinic acid into a calibrated flask of 100-ml capacity, add 3.2 ml of M sodium hydroxide and sufficient water almost to dissolve the succinic acid (about 10 ml).Add 10ml of lanthanum nitrate solution (173mg of La(N0,),.6H20 in 100ml of water) and make up to 100 ml with water. Check the pH potentiometrically and adjust it to 4.6 with M sodium hydroxide, if necessary; the small increase in volume caused by this adjustment is of no consequence. Now add, by pipette, to the buffered lanthanum solution an equal volume of 0-0003 M solution of alizarin complexan (23-1 mg of the complexan dissolved in 0.2 ml of M sodium acetate and made up to 200 ml with water) and mix by constant swirling, then add re-distilled t-butyl alcohol so that its final concentration is 20 per cent. v/v. The buffered lanthanum solution and the mixed reagent should be freshly prepared for each batch of determinations.4. It has been found necessary to rinse the reaction tubes with the alizarin complexan reagent before the determinations to remove traces of contaminating substances. This can readily be done by filling the first of a set of 5-ml stoppered tubes with the solution and466 HALL DISTRIBUTION AND DETERMINATION OF FLUORINE [Afih!&st, VOl. 93 transferring the rinsings from tube to tube. After allowing them to drain for a few minutes, remove the remaining reagent from the tubes with a dropping pipette drawn out to a long capillary. 5. Extraction of the fluorochelate with hydroxylammonium chloride - isobutyl alcohol is convenient with an initial volume of 1.5 ml of solvent, followed by two volumes of 1 ml, the final volume being made up to 4.0 ml.Centrifuging between extractions is unnecessary, but the final washed and chilled extract needs to be centrifuged for a few moments to clarify it. 6. Originally it was suggested that the extract of the fluorochelate in hydroxylammonium chloride - isobutyl alcohol should be washed with water. It has since been found that a more efficient removal of excess of lanthanum chelate is achieved by washing the extract with 1 ml of the succinate buffer (pH 4*6), diluted twenty times with water. DISCUSSION Several modifications are suggested above, which are thought to improve the published method3 for the determination of microgram amounts of fluorine in biological materials. Of the problems associated with the determination of this element, that of contamination during ashing was found to be the most serious.The author has recently found that some German workers use a muffle furnace lined with stainless steel to avoid the difficulties encountered with conventional equipment. The degree of contamination was found to be progressively more serious with conventional apparatus at temperatures above 400" C, and with increasing time. Ashing for long periods at 400" C may cause as much contamination as ashing for 30 minutes at 600" C. In this laboratory, a Simon-Meuller crucible furnace, with a porcelain interior, was used successfully for many determinations but eventually caused contamination. Even hot-plates capable of reaching a surface temperature of 500" to 600" C were found to be unsuitable.It is possible that the insulating materials enclosing the elements could be the source of the fluoride contamination. The use of a small spirit burner, although unsophisticated, has undoubtedly overcome the problem, even for the difficult determination of total fluorine in soils involving fusion with potassium hydroxide. Temperatures in the lower half of the crucibles were found to vary between 410" and 440" C (mean 420" C). The temperature of the floor of the crucible would almost certainly be higher, possibly about 550" C. These measurements were made with a mercury thermometer calibrated to 550°C and, although they can be regarded as only approximate, they indicate that a temperature high enough for efficient ashing was achieved, and at the same time losses caused by undesirably high temperatures were avoided.Stabilising colloids have been used to advantage for many years in analytical chemistry. Recently Hall, Gray and Flynnl5 found gelatin to be effective in protecting the Titan yellow complex in the determination of magnesium in soil extracts, and Martin and Stephenl6 have re-examined gum ghatti in their work on the nephelometric determination of the nitrate ion. With the diffusion procedure for the separation of hydrofluoric acid, it was found necessary to grind samples to a very small particle size, and a wide variety of colloids was investigated for the preparation of stable suspensions. Poly(viny1 alcohol) and gelatin in these circum- stances would not hold up suspensions of sandy soils ; methylcellulose, carboxymethylcellulose and some of the natural gums, including gum ghatti, were more effective, but agar was easily the best for both soil and plant preparations. Triethanolamine was useful for plant material but presented difficulties during ashing.No trouble has been experienced in trans- ferring the suspensions by pipette, provided the concentration does not exceed 50mg of sample per ml of suspension; the optimum concentration for a stable suspension was 20mg per ml. Although several workers have successfully used other apparatus (including Perspex Conway-type diffusion units1' sealed with silicone grease) for the separation of the fluoride as hydrofluoric acid, the author has not found these alternatives satisfactory for the type of material mentioned above. A small polythene bottle sealed with a hard wax proved to be the simplest and most effective diffusion unit, but occasionally losses of hydrofluoric acid were measured when the original softer wax was used.The method for the spectrophotometric determination of the fluoride ion absorbed on to succinate-treated papers was devised for sub-microgram amount^.^ For larger amounts, when several micrograms of hydrofluoric acid may diffuse from an aliquot of the sample,July, 19681 COMPOUNDS I N BIOLOGICAL MATERIALS, INCLUDING SOILS 467 the absorbing paper may need to be extracted with a much larger volume of lanthanum - alizarin complexan reagent; 2 ml of this extract can then be used for the extraction of the fluorochelate.Alternatively, the sample can be suitably diluted with 0.1 per cent. agar and re-diff used. In the differentiation of organic from inorganic fluorine, the effects of silica in plant tissues and soils may confuse the results. Fluorosilicates form part of the fluorine in soils, and it is well established that silica is present in the roots, stems and leaves of many plants, although the amounts vary considerably. In their studies of moorland plants, Thomas and Trinderl8 found 0.09 per cent. of silica (SiO,) (on dry weight) in the blaeberry (Vacciaium myrtillus) and 6.64 per cent. in white bent (Nardus stricta). Remmert, Parks, Lawrence and McBurneylg found that silica seriously interfered with the determination of fluorine in plant specimens. They determined lower levels of fluorine in ashed grass than from direct distil- lation, and attributed the difference to occlusion by silica.In the present work, an analogous situation was experienced when the diffusible fluoride levels of some herbages were invariably higher than the apparent total fluorine, after ashing. However, when the ash of the material was fused with potassium hydroxide the total fluorine then correlated closely with the diffusible fluoride. In those tropical plants containing fluorinated carbon compounds (which are stable in the presence of 47 per cent. w/w perchloric acid), the assumption that the difference between the diffusible fluoride and the total fluorine, determined after ashing or fusion, represents only the organically combined fluorine is vitiated in those samples in which the amount and form of silica interferes with the total fluorine determination.It is notable, however, that Peters and Shorthouse,20 in their studies with Acacia georginae and other plants, did not experience interference by silicates in the deter- mination of fluorine and, in this laboratory, all of the fluorine of sodium fluorosilicate was quantitatively determined after diffusion with perchloric acid; the problem posed by silica is, therefore, somewhat complex. Not all of the difficulties that silica introduces into the analytical partition of fluorine in plants have been resolved, and work on this facet is still in progress. The superiority of potassium hydroxide over the other alkalis used to degrade the minerals of soil is clearly shown in Table 11.Amounts of potassium hydroxide larger than 0.5 g, with prolonged heating under the conditions described, did not increase the fluorine values, so it is probable that with the good replication and recovery of added fluoride the figures given are reliable. Shell and Craig21 with much larger amounts of sample, used a mixture of zinc oxide and sodium carbonate a t 1100" C to degrade fluorosilicates in minerals. In the microgram range, serious loss of fluorine could be expected at such a high temperature. Since this paper was first submitted for publication, Evans and Sergeant22 have described the determination of fluorine in soils and minerals, after fusion of 200mg of sample with sodium carbonate. Dr. Evans kindly provided the author with three of his analysed minerals, which have now been examined for fluorine by the method described above.The results are shown in Table 111, and it is evident that the two methods give similar values. TABLE I11 FLUORINE VALUES OF MINERALS Fluorine found, p.p.m. r 3 Evans and Sergeant's Mineral analysed method Present method Tonalite T-1 . . .. .. .. 450, 460 469, 479 Biotitic green schist . . .. .. 700 to 760 708, 725 Porphyritic basalt . . .. .. 1200 1180, 1220 I am grateful to Professor J. H. Burnett and Professor S. L. Ranson of the Department of Botany, University of Newcastle upon Tyne, for kindly providing the facilities for much of this work. My thanks are also given to Mr. N. Trinder, Regional Nutrition Chemist, National Advisory Service, Newcastle upon Tyne, for his help in the preparation of this paper.468 HALL 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. REFERENCES Singer, L., and Armstrong, W. D., Analyt. Chem., 1954, 26, 904. Hall, R. J., Analyst, 1960, 85, 660. Belcher, R., Leonard, M. A., and West, T. S., J. Chem. Soc., 1958, 2390. Leonard, M. A., and West, T. S., Ibid., 1960, 4477. Marais, J. S. C., Onderstefioort. J . Vet. Sci. Anim. Ind., 1944, 20, 67. Murray, L. R., McConnell, J. D., and Whittem, J. H., Aust. J . Sci., 1961, 24, 41. McEwan, T., Nature, 1964, 202, 827. Peters, R. A., Hall, R. J., Ward, P. F. V., and Sheppard, N., Biochem. J., 1960, 77, 17. Peters, R. A., and Hall, R. J., Nature, 1960, 187, 573. Bowen, H. J. M., in Shallis, P. W., Editor, “Proceedings of the S.A.C. Conference, Nottingham, Hall, R. J.. Proc. SOC. Analyt. Chem., 1966, 3, 162. Hardin, L. J., MacIntire, W. H., and Tubb, M. E., J . Ass. 08. Agric. Chem., 1954, 37, 552. Hall, R. J., Gray, G. A., and Flynn, L. R., Analyst, 1966, 91, 102. Martin, J. M., and Stephen, W. I., Analytica Chim. Acta, 1967, 39, 62s. Frhre, F. J., Analyt. Chem., 1961, 33, 644. Thomas, B., and Trinder, N., Emfi. J. Ex$. Agric., 1947, 15, 237. Remmert, L. F., Parks, T. D., Lawrence, A. M., and McBurney, E. H., Analyt. Chem., 1953, Peters, R. A., and Shorthouse, M., Nature, 1967, 216, 80. Shell, H. R., and Craig, R. L., Ana’lyt. Chem., 1954, 26, 996. Evans, W. H., and Sergeant, G. A., Analyst, 1967, 92, 690. -, Ibid., 1963, 88, 76. -, Ibid., 1963, 88, 899. 1965,” W. Heffer & Sons Ltd., Cambridge, 1965, p. 26. 25, 450. Received December lst, 1967

ISSN:0003-2654    

DOI:10.1039/AN9689300461

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

AvzaZyst, July, 1968, Vol. 93,++, 469-474 469 Spectrophotometric Determination of Micro Amounts of Aluminium in Plant Material with 8-Hydroxyquinoline BY C. R. FRINK AND D. E. PEASLEE* (The Connecticut Agricultural Experiment Station, New Haven, Connecticut) The 8-hydroxyquinoline method, previously found to be more satisfactory than the aluminon method for the analysis of soil extracts, has been examined for its suitability for determining aluminium in plant tissues. An initial extraction with chloroform of the diethyldithiocarbamate complexes of the large amounts of heavy metals found in plant material has been devised. The resulting method was tested on synthetic solutions and compared with emission-spectrochemical procedures in the analysis of plant materials. The lower limit for reliable determination by the proposed method corresponds to 4 p.p.m.of aluminium in the dried plant tissue. At this lower limit, the following interfering elements in the tissue at the percentage con- centrations indicated are tolerated in the method : copper, 0-005 ; zinc, 0-030 : iron, 0.030; manganese, 0.10; phosphorus, 0.20; and calcium, 4.0. For tissue containing 20 p.p.m. of aluminium, or more, at least five times these amounts are tolerated. THE determination of small amounts of aluminium in plant tissue in the presence of high concentrations of interfering ions presents a considerable analytical challenge. Recently, several methods have been proposed; two are based on the triammonium aurin tricarboxylate (aluminon) lake reaction,l g 2 while two others involve solvent extraction of the complex formed between aluminium and 8-hydro~yquinoline.~ p4 In our laboratory, aluminon methods have failed to yield reproducible standard curves, while the 8-hydroxyquinoline method has proved extremely reproducible.6 Further, for analyses of plant digests, one of the aluminon procedures1 requires a preliminary separation by elution through an ion-exchange column ; the other2 involves separation by precipitation with ammonia solution and centrifugation, followed by adjustment of sample acidity with a pH meter.For routine analyses, these procedures are time consuming and require the analyst’s attention for each individual sample. In addition, the concentrations of interfering ions tested2 were much lower than those observed in plant tissue in subsequent studies.1 Rubins and Hagstrom4 have described a sensitive and accurate method based on the fluorescence of the extracted aluminium 8-hydroxyquinolinate complex.In addition to a fluorimeter being required, the high concentrations of interfering ions observed in some plant tissue do not appear to be tolerated with their method. Further, for the initial ex- traction of iron it involves the use of bathophenanthroline, which is a rather expensive reagent unless iron is to be determined.4 Extraction of the aluminium 8-hydroxyquinolinate complex into chloroform was used by Middleto$ to determine aluminium in leaves of the rubber tree, but no precautions to remove interfering ions were described. It is clear from previous work5 that several ions likely to be present in plant digests could cause severe interference in the 8-hydroxyquinoline method.Thus, to provide a spectrophotometric procedure in which high concentrations of interfering ions would be tolerated, without the need for tedious precipitation or ion-exchange procedures, we undertook the investigations described below. The resulting procedure, which involves an initial extraction of the diethyldithiocarbamate complexes of heavy metals with chloro- form, permits spectrophotometric determination of aluminium in 18 samples in about 2 hours. 0 SAC and the authors. * Present address : Department of Agronomy, University of Kentucky, Lexington, Kentucky.470 FRINK AND PEASLEE SPECTROPHOTOMETRIC DETERMINATION OF MICRO [Analyst, Vol.93 For tissue containing as little as 4 p.p.m. of aluminium, the following elements, with their percentage concentrations in the tissue, are tolerated: copper, 0.005; zinc, 0.030; iron, 0.030; manganese, 0.10; phosphorus, 0.20; and calcium 4.0. These are at least 10 times the relative concentrations of interfering ions tested for other methods.294 REAGENTS- Concentrated hydrochloric acid, glacial acetic acid and concentrated ammonia solution were distilled in a glass still. As the resulting ammonia solution was about 10 N, it was not used in the concentrated buffer described below. Concentrated nitric, sulphuric and perchloric acids were not purified because their distillation is somewhat hazardous. Purifica- tion of the chloroform used was not found to be necessary.All aqueous reagent solutions were prepared with de-ionised distilled water. Bufer solution-Mix 275 ml of glacial acetic acid and 310 ml of concentrated ammonia solution, cool, and dilute with water to 500ml. The final pH should be adjusted to 6.2, if necessary. 8-Hydroxyquinoline solution-Dissolve 20 g of 8-hydroxyquinoline in 1 litre of chloroform and store in a dark glass bottle. This reagent is rather variable and some batches are highly coloured. We found the “Baker Analyzed’’ reagent to be satisfactory. Diethyldithiocarbamate solution-Dissolve 3 g of sodium diethyldithiocarbamate in 100 ml of water, filter through Whatman No. 41 paper, and store in the cold. Prepare freshly every few days. Thymol blue indicator-Dissolve 0.1 g of thymol blue in 10 ml of ethanol and dilute to 50 ml with water. Aluminium standards-Prepare a stock solution containing 50 pg of aluminium per ml in 0.1 N hydrochloric acid, either as previously de~cribed,~ or, as in the present study, from recrystallised aluminium chloride standardised independently by precipitation of aluminium 8-hydroxyquinolinate.Prepare a working standard containing 5 pg of aluminium per ml by appropriate dilution of the stock solution with 0.1 N hydrochloric acid. DIGESTION OF PLANT MATERIAL- Three different plant tissues were analysed : tomato tops, tobacco leaves and apple leaves. The materials were dried at 60” C in a forced-draught oven and ground in a Wiley mill to pass a 40-mesh sieve. Then, 1.0-g samples were treated with 5 ml of concentrated nitric acid and digested with 5 ml of a mixture of nitric, sulphuric and perchloric acids (10 + 1 + 3), following the procedure of Johnson and Ulrich.6 After digestion, the salts were dissolved by boiling with water,6 and the silica residue was washed once by centri- fugation with 30 to 40 ml of 6 N hydrochloric acid.The acid digest was then diluted to 100 ml with water. For tissue containing less than 8 p.p.m. of aluminium, the final volume should not be more than 50nil. DETERMINATION OF ALUMINIUM- Transfer, by pipette, an appropriate aliquot (up to 25ml) of the plant digest or the standard solution, containing 2 to 20pg of aluminium, into a 120-ml Squibb pear-shaped separating funnel calibrated at about 50 ml. Add 1 ml of N acetic acid, 2 to 4 drops of thymol blue indicator, and neutralise carefully with 6 N ammonia solution until the red colour disappears.The resulting solution should have a pH of between 5.1 and 5-2. Add 2 ml of the diethyldithio- carbamate solution, and rapidly make three consecutive extractions, each with 5-ml portions of chloroform, shaking for 5 minutes each time and discarding the chloroform phase. Details of the extraction method have been previously de~cribed.~ After the third extraction, allow the solution to stand for 15 minutes to decompose any remaining diethyldithiocarbamate. Add 5.0 ml of the 8-hydroxyquinoline solution in chloroform, and extract for 5 minutes. Filter the chloroform phase through a cotton pledget into a 1-cm cell and measure the absorbance at 385 mp. The extracted chloroform phase from the reagent blank should be used as the reference solution to minimise the effect of an absorption peak at 372 mp, as discussed below. Through- out the procedure care must be exercised to prevent contamination of the glassware, and also to avoid losses of aluminium by ads~rption.~ EXPERIMENTAL Add 5.0 ml of buffer solution, dilute to 50 ml with water, and mix well.July, 19681 AMOUNTS OF ALUMINIUM IN PLANT MATERIAL WITH 8-HYDROXYQUINOLINE 471 EMISSION-SPECTROCHEMICAL ANALYSIS- Plant materials were also analysed in two independent laboratories by emission-spectro- chemical procedures.The methods used by laboratory No. 1 have been previously described.' In laboratory No. 2, the samples were dry ashed in quartz crucibles and dehydrated with concentrated hydrochloric acid.The residue was extracted with N hydrochloric acid con- taining 0.5 per cent. w/v of lithium as a radiation buffer, and 0.02 per cent. w/v of nickel as an internal standard. Analyses were performed by a rotating-disc solution technique, with parameters described by Baker and Greweling.8 DEVELOPMENT OF METHOD The larger amounts of copper, zinc, iron and manganese found in plant materials require extensive modifications of procedures that have been developed for the determination of aluminium in soil extracts.6 Complexing agents, which either prevent extraction of these metals or permit their extraction before the extraction of aluminium, have been used. We sought a single agent that would extract large amounts of all of the interfering ions and tested several, including di t hizone, 8- h y dr ox y quinaldine and diet h yldi t hiocarb amat e , with chloroform or carbon tetrachloride as solvents, and adjusting the pH to various levels.The most satisfactory combination appeared to be extraction of the diethyldithiocarbamate complexes with chloroform at pH 6, but, for the reasons described below, extraction at pH 5 was found to be preferable. Extraction of the diethyldithiocarbamate complexes is usually accomplished in alkaline solution but, as magnesium is extracted from alkaline solution by 8-hydroxyquinoline, it must be acidified before extraction of aluminium. This latter procedure gave low recoveries of aluminium, apparently because of the precipitation of aluminium hydroxide, which failed to dissolve on acidification.9 Hence, extraction of the diethyldithio- carbamate complexes from acidic solutions was required.Tests on aluminium standards, however, indicated that the extraction of aluminium was still incomplete after extraction of the diethyldithiocarbamate complexes with chloro- form at pH 6. Aluminium was not extracted by diethyldithiocarbamate, contrary to the suggestion of Goldstein, Manning and Menis,lo because a second extraction with 8-hydroxy- quinoline removed the remaining aluminium from the aqueous phase. Further tests estab- lished that diethyldithiocarbamate was not a factor; merely by shaking the aqueous phase with either chloroform or carbon tetrachloride before extraction of aluminium 8-hydroxy- quinolinate in this method, or that of Frink and Peech,s low recoveries of aluminium were caused.Lowering of the pH gave higher recoverieslo; similarly, an increase in the acetate concentration at pH 6 gave higher recoveries. No ready explanation of this phenomenon is apparent. Okura, Goto and Yotuyanagill reported that only monomeric aluminium ions are extracted by 8-hydroxyquinoline. However, as these solutions can be shown to be supersaturated with respect to crystalline aluminium hydroxide (gibbsite) at pH 6, it seems likely that by shaking such solutions with chloroform or carbon tetrachloride the precipitation of the hydroxide is initiated or promoted. Further studies were required of this modified method at pH 5 in the presence of the concentrated acetate buffer. Despite the relatively short half-life of diethyldithiocarbamate in acidic solution^,^ we found that the heavy metals could be successfully extracted at pH 5 : the time of contact of diethyldithiocarbamate with the aqueous phase, however, should be kept to a minimum.In addition, at pH 5, considerable amounts of acetate enter the chloro- form phase, thus causing a change in the dissociation of 8-hydroxyquinoline, and creating an absorbance peak at 372rnp.12 The effect of this peak is to increase considerably the absorbance of the chloroform phase extracted from the reagent blank. Therefore, pH and acetate concentration must be carefully controlled. To avoid the tedious adjustment of acidity with a pH meter, which many procedures require at this point, several indicator and buffer combinations were tested.We found that the acidity could be conveniently and reliably adjusted to between pH 5.1 and 5.2 by the recommended procedure. The resulting yellow colour of the indicator at this pH does not interfere because it is removed by the initial extraction with chloroform. Other procedural details, such as time of shaking, the drying of the chloroform phase and stability of the aluminium 8-hydroxyquinolinate complex were previously investigateds; the lowering of the pH from 6 to 5 for extraction should not affect these findings and, therefore, will not be discussed here.472 FRINK AND PEASLEE : SPECTROPHOTOMETRIC DETERMINATION OF MICRO [Analyst, Vol. 93 Several interfering ions were tested, both singly and in various combinations, as shown in Table I. The amounts chosen represent the upper limits of these elements likely to be found in 1 g of plant material grown in acidic soils.As the aliquot necessary for the deter- mination of aluminium at concentrations in the tissue of 20 p.p.m., or more, represents only 0.1 g of plant material, it is obvious that, in most instances, ten times the expected amounts of the individual interfering ions can be tolerated with this method. In the event of iron and manganese interference, the tolerance is about five times the anticipated amount. The synthetic plant digest (Table I) contains five times the expected total amount of all interfering ions, and in no instance was the amount of aluminium recovered significantly different from that taken. In addition, recovery tests were made with 2 and 4-ml aliquots of actual plant digests from five different samples.An analysis of variance showed no significant differences between aliquot sizes, thus giving no evidence for the presence of negative errors. RESULTS AND DISCUSSION TABLE I DETERMINATION OF ALUMINIUM BY THE PROPOSED METHOD IN THE PRESENCE OF VARIOUS INTERFERING IONS Amount of aluminium taken, pg Interfering ion added, pg Copper Zinc Iron - I - - - 50 - 300 - 150 300 - - - - - - - - - - 60 300 150 50 300 300 - - - Synthetic plant digest* Manganese Phosphorus Calcium - - - - - 600 1000 500 1000 - 2000 - - - 40,000 - 2000 40,000 - - - - - - 6 10 26 Aluminium found, p g - 0.0 10.0 20-2 0.2 10.5 20.7 0.2 10.3 21.5 0.4 10.0 19.9 2.0 11.6 21.3 0.6 10.4 20.2 1.2 10.3 22.0 0-8 10-8 20.2 3.5 13-8 23.5 0.0 9-8 19.9 0-2 8.7 20.6 0.2 9.8 19.7 0.4 10.1 20.0 * Contains one half of the maximum amounts of each of the interferences tested singly above.In general, the interferences observed were in agreement with those previously reported.9 Copper, iron and manganese are all extracted as the 8-hydroxyquinolinate complexes and, if not removed by the proposed diethyldithiocarbamate extraction, will lead to apparently high results. Although Rubins and Hagstrom4 cite previous work that indicates that zinc 8-hydroxyquinolinate is not extracted, we found that zinc forms a white precipitate in the aqueous phase, which subsequently dissolves in the chloroform phase and causes apparently high results. As Rubins and Hagstrom4 found that zinc did not interfere in their procedure, we assume that zinc 8-hydroxyquinolinate does not fluoresce.As previously reported,6 both calcium and phosphorus (as orthophosphate) may lead to apparently low results, presumably because of the formation of insoluble aluminium phosphates in the one instance and of a calcium 8-hydroxyquinolinate complex, insoluble in chloroform, in the other. Magnesium was previously reported6 to interfere in a similar manner; however, the interference was less severe than with calcium. As the amounts of magnesium in plant digests are generally less than the amounts of calcium, this source of interference was not investigated further. From these tests, we can conclude that the proposed method should be free from inter- ferences. However, we also wished to test the method in the actual analysis of plant material.Because published proceduresl~2s3s4 have lower tolerances for interfering ions, or lower sensi- tivity, or both, it seemed of little consequence to use these methods as a basis for comparison. Therefore, we chose emission-spectrochemical analysis as an independent analytical procedure. As this method may lack precision and accuracy for tissue containing low concentrations of aluminium, we selected tissue containing higher amounts, when both spectrochemical and spectrophotometric methods could be used.July, 19681 AMOUNTS OF ALUMINIUM IN PLANT MATERIAL WITH 8-HYDROXYQUINOLINE 473 Results of the comparative analyses of 18 samples are shown in Table 11, and indicate considerable variability between the two spectrochemical methods, as might be expected.The results obtained by laboratory No. 1 are generally lower than those obtained by the proposed method at low concentrations of aluminium in the tissue, and the same or higher at high concentrations. The results obtained by laboratory No. 2 are generally the reverse. Some of these discrepancies are undoubtedly caused by different methods of extracting aluminium from the plant ash. However, the agreement between the proposed method and the average spectrochemical analyses is considered quite good ; indeed, the correlation coefficient between the two is 0,986. As the differences shown in Table I1 reflect sampling and ashing errors, as well as analytical errors, it seems unlikely that the results suggest any consistent bias in aluminium analyses by the proposed procedure.The precision of the proposed method was tested on standard solutions and plant digests. The mean coefficient of variation was 5.44 per cent. for six replicate analyses of five different standard solutions containing from 0 to 20pg of aluminium. This is higher than the co- efficient of variation of 2-89 per cent. observed for thirty similar analyses conducted during initial studies of the method when aluminium was extracted at pH 6. The greater variability at pH 5 apparently arises from the increased absorbance caused by the larger amounts of acetate in the chloroform phase, as previously discussed. Duplicate analyses were made of the digests of the 18 samples shown in Table 11. An analysis of variance of the results for each kind of tissue gave a mean coefficient of variation of 6-63 per cent., which is only slightly larger than that observed for standard solutions.It should be emphasised that these estimates of the precision of the proposed method were not obtained from special replicate analyses run side by side, but rather from analyses run over a considerable period of time under ordinary laboratory conditions. Thus, they are somewhat larger than those frequently reported, but reflect more accurately the reliability of the method in routine analysis. TABLE I1 DETERMINATION OF ALUMINIUM IN PLANT TISSUE BY THE PROPOSED METHOD AND BY EMISSION-SPECTROCHEMICAL METHODS Aluminium found, p.p.m. Sample Tomato tops 1 2 3 4 5 6 7 8 Tobacco leaves 1 2 3 4 6 Apple leaves 1 2 3 4 5 * ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. I Proposed method 67 68 68 87 88 90 100 114 156 162 217 228 314 249 289 448 546 562 Emission-spectrochemical method Laboiatory 1 40 30 40 60 50 60 60 80 102 137 172 195 280 230 320 440 610 550 Laboratory 2 79 79 74 84 87 100 124 124 157 176 209 221 258 200 264 44 1 546 500 Meh 60 54 57 72 68 80 92 102 130 156 190 208 269 215 292 440 578 525 CONCLUSIONS A survey of existing spectrophotometric methods for the determination of aluminium in plant material indicated that none was entirely satisfactory for tissue containing small amounts of aluminium and large amounts of interfering ions. The 8-hydroxyquinoline method, previously found to be more reliable than the aluminon method for the analysis of soil extracts, was therefore chosen for further study. An initial extraction with chloroform of the diethyldithiocarbamate complexes of the large amounts of heavy metals found in plant474 FRINK AND PEASLEE material was devised.The resulting method was tested on synthetic solutions and then compared with emission-spectrochemical procedures. These tests showed that the proposed method will enable aluminium to be determined in the presence of a &fold excess of the interfering ions expected in plant digests, has good precision and high sensitivity, and is particularly suitable for plant material containing less than 100 p.p.m. of aluminium. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. REFERENCES Page, A. L., and Bingham, F. T., Soil Sci. Soc. Amer. Proc., 1962, 26, 351. Yuan, T. L., and Fiskell, J. G. A., J . Agric. Fd Chem., 1959, 7 , 115. Middleton, K. R., Analyst, 1964, 89, 421. Rubins, E. J., and Hagstrom, C. R., J . Agric. Fd Chem., 1959, 7 , 722. Frink, C. R., and Peech, M., Soil Sci., 1962, 93, 317. Johnson, C. M., and Ulrich, A., Calif. Agric. Exp. Sta. Bull., 1959, 766, 26. Mathis, W. T., Analyt. Chem., 1953, 25, 943. Baker, J. H., and Greweling, T., J . Agric. Fd Chem., 1967, 15, 340. Sandell, E. B., “Colorimetric Determination of Traces of Metals,” Third Edition, Interscience Goldstein, G., Manning, D. L., and Menis, O., Talanta. 1959, 2, 52. Okura, T., Goto, K., and Yotuyanagi, T., Analyt. Chem., 1962, 34, 581. Margerum, D. W., Sprain, W., and Banks, C. V., Ibid., 1953, 25, 249. Publishers, New York and London, 1959, p. 219. Received December 18th, 1967

ISSN:0003-2654    

DOI:10.1039/AN9689300469

出版商:RSC    

年代:1968

数据来源: RSC

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Analyst, July, 1968, Vol. 93, fi. 475 475 Direct Determination of Manganese in Soil Extracts by Atomic-absorption Spectroscopy BY M. NADIRSHAW AND A. H. CORNFIELD (Chemistry Department, Imperial College of Science and Technology, London, S. W.7) SEVERAL extracting reagents are available for assessing either particular fractions of man- ganese in soils or the potential availability of soil manganese to plant^.^.^,^ The traditional colorimetric methods used for determining manganese in such extracts require a tedious preliminary treatment to eliminate the effects of acids or salts, and to destroy organic matter extracted from the soil as well as that present in some of the extracts. It appeared that atomic-absorption spectroscopy would be a suitable method for determining manganese directly in these extracts, as the temperature of the flame would be high enough to destroy organic matter.A study was therefore made, in which direct atomic-absorption spectroscopy was compared with a chemical method for extracts of several soils. The extracting reagents tested were- (i) N ammonium acetate (pH 7.0),l which extracts exchangeable and water-soluble manganese( 11) ; (ii) N ammonium acetate (pH 7.0) containing 0.2 per cent. of hydroquinone,2 which extracts “active” manganese, probably manganese(III), in addition to exchangeable and water-soluble manganese(II), and has been shown to be a better indicator of the manganese-supplying power of soils to plants than reagent (2); (iii) Morgan’s reagent3 (0.5 N acetic acid - 0.75 N sodium acetate, pH 44), which has been widely used for assessing the status of major and trace elements in soils; and (iv) 0.5 N acetic acid, which was tested as a possible replacement of Morgan’s reagent, as the latter tended to clog the burner slit by deposition of sodium carbonate after about 20 samples had been aspirated.Five soils with textures ranging from sand to clay, and at pH 4.8 to 7.0, were extracted (after air-drying and grinding to pass a 2-mm sieve) by shaking 25-g portions of soil with 100ml of each extracting reagent for 15 minutes and then filtering through a Whatman No. 1 filter-paper, with dry apparatus. The filtrates were aspirated directly into a Unicam SP90 atomic-absorption spectrophotometer, with a manganese hollow-cathode lamp and the following operating conditions: wavelength 279.5 nm, lamp current 12 mA, slit width 0.1 mm, burner height 1 cm, and 5 litres of air and 1.2 litres of acetylene per minute.Standard graphs for each extractant were prepared to cover a narrow range (high gain) and a broader range (lower gain) of manganese concentrations. When a particular extract contained a high concentration of manganese it was diluted with the appropriate extractant, so that the determination could be made at maximum sensitivity to reduce the effects of possible interfering factors. The colorimetric periodate oxidation method, in the presence of orthophosphoric acid following evaporation of a suitable aliquot of each extract and destruction of organic matter with aqua regia, was used as the chemical method for comparison. For each extractant the results obtained by direct atomic absorption (preceded only by dilution when necessary) agreed to within 4 parts per 100, or better, with those obtained by the chemical method. The coefficient of variation ranged from 0.5 to 6.7 per cent. in the atomic-absorption method and from 1.0 to 6.7 per cent. in the colorimetric method. In addition, recovery tests were made of known amounts of manganese added to each type of extract of each soil. The average recoveries ranged from 97.7 to 99.0 per cent. The authors thank the Agricultural Research Council for the loan of a Unicam SP90 atomic-absorption spectrophotometer. REFERENCES 1. 2 . 3. Sclioellenberger, C. J., and Simon, R. H., Soil Sci., 1945, 59, 13. Leeper, G. W., Ibid., 1947, 63, 79. Lunt, H. A., Swanson, C. L. W., and Jacobson, H. G. M., Connecticut Agricultural Experiment Received April 14th, 1967 Amended ApriE 24112, 1968 Station, 1950, Bulletin 541. 0 SAC and the authors.

ISSN:0003-2654    

DOI:10.1039/AN9689300475

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

476 r I 1 I I I I I I I I Analyst, July, 1968, Vol. 93, $9. 476477 Analytical Methods Committee Nitrogen Factor for Barley REPORT PREPARED BY THE MEAT PRODUCTS SUB-COMMITTEE THE Analytical Methods Committee has received the following Report from its Meat Products Sub-committee. The Report has been approved by the Analytical Methods Committee and its publication has been authorised by the Council. REPORT The Meat Products Sub-committee of the Analytical Methods Committee responsible for the preparation of this Report was constituted as follows: Dr. S. M. Herschdoerfer, (Chairman), Mr. S. Back, Mr. P. J. Cooper (resigned February, 1967), Mr. P. 0. Dennis. Mr. H. C. Hornsey, Dr. A. J. Kidney, Mr. T. McLachlan, Dr. R. A. Lawrie, Dr. A. McM. Taylor, Mr. G. Walley (appointed February, 1967), Mr.R. E. Weston (appointed February, 1967) and Mr. E. F. Williams, with Mr. P. W. Shallis as Secretary. In continuing its work on establishing nitrogen factors for use in the analysis of meat products, the Sub-committee has found it necessary also to establish correction factors to be applied when a meat product contains a relatively high proportion of a cereal filler. Most comminuted meat products manufactured in the United Kingdom contain a percentage of cereal filler. Sausages usually are made with some rusk, and the Sub-committee has twice reported on the nitrogen content of rusk.lp2 In the manufacture of blood puddings, barley is the usual filler added, and the Sub- committee has collected analytical results for the nitrogen contents of more than 1000 samples of pearl barley.The results of these analyses are shown in Fig. 1. Range (N, as % of No. of samples carbohydrate) Mean 500* 153* I 1-79 .80 1 492" - 1-81 18 I *49- I a93 I -67 1.41-1 *87 I -68 I .45- I -90 I .80 I .30--1*40 I *36 I a71 - I -79 I .98 I .69-2.2 I I -95 I -55-2.25 1 *93 - - *These results were obtained from commercial organisations and no figures for the ranges of results were available . 1.77 I I I I I I I I I I I 1.2 I *4 I .6 1.8 2.0 2.2 Nitrogen, % of carbohydrate Fig. 1. Nitrogen contents of barley expressed as a content of carbohydrate. Horizontal lines 0 SAC. represent the range of nitrogen contents, short vertical lines indicate the average values.NITROGEN FACTOR FOR BARLEY 477 RECOMMENDATION The Sub-committee recommends that 1.8 per cent. should be used as the correction for the nitrogen content of pearl barley. REFERENCES 1. 2. - , Ibid., 1965, 90, 579. Analytical Methods Committee, Analyst, 1961, 86, 560.

ISSN:0003-2654    

DOI:10.1039/AN9689300476

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

478 - 2.64 3.27 3.32 b 3.22, 3.01 3.09 3.34 i Analyst, July, 1968, Vol. 93, $fi. 478479 I I I I I I l I I I I I I 1 1 1 1 2.4 2.6 2.8 3.0 3.2 3-4 Analytical Methods Committee REPORT PREPARED BY THE MEAT PRODUCTS SUB-COMMITTEE Nitrogen Factor for Blood THE Analytical Methods Committee has received the following Report from its Meat Products Sub-committee. The Report has been approved by the Analytical Methods Committee and its publication has been authorised by the Council. REPORT The Meat Products Sub-committee of the Analytical Methods Committee responsible for the preparation of this Report was constituted as follows: Dr. S. M. Herschdoerfer (Chairman), Mr. S. Back, Mr. P. J. Cooper (resigned February, 1967), Mr. P. 0. Dennis, Mr. H. C. Hornsey, Dr. A. J. Kidney, Mr. T.McLachlan, Dr. R. A. Lawrie, Dr. A. McM. Taylor, Mr. G. Walley (appointed February, 1967), Mr. R. E. Weston (appointed February, 1967) and Mr. E. F. Williams, with Mr. P. W. Shallis as Secretary. The Sub-committee, in continuing its investigations on the nitrogen contents of various types of meat,l to has examined a number of samples of blood, which is used in the manu- facture of blood puddings, and the results are shown in Fig. 1. Labor- No.of atory samples A 2 PIG - Samples from individual pigs taken immediately after slaughter over several days, including both morning and afternoon slaughter B 6 Samples from individual pigs taken immediately after slaughter on a single morning from pigs that had been rested overnight B 6 Samples from individual pigs B 5 Samples from individual pigs taken immediately after slaughter C 32 Corn posite Sam ples rep resenting blood from about 50 pigs D 4 Range 2.63- 2.65 3.09- 3.48 3.16- 3 a47 2.74- 3-17 2.32- 3.44 3.27- 3 *40 Nitrogen, % of whole blood Fig.1. Nitrogen contents of pigs’ blood. Horizontal lines represent the range of nitrogen contents, short vertical lines indicate the average values. The analyses were carried out on pigs’ blood, which is the usual raw material for blood It is interesting to note the wide range of the figures quoted by laboratory C, indicating puddings. the degree of inaccuracy necessarily attached to an analysis of black puddings. RECOMMENDATION The Sub-committee recommends an average factor of 3.2 for determining the blood 0 SAC. content of products manufactured from pigs’ blood.NITROGEN FACTOR FOR BLOOD 479 ACKNOWLEDGMENT The Sub-committee thanks those organisations listed below for their assistance- C. & T. Harris (Calne) Ltd. J. Sainsbury Ltd. T. Wall & Sons (Meat & Handy Foods) Ltd. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. Analytical Methods Committee, Analyst, 1961, 86, 557. - , Ibid., 1963, 88, 422. - , Ibid., 1963, 88, 683. - , Ibid., 1964, 89, 630. - , Ibid., 1965, 90, 256. - , Ibid., 1965, 90, 581. - , Ibid., 1966, 91, 538. - , Ibid., 1967, 92, 326.

ISSN:0003-2654    

DOI:10.1039/AN9689300478

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

480 Analyst, July, 1968, Vol. 93, p p . 480-484 Book Reviews KIRK-OTHMER ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY. VOLUME 13. Second Edition. MANGANESE COMPOUNDS TO NITROPHENOLS. Edited by HERMAN F. MARK, JOHN J. MCKETTA, jun., DONALD F. OTHMER and ANTHONY STANDEN. Pp. xiv + 894. New York, London and Sydney: Interscience Publishers, a division of John Wiley & Sons Inc. 1967. Price A23 10s.; price per volume for subscribers to the complete set of 18 volumes A17 10s. This volume is Number 13 of the series, which means it starts the last third of the complete issue (see also Analyst, 1963, 88, 899, et seq.). Metallic elements, which are the subject of what now appears to be a standard style of monograph, are manganese, mercury, molybdenum, nickel and niobium. There is a short but useful section on the analysis of niobium ores and compounds that indicates some of the difficulties involved in this type of work.This applies particularly in the presence of tantalum. The introduction of liquid - liquid and ion-exchange techniques has proved very helpful in this connection, but in many instances it is necessary to stop with a mixture of niobium and tantalum oxides and to determine the relative amounts of these from standards by the use of emission or X-ray spectrography. The monographs on the other four metals are of interest, but they break no new ground from an analytical point of view. Food analysts will be specially interested in the monographs on Margarine, Meat and Meat Products, Milk and Milk Products and Molasses. As usual, they reflect American quality standards; for margarine there is a full section on legal aspects.These could be useful for reference purposes to workers in this country. The meat monograph comprises 17 pages, and its scope is wide, ranging through structure and composition, production, processing and by-products to the uses of animal fats, such as lard, shortening and oleo. Milk also comprises an important monograph (of 71 pages), and it also covers milk products, such as cheese, ice cream, dried milk and milk by-products. The treatment is mainly from a manufacturing point of view, and the short section on instant-dried whole milk will be of particular interest in this country, especially as grading requirements for different types of such milk are tabulated. Milk by-products dealt with include lactose, casein, and even alcohol and yeast produced by fermentation, as well as vitamins and whey vinegar.Strangely, there is no mention of the important use of casein in paper coating, although other uses are mentioned. Nor does the monograph on molasses mention their use in admixture with ground bagasse pith as a cattle food, although, here again, other uses of molasses of this nature are mentioned. In fairness it should be added that the coverage of this work is so very comprehensive that there is a tendency for the reviewer to seize on omissions and give them prominence perhaps beyond their real importance, merely because the over-all standard is so high. Under the heading of what may be described as operational techniques, there are several interesting monographs, including Mass Spectrometry, Mechanical Testing, Metal Surface Treat- ments, Microencapsulation, Microscopy-Chemical, and Mixing and Blending. The monograph on microencapsulation (21 pages) deserves to be singled out for special mention because this is a highly technical and topical subject about which relatively little is known.The fact that so much has been printed on a subject so thick with trade secrets may be regarded as something of a “scoop” for this encyclopedia. The applications of encapsulation are much wider than are generally realised. Examples are the production of non-tacky adhesives, an apparent contradiction in terms, but of obvious significance when referring to the adhesive before use; improved forms of agricultural chemicals; food products, for instance, the encapsulation of flavour oils to allow them to be handled as a dry powder; the production of non-carbon copying papers; and detergents, paints, pharmaceuticals, fuels and rubber chemicals.The section on Microchemistry in the same category is relatively brief, namely 9 pages, $Zus 114 references; it will certainly be useful to the general reader, but analysts are unlikely to learn very much that is new. Much the same applies to the monograph on chemical microscopy, although there is an interesting section on contemporary developments. This includes the use of ultraviolet radiation to obtain contrast when a specimen contains a group that absorbs strongly at some determined wavelength. Fluorescence microscopy is now a well accepted technique, and dispersion staining is gaining acceptance in this type of work as a method of recognising particulate substances from the colour resulting from the difference between the dispersion of refractive index of a solid specimen and that of a reference liquid.A recent useful development in this field, in which the Becke Line is used to determine the refractive index of a crystal in aBOOK REVIEWS 481 similarly refracting medium is, however, not mentioned. Also in this category there is a monograph on Microorganisms (34 pages) that describes the nature and properties of the organisms under their various headings, namely, viruses, bacteria, fungi, algae and protozoa. Structural details are dealt with, and also cultivation and special culture techniques, but microbiological analysis is not covered; there are four pages of references.What may be described as the organic chemistry monographs include the Methacrylic Com- pounds, with their well known industrial applications, Naphthalene and its Derivatives and asso- ciated Naphthenic Acids , Nitration, and nitro-compounds including Nitroparaffins and Nitrophenols. The naphthenic acids are a relatively restricted class of products that is rapidly assuming increasing importance. In 1965, over 24 million pounds were produced in the U.S.A. alone. The principal uses are in lubricants and dryers, as industrial catalysts for the oxidation of hydro- carbons, as preservatives for wooden fabrics, in rust inhibitors and in emulsifiers. Finally, there is the category of what the reviewer has come to regard as fringe and often unexpected subjects, which in the present volume include Marketing and Marketing Research, Matches and Micas.The two pages on marketing have, of course, no analytical implications, but the treatment used will certainly appeal to scientists as a matter of general interest, if only because of its method of approach. Apparently, product life cycles can be reduced to mathematical expression in terms of charts showing cost - risk - quality and price - volume - profit relationships. This, it seems, leads to the conception of “Driving Force,” which answers the question why a particular product should be bought, and this also can be expressed mathematically and analysed statistically. Price - volume exclusion charts may also appeal to those with an analytical turn of mind, as they deduce what can be sold above a certain volume unless the price is below a certain figure.The more mundane subject of matches is dealt with shortly in some 7 pages, but here again these contain information that seldom gets into print, and the formulations given and comments on toxicity and safety are well worth noting for reference purposes. It is again apparent that the usefulness and interest of this series, restricted perhaps in some instances, is well maintained in this latest volume. JULIUS GRANT MODERN CEREAL CHEMISTRY. By D. W. KENT-JONES, Ph.D., B.Sc., F.R.I.C., and A. J. AMOS, O.B.E., Ph.D., B.Sc., F.R.I.C. Sixth Edition. Pp. x + 730. London: Food Trade Press Ltd. 1967.Price 190s. No textbook on cereal chemistry is better known the world over than that of the authors. The new edition has been prepared with the same care as its five predecessors. The printing in Brightype litho is admirably clear, although type sizes appear to vary somewhat in the 730 pages. The emphasis of the book is on wheaten flour, its milling, treatment, testing, baking into bread, cake and biscuits and uses for special purposes, including brewing and breakfast foods. Despite this emphasis, however, there is to be found valuable and up-to-date information on Barley, which has a chapter to itself contributed by the late Mr. H. M. A. Cherry Downes and Dr. A. Macey, together with a further chapter on Rye, Oats, Maize, Rice and the Potato. Soya is included in this chapter because of its utility in improving the protein value of cereals, and the authors are fully up to date in referring to its recent use in foods specially designed for calorie- controlled diets.Indeed, being up to date is clearly something of which the authors can be proud, for some of their references are to within months of the publication of the book, yet they seem not to have been hastily included but carefully considered, even although the value of the Brabender Do-corder might seem to some to have been scantily dismissed. In the chapter on Animal Feedingstuffs the text was again up to date in the inclusion of a short section on the Aflatoxins, and their detection in feedstuffs is well described in the latter part of the book dealing with general analytical procedures.It was a little disappointing not to see the obvious connection made with mycotoxins generally when Aspergillus flavus, the causative organism of aflatoxin, was so frequently mentioned in the chapter on the fungal microflora of cereals and cereal products. Minor criticisms of this nature should, however, in no way detract from the general excellence of the new edition, including the Index. There is a wealth of references to original research work in every aspect of cereal science and technology and, although the price has risen to nine pounds ten shillings, no serious worker in the field should deny himself the information available by failing to purchase this new volume. If, as one suspects, Dr. Kent-Jones made the revision a retirement project, one can truly say to him and his co-author, Dr.Amos, posterity will be grateful. J. B. M. COPPOCKBOOK REVIEWS [Analyst, VOl. 93 482 METHODS IN GEOCHEMISTRY AND GEOPHYSICS. 7. ATOMIC ABSORPTION SPECTROMETRY IN GEOLOGY. By ERNEST E. ANGINO and GALE K. BILLINGS. Pp. x + 144. Amsterdam, London and New York: Elsevier Publishing Company. 1967. Price 70s. It is sometimes salutary for a chemist to look into the work of other scientists and tech- nologists in order to gain a fresh outlook on a familiar topic. Geochemists have long been con- cerned with analytical techniques, obviously taking a particularly applied interest. In this series of monographs the subjects include chromatography, X-ray emission and chemical analysis of, e.g., silicates. This new title is obviously topical, but whether the contents are deserving of merit is debatable. The approach is mainly experimental, following an elementary theoretical introduc- tion.Thus, the parts of the equipment are briefly reviewed and complete commercial instruments are listed. Interferences, general and specific, receive considerable attention but the treatment is not exhaustive. Part I1 of the book, 64 pages, is concerned with applications to water, ore, silicate, sediment, and isotope analyses ; generally, sufficient experimental details are gi ven for the reader to start the analyses, but it will be realised that in this approach not all elements that can be examined by atomic-absorption spectrometry will be included and references, which are liberally supplied, must be consulted for details.The treatment of data receives scant attention and more modem techniques are barely mentioned. The book may appeal to geochemists who feel safer with a book written by authors in the same subject, but chemists will find no advantage over books already available to them. A CONTRIBUTION TO THE ANALYTICAL CHEMISTRY OF SILICATE ROCKS: A SCHEME OF ANALYSIS FOR ELEVEN MAIN CONSTITUENTS BASED ON DECOMPOSITION BY HYDROFLUORIC ACID. By F. J. LANGMYHR and P. R. GRAFF. Pp. 128. Oslo: Universitetsforlaget. 1965. Basically, the booklet is a medium for publishing a method for the analysis of silicate rocks involving the use of hydrofluoric acid decomposition in preference to alkali fusion. As such it reveals a novel approach and contains a number of techniques worthy of serious consideration.The details of the method and discussion of difficulties and interferences are voluminous if not comprehensive; in fact, it may be thought that some of the matters raised are unlikely to be relevant in practice. The booklet is divided into five main sections, the first two dealing with criticisms of the traditional scheme of analysis, its early modifications and several newer “novel” schemes. The third section is a discussion of the use of hydrofluoric acid as an agent for decomposing silicate rocks, while the fourth and fifth cover details of the proposed scheme and a detailed discussion of its efficiency vis-d-vis other selected schemes, respectively. It is the first three sections that the reviewer, whose interest is centred on the analysis of ceramics, finds not altogether acceptable.The authors quote Chirnside ( J . SOG. Glass Technol., 1959, 43, ST) in the course of their dis- cussion as an argument against some of the “novel” schemes of analysis. In the same paper, Chirnside also says “I think it proper and necessary to point out-that the advocates of some of these newer schemes often unfairly compare and contrast their value with the classical tech- niques, not of today but of fifty years ago. They ignore, or seem to be completely unaware of, the modifications and improvements that have taken place in what might be broadly called ‘classical techniques’. . . .” The authors are guilty of the same error. In their criticism of con- ventional and “modified” conventional schemes they have not noted a whole range of papers published as a result of co-operative work by analysts in the glass, ceramic and steel industries.In particular, the work of the Society of Glass Technology Analysis Committee, which will be found in the society’s journal, and that of the British Ceramic Research Association and its co- operative committees, published in the Transactions of the British Ceramic Society, overcome many of the objections that the authors cite in justification of their rejection of the traditional approach. It is a great pity that the past few years have shown an increasing dichotomy of thought between the geological and the ceramic analyst, whose problems are essentially similar. In the section on the use of hydrofluoric acid as a means of decomposition, the authors make the positive claim that fluorine can be and is eliminated completely by sulphuric acid.In this connection one finds it regrettable to read “It is unfortunate that Hillebrand did not support his wide ranging decision with experimental data’’ in the paragraph immediately following a reference to unpublished results of the authors themselves-quoted to disprove Hillebrand. The finding is entirely contradictory to a considerable volume of experience by British ceramic analysts D. A. PANTONY Norges Geologiscke Undersokelse Number 230.July, 19681 BOOK REVIEWS 483 that sufficient traces of fluorine remain to interfere with the acourate determination of alumina, certainly by the EDTA method. Langmyhr has now published “evidence” (Analytica Chim.Acta, 1967, 39, 516) in which he shows that evaporation with sulphuric acid does eliminate fluorine, but without the presence of a sample. Although the authors appear to share Chirnside’s strictures on the quality of the techniques of separation, they are open to similar criticism, e.g., filtering an ammonia-group precipitate through a grade 3 sintered-glass Gooch crucible and then washing the precipitate four or five times with a total volume of wash liquor of 10 ml f 1 ml. This is surely not only unsatisfactory but impracticable. The authors themselves are unhappy about their alumina results obtained after this separation and Wanninen and Ringbom’s technique for the titration of alumina (Analytica Chim. Acta, 1955, 12, 308), and it would appear probable that the fault lies in the poor handling of the ammonia-group precipitate, or in the fact that fluorine is still present. A similsr method of determination, but removing the silica by dehydration and excluding any precipitation of the ammonia-group oxides (B.S.1902 : Parts 2A and 2B), gave a total range of 0.6 per cent. at the 88 per cent. level over eighteen determinations by nine laboratories, with a standard deviation of 0-17 per cent., as against the authors’ figures of about 0.4 per cent. standard deviation for ten results by one analyst. Further possible substantiation of fluoride retention may well exist in the total iron figures, which should be better than they are. The methods that the authors propose are worth study; they show a number of interesting points of technique.In addition, the booklet contains a wealth of information tucked away in the guise of discussion. It is a pity that the authors were not content to let the quality of their work speak for itself rather than entering a detailed discussion of the weaknesses of other methods. It is this approach that serves to demonstrate their failure to be aware of the very considerable progress that has been made in the field in the last few years and a regrettable bias against more traditional approaches. H. BENNETT THE FORMATION AND PROPERTIES OF PRECIPITATES. By ALAN G. WALTON. Pp. xii + 232. New York, London and Sydney: Interscience Publishers, a division of John Wiley & Sons Inc. 1967. Price 88s. In the preface to this book, Professor Walton states “.. . the formation and properties of precipitates should be regarded as interrelated phenomena which, when separated, are more or less intelligible but together form a very complicated picture. I t is only by examination of each piece that the entire picture can conceivably be integrated and understood as a whole.” The book certainly provides a well balanced and logically developed account of the present state of our knowledge, or ignorance, of the phenomenon of precipitation. Professor Walton is to be congratulated for presenting such an excellent survey, which should prove extremely valuable to those working in this area of chemical research. The opening chapters, dealing with nucleation and the kinetics of crystal growth, lay the foundations for the discussions in the succeeding chapters of co-precipitation, surface properties and morphology.Whenever possible, the presentation is quantitative, but mathematics is not allowed to dominate the treatment of the subject. When mathematics is used, the author interprets the physical significance and provides relevant experimental results. Reading is facilitated by the division of each chapter into several sections, and four of the chapters end with useful summaries. The final chapter, dealing with precipitation from complex precipitation systems, is con- tributed by Dr. Helga Fiiredi of the Ruder BoSkoviC Institute, Zagreb. Experimental methods are outlined and examples are given of the applications of graphical methods to the representation of complex systems. This treatment is, of course, somewhat empirical, and contrasts with the more fundamental approach of the remainder of the book.Nevertheless, this chapter is a useful review of published work, most of which has previously been available only in Croatian journals. A considerable quantity of experimental data is presented, and several indications are given of further lines along which fruitful research might be pursued. The importance of precipitation studies in diverse fields such as analytical and physical chemistry, physiology and geology is stressed. Each chapter ends with a formidable list of references, including papers as recent as 1966. The book is well indexed with separate author, subject, organic and inorganic compound indexes. It is well bound and printed, and appears, to the reviewer, to be virtually devoid of errors or misprints.The book is copiously illustrated with graphs, photographs and drawings. E. NEWWAN484 BOOK REVIEWS [Analyst, Vol. 93 ADVANCES IN ELECTROCHEMISTRY AND ELECTROCHEMICAL ENGINEERING. Edited by PAUL DELAHAY and CHARLES W. TOBIAS. Volume 6. ELECTROCHEMISTRY. Edited by PAUL DELAHAY. New York, London and Sydney: Interscience, Publishers, a division of John Wiley & Sons Inc. 1967. Price 155s. This, the sixth volume of an admirable series, is nearly 100 pages longer than any of its predecessors. However, quality has not suffered at the expense of quantity; all the articles are of the high standard we have come to expect, as well as covering subjects of vital interest to the modern electrochemist. Thus, the oxygen electrode and porous electrodes are essential features of the practical electrochemistry of fuel cells and electrosynthesis, while electrochemical methods provide an important method for the study of metal complexes; the structure of the electrical double layer must be understood in order to elucidate fully the mechanism of electrode reactions, and the study of such processes as insulators is an exciting new field that may yield practical results in the future.The extra length of the present volume is caused by the massive 200-page article by Barlow and Macdonald on the theory of inner layer structure, i.e., the structure of the region extending by one or two molecular diameters from the metal surface into the electrolyte.Much of this article consists of the detailed mathematical analysis of the consequences of a simple model, but although the model may be simple the mathematics is not. Most readers will be grateful that the sections on “qualitative discussion” and “discussion of results” bulk so large and include clear statements about the physical meaning of the models involved. Readers not concerned in the controversies will also welcome the leavening of lively remarks mainly about other theoretical approaches and the development of the subject. Recent reviews by Levine, Mingins and Bell, J . Electroanal. Chem., 1967, 13, 280, and by Hunvitz (in “Electrosorption,” edited by E. Gileadi, Plenum Press, New York, 1967) give other points of view on this subject. Hoare provides a comprehensive and balanced account of the oxygen electrode on noble metals.The 327 references indicate the great effort that has been devoted to solving this problem, which is so important for efficient electrochemical energy conversion. It is evident that no single mechanism for this reaction can be given and that all the factors governing the rate are not yet understood. Nevertheless, this review is a major step on the way to putting the many details together in a coherent picture. Koryta’s article on the electrochemical reactions of metal complexes is the shortest in this volume, but it is well packed with valuable information. He discusses the kinetics of direct dis- charge of metal complexes, as well as the effect of chemical reactions in the bulk of the solution. Adsorption and double-layer effects are illustrated largely with work from the Polarographic Institute in Prague where many of these ideas were developed. The treatment of porous and rough electrodes by de Levie should be required reading for anyone trying to interpret results obtained with solid electrodes, however smooth these are believed to be. This article in itself could justify the marriage of theoretical and applied electrochemistry to which this series is dedicated. The fact that Riemann studied the problem of current distribation in 1855 is a reminder that this marriage was consummated more faithfully in the early years of electrochemistry. In the final article Mehl and Hale suinmarise the present state of that unexpected newcomer to electrochemistry, “Insulator Electrode Reactions,” a promising offspring from solid-state physics. The rapid development of the electrochemical study of insulators is mainly attributable to the work done by their group at the Cyanamid Institute in Geneva. They have provided a clear and readable account of the essential background as well as of the peculiarly electrochemical aspects. The printing and layout of this volume are of the usual high standard that we expect from this publisher. R. PARSONS Pp. xii + 482.

ISSN:0003-2654    

DOI:10.1039/AN9689300480

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

484 BOOK REVIEWS [Analyst, Vol. 93 Errata DECEMBER (1963) ISSUE, p. 931, equation a t centre of page, last term. p.p.m.” 16 Weight of sample p.p.m.” read “ 8 Weight of sample For ‘ I MARCH (1968) ISSUE, p. 159,Qth line under “BUFFER SYSTEM.” IBID., p. 163, Table II, 4th column, last line. For “increased” read “decreased.” For “0.006” read “0.0006.”

ISSN:0003-2654    

DOI:10.1039/AN9689300484

出版商:RSC    

年代:1968

数据来源: RSC