摘要:

Oct., 19581 ARCHER 57 1 The Argentimetric Titration of Halide and Cyanide Ions with Dithizone as Indicator BY E. E. ARCHER (The Distillers Company Ltd., Research and Development Department, Great Burgh, Epsom, Surrey) Methods are described for the argentimetric titration of halide and cyanide ions with dithizone as indicator. It has been found possible to apply the methods to some practical problems, including the determination of halogens in organic compounds. THE argentimetric titration of bromide, iodide and cyanide ions with dithizone as extraction indicator has been described by Karabash.l His methods have been tried in this laboratory and found to be extremely sensitive. However, since a two-phase system is used, which must be shaken after every addition of titrant, the methods are time-consuming and hardly applicable for general routine use. In the work described, titrations are carried out either in water - acetone or water - alcohol mixtures.Bromides, iodides and cyanides can be titrated in the presence of con- siderable amounts of water. Chlorides can only be successfully titrated if the water content of the solution is kept low and a non-aqueous solution of silver nitrate is used as titrant. The methods have been applied to the determination of halogens in organic compounds, both after digestion by the Carius method and after combustion in oxygen by a modified form of Schoniger's adaptation2 of Mickl and Pech's m e t h ~ d . ~ ? ~ In the application to the Carius method, the precipitate of silver halide from the digestion tube is either dissolved in hot concentrated sulphuric acid and determined by titration with potassium iodide solution, or it is dissolved in concentrated ammonia solution and determined by titration with potassium cyanide solution. When iodides and bromides in acidified water - acetone solution to which a little dithizone has been added are titrated with silver nitrate solution, the end-point is marked by a change from the green colour of dithizone to the orange-yellow colour of the silver - keto-dithizone complex.During the titration, there appears to be a certain amount of absorption of dithizone by the silver halide precipitate, and, near the end-point, this absorbed dithizone changes to a reddish purple colour, which tends to obscure the final colour change to orange- yellow.This effect can be overcome by adding a very small amount of dithizone initially, and, near the end-point, adding about three to five times the initial amount of dithizone. The red-purple colour is then entirely masked and the end-point is marked by a bright orange- yellow colour. The titration of chlorides in this manner can only be carried out when the solution to be titrated is a water - acetone mixture containing not more than 3 per cent. of water. The titrant can be silver nitrate in either ethanol or n-propyl alcohol. When ethanol is used as solvent, a colour change from green to reddish purple takes place well before the end-point, which is marked by a change in colour from red to yellow. When n-propyl alcohol is used as solvent, the colour change is very similar to that produced when iodides or bromides are titrated with aqueous silver nitrate.In view of this, and because of its higher boiling-point, n-propyl alcohol is the preferred solvent. The method devised for determining cyanides is based on the classical Liebig method, in which potassium iodide is added to the alkaline cyanide solution, and the solution is titrated with standard silver nitrate solution. The method depends on the fact that one silver ion combines with two cyanide ions to form a complex ion. When this ratio is exceeded, free silver ions are present and a precipitate of silver iodide is produced. In the proposed method, the titration is carried out in water - alcohol mixture to which a little dithizone has been added.At the end-point, free silver ions are present and there is a sharp change in colour from orange-yellow t o a deep red-purple, owing to the formation of the silver - enol-dithizone complex. The sensitivity of the method is about ten times as great as that of the Liebig method and the end-points are extremely sharp when 0.01 N silver nitrate is used as titrant. Silver can also be titrated with a standard potassium cyanide solution; this forms the basis of the proposed method for determining chlorine in organic compounds after digestion by the Carius method.572 ARCHER: THE ARGENTIMETRIC TITRATION OF HALIDE AND [Vol. 83 The use of 9-dimethylaminobenzylidenerhodanine as indicator for the titration of cyanides has been de~cribed.~ Tests in this laboratory indicate that the proposed dithizone method gives greater changes in both colour and intensity than the P-dimethylamino- benzylidenerhodanine method, and that it can be applied to initially highly coloured solutions, to which the latter method is inapplicable.TITRATION OF IODIDE WITH SILVER SOLUTION AND OF SILVER WITH IODIDE SOLUTION REAGENTS- Acetone-Commercial grade acetone of low water content is suitable. Dithizone solution-A 0.01 per cent. solution of dithizone in acetone. Sulphuric acid, diluted (1 + 1 v / v ) . Silver nitrate solution-A 0.01 N aqueous solution of silver nitrate prepared by diluting an accurately standardised 0.1 N solution. Potassium iodide solution, about 0.01 N-Prepared by diluting a 0.1 N solution of potassium iodide that has been standardised gravimetrically.PROCEDURE- Titration of iodide with silver nitrate solution-By pipette, put into a 250-ml conical flask an aliquot of the sample solution containing about 0.05 to 0.2 milli-equivalent of iodide ion. Dilute to about 10 ml with water, and add 2 ml of diluted sulphuric acid (1 + 1) and 50 ml of acetone. Cool, and add 1 ml of dithizone solution. Titrate with silver nitrate solution until the colour of the solution begins to change to a greenish yellow. Add a further 3 ml of dithizone solution, and titrate until the solution is a clear orange-yellow colour that does not change on the further addition of silver nitrate solution. A blank correction must be made for the silver nitrate solution needed to change the dithizone itself from green to yellow.To determine this correction, place in a 250-ml flask the reagents as before, cool, and add 4 ml of dithizone solution. Titrate from green to orange- yellow in the same way as for the sample. Four millilitres of 0.01 per cent. dithizone solution are equivalent to about 0.15 ml of 0.01 N silver nitrate solution. Titration of silver with potassium iodide solution-The titration of silver with potassium iodide solution forms the basis of the titrimetric finish of the Carius digestion. In this test, the colour change is from the orange-yellow of silver keto-dithizonate to the green of dithi- zone. Since the green colour is more dominant than the orange-yellow, a green colour appears before all the silver dithizonate has changed to silver iodide and free dithizone.For this reason, it has been found to be better to overshoot the end-point deliberately by a small amount and then to titrate back to the orange-yellow colour with silver nitrate solution. By pipette, put into a 250-ml flask an aliquot of the sample solution containing about 0.05 to 0.2 milli-equivalents of silver ion. Dilute to about 10 ml with water, and add 10 ml of diluted sulphuric acid (1 + 1). (This amount of acid was used in the experimental work, as it is equal to the amount used to dissolve the silver halide in the application to the Carius method.) Add 1 ml of dithiz- one solution, and titrate with potassium iodide solution until a definite green colour appears. Add a further 3 ml of dithizone solution, and titrate with silver nitrate solution until a clear orange-yellow colour is again produced, The titration value is then- This solution should be freshly prepared.The procedure is as follows. Cool, and add 50 ml of acetone. Potassium iodide titre + dithizone blank titre - silver nitrate titre. Determine the dithizone blank correction exactly as before. TABLE I TITRATION OF POTASSIUM IODIDE SOLUTION WITH SILVER NITRATE SOLUTION Amount of 0.009932 N Titre of 0.01 N silver Theoretical potassium iodide solution taken, nitrate solution, result, ml ml ml 5 4.976, 4.969, 4.971 4-966 10 9,933, 9.926, 9.928 9.932Oct., 19581 CYANIDE IONS WITH DITHIZONE AS INDICATOR 573 TESTS OF THE METHOD- In a check of the method for titrating iodide with silver nitrate solution, 5 and 10-ml portions of 0.009932 N potassium iodide solution were titrated with 0.01 N silver nitrate solution as described.In a check of the method for titrating silver with potassium iodide solution, 5 and 10-ml portions of 0.01 N silver nitrate solution were titrated with 0.009932 N potassium iodide solution as described. The results are shown in Table 11. The results are shown in Table I. TABLE I1 TITRATION OF SILVER NITRATE SOLUTION WITH POTASSIUM IODIDE SOLUTION silver nitrate solution taken, potassium iodide solution, result, ml ml rnl 5 5-04, 5.03, 5.04 5.036 10 10.08, 10.08, 10.075 10.072 Amount of 0.01 N Titre of 0.009932 N Theoretical TITRATION OF BROMIDE The procedure for the titration of bromides is slightly different from that for iodides. It has been found that end-points are sharper if 10ml of diluted sulphuric acid (1 + 1) are used instead of 2 ml.The problem has not been studied at such length as has the titration of iodides and chlorides. However, it has been found that accurate results can be obtained on standard solutions of potassium bromide. TITRATION OF CHLORIDE This method has been devised mainly for application to the determination of chloro compounds by Schoniger's adaptation2 of Mickl and Pech's It has also been shown that the method can be applied to the direct titration of microgram amounts of chloride ion. REAGENTS- standardised 0.2 N aqueous solution of silver nitrate with n-propyl alcohol. microgram amounts of chloride ion. PROCEDURE- (a) For 0.02 to 0-05 milli-equivalent of chloride ion-By pipette, transfer to a 250-ml flask a 1-ml portion of the sample solution containing 0.02 to 0.05 milli-equivalent of chloride ion.Add 50 ml of acetone and 0.2 ml of diluted sulphuric acid (1 + 1). Add 1 ml of 0.01 per cent. dithizone solution, and titrate with the solution of silver nitrate in n-propyl alcohol until the dithizone begins to change to an orange-yellow colour. Add a further 3 ml of 0.01 per cent. dithizone solution, and titrate until the solution is an orange-yellow colour. At the end-point, the addition of a further drop of titrant should produce no change in colour. To determine this cor- rection, place 4 ml of 0.01 per cent. dithizone solution in a flask containing 50 ml of acetone and 0.2 ml of diluted sulphuric acid (1 + l), and titrate to a clear orange-yellow colour. To standardise the silver nitrate solution, place, by means of a pipette, 1 ml of accurately standardised 0.05 N hydrochloric acid in a 250-rnl flask, and then carry out the procedure described above.( b ) For microgram amozints of chloride ion-By pipette, transfer t o a 5-ml beaker an aliquot of the sample solution containing up to 50 pg of chloride ion. If the sample is acid, make just alkaline to phenolphthalein with dilute sodium hydroxide solution. Stand the beaker in a water bath, and evaporate to dryness. Meanwhile, set up an Agla syringe-type microburette over a magnetic stirrer. Fill the burette with 0.004 N silver nitrate solution in n-propyl alcohol. Add to the beaker 0.05 ml of water, and then slowly add 1 ml of acetone, swirling the beaker when the first few drops have been added. Add 1 drop of diluted sulphuric acid (1 + 1) and 0.1 ml of 0.003 per cent.dithizone solution. Place a small glass-covered stirring bar in the beaker, and stand the beaker on the magnetic stirrer. Titrate with silver Silver nitrate solution, 0.004 N in n-$ropy1 alcohol-Prepared by diluting an accurately Dithizone solution, 0.003 per cent, in acetone-This solution is used for the titration of A blank correction must be deducted for the dithizone used.574 ARCHER: THE ARCENTIMETRIC TITRATION OF HALIDE AND [Vol. 83 nitrate solution from the syringe-type burette until the colour of the solution begins to change to a reddish yellow. Add 1 ml of acetone, washing down the sides of the beaker during the addition. Add 0.2 ml of 0.033 per cent. dithizone solution, and titrate to an orange-yellow colour.Carry out a blank titration on 2 ml of acetone, 1 drop of diluted sulphuric acid (1 + 1) and 0.3 ml of dithizone solution. Deduct this value from the sample titre. TESTS OF THE METHOD- In a check of procedure (a), 1-ml portions of hydrochloric acid solutions of different The concentrations were titrated with 0.004 N silver nitrate solution in n-propyl alcohol. results are shown in Table 111. TABLE I11 TITRATION OF HYDROCHLORIC ACID WITH SILVER NITRATE SOLUTION hydrochloric acid of hydrochloric nitrate solution in Theoretical Amount of Concentration Titre of 0.004 N silver taken, acid, n-propyl alcohol, result, ml N ml ml 1 0.0 1 2.50, 2.49 2.50 1 0.02 5.02, 5.01, 5.00 5-00 1 0.04 10.01, 10.01 10.00 It has been found that results of similar accuracy can be obtained by titrating with 0.01 N aqueous silver nitrate delivered from an Agla syringe-type microburette.Not more than 0.5 ml of titrant can be added, since, with more than 3 per cent. of water present, the sharpness of the end-point is impaired. For normal work, a solution of silver nitrate in n-propyl alcohol delivered from an ordinary burette is preferred, as syringe-type burettes are rather fragile. In a check of procedure (b), 1-ml portions of a 0.001 N solution of sodium chloride were transferred by pipette to 5-ml beakers and titrated as described. The results are shown in Table IV. TABLE IV TITRATION OF SODIUM CHLORIDE SOLUTION WITH SILVER NITRATE SOLUTION chloride solution taken, nitrate solution, less blank, Recovery, Amount of 0.001 N sodium Titre of 0.004 N silver Titre ml ml ml % 0 0.0110 - - 1 0.2610 0.2500 100-0 1 0.2618 0.2508 100.3 1 0,2612 0.2502 100.1 1 0.2610 0.2500 100.0 It appears that the method as described is directly applicable to the determination of One millilitre of tap-water was transferred by pipette to a 5-ml This gave a result of 14.2 p.p.m.At the same time, 1 litre of tap-water was evaporated to a small volume This gave a result of 14.1 p.p.m. chloride in tap-water. beaker, and the titration was carried out by procedure (b). of chloride ion. and the chloride was determined by the Volhard procedure. of chloride ion. PROCEDURE- By pipette, transfer to a 250-ml flask an aliquot of the sample solution containing up to 0.15 milli-equivalent of cyanide ion.Add 50 ml of 95 per cent. ethanol, 1 ml of N sodium hydroxide solution and 2.0ml of 0.01 per cent. dithizone solution in acetone. Titrate with 0.01 N silver nitrate solution to a deep red-purple colour. Near the end-point the solution changes in colour from orange-yellow to a dull red, but the actual end-point is sharp and distinctive. Carry out a blank titration exactly as above, but omitting the sample, and deduct the value found from the sample titre. At the end-point there should not be more than 20 ml of water present, including the volume of titrant added. TITRATION OF CYANIDE If more water is present, the end-point is less sharp.Oct., 19581 CYANIDE IONS WITH DITHIZONE AS INDICATOR 575 TESTS OF THE METHOD- prepared and diluted accurately 1 + 9 with water.solution was determined by the Liebig method. different amounts of the solutions, and the results are shown in Table V. In a check of the method, an approximately 0.1 N solution of potassium cyanide was The cyanide content of the strong The proposed method was carried out on TABLE V TITRATION OF POTASSIUM CYANIDE SOLUTION WITH SILVER NITRATE SOLUTION Potassium cyanide Amount of potassium Titre of 0.01 N silver Theoretical solution used cyanide solution taken, nitrate solution, result, ml ml ml Dilute 5 2.86, 2.88 2*87* Dilute 10 5.72, 5.74, 5.73, 5.74 5.74* Strong 2 11.50. 11.49 11.48t * Calculated from the result by Liebig's method. t Result obtained by Liebig's method. APPLICATION OF THE METHOD- The method has been applied to the determination of traces of cyanide in acrylonitrile.In a series of tests, a 0.1 N solution of potassium cyanide was standardised by the Liebig method and then diluted 1 + 9. Various amounts of this dilute solution were added to 1-ml portions of pure acrylonitrile, and the proposed procedure was carried out. The results are shown in Table VI. TABLE VI TITRATION OF SMALL AMOUNTS OF CYANIDE IN Amount of dilute potassium cyanide solution added to acrylonitrile, ml 0.5 1 2 3 4 5 Titre of 0.01 N silver nitrate solution, ml 0.72 1-42 2.84 4.25 5.67 7.08 ACRYLONITRILE Calculated theoretical result, ml 0.7 1 1.42 2.84 4.26 5.68 7.10 TITRATION OF SILVER WITH CYANIDE SOLUTION REAGENTS- grade potassium cyanide in water made up to 500 ml. made up to 100ml. PROCEDURE- By pipette, transfer to a 250-ml flask an aliquot of the sample solution containing up to 0.20 milli-equivalent of silver ion.Add 0.5 ml of ammonia solution, sp.gr. 0.880, and 1 ml of potassium hydroxide solution. Add 50 ml of 95 per cent. ethanol and 2.0 ml of 0.01 per cent. dithizone solution in acetone. Titrate with the potassium cyanide solution from a 10-ml burette until the solution changes from red to orange-yellow. Note the burette reading, and then titrate from a 10-ml burette with 0.01 N silver nitrate until the solution is a deep red-purple. Carry out a blank titration on the reagents with 0.01 N silver nitrate to the red-purple colour. To standardise the potassium cyanide solution, repeat the procedure on 2 ml of accurately standardised 0.1 N silver nitrate. Calculate the factor, F , of the potassium cyanide solution from the following equation- Potassium cyanide titre, ml Potassium cyanide solution, about 0.025 N-A solution of 1.7 g of analytical-reagent Potassium hydroxide solution-A solution of 40 g of potassium hydroxide in water Note the burette reading.[20.00 + silver nitrate titre, ml - reagent blank value, ml] x 0.01 F =576 ARCHER: THE ARGENTIMETRIC TITRATION OF HALIDE AND [Vol. 83 The titration value of the sample can then be calculated in ml of 0.01 N titrant from the following equation- Potassium cyanide titre, ml x F - silver nitrate titre, ml + reagent blank value, ml 0.01 Net titration = TESTS OF THE METHOD- To check the validity of the method, four 1-ml and four 2-ml portions of 0.1 N silver nitrate solution were titrated with potassium cyanide solution, and, from the results, the factor of the potassium cyanide solution was calculated.The results with the 1-ml portions of 0.1 N silver nitrate solution were 0.02272, 0.02278, 0.02272 and 0.02275, and with the 2-ml portions, 0.02273, 0.02278, 0.02275 and 0.02274. The additions of ammonia solution and potassium hydroxide solution were made in order to reproduce the conditions that were found to be suitable for dissolving a precipitate of silver chloride from a Carius digestion. If the problem in hand was simply the deter- mination of a soluble silver salt, almost certainly only a small amount of alkali would be necessary, as in the titration of cyanide, but this has not been confirmed by experiment. DETERMINATION OF HALOGENS IN ORGANIC COMPOUNDS AFTER DIGESTION BY THE CARIUS METHOD Although the Carius method for halogens is the method preferred by many analysts, one of the main drawbacks is the gravimetric finish.Titrimetric finishes for bromide and iodide have been s u g g e ~ t e d . ~ ~ ~ These methods are potentially dangerous, as the tubes are handled outside the furnace after digestion. In the proposed methods, the sample is digested in the normal way in the presence of silver nitrate. After digestion, the precipitate of silver halide is washed and either dissolved in concentrated sulphuric acid and then determined by the potassium iodide titration procedure, or it is dissolved in ammonia solution, spgr. 0.880, and then determined by the potassium cyanide titration procedure.The sulphuric acid solution method can be applied to chlorides, bromides and iodides, but the ammonia solution method can only be applied to chlorides. APPARATUS- To separate the silver halide, a filter-stick similar to the well known Emich filter-stick is used. A piece of glass tubing about 16 cm long, 3 mm internal diameter and 5 mm external diameter is used for its construction. About 0.5 cm from one end, the tube is constricted to about 1.5 mm internal diameter. For use, glass-wool is pushed into the constricted end and cut off level with the end of the tube. Suction is applied and the stick is dipped in a slurry of prepared Gooch asbestos, so that a pad of asbestos is formed over the glass-wool. PROCEDURE- General preliminary treatment-Take sufficient sample to give an equivalent of 0.1 to 0.2 milli-equivalent of halide ion and digest in the usual way in a sealed tube with fuming nitric acid and silver nitrate.Transfer the contents of the tube to a 250-ml conical flask. If chlorine is being determined, wash the tube with a little concentrated ammonia solution, swirl to dissolve the precipitate of silver chloride, and then re-precipitate by adding concen- trated nitric acid. Coagulate the precipitate by standing the flask, protected from light, in a boiling-water bath for 20 minutes. Cool the flask, and, with the filter-stick, remove the supernatant liquid. Remove the filter-stick from the suction line, and push a stainless-steel wire down it to dislodge the glass- wool and asbestos pad into the 250-ml flask.The sample is now ready for further treatment, the form of which will depend on whether chlorine, bromine or iodine is present and whether the sulphuric acid or ammonia method of dissolution is to be used. Determination of chlorine and iodine by sulphuric acid treatmentstand the flask on a water bath until the small amount of liquid adhering to the glass-wool and asbestos has evaporated. Add 5 ml of concentrated sulphuric acid, and stand the flask on a hot-plate so regulated that the sulphuric acid gently boils. Maintain at the boiling-point for 30 minutes. Cool the flask, add 15 ml of water, cool again, and add 50 ml of acetone. Complete the deter- mination as described for the titration of silver with iodide solution on p. 572. Determination of bromine by sulphuric acid treatment-It has been found to be difficult to dissolve silver bromide directly with hot sulphuric acid.Also, after dissolution, there Wash twice with dilute (about 0.1 N ) nitric acid.Oct., 19581 CYANIDE IONS WITH DITHIZONE AS INDICATOR 577 is usually present an oxidising substance (probably bromate) , which oxidises the dithizone and makes the titration method inapplicable. However, this can be overcome as follows. To the washed precipitate of silver bromide in a 250-ml flask, add 0.4 g of analytical- reagent grade potassium iodide and about 0.5 ml of water. Swirl to dissolve the potassium iodide and thoroughly moisten the precipitate of silver bromide. The silver bromide either dissolves completely or is converted into a curd-like precipitate of silver iodide.Add 5 ml of concentrated sulphuric acid, and proceed exactly as for the determination of chloride. Iodine is given off; normally it is completely expelled in about 10 minutes. Determination of chlorine by dissolution in aqueous ammonia-This is the method of choice for the determination of chlorine, since the rather lengthy heating with sulphuric acid is avoided. To the washed precipitate of silver chloride in a 250-ml flask, add 0.5 ml of ammonia solution, sp.gr. 0.880. Swirl to dissolve the precipitate, and then complete the determination as described for the titration of silver with cyanide solution on p. 575. RESULTS- A wide range of substances has not been examined, as the Carius digestion procedure is considered extremely reliable. Since the method was shown to give good results with the substances examined, it should work on all substances that are completely oxidised in the Carius digestion.The sample of poly(viny1 chloride) used in the tests was extremely pure; several replicate tests by the macro Parr bomb method gave the theoretical result of 56.8 per cent. of chlorine. The results obtained are shown in Table VII. TABLE VII DETERMINATION OF HALOGENS IN ORGANIC COMPOUNDS AFTER CARIUS DIGESTION Theoretical Substance Halogen found, yo halogen content, yo By sulfihuric acid tveatment- Poly(viny1 chloride) . . 56.6, 56.8, 56.6, 56.8 56.8 Bromobenzene . . . . 50.7, 50.8 50.8 Iodobenzoic acid . . . . 51.1, 51.2, 51.3, 51.1 51.1 By dissolution in aqueous ammonia- Poly(viny1 chloride) . . 56.6, 56.7, 56.8, 56.7 56.8 DETERMINATION OF HALOGENS IN ORGANIC COMPOUNDS BY A MODIFIED FORM OF SCHONIGER’S ADAPTATION OF MICKL AND PECH’S METHOD Schoniger’s adaptation, direct combustion in a flask in an atmosphere of oxygen, is undoubtedly one of the most rapid and convenient methods devised for the determination of halogens in organic compounds.The method can be used only on compounds that do not volatilise a t room temperature. By using the proposed method of absorption and titration, considerably less working time is involved than in the original method. The apparatus is a somewhat modified formmof that used in Schoniger’s original adapta- tion. The sample is wrapped in filter-paper and supported in the combustion flask on a small platinum platform. The chlorine evolved is absorbed in a small volume of water saturated with sulphur dioxide.Sulphur dioxide does not interfere in the direct titration of chlorides, so that no after-treatment of the sample before titration is necessary. The method has been applied to poly(viny1 chloride), poly(viny1idene chloride) and their copolymers with various other substances. It has been found that the method is not of completely general application ; some substances evolve a lot of unburnt carbon during combustion. This makes titration difficult, and invariably in such instances the results for chlorine are low. However, the method has, in practice, proved to be extremely useful for substances to which experiment has shown it to be applicable. A large number of samples can be dealt with in much less time than by any other method.APPARATUS- and Quartz flask with a B34 standard neck. The sample is fired by means of a hot Pyrex-glass rod. The apparatus used is as shown in Fig. 1. The vessel is a thick-walled 500-ml Quickfit The platinum platform is about 2 cm x 1.3 cm.578 ARCHER: THE ARGENTIMETRIC TITRATION OF HALIDE AND [Vol. 83 A few holes are punched in it to facilitate the passage of oxygen during combustion The platform is annealed to the two glass rod supports, which are in turn sealed on to a B24 - B34 expansion cone. The end of the rod is arranged to come about 0.5 cm above the platform when fitted in position. The firing rod is attached to a B24 cone. Platinum platform Fig. 1. Combustion apparatus PROCEDURE- To weigh out the sample, take a piece of Whatman No.40 filter-paper cut out to form a rectangle about 3 cm x 4 cm. Fold the paper in three along the shorter side, so that the centre section lies flat with the other sections standing up at right angles. When handling the paper use tweezers and a flat spatula, since chlorides can be introduced from the fingers, particularly during hot weather. Place 4 to 8 mg of sample centrally on the filter-paper, and re-weigh. Remove from the balance, and fold the filter-paper, applying pressure with the spatula so that the sample is wrapped tightly in several thicknesses of paper. During abnormal weather conditions, when there has been a great change in humidity over a short period, it has been found that filter-paper cannot be weighed to constant weight. This can be overcome by placing the paper in the balance case for a short while before weighing.Take one of the thick-walled 500-ml flasks and blow a steady stream of oxygen into it for a few seconds. Place the wrapped sample on the platinum platform, and moisten round the B34 cone with a drop of water. Lower the cone and platform in position in the flask. Take the firing rod and moisten with a drop of water round the B24 cone. Heat the end of the rod to glowing red heat in a blowpipe flame and lower into the flask so that it touches and fires the sample. While the sample is burning, hold down the firing rod. Set the flask aside for 1 hour before starting the titration procedure. No experiments have been carried out to determine the minimum time needed for complete absorption of the chlorine evolved, but experiment has shown that 1 hour is adequate. It is probable that absorption takes place almost entirely on the droplets of water that condense on the sides of the flask. After the flask has stood for 1 hour, loosen the joints, and wash down with 50 ml of acetone from a small wash-bottle. Add 0.2 ml of diluted sulphuric acid (1 + l), and titrate with 0.004 N silver nitrate solution in rt-propyl alcohol as described for the titration of chlorides on p. 573. It is advisable to carry out a blank determination on a piece of filter-paper the same size as that used in the determination. For some batches of filter-paper, a blank value of the order of 0.1 ml of 0.004 N silver nitrate solution has been found. RESULTS- experimental copolymer. Transfer the paper to a microbalance, and weigh. Add 0.5 ml of water saturated with sulphur dioxide from a siphon. The method was applied to the determination of chlorine in poly(viny1 chloride) and an The results are shown in Table VIII.Oct., 19581 CYANIDE IONS WITH DITHIZONE AS INDICATOR TABLE VIII DETERMINATION OF CHLORINE IN ORGANIC COMPOUNDS AFTER COMBUSTION IN OXYGEN Theoretical Substance Chlorine found, yo chlorine content, yo Poly(viny1 chloride) .. 56.8, 56.7 56-8 Experimental copolymer . . 22-2, 22-1, 22-3, 22-3 22.2* * Determined by the Carius method. 579 1. 2. 3. 4. 5. 6. 7. REFERENCES Karabash, A. G., Zhur. Anal. Khim., 1953, 8, 140. Schoniger, W., Mikrochim. Ada, 1955, 123. Mickl, O., and Pech, J., Chem. Listy, 1952, 46, 382. Ryan, J . A., and Culshaw, G. W., Analyst, 1944, 69, 370. White, L. M., and Kilpatrick, M. D., Anal. Chem., 1950, 22, 1049. White, L. M., and Seear, G. E., Ibid., 1950, 22, 1047. , , Ibid., 1953, 47, 904. - _ _ Received March 6th, 1958

ISSN:0003-2654    

DOI:10.1039/AN9588300571

出版商:RSC    

年代:1958

数据来源: RSC

摘要:

Oct., 19581 CYANIDE IONS WITH DITHIZONE AS INDICATOR 579 Nomograms for Calculating and Testing the Morton and Stubbs Correction in the Spectrophotometric Assay of Vitamin A BY G. PANCRAZIO AND V. DUSE (Research Laboratory, ORMA, Istituto Terapeutico Romano, Rome) Two nomograms (for vitamin-A alcohol in isopropyl alcohol and for vitamin-A acetate in absolute ethanol) are given for the rapid application of the Morton and Stubbs correction without numerical calculation. The Morton and Stubbs correction sometimes leads to erroneous results, and a practical test for the reliability of Ecor. is proposed. The test can be carried out in a few minutes by using nomograms, and makes it possible to ascertain whether or not the irrelevant absorption is approximately linear over the wavelength range between the two fixation points at six-sevenths.THE Morton and Stubbs correction procedure1 in ultra-violet absorption assay of vitamin A has been widely adopted as an official method. The use of the correction is reported by International,2 British3 and American4 Pharmacopoeias, as well as by the Istituto Superiore di Sanit&,6 the Association of Vitamin Chemistss and the Association of Official Agricultural Chemists' in their treatises on analysis. The procedure involves measurement of extinction, E, at the wavelength of maximum absorption of the pure vitamin and at two other wavelengths at which E for the pure vitamin is exactly six-sevenths of Emax. The irrelevant absorption is then subtracted from the gross value of Emax. by means of the Morton and Stubbs equation to give Ecorr.As conventionally calculated, the Morton and Stubbs correction is tedious and time- consuming. Several simplifications of the mathematics have been proposed, based on numerical Tables, graphical procedures or a combination of both. Examples of the first type are the simplified formulae of ProkhovnikS and Korrg and the Tables of RogerslO; the geometrical development of Vignaull exemplifies the second type of simplification, and the combined calculations and nomograms of Oser12 and McGillivray13 are examples of the third type. The proposed nomograms make it possible not only to apply the Morton and Stubbs correction rapidly and without numerical calculation, but also to check, in a few minutes, the reliability of ECor,. We found it to be necessary to evolve a suitable routine test, because, during our work on the stability of some water-soluble preparations of vitamin A, the Morton and Stubbs correction often led to erroneous results.For example, Ecor,. was sometimes greater than Emax,, and, in some instances, the value of Ecorr. increased during storage.580 PANCRAZIO AND DUSE : NOMOGRAMS FOR CALCULATING AND The validity of the Morton and Stubbs geometrical correction procedure depends on the assumption (which cannot be tested e~perimentallyl~) that the irrelevant absorption at the fixation points is linearly related. There was good reason to believe that this assumption [Vol. 83 80 70 0.250 60 40 3 0 4 [0’250 40 H E A 30 20 10 0.400 90 80 -It 3 k 0 . 3 0 0 60 0.250 40 F D C B Fig.1. Nomogram for vitamin-A alcohol in isopropyl alcohol was invalid, as irrelevant-absorption curves derived ge~metricallyl~ were not smooth between the fixation points. (In most instances for which we obtained unreliable results, the curves showed marked peaks and troughs.)Oct., 19581 TESTING THE MORTON AND STUBBS CORRECTION 581 Further, it is impossible in routine work to apply the correction procedure if the sixteen wavelengths proposed by Cama, Collins and Morton16 are used, as the procedure is too laborious. 0,350 1:: 70 60 30 0.350 20{ 1 4 0 30 20 90 10 "1 b 0 . 3 0 0 90 80 0.250 70 34 10.250 E-40 70 60 0.350 40 30 20 10 0.300 90 a0 70 60 0.250 40 30 20 0.2 I0 70 60 0.350 40 30 20 10 0.300 90 a0 70 60 0.250 40 30 20 t 0.210 F H k A F D C G B Fig.2. Nomogram for vitamin-A acetate in absolute ethanol Fig. 1 shows the nomogram for vitamin-A alcohol in isopropyl alcohol, and Fig. 2 shows We used the data of Cama, Collins and that for vitamin-A acetate in absolute ethanol. Morton17 for ultra-violet absorption of pure all-trans vitamin A.582 PANCRAZIO AND DUSE : NOMOGRAMS FOR CALCULATING AND [Vol. 83 Fig. 1 is based on the more commonly used equation- Ecorr, = 7 (E325 - O*375E,,o - 0.625EU) . . .. * * (1) which pre-supposes that E,,, = E, = 0*857E325 for all-trans vitamin-A alcohol, although the values given by Cama, Collins and Morton are a little different. The applicability test requires the measurement of extinction at 318 and 330 mp, at which wavelengths the coefficients of Cama, Collins and Morton are 0.932 and 0.935, respec- tively. For simplicity, both these were made equal to 0,935, and, by using this value, we derived the following equation- Ecorr, = 15.385 (E,,, - 0*417E3,s - 0*583Em0) .. .. * - (2) Ecorr. = 7 (E,,, - O.CU~E,,,.~ - 0*568E3,,) . . .. * * (3) Fig. 2 is based on Cama, Collins and Morton’s equation- For the applicability test we chose 317 and 333 mp, at which the extinctions are both equal to 0.924E3,,. For convenience, the factor 0.924 was decreased to 0.923, and, by using this value, we derived the following equation- Ecorr, = 13 (EaZ. - 0.4375E317 - 0.5625Em) . . .. * * (4) Each nomogram is composed of eight parallel straight lines, A, B, C, D , E, F, G and H ; A, B, C, D and E are used to find the value of Ecorr,, and F, G and H are used for the applicability test.Three different scales are used: one for A, B, C, F and G, another for D and E and a third for H. The figures on lines A, B, C, D, F and G of Fig. 1 represent extinction values at wavelengths 310, 334, 325, 318 and 220 mp, respectively. Similarly, the figures on lines A, B, D, F and G of Fig. 2 represent extinction values at wavelengths 311.5, 337, 326, 317 and 333 mp, respectively. The figures on line C represent (0.375E,,o + 0*625E,) on Fig. 1 and (0.432E3,,., + 0-568E,,) on Fig. 2. Line E, on both Fig. 1 and Fig. 2, gives the values of Ecorr. Line H gives 0.935Ecorr. on Fig. 1 and 0.923Ecorr. on Fig. 2. Directions for the use of Fig. 1 are given below: the procedure for Fig. 2 is the same. U S E OF NOMOGRAMS DETERMINATION OF ECorr.- If u,, b, and d, are the extinction values at wavelengths 310,334 and 325 mp, respectively, a line on the nomogram from a, to b, intersects line C at c,.The continuation of a second line from c1 to d, intersects line E at a point that corresponds to the value of Ecorr.. We often found that application of the Morton and Stubbs correction resulted in a value for Ecorr. that was greater than that of em ax.^ In such instances, c, lies below d, on the nomogram, and it is pointless to continue the determination of Ecorr. by the Morton and Stubbs procedure. APPLICABILITY TEST- The two fixation points at six-sevenths chosen by Morton and Stubbs do not have a true chemical significance. Morton and Stubbsl remark that the “only significance of the 617 ratio is that it is empirically appropriate in relation to the wavelength range covered, and to the performance of the spectrophotometer.” Gridgemad* applied three different sets of fixation points (as well as those at 6/7) to the absorption data of five vitamin samples described and discussed by Adamson, Elvidge, Gridgeman, Hopkins, Stuckey and Taylor,lg and pointed out that “except perhaps for cod-liver oil, where there is some chemical evidence for the suitability of the 617 points, there is nothing on which to base a decision as to which of the four sets of fixation points is best.” From these considerations, we concluded that, in general, if at least one set of suitably chosen fixation points gives values close to the values at 617, the Morton and Stubbs correction is more likely to be valid.If, on the other hand, the values of Ecorr. are far apart, there is no reasonable basis for application of the Morton and Stubbs correction, which, therefore, is not reliable. This reasoning led us to substitute the slope of the curve between the two 617 points (in practice, a near-linearity) for the linearity of three fixation points. This assumption is closer to the basic principle of the Morton and Stubbs correction. In fact, Mortonz0 writes: “The assumption is made that the irrelevant absorption is linear over the narrow wavelength range chosen.” It is a purely mathematical requirement, not acceptable from the chemicalOct., 19581 TESTING THE MORTON AND STUBBS CORRECTION 583 standpoint, to ask for-“specifically the linearity of three points; the absorption in between these chosen points may vary irregularly”21: “the contour of the curves between and beyond these points being immaterial.”ls The assumption that the irrelevant-absorption curve is approximately linear limits the instances in which the Morton and Stubbs correction can be applied.If this assumption, however, can be verified, values of Ecorr. will have a greater degree of validity for vitamin A preparations of any type. Further, the assumption can be tested, both by a geometrical procedure15 and by calculating sets of equations of the Morton and Stubbs type, based on different sets of fixation points in the wavelength range between the 6/7 points. By means of the applicability test, it is possible to ascertain whether or not two inter- mediate subsidiary points are linearly related to three Morton and Stubbs fixation points, i.e., to ascertain the near-linearity of the irrelevant-absorption curve with sufficient accuracy.Our test, therefore, is not exact, but it is rapid and sufficiently accurate for practicalpurposes. These two wavelengths fall almost midway between Morton and Stubbs’s first fixation point and Amax., and between A,,,, and Morton and Stubbs’s second fixation point, respectively. The test is applied in the following manner. Ecorr. is first determined as described previously, and the value of h,, the point on line H that corresponds to Ecorr., is noted. The differences, (E,,, - A,) and (Eso - h,), are then calculated. The point dz on line D that corresponds to the value of Ecorr.is noted, and the two points are joined by a single straight line, which intersects line F at point fi. If the irrelevant-absorption curve is approximately linear, m will be equal to (f, - fi) and n will be equal to (g, -fz). Small differences in these equalities do not invalidate the applicability of the Morton and Stubbs correction. An alternative procedure is to calculate equation (2) for the nomogram in Fig. 1 or equation (4) for the nomogram in Fig. 2. If the values of E,o,r. so determined are sufficiently close to those obtained by solving equations (1) and (3), respectively, the Morton and Stubbs correction will be reliable. EXTENSION OF USE OF NOMOGRAMS- Determination of Eeorr, is also possible for extinction readings that are not included on the nomograms. The readings must be multiplied or divided by a suitably chosen factor, i.e., one that brings extinction values within the range covered by the nomograms. Obviously, the resulting Ecorr, must be divided or multiplied by the same factor. The same procedure can be applied to the applicability test.The applicability test requires two subsidiary readings a t 318 and 330 mp. (These differences are m and f i , respectively.) The line joining points 11, and b, intersects lines F and G at f, and g,, respectively. This procedure is, however, time-consuming. RESULTS AND CONCLUSIONS We have determined Ecorr., both with the nomograms and by means of the Morton and Stubbs equation, in a number of instances. Differences between the two sets of values for Ecorr.averaged kO.002. Skilful use of the nomograms can consistently keep the error within the same range. The use of nomograms of the proposed type is not limited to the analyses described. It is easy to construct similar nomograms for all ultra-violet analyses of vitamin A, e g . , in cyclohexane, and also for those instances in which application of equations of the Morton and Stubbs type is required. We consider it to be unnecessary to report here the mathematical calculationsz2 on which our nomograms are based. REFERENCES 1. 2. Pharmacopoeia Internationalis, First Edition, World Health Organisation, Geneva, 1951, 3. 4. 5. 6. 7. Morton, R. .4., and Stubbs, ,4. L., Biochem. J., 1948, 42, 195. Volume I, p. 367. British Pharmacopoeia, 1953, p. 844. United States Pharmacopoeia, Fifteenth Revision, Mack Publishing Co., Easton, 1955, p.941. Istituto Superiore di Sanita, “Metodi d i Controllo della Vztamine,” Rome, 1953, p. 9. Association of Vitamin Chemists Inc., “Methods of Vitamin Assay,” Second Edition, Academic Lepper, H. A., Editor, Official Methods of Analysis,” Seventh Edition, The Association of Official Press Inc., New Yo;!, 1951, p. 38. Agricultural Chemists, Washington, 1950, p. 767.584 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. NOTES [Vol. 83 Prokhovnik, S. J., Analyst, 1952, 77, 185. Korr, L., Chemist Analyst, 1953, 42, 15. Rogers, A. R., Analyst, 1955, 80, 903. Vignau, M., Bull. Soc. Chim. B i d , 1951, 33, 868. Oser, B. L., Anal. Chew., 1949, 21, 529. McGillivray, W. A,, Ibid., 1950, 22, 494. Bagnall, H. H., and Stock, F. G., Analyst, 1952, 77, 356. Mariani, A., and Gaudiano, A., Rend. Ist. Sue. Sunit&, 1950, 13, 632. Cama, H. B., Collins, F. D.,.and Morton, R. A., Biochem. J., 1951, 50, 60. Gridgeman, N. T., Analyst, 1951, 76, 449. Adamson, D. C. M., Elvidge, W. F., Gridgeman, N. T., Hopkins, E. H., Stuckey, R. E., and Taylor, Morton, R. A., J . Pharm. Pharmacol., 1950,2, 137. Bagnall, H. H., and Stock, F. G., Ibid., 1952, 4, 81. Morgantini, E., Rend. Semin. Mat. Univ. Padova, 1947, 15. I 3 , Ibid., 1951, 50, 48. --- R. J., Ibid., 1951, 76, 445. Received October 23rd, 1957

ISSN:0003-2654    

DOI:10.1039/AN9588300579

出版商:RSC    

年代:1958

数据来源: RSC

摘要:

584 NOTES [Vol. 83 Notes DETERMINATION OF CALCIUM IN BIOLOGICAL MATERIAL THE disadvantages in the determination of calcium in biological fluids by precipitation as oxalate and titration with potassium permanganate are now generally recognised. MacIntyrel has shown that significant losses of oxalate occur during the washing of the precipitate, and there may also be an error owing to co-precipitation of magnesium. Further, dilute permanganate solutions are not stable and the end-point is not easy to discern. Direct titration with ethylenediaminetetra- acetic acid (EDTA) has formed the basis of several methods for the determination of calcium in serum. Here again there are difficulties in recognising the end-point of the titration, especially with indicators specific for calcium, such as murexide.Also, the high pH may cause precipita- tion of calcium phosphate, which will necessitate a slow titration to allow the insoluble phosphate to react completely with EDTA. Better end-points have been reported by using a calcein- thymolphthalein indicator.2 ps However, Korbl and Vydra4 found that calcein itself did not, in fact, give any colour changes with metal ions, but only fluorescence changes. Moreover, special precautions have to be taken to avoid interference arising from the presence of large proportions of magnesium.2 Some of the difficulties in recognising the end-point with these indicators may be due to the presence of heavy metals in the samples! Better results should be obtained by precipitating the calcium as oxalate, dissolving the precipitate in acid and then titrating with EDTA.Davidsson,* who used a method of this type, endeavoured to improve the colour change at the end-point by using as indicator an Eriochrome black T solution containing small amounts of magnesium. When all the calcium had been chelated, there was a sharp colour change, owing to the formation of the magnesium - dye complex. Nielsen7 introduced the idea of dissolving the precipitated oxalate in excess of EDTA and titrating back with a standard magnesium solution. It is readily applicable to all biological fluids and to the ashed samples of faeces, tissues and foods. Such conditions may obtain in urine. The proposed method is based on this principle. METHOD REAGENTS- oxalate and 0.315g of crystalline oxalic acid in water made up to 500 ml.Ammonium oxalate - oxalic acid buffer solution, PH 5.0-A solution of 6.75 g of ammonium Hydrochloric acid, 0.2 N. EDTA stock solution, 10 milli-equivalents per litre-A solution of 1.861 g of disodium ethylene- diaminetetra-acetate dihydrate in water made up to 1 litre. Ethanolamine, 9uri;Fed-The “Organic Reagent for Organic Analysis” grade, Hopkin and Williams Ltd., was used. Standard magnesium stock solution, 50 milli-equivalents per litre-A solution analytical-reagent grade magnesium acetate tetrahydrate in water made up to solution should be stored in a Pyrex-glass bottle. obtained from of 1-3405g of 250ml. This Indicator solution-A solution of 25 mg of Eriochrome black T in 25 ml of 2-methoxyethanol. EDTA - ethanolamine reagent solution-A mixture of 3 ml of ethanolamine and 50 ml of This solution should be prepared at frequent This solution is stable at room temperature for 3 to 4 weeks.EDTA stock solution diluted to 100 ml with water. intervals, i.e., every 2 or 3 weeks.Oct., 19581 NOTES 585 Standard magnesium working solution, 5 milli-equivalents per litre-Ten millilitres of standard magnesium stock solution diluted to 100ml with water. This solution should be prepared at frequent intervals. STANDARDISATION OF EDTA STOCK SOLUTION- By pipette, 2.0 ml of EDTA - ethanolamine reagent solution are placed in a 15-ml centrifuge tube and 5 drops of indicator solution are added. The solution is titrated with standard magnesium working solution from a microburette until the indicator changes sharply from blue to red. Two milillitres of standard magnesium working solution should be required, and, if necessary, the EDTA stock solution should be adjusted to give this titre. PROCEDURE- Ashed samples of faeces, tissues or foods are dissolved in small amounts of hydrochloric acid.The solutions are diluted with water and the pH is adjusted to about 5.0 with 0.5 N sodium hydroxide before being made up to a suitable known volume. One-millilitre portions of these solutions or of biological fluid (serum, urine or cerebrospinal fluid) are added to 2 ml of ammonium oxalate - oxalic acid buffer solution in centrifuge tubes. For dilute urines, enough sample is used t o give an adequate calcium precipitate. The contents of the tubes are mixed and the tubes are set aside for 30 minutes; they are then spun in a centrifuge for 5 minutes (3000g), after which the supernatant layers are carefully poured off and saved for the determination of magnesium if necessary.Each tube is allowed to drain on filter-paper and then the precipitates are dissolved in 1-ml portions of 0.2 N hydrochloric acid. A 2-ml portion of EDTA - ethanolamine reagent solution and five drops of indicator solution are added to each and the mixtures are titrated with the standard magnesium working solution until the colour changes from blue to red. With urine or other specimens in which the calcium value is high, a turbidity may form when the 2.0 ml of EDTA - ethanolamine reagent solution are added. This is caused by the precipitation of excess of calcium by the base, and can be overcome by adding further 2.0-ml portions of EDTA - ethanol- amine reagent solution until the precipitate has dissolved.The determination can then be completed. CALCULATION- The amount of calcium present is calculated from the equation- where T is the titre of standard magnesium working solution in millilitres. used must be substituted for 2 in the above equation. Calcium present, milli-equivalents per litre = (2 - T) x 5, If more than 2 ml of EDTA - ethanolamine reagent solution are required, the total volume RESULTS The precipitation is carried out a t pH 6.0 in order to avoid the co-precipitation of magnesium.8 Ethanolamine, as used by Sobel and H a n ~ k , ~ was found to be a more satisfactory buffer than an ammonium hydroxide - ammonium chloride buffer solution.At the concentrations recommended, the pH of the final solution is 10.0, which SchwarzenbachlO has shown to be the optimum for the colour change of Eriochrome black T with magnesium. We found it easier to dissolve the precipi- tated oxalate in dilute acid than to try dissolving it directly in the EDTA solution. TABLE I RESULTS OF RECOVERY EXPERIMENTS Calcium added, milli-equivalents per litre - 0 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 Magnesium added, Calcium calculated, Calcium found, milli-equivalents milli-equivalents milli-equivalents per litre per litre per litre - 0 5.0 4.0 3.0 3.0 2.0 2.0 1.0 0 - - - 5.68 6.68 7.68 8.68 9.68 10.68 11.68 4.7, 4*7* 4.65, 4.7 4.7, 4.65 5.60, 5.7 6.65, 6.7 7.7, 7.7 8.60, 8.7 9.7, 9.7 10.6, 10.7 11.8, 11.7 Mean recovery, % - - - 99.4 99.7 100.5 99.6 100.5 99.8 101.0 * Results for the direct determination in serum.5 86 NOTES [Vol. 83 In order to test the specificity of the method and the recovery of calcium from serum, a series of solutions containing the proportions of calcium and magnesium shown in Table I was prepared.To 1-ml portions of a pooled serum were added 1 ml of each of these solutions and then 2 ml of ammonium oxalate - oxalic acid buffer solution : the determination of calcium was then completed by the proposed method. The results in Table I indicate that calcium is cleanly and quantitatively precipitated, even in the presence of large amounts of magnesium. The reproducibility of results by the method is good. In a series of 60 analyses, including those quoted in Table I, the standard deviation of the differences between duplicate results, expressed as a percentage of the mean value, was f 1 per cent.As a further check on the repro- ducibility of results by the method, samples of the same serum were analysed in duplicate by five different analysts in three different laboratories, the results being as follows- Analyst No. . . .. .. . . .. . . l 2 3 4 5 Mean calcium found, milli-equivalents per litre . . 5.2 5.4 5.1 5.2 5.3 The method is rapid, since no washing of the calcium precipitate is necessary and the final titration can be carried out quickly. A further advantage is that over-titration can easily be corrected by addition of more EDTA - ethanolamine reagent solution and continuation of the titration.We have been using 1-ml samples for the routine analysis of serum and cerebrospinal fluid, because we determine magnesium in the supernatant liquid after the precipitation of calcium. If only calcium is required, 0.5 ml of serum can be used in the proposed method. Finally, the method could readily be adapted for use with other complexometric indicators that may become available. NORMAL VALUES The mean serum calcium in a series of 17 normal adults (male and female laboratory personnel) determined by the proposed method was 4.92 milli-equivalents per litre, with a standard deviation of k0.27 milli-equivalent per litre. Cerebrospinal fluids from 20 patients (children and adults), in whom investigation showed no abnormality of the central nervous system, were found to have a mean calcium content of 2.36 i.0.2 milli-equivalents per litre. This value is in fairly good agreement with that found by other workers,11,12 b u t there is a slightly wider range, owing most probably to the greater heterogeneity of our series, both in respect of age and physical condition. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. MacIntyre, I., Biochem. J., 1957, 67, 164. Tucker, B. M., Analyst, 1957, 82, 284. Baron, D. N., and Bell, J. L., Clin. Chim. Ada, 1957, 2, 327. Korbl, J., and Vydra, F., Chem. Listy, 1957, 51, 1457. Cheng, K. L., Chemist Analyst, 1956, 45, 79. Davidsson, D., Biochem. J., 1956, 62, 3 7 ~ . Nielsen, H., N o d Med., 1952, 48, 1059. Powell, F. J. N., J. Clin. Path., 1953, 6, 286. Sobel, A. E., and Hanok, A., Proc. SOC.Exp. Biol. Med., 1951, 77, 737. Schwarzenbach, G., Analyst, 1955, 80, 713. Stutzman, F. L., and Amatuzio, D. S., Arch. Biochem. Biophys., 1952, 39, 271. Harris, W. H., and Sonnenblick, E. H., Yale ,I. B i d . Med., 1955, 27, 297. PATHOLOGY DEPARTMENT A. A. HENLY LITTLE BROMWICH GENERAL HOSPITAL R. A. SAUNDERS BIRMINGHAM, 9 Received April 24th, 1958 THE EFFECT OF SELECTED 0Ii:GANIC COMPOUNDS ON THE DETERMINATION OF SILICA BY THE MOLYBDENUM BLUE METHOD THE influence of inorganic materials1~*~8 on the determination of silica by the molybdenum blue method has been extensively studied, but little work has been reported on the influence of organic materials. It was considered to be of interest, therefore, to determine the effects of some common organic materials on the colorimetric determination of silica, since the normal method of deter- mination by evaporating to dryness, burning off the organic material and then fusing with sodium carbonate is both tedious and liable to considerable error if the amounts of silica present are small.The colorimetric technique used was similar to that described by Prentice and Ritchie,s but the molybdosilicic acid mas developed in a solution 0.1 N with respect to sulphuric acid.4Oct., 19581 NOTES 587 RESULTS The effects noted were classified in five groups. The first group produced a small additive effect on the amount of silica determined. This group included many of the sugars with a reducing group, e g . , rhamnose, sorbose, mannose, L-arabinose and xylose. Up to 200 mg of any of these sugars, when added to a solution containing only a small amount of silica (0.1 mg), caused an error in the determination of less than 4 per cent.The second group produced an additive effect that was followed by a decrease in the amount of silica determined. The third group produced a depressive effect, which increased with the amount of material added, until a precipitate was formed; this group included glycine and n-butyric acid. It was noted that €-amino-n-caproic acid and DL-a-aminoisobutyric acid caused precipitation if only 100mg were added. The fourth group produced no effect until a certain amount of material was present, after which the amount of silica found decreased rapidly with further addition of organic matter; this group included mannitol, dulcitol, sorbitol, erythritol and gluconic acid.The fifth group consisted of a number of compounds that had no effect on the determination of silica. These were as follows, the limiting amount of organic material investigated being shown in parenthesis- Sucrose (2 g), inositol (500 mg), pure ethylene glycol (1 ml), succinic acid (500 mg), arabonic acid (400 mg), galactonic acid (400 mg), glutamic acid (300 mg) and glucuronic acid (200 mg). Fructose was the only substance to exhibit this behaviour. DISCUSSION OF RESULTS The most interesting results are those of the fourth group. The concentration of polyhydroxy compound required to produce interference was found to be independent of the silica content within the range investigated (0.05 to 0-2 mg of silica). This silica content is, however, much less than the smallest amount of organic matter that causes interference (60 mg of mannitol).To determine the factors that cause interference, the conditions of development of the molybdosilicic acid in the presence of organic matter were examined critically. This investigation showed that the amount of polyhydroxy compound required to prevent complete formation of the molybdosilicic acid was dependent on the amount of ammonium molybdate present. If excess of ammonium molybdate was added, molybdosilicic acid development was complete even at relatively high concentrations of interfering compound. It seemed obvious from these results that interference was caused by complex formation between the molybdic acid and polyhydroxy compound.Complex formation between molybdic acid and mannitol has been reported by Frey.6 Complex formation between molybdic acid and the other interfering polyhydroxy compounds has been confirmed in this laboratory, conductimetric and potentiometric techniques being used. Addition of erythritol, mannitol or gluconic acid to a fully developed solution of molybdosilicic acid had no effect on the intensity of the yellow colour, and, on reduction to molybdenum blue, the full amount of added silica was determined experimentally. The mannitol - molybdic acid complex appears to be stronger than the erythritol complex, as molybdosilicic acid was not produced in a solution containing 120 mg of mannitol within 1 week at room temperature, whereas development of molybdosilicic acid was almost complete within 45 minutes in a solution containing 300mg of erythritol.The effect of fructose on the determination of silica can be readily explained, as fructose combines with ammonium molybdate in acid solution to form a blue complex.6 A method based on this reaction has been described for the determination of small amounts of fructose. All the amino acids examined caused appreciable interference, even in small concentrations. This may be attributed to several causes, such as complex formation between amino acids and both molybdic and molybdosilicic acid. The heteropolyacids are known to form complexes with compounds containing amino groups. REFERENCES Isaacs, M. L., Bull. Sac. Chim. Bid., 1924, 6 , 157. Straub, F. G., and Grabowski, M. A., Ind.Eng. Chem., Anal. Ed., 1944, 16, 574. Prentice, A., and Ritchie, P. D., J . A@$l. Chem., 1956, 6, 2 1 . Alexander, G. B., J . Amer. Chem. Sac., 1953, 75, 5655. Frey, H., Ann. Chim., 1943, 18, 1. 1. 2. 3. 4. 5.588 NOTES Scott, L. D., J . Lab. C1i.n. Med., 1934, 19, 623. 6. WHITEHAVEN COLLEGE O F FURTHER EDUCATION DEPARTMENT OF CHEMISTRY FLATT WALKS WHITEHAVEN, CUMBERLAND [Vol. 83 E. RICHARDSON Received February loth, 1958 THE DECOMPOSITION OF CYANATES IN ACID SOLUTION, WITH REFERENCE TO IN the analysis of, e.g., rocks or steels, the presence of appreciable amounts of chromium may give rise to serious errors during the hydrolytic precipitation of the hydrated oxides of group 3, owing t o the formation of chromammines, such as [Cr(NH,) a]3+, the hydroxides of which are soluble in solutions buffered with ammonium salts, causing incomplete precipitation of chromium.Formation of chromammines may be prevented by very slow addition of ammonia to the boiling solution, as in the elegant method of Trombe1$8 of passing a stream of air containing ammonia gas through the solution. Or it may be avoided by slow production of ammonia in the solution by hydrolysis of a cyanate3 (see Table I, reactions 1, 2 and 3). This method has the great advantage of increasing the particle size and filterability of the precipitate. Dupuis and Duval2 have shown indeed that a definite hydrate can be formed. Mecipitation is rapid and quantitative for all the metals of this group. THE ANALYSIS OF CHROMIUM-BEARING MINERALS AND ALLOYS EXPERIMENTAL When the method was applied to chromite analysis, however, it was found that the methyl red indicator added to the solution a t a later stage for the determination of magnesium was destroyed.This was attributed to the presence of some decomposition product of the cyanate that possessed mild oxidising powers. Very prolonged evaporation with hydrochloric acid was necessary to remove this product before the indicator could be used. As methyl red is an azo compound, i t was thought that the indicator was being attacked a t the azo bond, and that other indicators of the sulphone- or phenol-phthalein type would be stable. Bromocresol green, chloro- phenol red and neutral red proved to be stable and serviceable, although methyl orange-another azo compound-was destroyed. Were this the only trouble, substitution of one of these indicators for methyl red in the established procedure would mend matters: but two further disturbing factors arise.First, during hydrolysis of the cyanate, an insoluble substance is formed, which is precipitated together with the chromium. This naturally causes errors if the mixed precipitate is weighed, but, where chromium alone is determined in the precipitate by titrimetric means, this might be assumed t o be harmless, whereas there is some disturbance of the procedure and an increased scatter in the results. Second, when nickel is present, as in nichrome, or when the initial peroxide fusion is carried out in nickel crucibles, the removal of the nickel with dimethylglyoxime is rendered difficult. Decomposition products of the cyanate appear to peptise the nickel precipitate so that filtration becomes difficult, to retard precipitation so that even with a large excess of precipitant some hours are required before precipitation is complete, and to render precipitation incomplete unless a very large excess-about ten-fold-of reagent is used.This need not necessarily cause errors, but i t is very inconvenient. An investigation to determine the nature and, if possible, the mechanism of formation of these decomposition products was undertaken. A sample of pure sodium cyanate, treated with dilute iron-free hydrochloric acid, gave an immediate white precipitate and a solution that oxidised methyl red, methyl orange, leucomethylene blue and leucosafranine-T, but did not affect neutral red, iodides or indicators of higher potential such as diphenylamine, dianisidine or erioglaucint:, nor did it attack the azo bonds of magneson I or magneson 11.This indicates a mild oxidant with a potential of about 0.35 to 0.40 volt, and the solution showed a potential to platinum - calomel of +0*33 volt on the hydrogen scale. The white precipitate gave no melting point, was recrystallisable from hot water-so could not be cyamelide-was found to contain sodium. and on analysis corresponded to monosodium dihydrogen cyanurate. Decomposi- tion of the polymer by heating with hydrochloric acid of concentrations from 0.1 to 2.0 M was investigated. The decomposition was extremely slow, and was complete in 2.0 M acid only after boiling for 15 hours; lower acid concentrations did not appear to hydrolyse it at all.Applica- tion of various acids to the decomposition of s0diu.m cyanate showed that hydrobromic, hydriodic, sulphuric, perchloric, phosphoric and acetic acids gave abundant precipitates of sodium cyanurate Its oxidising powers were! the same as those of the solution.Oct., 19581 NOTES 589 and oxidising solutions, further decomposition being negligible. Nitric acid alone gave no polymer and no oxidising solution, although once the cyanurate had been formed it was stable t o nitric acid. TABLE I REACTIONS DURING DECOMPOSITION OF SODIUM CYANATE 1. 2. 3. 4. 5 . 6. 7. 8. 9. 10. 11. 12. 13. 14. Reaction NaCNO + Na+ + CNO- CNO- + H+ % HCNO HCNO + H,O --f NH, + CO, NH, + HCNO + NH,CNO f NH, O = ~ < N H , O=C<NH, NH, + H,O -f CO, + 2KH, OH 2 N=C-NHz + 4H20 + 2 O=<, + 6H+ + 6e NH, 0=qNH, + H,O -+ CO, + N, + 6H+ + 6e 2 O = < z 2 + 2C0, + N, + 6H+ + 6e NO,- + 2H+ + e + NO,- + H,O 4 O=C{NH, + 6N0,- + 4C0, + 7N, + 8H,O NH, Remarks HCNO is undissociated Main reaction Formation of urea Hydrolysis of urea Formation and hydrolysis of car- bamic acid Removal of urea .=,(OH + NO,- + H+ +- CO, + N, + 2H,O OH 0 NH, Polymerisation of cyanic acid H H OH v Xitric acid thus apparently destroys some intermediate product necessary either as a catalyst or as a starting material for the polymerisation.Probable intermediates are urea or carbamic acid, which may be formed by reactions 4 and 6 (see Table I). This was confirmed by adding pure urea to the cyanate and nitric acid (the cyanate hydrolysis being much more rapid than the urea hydrolysis-reaction 5, Table I-at lower temperatures) when immediate formation of the polymer occurred, together with formation of an oxidising solution.The nitric acid is therefore removing urea and preventing i t from catalysing the polymerisation, and this must proceed via preliminary reduction of the nitric acid to nitrous acid in some such manner as is formulated in Table I, re- actions 7 to 10. This was confirmed by adding small amounts of pure sodium nitrite to samples of the acids previously enumerated. On reaction with cyanate, no polymer formation occurred, and the solutions after effervescence ceased had no oxidising powers.590 NOTES [Vol. 83 The nitrite must react by removing the urea (see Table I, reaction 1 l), since it gives no reaction with cyanurate once this is formed, and the function of the urea must be catalytic or carrier- catalytic in the polymerisation of cyanic acid, because no polymerisation of urea alone could be effected under any conditions of concentration or temperature in hydrochloric acid and sodium chloride solutions, even in the presence of small traces of cyanate.The scheme of reactions is shown in Table I, with reaction 13 for the polymerisation of cyanic acid, and reaction 14 as a possible oxidative reaction of the polymer. Alternative reactions involving carbamic acid instead of urea are shown in the Table at 6, 9 and 12. METHOD In using cyanate for the precipitation of hydrated oxides in chromite analysis,4 it is recom- mended that one of the following procedures be adopted.(4 (ii) (iii) For The peroxide fusion should be leached with nitric acid, the chromate reduced with sulphur dioxide and the silica dehydrations carried out with nitric acid. Hydrochloric acid may be used up to the second silica dehydration, and the residue after baking extracted with nitric acid Hydrochloric acid may be used throughout, but, before adding the cyanate, a small amount of sodium nitrite should be added. example, in procedure (i), concentrate the combined filtrates and washings from the silica dehydrations to 200 to 250 ml, cool, add ammonia until a faint permanent precipitate appears, re-dissolve the precipitate with 2 ml of nitric acid, add a solution of 3 g of sodium cyanate with care to avoid loss by effervescence, heat the solution to boiling and keep at that temperature for 5 minutes.Filter on a fast-filtering paper and wash with a 1 per cent. solution of ammonium nitrate that has been neutralised to phenol red. Addition of excess of ammonia t o the filtrate t o recover traces of chromium4 is not necessary provided ample sodium cyanate is used. Add excess of 1 per cent. solution of the sodium salt of dimethylglyoxime to the solution, render faintly ammoniacal, digest at just below boiling-point, filter and wash. Re-acidify the filtrate and washings with hydrochloric acid, evaporate the solution to small volume and precipitate magnesium in the usual manner. The use of nitric acid is advantageous in tha,t when the solution is evaporated for the deter- mination of magnesia, the excess of ammonium salts, which are objectionable in magnesia determination, is decomposed. RESULTS All three procedures have been used with success, as the results of the analyses shown in Each result is the mean of three determinations, one by each of the procedures Table I1 indicate. mentioned. TABLE I1 U.S. Bureau of Standards Ferrochrome: Sample No. 64 Hoepfner Chromeisensteins : Sample So. X-1 . . * . Sample No. XII-2 . . . . Sample No. 49G . . . # Sample No. 49AG . . * . Bureau of Analysed Samples Chrome ironstones: RESLJLTS Cr, % Given 67.9 ' ' {Found 67.8 SiO,, % - - Given - * ' {Found - n.d. n.d. 3.50 3.49 Fe, % 24.05 24.1 Cr,O,, % FeO, Yo 28.15 11.05 28.10 11.15 49.73 17.25 49.9 17.19 45.05 26.4 45.11 26.35 49.5 13.55 49.53 13.53 Si, % 2.05 2.1 MgO, yo - - - - 9.24 9.30 16.60 16.55Oct., 19581 BOOK REVIEWS REFERENCES 1. 2. 3. 4. Trombe, F., Compt. Rend., 1942, 215, 539; 1943, 216, 888; 1947, 225, 1156. Dupuis, T., and Duval, C., Anal. Chim. Actu, 1949, 3, 345. Ripan, F., Bull. SOC. Stiinfe, Cluj, 1928, 4, 28; Chem. Abstr., 1928, 22, 3104. Dorrington, B. J. F., and Ward, A. M., Analyst, 1930, 55, 625. 591 WASHINGTON SINGER LABORATORIES THE UNIVERSITY EXETER E. BISHOP Received November 12th, 1957

ISSN:0003-2654    

DOI:10.1039/AN9588300584

出版商:RSC    

年代:1958

数据来源: RSC

摘要:

Oct., 19581 BOOK REVIEWS 591 Book Reviews TRACE ANALYSIS. M.D. Ltd. 1957. Price $12.00; 96s. Edited by JOHN H. YOE, M.S., M.A., Ph.D., and H. J. KOCH, JUN., A.B., New York: John Wiley & Sons Inc.; London: Chapman & Hall This book is a collection of the papers presented at a symposium on trace analysis held in New York in November, 1955. The symposium was jointly financed by the Rockefeller Founda- tion and the Sloan - Kettering Institute, and the purposes of the symposium were defined as- (a) To bring together for comparison and discussion authorities in the various scientific disciplines that are related to the analysis of trace constituents in industrial, agricultural, biological and medical fields. (b) To consider which of the various techniques are directly applicable to the various fields of investigation.(c) To discuss the separation and concentration of millimicrogram amounts of metals and contamination hazards. The programme of the Symposium was based on three major divisions: “Methodology”; “Instrumentation” ; “Separation, Concentration and Contamination Hazards.” Under “Metho- dology,” papers were given by eminent chemists on twenty different techniques. The list included R. L. Mitchell and A. A. Smales from this country on emission spectrochemical analysis and neutron-activation analysis, respectively, and, to mention only a few of the remainder, B. L. Vallee on flame spectrometry, N. H. Furman on potentiometry and L. B. Rogers on coulometry. The general standard of these contributions is high, but that of the discussions is more variable.Pp. xiv + 672.592 BOOK REVIEWS [Vol. 83 There are two papers under “Instrumentation,” both by Ralph H. Muller, the first headed only “Instrumentation” and the other “The Interaction of Beta Particles with Matter.” Dr. Muller, as always, has some stimulating things to say, and he starts his paper on instrumentation by remind- ing us that analytical chemistry has always depended on instruments and that “a precise analytical balance is one of the finest examples of an elegant instrument.” He goes on to distinguish on the one hand between those methods in which, through the agency of modern equipment, some property other than mass is measured as the final stage of a chemical analysis and, on the other, those newer techniques, such as microwave absorption and nuclear magnetic resonance, which are of growing usefulness to the analyst and by means of which classical chemical analysis is supplanted. He asserts that, because of confused thinking on these matters, “the classical analyst is mildly infuriated by the inference that it (instrument measurement) is something new” and “the physicist and instrumentation specialist regard present-day instrumental analysis as an interim solution which is still hampered by old-fashioned thinking and practices.” In the opinion of the reviewer, this confusion between measurement and analysis presents a real danger to the younger analyst, and Dr.Miiller has done well to focus attention on the problem. Of equal service is the contribution by W. W. Meinke of Ann Arbor on trace-element sensi- tivity.His paper deals with a number of comparisons of the results of activation analysis with those obtained by other methods-spark and arc emission spectrography, flame spectrometry, amperometric methods and “chemical” methods Readers will be surprised to learn how often a chemical or a flame-spectrometric method is the most attractive. The final chapter, by R. E. Thiers of the Harvard Medical School, “Separation, Concentration and Contamination,” is a most fitting conclusion to the book. The author sets out in proper perspective the difficulties and hazards to which all trace analytical techniques are subject, and gives much quantitative information that is of value to the experienced analyst who is only too well aware of the difficulties that beset him and which may so seriously affect his results.The last comment in the discussion on this paper by B. L. Vallee, and the last sentence in the book, are appropriate-“Considerations such as these, often overlooked in favour of methodology, deserve emphasis to retain our perspective with regard to the reasons for and utilisation of analytical data.” The organisers of the Symposium are to be congratulated on having made available to analysts such a valuable collection of papers. R. C. CHIRNSIDE ABSORPTION SPECTROPHOTOMETRY. By G. P. LOTHIAN, MA., F.1nst.P. Second Edition. This is the second edition of a book first published in 1949. Most of the chapters have been rewritten and brought up to date, but the general plan is retained. Part I, on the principles of spectrophotometry, reviews the early work and ably disentangles various points of terminology. The classical laws of absorption and the problems of accuracy in spectrophotometry are reviewed in some detail and with discernment.There is an excellent chapter on calculations leading to the analysis of mixtures by either infra-red absorption or ultra-violet absorption. Part I1 consists of two chapters, one on the investigation of chemical structure and chemical reaction and the other on some illustrations of the successful application of spectrophotometry to analysis. The topics dealt with include first the general principles of design of monochromators, photometers, photoelectric colorimeters, absorptiometers and spectrophotometers. Then follows an account of thermal- detector spectrophotometers and clear descripti.ons of some commercially available infra-red spectrophotometers.There are shorter chapters on photographic and visual spectrometers and also on cells, standards and solvents. Finally, there are useful suggestions for further reading, and a bibliography. The middle section of his book is a short but interesting enough essay. The first and third parts, however, are admirably planned to meet the needs of the majority of users of spectrophotometers. Most workers nowadays like to understand how the instruments work, but they find that it saves time to seek help when anything goes wrong. Indeed, much of the servicing falls to the specialis: electronic technician. If this delegation allows users to devote more of their energy to the application of spectrophotometry, it need not be regretted.R. A. MORTON Pp. viii + 246. London: Hilger & Watts Ltd. 1958. Price 52s. The nature of absorption processes is outlined briefly. Part 111 consists of six chapters on the technique of spectrophotometry. Mr. Lothian’s emphasis is that of a physicist.Oct., 19581 BOOK REVIEWS 593 ORGANIC REACTIONS. Volume IX. Editor-in-Chief : ROGER ADAMS. Pp. viii + 468. New 1957. Price $12.00; 96s. Once again synthetic organic chemists are indebted to the Editor-in-Chief of this series and his colleagues for having collected together reliable, critical and authoritative articles on a number of useful general reactions, seven such being dealt with in this volume. By far the longest article is that by A.C. Cope, H. L. Holmes and H. 0. House on “The Alkylation of Esters and Nitriles,” which forms Chapter 5 of the volume, occupies 225 pages and gives 1080 references. It deals with the first stage of that classical reaction, the malonic ester synthesis, and its relatives, treating in a masterly fashion the C-alkylation of malonic and cyano- acetic esters, malononitriles, monocarboxylic esters and mononitriles. This chapter alone will ensure that the present volume will be one of the most widely used of the whole series. Further such articles on standard classical reactions would, the reviewer feels sure, be welcomed by all organic chemists. The other six chapters deal with rather less widely used reactions, all of which are, however, useful and welcome additions to the series.They comprise: “The Cleavage of Non-enolizable Ketones with Sodium Amide,” by K. E. Hamlin and A. W. Weston, 36 pages, 96 references; “The Gattermann Synthesis of Aldehydes,” by W. E. Truce, 36 pages, 109 references; “The Baeyer - Villiger Oxidation of Aldehydes and Ketones,” by C. H. Hassall, 34 pages, 164 references; “The Reactions of Halogens with Silver Salts of Carboxylic Acids,” by C. V. Wilson, 56 pages, 103 refer- ences; “The Synthesis of /3-Lactams,” by J . C. Sheehan and E. J. Corey, 21 pages, 44 references; and “The Pschorr Synthesis and Related Diazonium Ring Closure Reactions,” by de L. F. de Tar, 54 pages, 225 references. No organic chemist can afford to be without this volume or, for that matter, any of the other eight volumes of the series.ION EXCHANGE RESINS. By R. KUNIN. Second Edition. Pp. xiv + 466. New York: John Wiley & Sons Inc.; London: Chapman & Hall Ltd. 1958. Price $11.00; 88s. This is more than “just a new edition” of the slim volume of the same title by Kunin and Myers that appeared in 1950. It has been considerably expanded and widened in scope, and it now comprises a comprehensive, up-to-date and well balanced survey of all aspects of the subject. To emphasise the broad coverage of this monograph, it is worth quoting the chapter titles in full: introduction and historical review; the theory and mechanism of ion exchange; cation exchange resin characteristics; anion exchange resin characteristics ; the synthesis of ion exchange resins ; applications, general considerations ; water softening by ion exchange ; the deionization of water ; ion exchange treatment of sugar and glycerine ; hydrometallurgical applications ; perm- selective membranes and their applications ; catalysis with ion exchange resins ; ion exchange in analytical chemistry; miscellaneous applications; methods of studying ion exchange resins; stability of ion exchange resins; the design and economics of ion exchange units.The author is the well known expert of the Rohm and Haas Company (of Amberlite fame) and he writes authoritatively and concisely. The text is profusely illustrated with diagrams and judiciously reinforced with references-1 170 of them. (Incidentally, a graph reproduced in the preface shows that already in 1955 about 1200 publications a year dealt with ion exchange-and the graph is rising steeply!) Although the treatment of some topics is necessarily rather perfunctory, it is difficult to imagine a more informative monograph within the compass of 466 pages; as the book is also excellently produced, it can be strongly recommended for all chemical libraries.York: John Wiley & Sons Inc.; London: Chapman & Hall Ltd. H. N. RYDON J. A. KITCHENER MATERIALS FOR GAS CHROMATOGRAPHY : STANDARDS AND DATA FOR “EMBAPHASE” STATIONARY PHASES AND “EMBACEL” KIESELGUHR. Published by May & Baker Ltd. Loose leaf. Pp. 23 + vi (appendix) + 7 data sheets. Dagenham: May & Baker Ltd. Gratis on application. In the past few years a great deal of gas-chromatographic work has been carried out in which particular separations have been effected on stationary phases held on supporting media, when both phase and support have often been of uncertain composition. It is obviously desirable that workers in one part of the world should be able to repeat the work of contributors elsewhere, and hence it is no surprise that attempts should be made to standardise most of the materials used in gas chromatography, In this connection the booklet fulfils a very useful purpose. Stationary594 BOOK REVIEWS [Vol.83 phases are described both by name and application, with useful references to the original literature. Specifications for stationary phases and supports are given in detail, and tests for the determina- tion of volatility and retention volumes of the phases and for the catalytic activity of supports are described.For example, on p. 18 the reader would be more confident about the reasoning if full details of the tests for catalytic activity of the kieselguhrs were given. On p 9, reference 33 for dinonyl sebacate refers to the determination of methyl cyclohexane in petroleum ether and not to the determination of monomers in plastics. Further, in the specifications for stationary phases, the initial loss in volatility should be given with reference to a temperature. Nevertheless, despite these blemishes, one can quote the North Country saying that “Good stuff lies in little room,” for this booklet bears out the contention. There is a certain tendency to overstate the case. Not all the references are correct. J .HASLAM THE EXTRA PHARMACOPOEIA (MARTINDALE). Published by direction of the Council of The Pharmaceutical Society of Great Britain. Twenty-fourth Edition. Volume I. Pp. xxxii + 1695. London: The Pharmaceutical Press. 1958. Price 65s. The original of this well known work of reference was written by William Martindale and appeared as a single volume of 313 pages in 1883. The book was an immediate success, ever larger editions being published in rapid succession, and in 1912 (when the book was being produced by the founder’s son, Dr. William Harrison Martindale, with the help of Dr. W. Wynn Westcott) the fifteenth edition was issued in two volumes, the therapeutics and pharmacy of drugs being dealt with in the first volume, and the second embodying information relative to chemical analysis and general laboratory work.This arrangement has been retained, whence the volume iunder review is devoted to descriptions of the properties and uses of drugs and pharmaceutical preparations. “Martindale” has become so well known as an essential work of reference to everyone whose business is in any way concerned with drugs that it would be redundant to enter into a detailed review. However, all interested readers may rest assured that this edition lives up to the fine traditions of its predecessors. As an indication, it may be mentioned that 137 closely printed pages are devoted to antibiotics, these being relxted to the British Pharmacopoeia 1958; again, one notices that the section dealing with Medicinal Dyes begins with a reference to the Reports on Colouring Matters of the Food Standards Committee of the Ministry of Agriculture, Fisheries and Food and the dyes have been given the five-figure numbers (whenever known) under which they appear in the “Colour Index,” Second Edition, 1956.The practising analyst will find the information about proprietary preparations particularly useful, this being more detailed than in previous editions. The magnitude of the work may conveniently be indicated by observing that the general index of 300 columns contains upwards of 18,000 references. “Martindale” is now compiled by the Scientific Publications Department of The Pharmaceutical Society of Great Britain; the Editor, Dr. K. R. Capper, the Assistant Editor, Mr. S. C. Jolly, and all the members of their staff merit high commendation for having produced this distinguished work of scientific reference.NOEL L. ALLPORT THE EXAMINATION OF WATER AND WATER SUPPLIES (THRESH, BEALE AND SUCKLING). By EDWIN WINDLE TAYLOR, M.A., M.D., R.Ch. (Cantab.), M.R.C.S., L.R.C.P., D.P.H. (Lond.). Seventh Edition. Pp. viii + 841. London: J. & A. Churchill Ltd. 1958. Price 100s. When contemplating the 841 pages of the $;eventh edition of “The Examination of Water and Water Supplies,” the conscientious reviewer may thankfully recognise that a textbook for which public demand has required seven editions and a reprint over a period of 54 years has an established place in the libraries of the world; he. may fairly approach his task by endorsing the commendations of his predecessors about the main body of the work and concentrating his attention upon new matter.Dr. Windle Taylor has wisely retained the logical arrangement that has always been an appreciated feature of the book, so that readers familiar with earlier editions can readily find their way about; but nearly every chapter in the latest edition contains something new and valuable, and room has been made by condensing and occitsionally omitting some of the rather discursive accounts of individual problems that were found in earlier editions. An entirely new feature is the reproduction of sixteen plates of photomicrographs in the chapter devoted to microscopical and biological examinations. They replace the twenty-four plates of sketches, which hithertoOct., 19581 BOOK REVIEWS 595 appeared a t the end of the book, and the change has sacrificed something of value.The non-expert microscopist will not usually find in his field of vision the clarity of micro-organisms in pure culture; the deposits he surveys will more frequently consist of encysted infusoria, zoogloea, fragments of quartz, larvae and the wing cases of insects, vegetable debris and sometimes textile fibres. The older sketches, with their accompanying explanations, were helpful aids to the recognition and identification of “settleable solids” : the new photomicrographs, excellent of their kind though they undoubtedly are, are not wholly adequate substitutes. They will find no guidance on the selection and use of testing equipment and only outlined proposals for separating radioactive material into its physiologically important components ; but the author presents, in an admirably concise way, much information about background activity, proposed limits for radio- activity in water supplies, methods of calculating and expressing radioactivity and similar aspects of this new and rather intimidating subject of special interest to the water examiner. The references from which much of the information is extracted are clearly given at the end of the chapter.A new chapter describes non-routine bacteriological examinations relating to many technical problems. Within a few pages the author includes much theoretical and practical information on the isolation, identification, significance and uses of nitrifying bacteria and sulphur bacteria: on the examination of soils for potential bacteria-induced corrosive properties, the testing of gland packings, washers and other water-works materials and the examination of water for taint-producing micro-fungi and actinomycetes. Not everyone will agree with Dr.Windle Taylor’s interpretation of the apparent speed with which nitrifying bacteria oxidise ammonia on rapid gravity filters, but the adequacy of the chapter for its intended purpose is beyond dispute. It forms a valuable addition to the text. The important chapter on water-borne diseases has been enlarged and brought up to date, and it now includes a section on the menace to foodstuffs from contamination with polluted water and sewage sludge. The section devoted to physical and chemical analysis of water describes methods that have been developed during the last 10 years, and extensive use has been made of the publications of the Institute of Water Engineers and the American Public Health Associa- tion.Some older methods have been omitted, but many analysts will think that the process might have been carried further. It seems unnecessary, for example, to include in full working detail two obsolete methods for determining hardness in addition to describing the use of EDTA. These methods are already well known to older practitioners and are better disregarded by the young. The original designers set the foundation of their work on the solid rock of basic principles. The value of each new storey lies in its ability to house the expanding knowledge of successive generations in harmony with the whole structure.Dr. Windle Taylor is unreservedly congratu- lated on the skill and expertise he has brought to the task of selecting and condensing all relevant advances of the past decade. No doubt there will be many more editions: with so much to praise and admire in this one, suggestions are offered only in a constructive and deferential spirit. Valuable space could be made available for newer information by omitting working directions for analyses that are now fully described in authoritative specialist publications. Methods of investigating suspected pollu- tion of surface waters by pesticides and herbicides are not yet far advanced, but the subject would seem to merit more extensive reference and documentation. The brief mention of plastic piping might have included a useful warning of the contamination that may occur from inward diffusion of coal gas and industrial vapours; the omission of any reference to methods by which residual silver was determined in water sterilised by the “Katadyn” process seriously detracts from the value of the recorded experience.Ever increasing demands on underground water supplies would justify more detailed guidance on the recognition of sea-water infiltration, and some reference might have been made to the absorption of residual synthetic detergents by activated carbon. Finally, the book has so much well merited authority that additional emphasis on the many dangers that may arise from complacent reliance on single-stage chlorination would not be out of place.The cost of the new edition, alas, is i5; but in its pages the man with a problem may have access a t will to accumulated knowledge and experience that is almost beyond price or praise. The consultant will continue to accept it as one of his best investments. Many readers will turn early to the chapter on radioactivity in water. J. G. SHERRATT596 PUBLICATIOIU‘S RECEIVED ALIPHATIC FLUORINE COMPOUNDS. By A. M. LOVELACE, DOUGLAS A. RAUSCH and WILLIAM POSTELNEK. Pp. x + 370. American Chemical Society Monograph No. 138. New York: Reinhold Publishing Corporation; London: Chapman & Hall Ltd. 1958. Price $12.50; 100s. Apart from some earlier work, particularly that of Swarts, the systematic study of organic fluorine compounds may be said to have begun. about 1935. To-day, fluorine is a constituent of a wide range of commercial products, among others refrigerants, aerosol propellants, lubricants, rodenticides and insecticides, dyes, drugs and plastics. The authors’ aim has been to present a comprehensive account of the preparation and simpler physical properties of all classes of aliphatic (i.e., acyclic and alicyclic) fluorine compounds. They do not claim that the Tables, extensive though they are, include every such compound that has been made. The first chapter reviews general methods of fluorination, in particular the formation of the carbon - fluorine bond. The remaining twelve chapters deal with specific groups of compounds -alkanes, alkenes, alcohols, ethers, etc. After a short introduction, methods are described in general terms; details may be found from the raferences given for each compound listed. The index does not name individual chemicals, but it readily affords location ; for example, fluoroacet- amide is covered by the entry “amides” and can then be traced in the appropriate Table from its empirical formula. The reader should not be depressed by seeing that i t may be made by method 1001; this merely means method 1 of chapter 10. Attention is drawn to the fact that special techniques are often necessary for the satisfactory analysis of fluorocarbon compounds. The literature has been combed u:p to 1955, with occasional later references. B. A. ELLIS

ISSN:0003-2654    

DOI:10.1039/AN958830591b

出版商:RSC    

年代:1958

数据来源: RSC

摘要:

596 PUBLICATIOIU'S RECEIVED Publications Received BIOLOGICAL TREATMENT OF SEWAGE AND INDUSTRIAL WASTES. Edited by Brother JOSEPH MCCABE, F.S.C., and w. w. ECKENFELDIZR, JUN. Anaerobic Digestion and Solids-Liquid Separation. New York: Reinhold Publishing Corporation; London: Chapman & Hall Ltd. 1958. Price $10.00; 92s. ESSENTIAL FATTY ACIDS. Edited by H. M. SINCLAIR. Pp. xviii + 268. London: Butterworths Scientific Publications; Kew York: Academic Press Inc. 1958. Price 50s. ; $9.50. EXPERIMENTAL DESIGNS IN INDUSTRY. Edited by VICTOR CHEW. Pp. xii -+ 268. New York: John Wiley & Sons Inc.; London: Chapm.an & Hall Ltd. 1958. Price $6.00; 48s. Verlag Franz Deuticke. 1958. Price Autrian S294. GAS CHROMATOGRAPHY. Edited by VINCENT J. COATES, HENRY J . XOEBELS and IRVIKG S.FAGERSON. Pp. xii + 323. Kew York and London: Academic Press Inc. 1958. Price $12.00; 86s. CHEMIE UXTER BESONDERER BERUCKSICHTIGUKG DER ~ONENAUSTAUSCHER. By Priv.-Doz. Dr. Ing. EWALD BLASIUS. Pp. xx + 370. Stuttgart: Ferdinand Enke Verlag. 1988. Price (paper) DM96: (cloth boards) DM99. N o . 46 of sevies Die chevvzische Analyse edited by Prof. DY. Gevhart Jandev. PRACTICAL CLINICAL BIOCHEMISTRY. By HAROLD VARLEY, MSc., F.R.I.C. Second Edition. Pp. viii - 635. London: William Heinernann Medical Books Ltd. 1958. Price 42s. BRITISH KATIONAL FORMULARY 1957: First Amssndment 1958. Pp. 11. London: The British Medical Association and The Pharmaceutxal Press. 1958. Price 8d. BRITISH PHARMACOPEIA 1958 : Amendments, August, 1958. Pp. 5 . London: The Pharmaceutical Press j o r The General Medical Council. 1958. Gratis. Copies of this lea$et may be obtained on afiplication, emlosing a staimped addvessed envelope, fvovn The Secretavy, British Pharmacopoeia Cowmission, Geneva1 Medical Council Ofice, 44 Hallam Street, London, W.l. ANNUAL REPORTS ON THE PROGRESS OF CHEnmTw FOR 1957. Volume LIV. Pp. 445. London: The Chemical Society. 1958. Price 40s. Volume 11. Pp. vi + 330. RADIOAKTIVE ISOTOPE IN DER BIOCHEMIE. By ENGELBERT BRODA. Pp. viii + 326. Vienna: CHROMATOGRAPHISCHE METHODEN IN DER ANAL,YTISCHEN UND PREPARATIVEN BNORGANISCHEN

ISSN:0003-2654    

DOI:10.1039/AN9588300596

出版商:RSC    

年代:1958

数据来源: RSC