ANALYTICAL CHEMISTRY1. INTRODUCTIONONCE again it has to be said that this Report is in the main concerned withoriginal papers rather than abstracts. The division into sections is on thesame general lines as last year and, as before, we have tended to mentioninorganic applications first followed by organic applications. In preparingthis Report we have, of course, noted certain matters which appear to us tomerit special attention. Repeatedly, in analytical work, and particularlyin titrimetry, we note a tendency to carry out chemical operations auto-matically and to make instrumental recordings of the results. There arecertain dangers that must, however, be watched. The chemical procedureson which the tests are based must be thoroughly sound, because if record-ings are made based on uncertain chemical operations, then many of thegreat advantages of these procedures will be lost.There seem to be a large number of papers appearing on non-aqueoustitrimetry and this field has expanded to include potentiometric and coulo-metric methods as well as conventional volumetric procedures.The numberof publications on gas chromatographic and particularly gas-liquid chromato-graphic methods continues to increase, and there are welcome signs that thisprocedure is finding application in many industries, other than the petroleumindustry, which has borne the brunt of the development work. In workon the micro-scale the oxygen-flask combustion method is being used to anincreasing extent in the preliminary opening up of organic substances.Thefact that only oxygen is used in the combustion process along with simpleabsorbents makes the procedure clean and acceptable in a large number ofcases.Analytical chemists who wish, on occasion, to read reviews on particularaspects of their work will find it worth while to follow the articles which areappearing in The Analyst at two-monthly intervals. These articles arewritten critically, and during the past year have included reviews on suchdiverse topics as the Analysis of Synthetic Detergents, The Infra-red Analysisof Solid Substances, X-Ray Fluorescence Analysis, Ferrous MetallurgicalAnalysis, and Gas Chromatography and its applications.Finally, we draw the attention of analytical chemists to the address ofthe retiring president of the Society for Analytical Chemistry, Dr.J. H.Hamence. In this address (Analyst, 1959, 84, 271), he describes in detailsome of the important events and developments which have taken place inthe Society over the past two or three years. Moreover, the address in-cludes some most interesting philosophical observations on the future ofanalytic a1 chemistry 374 ANALYTICAL CHEMISTRY.2. GENERALACCURACY, a subject of prime interest to all analysts, has been speciallystudied by Bishop,l who has recorded the conclusions reached after hiscritical re-examination and assessment of the mechanical precision intitrimetric procedures. He has paid particular attention to such matters asdrainage errors in burettes, and suggests that the pipette-dilution methodoffers some improvement in the precision of volumetric methods. Anyfurther increase in mechanical precision, it is said, affords little or no im-provement in the accuracy of determination owing to problems of end-pointdiscrimination and limits in the purity of normal reagents.In a secondpaper the same author describes his findings on weight titrimetric analysis,using a form of needle-valve weight burette. Even under most favourableconditions there appears to be a limit to the accuracy of the analyticalresults, which is governed by physicochemical considerations and is at leastone power of 10 less than the maximum attainable mechanical precision ofmeasurement .Electrodes sensitive to specific elements are a great help in many ana-lytical problems.Bower has described the results obtained with an experi-mental sodium aluminosilicate glass electrode manufactured by BeckmanInstruments Inc. The electrode was insensitive to calcium and magnesiumbut sensitive to sodium, potassium, and hydrogen ions, giving theoreticalrelationships between E.M.F. and cationic activity. The author alsodescribes a procedure using the electrode for the determination of sodiumin waters. The water sample is diluted if necessary, the pH adjusted to 7,and any potassium precipitated as the tetraphenylboron derivative, beforemaking the E.M.F. measurements.On the use of high-frequency measurements in analysis, the work ofWeber and Cruse 4 indicates that such measurements are of particular valuein the registration of phase changes and hence in the plotting of phasediagrams.They illustrate this by observations on the systems tin-zinc,lead-tin, and bismuth-antimony. Another topic of general interest hasbeen discussed by Fischer et a2.,6 who have shown that variations in thephysical form of precipitates can be tolerated better in turbidimetrk titra-tions than in turbidimetric determinations involving comparison of turbidi-ties with standards. They find that the addition of a non-ionic surface-active reagent enhances nucleation at the expense of crystal growth in some,but not in all, precipitation reactions.Bagshawe 6 has contributed an excellent review on the determinationof about 25 elements in steel. These elements may be added intentionallyas alloying constituents or be present inherently as native impurities.Thereview is written critically and with a nice sense of balance. It should beread by analysts not directly concerned with the steel industry because it1 E. Bishop, Analyt. Chim. Acta, 1959, 20, 315.2 E. Bishop, Analyt. Chim. Acta, 1959, 20, 405.a C. A. Bower, Proc. Soil Sci. SOC. Amer., 1959, 23, 29.4 Th. Weber and K. Cruse, 2. analyt. Cham., 1959, 166, 333.6 R. B. Fischer, M. L. Yates, and M. B. Batts, Analyt. Chim. Acta, 1959, 20, 501.B. Bagshawe, Analyst, 1959, 84, 475HASLAM AND SQUIRRELL: GENERAL. 375contains a great deal of useful information which the author has been ableto sift very carefully as an active member of the B.I.S.R.A. Methods ofAnalysis Committee.Solvent extraction methods for the determination ofmetals are becoming more numerous. Khorasani and Khundar' havedeveloped a procedure for the rapid determination of antimony in theantimonates of lead, tin, mercury, nickel, and chromium. The method isbased on the selective extraction of antimony@) from a hydrochloric acidsolution with ethyl acetate. The antimony in the extract is determinediodometrically. Iron(m), cobalt(zI), cadmium(II), and large amounts ofcopper and tin interfere with the extraction. Jantik and Korbl,* however,have described a new extraction method for the separation of copper. Thecopper is converted into its complex pyridino-bromide or -iodide and is thenextracted with chloroform before determination by a complexometricprocedure.The interference of zinc can be masked by the addition ofiminodiacetic acid but this procedure fails in the case of cadmium andmercury.Ehrlich and ICeil have developed a useful method for the determinationcf small amounts of silica in oxides such as TiO,, Al,O,, V,O,, and ZrO, andin certain metallic salts such as ferric salts. In the presence of hydrofluoricand sulphuric acid and in a silver flask the silicon is volatilised as hexa-fluorosilicic acid, the distillate being collected in a polythene receiver. Thesilica in the distillate is determined by a procedure involving stannouschloride reduction of silicomolybdate. For the rapid determination ofchloride in silica and other solids, Robinson lo prefers to heat the sample ina combustion tube with sulphuric-nitric acid in a stream of nitrogen.Thechloride evolved is collected in a sodium carbonate or a de-ionised waterscrubber and may then be determined by potentiometric titration or by acolorimetric procedure if the amount is very small. Advantages of themethod are that, when required, up to 1.5 g. of sample can be used and ananalysis can be completed in 20 minutes.Hoffmann l1 has put forward a very ingenious method for the determin-ation of traces of sulphide in paint films. The film is treated with sodiumazide and iodine solution, a control on the same reagents being run alongside.Owing to the catalytic effect of sulphide on the iodine-azide reaction, nitrogenis produced with a paint film containing sulphide.The experiments areconducted in such a way that this difference between sample and controlsides, i.e., due to nitrogen, exerts a pressure which can be measured. A mostuseful method l2 for the determination of small amounts of organically boundsulphur in non-olefinic hydrocarbons has also been worked out. Thesulphur compound is reduced to nickel sulphide with Raney nickel and afteracidification the liberated hydrogen sulphide is absorbed in a mixture ofsodium hydroxide solution and acetone before titration with standardmercuric acetate solution, dithizone being used as indicator. An analysisS. S. M. A. Khorasani and M. H. Khundar, Analyt. Chim. Acta, 1959, 21, 24.F. JanCik and J. Korbl, Talanta, 1958, 1, 55.P. Ehrlich and Th.Keil, 2. analyt. Chem., 1959, 166, 254.lo J. W, Robinson, Analyt. Chim. A d a , 1959, 20, 256.l1 E. Hoffmann, 2. arzalyt. Chem., 1959, 166, 168.l 2 T,. Granatelli, Ana.lj*t. Chern., 1959, 31, 434376 ANALYTICAL CHEMISTRY.takes less than 16 hours and good accuracy is obtained for as little as 5 y ofsulphur. As much as 50 g. of sample can be used.F. L. Hahn l3 has developed an ingenious method for the rapid deter-mination of carbonates. The sample is contained in a flask under reducedpressure, and strong acid is added, carbon dioxide being evolved from thesample. Momentary equilibration with the external atmosphere is nowmade so that the pressure within the flask is atmospheric. Sodium hydr-oxide solution is now allowed to flow into the flask, and this proceeds untilequilibrium between the external atmosphere and that in the flask is re-established.The volume of sodium hydroxide solution sucked into theflask is equivalent to the volume of carbon dioxide evolved from the sample.The Metal Impurities Sub-committee of the Analytical Methods Com-mittee of the Society for Analytical Chemistry has carried out a consider-able amount of work on various methods of destruction of organic matterbefore determination of trace elements. This sub-committee has publisheda very useful note l4 on perchloric acid and its handling in analytical work;this acid is used in appreciable quantities in wet digestion procedures. Thenote draws attention to the properties, uses, storage, and handling of theacid as well as the dangers which may occur in wood fume cupboards ifperchloric acid is in regular use in such surroundings.The determination of materials present in the air of chemical plants andin the atmosphere in general is of ever-increasing importance, and severalpapers on this subject have been published throughout the year.Gage,15for example, has described an indicator tube method for the determinationof trichloroethylene vapour in air. The sample of air is drawn through twotubes which are joined in series immediately before test. The first tubecontains silica gel impregnated with potassium permanganate and ortho-phosphoric acid. The second tube contains silica gel impregnated witho-tolidine hydrochloride and serves to measure the chlorine liberated in thefirst tube.Detector tubes have many advantages but, unfortunately, thereagent systems employed are not always extremely stable. Grosskopf l6has overcome some of these difficulties, e.g., in the determination of form-aldehyde. He provides a tube in which the carrier material is impregnatedwith sulphuric acid. Just before the test is commenced an ampoule con-taining a solid solution of a xylene isomer in paraffin is broken above thecarrier material. The air under test is drawn through the detector tube,carrying with it the xylene and any formaldehyde to the sulphuric acid.Under these conditions, reaction is instantaneous, and a red colour is obtainedproportionate to the formaldehyde concentration, In the determination ofozone in the air of rooms, it seems desirable to carry out the test by passingthe air at a definite rate through a solution of potassium iodide containingaluminium chloride and ammonium chloride a t pH 4-4.The flasks usedmust be blackened and great care must be taken over the purity of thedistilled water used. In this test, due to Hunold and Pietrulla,17 the blankl3 F. L. Hahn, Z. analyt. Chem., 1969, 166, 243.l4 Analyst, 1959, 84, 214.16 J . C. Gage, Analyst, 1959, 84, 609.l6 H. Grosskopf, 2. analyt. Chem., 1959, 170, 271.1' G. A. Hunold and MT. Pietrulla, Z. analyt. Chem., 1959, 165, 20HASLAM ANL, SQUIRKELL: GENERAL. 377is very important and is apparently best determined by passage of a knownvolume of air, freed from ozone by passage over Hopcalite, through a similarpotassium iodide solution to that described above.Included in the papers of general interest in organic analysis is that ofAdey and Cox18 who have put forward a method for the determination ofup to 2% of a-picoline in pyridine on the assumption that the impurities inthe pyridine are a-picoline and water. A definite weight of the pyridinesample under test is added to a precise amount of a 20% (w/w) solution ofpotassium chloride.The clear mixture is heated until the lower solutiontemperature is reached as indicated by the appearance of turbidity. Underthe conditions used, pure pyridine gives a solution temperature of 27.0".A mixture of 1% (w/w) a-picoline and 99.0% (w/w) pyridine gives a solutiontemperature of 26.3".Macdonald's work19 has led to the production of a neutral reagent forthe determination of fat in milk and milk products.The reagent containstrisodium citrate, sodium salicylate, and disodium ethylenediaminetetra-acetate which dissolve the solids other than fat, a polyoxyethylene derivativeof sorbitol trioleate and alcohol which assists in the fat separation, and a smallamount of butyl alcohol which ensures that the results are the same as bythe conventional Gerber procedure.Mixtures of sulphanes and sulphur have been analysed by Schmidt andTalsky.20 The sulphanes are determined by estimation of the hydrogensulphide produced by attack on this mixture with excess of cyanide, whilstthe sulphur is found by difference between the thiocyanate produced byhomogeneous and heterogeneous cyanide reaction on the mixture.In thedetermination of nitrogen in organic compounds by the Kjeldahl method,Schulek et aLZ1 make out a strong case for the collection of ammonia, distilledfrom Kjeldahl digestion products, in cold boiled-out water rather than inacid.An official method is available in this country for the determination ofalkylbenzene sulphates in river waters and sewage. It is believed, however,that various organic substances present in natural waters are liable tointerfere with the official test. Webster and Halliday22 have sought toovercome these difficulties in a procedure in which the sample is first sub-jected to acid hydrolysis. A definite process is then employed for theisolation of the detergent-l-methylheptylamine complex from the neutralisedhydrolysate.The final Methylene Blue test is carried out by the principleof the official method.The analysis of rubbers and elastomers containing acrylonitrile copoly-merised with styrene and vinylpyridines is becoming an important task inthe plastics and rubber industries. Three important papers on this subjecthave appeared in Analytical Chemistry this year. The first 23 describes thedetermination of residual acrylonitrile monomer in acrylonitrile-styreneI<. A. Adey and J. D. Cox, Analyst, 1959, 84, 414:l9 F. J. Macdonald, Analyst, 1959, 84, 287.2o M. Schmidt and G. Talsky, 2. anaZyt. Ckem., 1959, 166, 274.21 E. Schulek, K. Burger, and M. Feher, 2. analyt. Chem., 1959, 167, 28.22 H.L. Webster and J. Halliday, AnaZyst, 1959, 84, 562.28 G. Claver and M. E. Murphy, Analyt. Chem., 1959, 31, 1682378 ANALYTICAL CHEMISTRY.copolymers. The sample is dissolved in NN’-dimethylforniamide, and thefree acrylonitrile determined by a direct polarographic test after the additionof tetrabutylammonium iodide electrolyte. The presence of styrenemonomer does not affect the test. Burleigh, McKinney, and Barker 24are concerned with the determination of vinylpyridine, acrylonitrile, andacrylic acid in elastomeric polymers. By use of a selected Kjeldahl catalystcontaining potassium sulphate, selenium, mercury, and mercuric oxide anda long digestion time they are able to determine the nitrogen due to bothpyridyl and nitrile groups, with considerable accuracy, The basic nitrogenis determined by titration with perchloric acid in non-aqueous media, andacrylic acid is titrated with sodium methoxide solution also in non-aqueousmedia.The authors give useful information on the choice of solvents forboth sample and titrant for use in the non-aqueous titration methods.The analysis of acrylonitrile-methylvinyipyridine copolymers has beenapproached from rather a different angle by Stafford and T ~ r e n . ~ ~ Thenitrile is hydrolysed by boiling with concentrated sulphuric acid, and theammonia from the salts so produced distilled from the solution after theaddition of alkali by the conventional Kjeldahl procedure. The pyridine isconveniently determined by ultraviolet spec trophotome tric measurementsmade on a sulphuric acid solution of the sample after sufficient hydrolysisto solubilise the polymer.Fischer’s reagent for the determination of water may readily be preparedwater-free and of good stability by a simple process due to Eberius andBohnes.26 Methanol and pyridine, which may each contain up to 0.2% ofwater are first mixed, then sulphur dioxide is added, followed by a smallamount of iodine.Liquid bromine is nowadded until the mixture shows the presence of free bromine by its browncolour. Under these conditions the preparation is free from water andappropriate amounts of iodine and sulphur dioxide are now added to com-plete the final preparation of the reagent. The process is just as effectivewhen ‘‘ methyl cellosolve ” is substituted for the methanol.Also on thesubject of water determination, Jordan and Fischer 27 make some interest-ing observations on two methods of determination of the water content ofacetone. The first method, which they modify, depends on the reactionbetween the water in the acetone and acetyl chloride, in pyridine; the acidproduced is titrated. In their second method, a mixture of the acetonewith an equal volume of petroleum is heated and the clearing temperatureis observed. This temperature depends on the water content of the acetone.Interesting observations are made on the drying of acetone and on thehygroscopic character of dry acetone.Acetyl determinations in organic compounds are usually carried out byhydrolysis with alkali, followed by addition of sulphuric or phosphoric acidand subsequent steam-distillation of the acetic acid produced.To speed upthe test it is necessary to keep the volume low, and, in the past, it has beenPyridinium iodide is produced.24 J. E. Burleigh, 0. F. McIGnney, and M. G. Barker, Analyt. Chenz., 1959, 31, 1684.25 C. Stafford and P. E. Toren, Analyt. Chem., 1959, 31, 1687.2* E. Eberius and H. Bohnes, 2. analyt. Chem.. 1959, 168, 330.27 I<. Jordan and W. R. Fischer, %. atzalyt. Clzem., 1959, 168, 182HASLAM AND SQUIRHELL: GENERAL. 379necessary to make small batchwise additions of water in the steam-distill-ation process. Kainz 2* has now put this part of the test on an automaticbasis, as a result of which much time is saved.Motor-driven syringe burettes have been commonly incorporated inautomatic titration equipment and recording apparatus has also beenwidely used.Miller and Thomason29 have developed a method for theautomatic thermometric titration of free acids in aqueous solutions of suchmetal ions as zirconium, uranium, copper, and thorium. The free acid,which may be hydrofluoric, sulphuric, or nitric acid, is determined by titra-tion with a standard base, delivered from a motor-driven syringe andrecording of the change in temperature as detected by a thermistor duringthe titration. The end-point of the titration is obtained by extrapolationof the straight-line portions of the curves to their point of intersection. Bythis method milliequivalent quantities of free acid can be determined withreasonable accuracy.Williams and his co-workers 30 have designed a simple and highly accuraterecording titration apparatus for the automatic titration a t constant pH ofthe acidic or basic compounds liberated by the reaction of hydrolysis enzymes.The titrant, to maintain constant pH, is delivered from a micrometer syringedriven by a servo-motor which simultaneously operates the pen of therecorder along one axis.The pen carriage is moved along the other axis atconstant speed which can be varied by use of a five-speed gear box.A simple automatic apparatus has been described by Haslani andSquirrell 31 for recording full-scale potentiometric titration curves. Theapparatus combines three pieces of commercially available equipment whicha t any time can be used independently.These consist of a constant-speedinjection apparatus driving a hypodermic syringe to deliver titrant a t adefinite rate, a pH meter for indicating pH or E.M.F. change produced bythe addition of titrant, and a recorder for registration of the output fromthe pH meter. The apparatus has great versatility in speed of injection andin sensitivity control; examples are given of its use in conventional potentio-metric titrations.Thoburn and his co-workers 32 have described an automatic colorimetrictitrimeter. The titration is monitored by a light beam passing through theglass titration beaker and falling on a photo-cell. A series of 8 filters coversthe entire visible range and can be selected for use with individual indicators,At the end-point the sharp change in transmittance, recorded by the photo-cell, causes a meter relay to operate, which in turn stops delivery of titrantfrom a motor-driven syringe.An automatic counting device on the syringedrive-motor records the titration in terms of counts which can be calibratedfor each syringe. In general the delivery rate is of the order of 2-4 ml. perminute with 288 counts per ml.Calcium and magnesium have been determined by Malmstadt and28 G. Kainz, 2. analyt. Chenz., 1959, 166, 32.2D F. J. Miller and P. F. Thomason, Analyt. Chem., 1959, 31, 1498.30 R. C. Williams, R. S. Ruffin, and L. A. Mounter, Analyt. Chem., 1959, 31, 611.31 J . Haslam and D. C. M. Squirrell, J . AppZ. Chem., 1959, 9, 65.32 J.M. Thoburn, C. M. Jankowski, and M. S. Reynolds, Analyt. Chem., 1959, 31,12438 0 ANALYTICAL CHEMISTRY.Hadjiioannou= in dolomites and limetones by using a direct automaticderivative spectrophotometric titration procedure with EDTA as titrant.Calcium is automatically titrated at pH 13 with Calcon as indicator, andthe total calcium plus magnesium are titrated at pH 10 by using EriochromeBlack T as indicator; the normal and second derivative spectrophotometrictitration curves can be recorded, and the titration automatically terminatedat the end-point. A 650 mp filter is used for both indicators.Matthews and Patchan% have developed a method for the automatictitration of peroxides in petroleum products. The sample is treated withpotassium iodide, and the iodine liberated titrated with standard sodiumthiosulphate solution automatically.The method is also applicable tohydroperoxides and diacyl-type peroxides. An advantage of the method isthat the iodine liberated is immediately and continuously reduced as it isformed back to iodide by the addition of the standard thiosulphate. Theiodine concentration is rarely allowed to exceed a very small value and thenonly momentarily.The coulometric principle has been applied to the determination of waterby the Karl Fischer method. Meyer and Boyd35 have determined thewater content of organic solvents containing as little as 5 y per ml., usingtheir apparatus which utilises electrically generated iodine in a solution ofdepleted Karl Fischer reagent in ethylene glycol.Kelley and his co-workers 36 have described an automatic cut-off attachment for the pHindicator unit so that it can be used to control this titration automatically.This control unit can also be used to control other pH, millivolt, or dead-stop titrations.A new continuous chloride-ion analyser has been described by Jones aridKehoe 37 which is easy to standardise and which has applications in qualitycontrol and for monitoring the chloride-ion concentration in industrialwastes. The principle is very similar to that for pH measurement, a con-ventional reference electrode being used in conjunction with a specialsensing electrode, basically silver-silver chloride. The potential developedat the sensing electrode depends directly on the concentration of chlorideions in the solution in which the electrodes are immersed, and this potentialdifference is amplified and recorded.For the automatic and continuousdetermination of uranium in a radioactive process stream, an automaticplant-type polarograph 38 has been designed, The uranium(v1) is reducedto uranium(v) at a dropping mercury electrode in a nitric acid electrolyte,and the resultant polarograni recorded every 74 minutes. A manuallyoperated feed for the standardisation solution is incorporated in the design.This minimises interfering side reactions.33 H. V. Malmstadt and T. P. Hadjiioannou, Analyt. Chim. Acta, 1958, 19, 563.34 J. S. Matthews and J. F. Patchan, Analyt. Chem., 1959, 31, 1003.35 A.S. Meyer, jun., and C. M. Boyd, Analyt. Chern., 1959, 31, 215.36 M. T. Kelley, R. W. Stelzner, W. R. Laing, and D. J. Fischer, Analyt. Chem.,57 R. H. Jones and T. J, Kehoe, I n d . Eng. Chem., 1959, 51, 731.313 G. J. Alkire, K. Koyama, K. J. Hahn, and C . E. Michelson, Analyt. Chern., 1958,1959, 31, 220.30, 1912IIASLAM AND SQUIRKELL QUALITATIVE AND QUANTITATIVE. 38 13. QUALITATIVE AND QUANTITATIVE INORGANIC AND ORGA NICQualitative.-Many new qualitative tests have been devised during theyear and a remarkable feature has been the extremely simple nature of thetests, no doubt facilitated by the introduction of new reagents. For example,Clark et aZ.S9 have extended the field of usefulness of zinc dithiol by devisingmany simple tests for the field testing of innumerable ores and minerals.Usually a solution of part of the ore is first prepared from a few fragments ofthe ore, and zinc dithiol or a solution of dithiol freed from zinc is applied,under particular conditions, to test portions of the solution.The coloursand reactions obtained are often quite revealing. Very few reagents havebeen proposed which are specific for iron(I1). It is suggested, however,4Othat if the test solution is maintained in a special Thunberg tube which canbe evacuated before addition to cacotheline reagent, then the blue colourobtained is quite stable a t pH 7.4 and, moreover, it is said to be specific foriron(r1).At the 1958 Microchemistry Symposium held in Birmingham, a new testfor fluoride was demonstrated. It is this test which forms the basis of anew spot test for the fluoride ion 41 which, it is claimed, is the only reactionof the fluoride ion responsible for the production of a new coloured species.In this test, in an acetate buffer, the fluoride ion produces a lilac blue doublecomplex with a red cerium ( ~ v ) alizarin-complexone complex.Weisz et aZ.,42 in their ring-oven procedure, have often made use ofsulphides in determinations of separated metals.The metal is precipitatedin the paper as its sulphide, then converted into the appropriate amount ofsilver sulphide by treatment with silver nitrate, etc. In estimating theamount of silver sulphide and hence of the metal in question, only one scaleis used, i.e., the silver sulphide scale prepared by application of the test toknown amounts of copper; calibration factors for use with other elementsare available in terms of the equivalent amount of copper.As a further aidin the use of the ring-oven method, Ballezo 43 has developed a simplifiedform of the oven in which the filter-paper, on which the various analyticalseparations are carried out, is mounted on a glass plate, held at a particulartemperature by the vapour of a boiling solvent in contact with it.In the organic field, a useful method44 has been developed for theidentification of the n-alkyl groups present as side chains in alicyclic andaromatic hydrocarbons, i.e., in such substances as alkylcyclohexenes, alkyl-benzenes, and alkylcyclohexanes. The side chain is split by the oxidativeaction of a definite chromic acid-sulphuric acid mixture.The resultingacids are distilled in steam, converted into their corresponding ethyl-ammonium salts, then separated and identified by paper-chromatographicANALYSIS39 R. E. D. Clark and C. E. Tamale-Ssali, Analyst, 1959, 84, 16.40 G. G. Rao, V. N. Rao, and G. Somidevamma, 2. analyt. Chem., 1959, 166, 11.41 R. Belcher, PI. A. Leonard, and T. S. West, Talunta, 1959, 2, 92.42 H. Weisz, M. B. Cklap, and V. V. Almatan, Mikyochim. Acta, 1969, 36.43 H. Ballezo, Mikrochzm. Acta, 1959, 314.44 M. JureCek, hf. SouCek, J. ChurACek, and F. Renger, 2. analyt. Chem., 1959, 65,109382 ANALYlICAL CHEMISTRY.test. It would appear, from the work of Tisler,46 that 9-chlorobenzoylisothiocyanate has outstanding advantages as a reagent for the character-isation of aromatic and aliphatic primary and secondary amines.Reactionusually takes place in the cold and the solid products, i.e., substitutedthioureas are usually very easily crystallised.A reaction given by aliphatic and aromatic polycarboxylic acids, aryl-allryl carboxylic acids, and aromatic monocarboxylic acids which can beused for the qualitative detection of these compounds in the presence ofother carboxylic acids and sulphonic acids has been detailed by Feigl andStark-Ma~er.~~ The acids when heated at 160" with alkali or ammoniumhalides yield halogen hydracids which can be detected with indicator paperor by the demasking of silver ferrocyanide. o-Nitrophenol also gives thisreaction and hence the test is useful for distinguishing this compound fromits isomers.Instead of using an interfacial test, Turney4' claims to haveextended the general utility of the Molisch carbohydrate test by adding adefinite weight of the substance under test to a definite weight of l-naphthol,then adding sulphuric acid and mixing immediately.Advantage has been taken of the condensation reaction between aliphaticketones containing the structure R*CH,-CO*CH,R' and 2-hydroxy-l-naphthaldehyde in a method due to Sawicki and Stanley@ for the colori-metric detection of small amounts of such ketones. The reaction is carriedout under special conditions in the presence of aluminium chloride with2-methoxyethanol as the reaction medium.It is the exothermic reactionbetween the 2-methoxyethanol and the reagent powder containing thealuminium chloride that provides the heat necessary for colour development.The test appears extremely simple to carry out, and a positive blue colourA,, 598 mp) can be obtained with amounts of ketone as low as 1-5 y in0.5 ml. of 2-methoxyethanol solvent.Feigl and Jungreis49 have utilised work previously carried out by Duffto develop new spot tests for phenols and dialkylanilines. The phenol isheated with a mixture of oxalic acid and hexamine; fonnylation takes place'and an o-hydroxyaldehyde is produced. This is detected by its reactionwith hydrazine to yield a fluorescent aldazine. The alkylated aniline istreated initially in the same way as the phenol with the production of a9-dialkylaminobenzaldehyde or a 9-monoalkylaminobenzaldehyde.Thisreaction product is detected by the formation of an orange-coloured Schiff'sbase with benzidine. Another useful test has been described by Pesez andBartos 5O for m-biphenols. These compounds form a red complex in highlyacid alcoholic media with diphenylacraldehyde. The sensitivity of the test issuch that 1 pg. of biphenol can be detected in 5 ml. of final coloured solution.Reaction also takes place with compounds having a methylene group inthe a-position to a carboxyl and with primary aromatic amines; in thesecases the reaction products are yellow.45 M. Tisler, 2. analyt. Chem., 1959, 165, 272.46 F. Feigl and C. Stark-Mayer, Talanta, 1958, 1, 252.47 T.A. Turney, Analyst, 1959, 84, 194.48 E. SaN-icki and T. W. Stanley, Analyt. Chem., 1958, 31, 122.49 F. Feigl and E. Jungreis, Analyst, 1958, 83, 666.60 M. Pesez and J. Bartos, Analyt. Chim. ,4cta, 1959, 20, 187TIASLA4M AND SQUIRREtL QUALITATIVE AND QUANTITATIVE. 383Knight and House 51 have tackled the complex problem of characteris-ing or analysing surface-active agents by a novel procedure. They preferto decompose the sample with phosphoric acid and examine the non-surface-active hydrophobic oil so produced. This examination involves gas-liquidchromatography and infrared spectroscopy. Aromatic, sulphonated,straight-chain alkyl sulphates, amides, and esters are decomposed to givegood yields of the parent hydrophobic materials. Dioctyl sulphosuccinategives a mixture of octyl alcohols and olefins and ethylene oxide; alcoholcondensates give olefins derived from the starting hydrophobic materials.Much other useful information on the classification of surface-active agentsby qualitative tests is given in the previously mentioned review by Smith.52Amin 53 has used the p$’-nitrophenylazobenzoyl derivative for the char-acterisation of thiols.He has prepared the derivatives of some nine thiolsin reasonable yield and found that they crystallise well and have well-definedmelting points. The derivatives can also be separated chromatographicallywhich is of great advantage when mixtures of thiols have to be characterised.Quantitative (Gravimetric).-A rapid gravimetric method for the deter-mination of aluminium in titanium and other alloys which is applicablewithout preliminary separation from such elements as manganese, vanadium,tin, chromium, iron, etc., has been described by Pender.54 The sample isdissolved in dilute hydrofluoric acid and oxidised with hydrogen peroxidebefore precipitation of the aluminium as sodium fluoroaluminate by additionof sodium fluoride.This salt is isolated, reprecipitated, washed, and driedunder specified conditions. The method requires only half the time neededby other methods and gives results comparable with those obtained by the8-hydroxyquinoline method. Ziegler and Horn% have shown that, at anappropriate pH value, molybdate may be separated from vanadate byextraction of the tributylammonium molybdenum thioglycollate complexof the molybdenum with methylene chloride as solvent.The methylenechloride extract is wet-digested, and the molybdenum finally determined aslead molybdate.2-Aminopicolinic acid, prepared by oxidation of 8--hydroxyquinoline,appears to be a very selective reagent for the precipitation of palladium.56This element is precipitated quantitatively over the pH range from normalwith respect to hydrochloric acid, to pH 12.5. It is possible to precipitatepalladium free from most of the common ions and the interference of coppermay be avoided by the use of EDTA, and that of silver by working at apH of 7 or above. After precipitation, the determination may be completedby solution of the palladium-containing precipitate in excess of potassiumcyanide solution and back titration of the excess cyanide with standardsilver solution.An interesting separation of silver from lead has beenproposed by Ziegler ef aL5’ The solution, at an appropriate pH, is treated51 J. D. Knightand R. House, J . Amer. Oil Cliemists’ SOL, 1959, 36, 195.53 W. B. Smith, Analyst, 1959, 84, 7 7 .F , ~ El S. Amin, J., 1958, 4769.54 H. W. Pender, Analyt. Cltem., 1959, 31, 1107.55 M. Ziegler and H. G. Horn, 2. analyt. Chem., 1959, 166, 362.56 A. I<. Majumdar and S. P. Bag, %. analyt. Chem., 1958, 164, 394.57 hf. Ziegler, H. Sbrzesny, and 0. Glemser, 2. nncrlyt. Chem., 1969, 167, 96384 ANALYTICAL CHEMISTRY.with isopropenylacetylene, silver isopropenylacetylide being produced.This substance is extracted with methylene chloride.On treatment of thesolvent layer with hydrochloric acid solution the silver is converted intochloride and is finally weighed as such. Miller and Thaw 58 have establishedconditions for the quantitative determination of tungsten. These involvethe addition of orthophosphate to the tungstate solution, after which theacidity is adjusted by the addition of hydrochloric acid. Tri-n-butyl-ammonium chloride is used as precipitant, and the precipitate of tris-tri-n-butylammonium 12-tungstophosphate is recovered, washed, and dried at 210".m-Ethylphenoxyacetic acid is understood to be a very selective reagentfor the determination of zirconium.59 The precipitation suffers no interfer-ence from most cations and even chromium and vanadium can be removedby reprecipitation.The precipitate is of variable composition and containsboth the mono- and the semi-hydrate of rn-Et~C,H,~O~CH,~CO~O.ZrO(OH).Hence the determination must be completed by ignition of the precipitateto zirconium dioxide.In a method which appears satisfactory for use in a plant-control labor-atory, Lysyj and his co-workers 6o determine carbon monoxide by a gravi-metric procedure. They prefer to convert the monoxide into the dioxideby passage over thermally decomposed silver permanganate as catalyst ; thedioxide thus formed is absorbed in a weighed Ascarite tube. Carbon mon-oxide concentrations between 0.1 and 1.5% (vlv) can be determined whenusing only 500 ml. of gas sample.Quantitative (Volumetric) .-Of the large number of conventional volu-metric methods described in 1959 we are able to mention but a few.Acompound called Siloxen,G1 which is readily prepared by the action of hydro-chloric acid on calcium silicide, has proved to be a chemiluminescent end-point indicator of considerable value in redox titrations where the colour ofthe solution or the reaction products causes difficulties in the titration. Itis particularly useful in the direct permanganornetric titration of iodides,ferrous iron, stannous, molybdenum(IrI), arsenite, and oxalate ions andhydrogen peroxide. It may also be used in the indirect permanganometrictitration of iodates, silver and vanadium(v) ions. Improved indicators forEDTA titrations are still being produced, and Omega Chrome Fast Blue 2G 62is now proposed for the direct titration of calcium, magnesium, manganese,and nickel and for the direct displacement titration of lead and cadmium.I t is suggested that improvements in cerrain EDTA spot tests may beeffected by the addition of fenugreek mucilage, a colourless polysaccharide.Yalman and his co-workers63 prefer to use an indirect method for thedetermination of calcium in the presence of phosphate.A 15-20% excessof standard EDTA solution is added to a hydrochloric acid solution of thesample containing phosphate. The solution is made alkaline with sodium58 C . C . Miller and D. H. Thaw, Aulalyst, 1959, 84, 440.59 A. B. Sen and S. Misra, 2. analyt. Chem., 1959, 168, 343.60 I. Lysyj, J.E. Zarembo, and A. Hanley, Analyt. Chem., 1959, 31, 902.61 L. Erdley, I. BuzBs, and L. Pdos, 2. analyt. Chem., 1959, 169, 187.62 A. A. Abdel el Raheem, 2. analyyt. Chem., 1959, 167, 98.63 R. G. Yalman, W. Bruegemann, P. T. Baker, and S. M. Garn, Analyt. Chem. ,1959, 31, 1230HASLAM AND SQUIRRELL: QUALITATIVE AND QUANTITATIVE. 385hydroxide, and the excess of EDTA back-titrated slowly with calciumchloride solution to the yellow-green colour of Calcein indicator. Morestandard EDTA is now added until the true pink brown Calcein end-point isobserved. Conventional iodide procedures for the determination of copperin carbonatite ores are not very satisfactory, and particularly so in thepresence of large mounts of calcium. In his proposed method, Toerien 134dissolves the ore in a mixture of nitric, orthophosphoric, and perchloric acidsand readily obtains a clear solution. Permanganic acid is reduced by oxalicacid solution, and iron complexed with sodium fluoride.The pH of thesolution is adjusted to between pH 2.5 and 3 with sodium acetate solution,before the final iodimetric determination of the copper.Ferric salts, a t the appropriate degree of sulphuric acid acidity, arespeedily reduced by hydroxylamine hydrochloride solution. This forms thebasis of a method of determination of iron,% the resulting ferrous solutionbeing titrated with sodium vanadate, N-phenylanthranilic acid being usedas indicator. Precautions have to be taken in the presence of tungsten andvanadium. A rather novel procedure has been devised by Jackwerth andSpecker 66 for the determination of bivalent mercury which does not sufferinterference from chlorides and bromides and the great majority of heavy-metal ions. Bismuth(II1) is added to the mercury(x1) solution which is thentitrated with standard iodide solution in the presence of cyclohexanone.Whilst the mercury(I1) is being complexed the organic layer is colourless oryellow, but at the end-point it becomes orange owing to the production andsolution in the organic phase of the bismuth complex.Rao and Suryana-rayanaG7 have put forward what they describe as a new method for thedetermination of molybdenum(v1). They rely on the fact that molyb-denum(v1) compounds, in hydrochloric acid at loo", are reduced immediatelyby hydrazine sulphate only to the molybdenum(v) condition; the molyb-denum(v) compounds may then be titrated with standard solutions ofvanadate or ceric sulphate.In connection with work on Ziegler catalysts it is often desirable to beable to express opinions about the proportion of Ti(I1) compounds presentin particular circumstances.To do this it is necessary to be able to realisethe two reduction equivalents of Ti@). It has been shown by Martin andStedefeder 68 that this may be accomplished by reaction with ferric chlorideat -50" to -70" in alcohol and in an atmosphere of carbon dioxide. If acatalyst contains both Ti@) and Ti(Ix1) compounds then by oxidation a tlow temperatures and later at 20-80" both reduction equivalents of theTi(@ are realised in a preliminary titration.Before a second titration,which determines total titanium, the catalyst containing Ti(I1) and Ti(II1)compounds is treated with S~-hydrochloric acid at room temperature, theTi@) being converted into Ti@); the total Ti@) is then determined bytitration with ferric chloride. The results of the two tests enable theproportions of Ti(I1) and Ti(II1) in admixture to be determined.64 F. v. S. Toerien, Analyst, 1959, 84, 565.65 G. G. Rao and G. Somidevamma, 2. analyt. Chem., 1959, 165, 432.66 E. Jackwerth and H. Specker, 2. analyt. Chem., 1959, 167, 269.67 G. Gopala Rao and M. Suryanarayana, 2. analyt. Chem., 1959,168, 177.68 H. Martin and J. Stedefeder, Annalen, 1958, 618, 17.REP.-VOL. LVI 386 ANALYTICAL CHEMISTRY.Much attention has been directed to the volunietric determination ofanions.For example, Szekeres and Bakkcs-Polgar 69 have suggested amethod of examination of alkali carbonates and bicarbonates in whichalcohol is added to a solution of the sample and the carbonate then titratedwith barium chloride to the phenolphthalein end-point. Excess of bariumchloride is now added, and the mixture boiled to break down the bicarbonate.The excess of barium is now titrated with sodium carbonate solution (phenol-phthalein indicator). In this way a measure of the bicarbonate is obtained.The problem of the determination of bromate and periodate in thepresence of one another has been solved in two ways.’O (a) After determin-ation of the total periodate and bromate iodometrically, a fresh portion ofthe material is titrated with bromide in hydrochloric acid solution.Theperiodate is reduced to iodate and the bromate to bromine. Sodiumhydrogen carbonate is now added and the hypobromite produced is allowedto react with urea solution. When this reaction is complete, the iodate isdetermined by reaction with iodide and acid. (b) The total periodate andbromate is determined as above. In a second portion of the sample theperiodate is reduced to iodate with hydrogen peroxide in sodium hydrogencarbonate solution. *4fter removal of excess of peroxide, the sum of theiodate plus bromate is determined iodometrically. Appropriate calculationsnow yield figures for the proportions of periodate and bromate in the originalmixture.The old Fajans titration, in which chloride ion is titrated with silvernitrate solution using fluorescein as adsorption indicator, is not alwayssuccessful with certain organic base hydrochlorides.This is due to the factthat in aqueous media the silver chloride formed in the course of the titrationmay be peptised by the associated cations to the almost clear highly dispersedsol. These difficulties may be avoided 71 by titration of the hydrochloridesin 70% methanol solution. Previous work by Erdey and Svehla72 onoxidising agents has now been extended to the determination of free halogens,hypohalogenites, halogenites, and halogenates, etc. In this method theoxidising agent first oxidises ferro- to ferri-cyanide, which is then determinedby titration with ascorbic acid solution, 2,6-dichlorophenolindophenol beingused as indicator.Also on the subject of oxidising agents, there is no doubtthat a method proposed by Rao and Laddha73 for the determination ofchlorate in the presence of perchlorate will prove to be controversial. Theseauthors suggest, though not with complete conviction, that the chloratemay be determined by titration of the acid solution with standard titanoussolution in the cold and in the presence of bromide with Quinoline Yellowas indicator.As a result of the work of E. BakLcs-Polgar 74 it is now possible to deter-mine phosphate volumetrically in the presence of otherwise interfering ions.The solution under test is first treated with 1,2-diaminocyclohexane-NNN’N’-69 L.Szekeres and E. BakBcs-Polgar, 2. anal-~t. Chem., 1959, 165, 85.70 L. Szekeres, 2. analyt. Chem., 1959, 165, 32.7 1 Th. Eckert, Arch. Pharm., 1959, 292, 320.72 L. Erdey and G. Svehla, 2. analyt. Chem., 1959, 167, 164.73 B. K. Sadananda Rao and G. S. Laddha, 2. analyt. Chem., 1959, 167, 410.74 E. BakBcs-Polgar, 2. analyt. Chem., 1959, 167, 353HASLAM AND SQUIRRELL : QUALITATIVE AND QUANTITATIVE. 387tetra-acetate (DCTA) which masks iron and aluminium at the appropriatepH. A.fter formation of these complexes excess EDTA is added to complexcalcium and magnesium. The excesses of EDTA and DCTA in the presenceof buffer and indicator are titrated with magnesium chloride solution.Alcohol is now added, after which the phosphate ion is titrated with standardmagnesium solution.Riedel 75 has also developed an interesting procedurefor the determination of phosphate. After removal of sulphate as thebarium salt, the phosphate is precipitated in perchloric acid medium by theaddition of a known amount of bismuth solution. The excess of bismuth isthen back titrated with EDTA in acid solution and in the presence of thebismuth phosphate. The test may be carried out in solutions containingphosphate and ferric salts; in that case the ferric salts are reduced at asuitable stage in the process.In a method again due to Bakiics-Polgar and Szekeres 76 for the deter-mination of phosphate and sulphate in the presence of one another, thephosphate is first titrated in aqueous-alcoholic medium a t pH 10 with stan-dard magnesium chloride as titrant and Eriochrome Black T as indicator.The magnesium is precipitated as magnesium ammonium phosphate andslight excess of magnesium ions is indicated by the colour change of theindicator.This excess of magnesium is removed by addition of EDTAsolution and this is accompanied by appropriate colour change. The sul-phate is now titrated with standard barium chloride solution, which at theend-point produces a final colour change because the excess of barium dis-places the magnesium from the magnesium complexone. H. Plaetschke 77has developed a rapid and simple method for the determination of sulphatein aluminium sulphate solutions. He uses an indicator solution preparedfrom the disodium salt of tetrahydroxybenzoquinone, potassium chloride,and sodium nitrite and to this is added a known volume of standard bariumchloride solution.A deficiency of the aluminium sulphate solution undertest is added, and the titration then completed by the addition of standardpotassium sulphate solution to the change point, i.e., rose to orange-white.Conditions have also been worked out 78 which are suitable for the titrimetricdetermination of 2-200 mg. of sulphate. The titration is carried out in50% propan-2-01 solution with lead nitrate as titrant; dithizone and 4-2'-pyridylresorcinol are used as indicators at pH values of 4 and 6 respectively.Contributing to the numerous volumetric methods applied to organicanalysis, Koszegi and Salg6 79 have shown that it is possible to determinehexamethylenetetramine, formaldehyde, and inorganic ammonium com-pounds by quantitative oxidation with bromate in acid solution at 100".The flasks used are designed to avoid loss of bromine in the test, and aniodometric titration procedure is employed in the determination of thebromate consumption.For the determination of acetyl groups in organiccompounds, Miizor and Meiselso prefer to dissolve or suspend the material75 K. Riedel, 2. analyt. Chem., 1959, 168, 106.76 E. Bakacs-Polgar and L. Szekeres, 2. analyt. Chem., 1959, 166, 406.77 H. Plaetschke, 2. analyt. Chem., 1959, 168, 264.78 R. Puschel, E. Lassner, and P. L. Reiser, 2. unaZyt. CJzevn., 1959, 166, 401.79 D. Koszegi and E. Salg6, 2. analyt.Chem., 1958, 184, 320.L. MAzor and T. Meisel, Amdyf. Chim. Acta, 1959, 20, 130388 ANALYTICAL CHEMISTRY.in absolute methanol and saponify with a known amount of potassiummethoxide solution. The excess of methoxide is then hydrolysed, and theresulting potassium hydroxide determined by titration with standard acidand an appropriate indicator.Kavaranaa finds that for the assay of acetylsalicylic acid in tablets, atitration with sodium methoxide solution in an anhydrous pyridine mediumto a phenolphthalein end-point, gives excellent results. The method hasthe great advantage that ather constituents usually associated with acetyl-salicylic acid in tablets, viz., phenacetin, caffeine (or caffeine sulphate),phenobarbitone, quinine sulphate, and excipients, do not appear to interferein the test.West and Skoog 82 have shown that acidic solutions of vanad-ium(v) are moderately strong oxidising agents for certain organic corn-pounds. Oxidation of a-hydroxy-acids produces carboxylic acid and carbondioxide, whilst oxidation of ethylene glycol, glycerol, and 1,3-propanediolyields formic acid. These authors also use the principle of the test in amethod 83 for the determination of glycerol. The excess of oxidant is titratedwith ferrous solution, N-phenylanthranilic acid being used as indicator.In the presence of zinc sulphate, hydroxylamine is oxidised to nitric acidand water, and hydrazine to nitrogen, by alkaline ferricyanide. In theabsence of zinc sulphate, however, hydrazine and hydroxylamine are bothconverted i - to nitrogen.Sant has utilised both these reactions in amost useful method for the determination of milligram quantities ofhydrazine and hydroxylarnine either alone or in admixture. The end-pointin the titration of ferricyanide with hydrazine and hydroxylamine sulphatesis denoted by the appearance of a clear white precipitate of zinc potassiumferrocyanide. Fritz and Schenk 85 prefer to use perchloric acid as catalystin the acetylation of hydroxy-compounds. The acetylation of alcohols withacetic anhydride in ethyl acetate solution is complete in 5 minutes at roomtemperature by this methad, and pyridine can also be used as solvent.When acetylation i s complete the excess of anhydride is decomposed withpyridine and water and determined with standard alkali in the normal wayagainst a blank on the reagents alone.Hindered alcohols, glycols, somesugars, and hydroperoxides also react quantitatively.Jaselkis 86 has detailed two useful procedures for the determination ofthe components of alkanethiol-dialkyl sulphide and -dialkyl disulphide mix-tures. In the first case the thiol in an aliquot part of the test solution istitrated with iodine, arid the dialkyl sulphide + thiol in a second aliquotpart are titrated with bromide-bromate solution in the presence of alkalineacrylonitrile to convert the thiol into sulphide. In the second case the thiolalone is titrated first, and then after reduction of the alkyl disulphide tomore thiol with zinc in acetic-hydrochloric acid-alcohol, the total thiols areagain titrated iodometrically.The method is quantitative for alkyl disul-phides of molecular weight higher than propyl disulphide.81 H. H. Kavarana, Indian J. Phavm., 1958, 20, 248.82 D. M. West and D. A. Skoog, Analyt. Chern., 1959, 31, 583.83 D. M. West and D. A. Skoog, Analyt. Chem., 1959, 31, 586.84 B. R. Sant, Analyt. Chim. Aeta, 1959, 20, 371.85 J. S. Fritz and G. H. Schenk, Analyt. Chem., 1959, 31, 1808.86 B. Jaselkis, Analyt. Chem., 1969, 31, 928HASLAM AND SQUIRRELL : QUALITATIVE AND QUANTITATIVE. 389A method which is said to be of wider application than others has beendescribed by Johnson and Fletcher 87 for the determination of vinyl ethersand other olefinic unsaturation. The sample is allowed to react with anexcess of mercuric acetate in methanol to form the addition compound,with the liberation of acetic acid.Sodium bromide is added to convert theexcess of mercuric acetate into the bromide, which permits direct titrationof the acetic acid with alcoholic potassium hydroxide solution. The wideapplicability of the method is demonstrated by results obtained on 16 vinylethers and 27 miscellaneous olefinic compounds. Wehle has put forwarda method for the determination of propan-2-01 which may be useful in theexamination of cosmetic preparations. The procedure is based on oxidationof the propan-2-01 to acetone by a solution of bromine in phosphoric acid.The excess of bromine, and any bromine which may have entered intocombination with the acetone, are determined by reaction with potassiumiodide solution a t appropriate temperature followed by titration of theliberated iodine with standard thiosulphate solution.Schulek, Burger, andFeh6r g9 are concerned with the alkali hydrolysis of organic nitro-compoundsand with the determination of ammonia, cyanide, nitrite, and nitrate in thehydrolysis products which are obtained. They rely on distillation a t acontrolled pH to separate the ammonia and cyanide from the nitrate andnitrate. The ammonia in the distillate is determined by titration, and thecyanide by application of the cyanogen bromide reaction. In the residualsolution nitrite is determined by application of the iodide reaction andnitrate by Devarda’s alloy reduction.Caso and Cefola9* havefound that sulphamic acid is an excellent primary standard for use in suchtitrimetry. It can be purified easily, dissolves readily in basic solvents suchas dimethylformamide and n-butylamine, and gives no gels or precipitatesin the course of titration with lithium methoxide in benzene-methanolsolution.It can also be used as a standard in conductometric titrations insuch media as dimethylformamide and glacial acetic acid, in which solventit is possible to titrate with perchloric acid in glacial acetic acid. Barnes 91has described a method for the non-aqueous determinatioh of acetylenichydrogen which is based on reaction of the monosubstituted acetylenic com-pound with silver perchlorate, with a subsequent liberation of hydrogen ions.The acid produced as a result of acetylide formation is titrated with a stan-dard solution of tris(hydroxymethy1)methylamine in methanol to screenedThymol Blue indicator.This method permits direct determination ofacetylenic hydrogen in water-immiscible solvents and easily hydrolysedesters.Amongst the other interesting papers on non-aqueous titrimetry that ofReiss 92 should be noted. He shows that substances such as quinine hydro-chloride and antipyrine, soluble in acetic anhydride, can be readily titratedWe turn now to work in non-aqueous media.87 J. B. Johnson and J. P. Fletcher, Analyt. Chem., 1959, 31, 1563.88 H. Wehle, Z . analyt. Chem., 1959, 169, 241.89 E. Schulek, I<. Burger, and M. FehPr, 2. anatyb. Chem., 1959, 167, 423.90 M.M. Caso and M. Cefola, AnaZyt. Chiwr. Acta, 1959, 21, 205.91 L. Barnes, jun., Autalyt. Chsh,, 1959, 31, 405.92 R. Reiss, 2. analyt. Chem., 1969, 167, 16390 ANALYTICAL CHEMISTRY.in that medium with solutions of perchloric acid in glacial acetic acid; thesame applies to substances such as hyoscyamine hydrobromide and nico-tinic acid, soluble in the course of the titration. Difficulty soluble substancessuch as aneurin hydrochloride and caffeine can be dissolved in formic acidbefore application of the test. Metal halides such as sodium chloride,strontium chloride, and potassium bromide respond to this latter test.Patchornik and Rogozinski 93 have presented a method for the determin-ation of the individual components of complex mixtures of organic andinorganic acids, acyl halides, anhydrides, and alkyl halides.The method isof high accuracy and is based on titration of the components in non-aqueousmedia with three standard base solutions, namely, sodium methoxide,tributylamine, and benzyltrimethylammonium hydroxide. The sameindicator is used for all titrations. Finally, Small 94 claims to obtain excel-lent results in the direct determination of active hydrogen in ethanolamine-type compounds. The sample is dissolved in tetrahydrofuran and titratedwith lithium aluminium di-n-butylamide in an atmosphere of nitrogen.4-Phenylazodiphenylamine is a satisfactory end-point indicator.4. PHYSICAL METHODSElectrical.-In this section we deal with electrical methods of all kinds,starting with the inorganic and organic applications of potentiometry.Standardisation in pH work is of interest to all, and Keyworth and Hahn 95are in favour of sodium hydrogen diglycollate as a reference buffer for thestandardisation of electrode systems and for other buffer purposes. Thematerial is non-hygroscopic and readily available in a primary standardgrade. A 0.2~-solution has a pH of 3-40 & 0.02 over a wide temperaturerange and dilution by a factor of two does not affect the pH by more than0.02 unit.Khalifa et aLg6 have extended their previous work on EDTA titrations,using mercuric nitrate as back titrant in alkaline medium, to problemsinvolving the analysis of binary mixtures of bismuth with such elements ascalcium, strontium, copper, zinc, cadmium, lanthanum, lead, nickel, ormanganese.In such cases two titrations are performed: (a) a titration ofthe bismuth alone with EDTA at pH 2.5, potassium iodide being used ascolorimetric indicator; and (b) a second titration at pH 8-5-9-5 in whichexcess of EDTA is added, and this excess back-titrated potentiometricallywith standard mercuric nitrate, using a silver amalgam indicator electrode.The second titration gives a measure of the total bismuth plus the otherconstituent of the binary mixture. Saxena and Bhatnagar 97 have madepotentiometric studies of the precipitation of copper ferrocyanide by titra-tions of copper sulphate with potassium ferrocyanide at various concen-trations, using a ferri-ferro-cyanide electrode system. As a result of thiswork they find that the sharp potentiometric end-point corresponds with93 A.Patchornik and S. E. Rogozinski, Analyt. Chem., 1959, 31, 985.94 L. A. Small, Analyst, 1959, 84, 117.95 D. A. Keyworth and R. B. Hahn, Talanta, 1951, 1, 41.96 H. Khalifa and A. Soliman, 2. analyt. Chem.. 1959, 169, 109.97 R. S. Saxena and C. S. Bhatnagar, Analyt. Chim Ada, 1959, 20, 494HASLAM AND SQUIRRELL : PHYSICAL METHODS. 39 1the formation of a compound K,Cu,[Fe(CN),],. The titration curves areregular and reproducible and thus the system presents a useful method forthe determination of copper in solution.Gansel 98 has described both macro- and micro-procedures for the directdetermination of silver in such materials as photographic films, emulsions,etc. He wet oxidises the organic matter and halides by treatment withsulphuric-nitric acid and finally titrates the silver sulphate so produced withstandard potassium bromide solution potentiometrically.An advantage ofthe method is that the complete process is carried out in the same vessel. Animportant advance in the determination of halogens in organic compoundshas been made by Menville and Parker.s9 The sample in a suitable solventis decomposed by the addition of dispersed sodium reagent and propan-2-01.When decomposition is complete (after 5 minutes) the excess of sodium isdestroyed with methanol, and the solution acidified with nitric acid beforepotentiometric titration of the ionised halide in the aqueous phase withsilver nitrate solution. Results of quite good accuracy have been obtainedon a wide range of organic halides.The determination of small amounts of chloride has been dealt with byseveral workers.For example, a new method which is both rapid andaccurate has been presented by Malmstadt and WinefordnerlOO for thedetermination of chloride in the range 10-6-10-1~. The method is basedon null-point potentiometry and uses two similar silver chloride electrodes,one of which is in contact with the test solution and the other with a knownreference solution contained in an isolation compartment or cell linked tothe solution under test by an asbestos fibre or similar contact. The methodconsists simply of changing the chloride concentration of the unknownsolution whilst maintaining the ionic strength constant until the concen-tration is identical with the known reference and a null reading on thepotentiometer is obtained.The total ionic strength is kept constant byusing large but identical quantities of electrolyte in both reference sampleand titrant solution. Very small amounts of chloride, i.e., less than 1 p.p.m.,in ethylene glycol have been titrated potentionietrically by Hanna andJura.lol The electrode system is simply a silver indicator electrode and acalomel electrode with the saturated potassium chloride solution replacedby potassium nitrate solution, as reference. The titration is carried outwith 0.0005~-silver nitrate solution in propan-2-01, conventional potentio-metric titration curves being obtained.The difficult problem of the determination of small amounts of chloridein titanium and zirconium has been dealt with quite successfully by Priceand Coe.lo2 In the final titration two identical silver-silver chloride elec-trodes are used, and a small e.m.f.is applied across the two electrodesimmersed in the stirred solution, containing chloride, under test. Chlorideions from the solution being tested and silver ions from the titrant, reactreversibly at the electrodes. The resulting current falls to a minimum at the98 E. E. Gansel, Analyt. Chem., 1959, 31, 1366.loo H. V. Malmstadt and J. D. Winefordner, A~zalyt. Chim. Ada, 1959, 20, 383.Io1 J. G. Hanna and J. Jura, Analyl. Claem., 1959, 31, 1820.lo3 D. Price and F. R . Coe, Annlyyt, 1959, 84, 65.R.L. Menville and W. E. Parker, Analyt. Chem., 1959, 31, 19013 92 ANALYTICAL CHEMISTRY.end-point of the titration and rises when excess of silver titrant is added.The authors have extended the principle of the test to the correspondingdetermination of chloride in paper.lo3In the organic field, Fritz and his co-workers l0Q have presented a methodfor the determination of carbonyl compounds which gives distinct end-points whether carried out with a potentiometric or indicator titrationfinish. The carbonyl compound is treated with 2-dimethylaminoethanoland hydroxylamine hydrochloride in methanol-propan-2-01. The excess ofhydroxylamine is then determined by titration with a standard solution ofperchloric acid in methyl cellosolve. Martius Yellow indicator mixed witha little Methyl Violet is used in the visual end-point procedure, the colourchange corresponding exactly with the point of maximum inflection in theconventional potentiometric titration curve.Sass loti has put forward aninteresting method for the identification and quantitative examination ofmixtures of saturated fatty acids from octanoic to stearic acid. These acidsare converted into the corresponding potassium salts, which are thendifferentiated by potentiometric titration with standard silver nitratesolution. Advantage is taken of the different solubility products of thesilver salts of the various acids.Willemart and FabrelOG have described a method for the analysis ofmixtures of thiols and organic disulphides.The total of thiols plus di-sulphides is determined by titration with a standard solution of potassiumbromide after the addition of potassium bromate and mineral acid to thesample solution. The following reactions occur :R.SH + 3Br, + 2H20 RS02Br + 5HBrR S 9 R + 5Br, + 4H,O -E 2R*SO,Br + 8HBrThe thiol alone can be selectively titrated in another aliquot part of thesample solution with the same solution of potassium bromate. In this,however, potassium bromide is replaced by potassium iodide and underthese conditions the thiol alone is titrated:HBrO, + 6HI + 6Hf ---+ HBr + 318 + 3H,OThe end-point in the titrations can be satisfactorily detected potentio-metrically under standard polarisation conditions, and from the titrationfigures obtained the proportion of thiol and disulphide in the mixture canbe calculated.Potentiometry in non-aqueous media has become a very valuable ana-lytical tool.Malmstadt and Vassallo lo' have combined the use of theirderivative potentiometric and spectrophotometric titration procedure andtri-n-butylmethylammonium hydroxide titrant, in a most useful method forthe titration of hydrochloric-sulphuric acid and nitric-sulphuric acid mix-tures in acetone. Under the conditions of the method, two end-points areobtained, the first corresponding to the hydrochloric or nitric acid and the103 D. Price and F. R. Coe, Analyst, 1959, 84, 62.lo4 J. S. Fritz, S. S. Yamamura, and E. C . Bradford, Analyt. Chem., 1959, 31, 260.106 C. Sass, Fette u. Seijen, 1959, 61, 93.106 R.Willemart and P. Fabre, Ann. Phurm. f r a q . , 1958, 16, 676.107 H. V. Malmstadt and D. A. Vassallo, Analyt. Chem., 1969, 31, 200HASLAM AND SQUIRRELL : PHYSICAL METHODS. 393first hydrogen of the sulphuric acid, and the second to the second hydrogenof the sulphuric acid. Both end-points are sharp and can be easily discernedfrom normal potentiometric curves or by visual detection. Considerationsof other titrants and solvents are given. Das and Mukherjee lO8 also titratesulphuric acid as a mono- or di-basic acid in a glycol-isopropyl alcohol mediumusing sodium hydroxide or an organic base, e.g., piperidine, as titrant. Thetitration is carried out potentiometrically or conductometrically and is usefulfor the quantitative evaluation of mixtures of sulphuric with other acidsincluding hydrochloric, nitric, perchloric, phosphoric, and acetic acids.Cundiff and Markmaslog have extended their work on the differentialtitration of strong acids with tetrabutylammonium hydroxide.They alsoinclude in their latest study the titration of mixtures of sulphuric acid withnitric, hydrochloric, perchloric, phosphoric, or sulphonic acids and theresolution of a typical mixture of a strong, weak, and very weak acid.They again emphasise the great versatility of this titrant.The application of constant-current potentiometry to the non-aqueoustitration of weak acids has been described by Shain and Svobodal10 whouse tetrabutylammonium hydroxide as titrant and acetone as solvent.Two platinum electrodes are used with a polarising current of 1 PA through-out the titration, whilst the potential difference between the electrodes isregistered by a pH meter or voltameter.In most cases a typical peak-shaped titration curve is obtained permitting extremely easy recognition ofthe end-point. Mathews and Welch l l 1 7 l l 2 have also critically examinedpotentiometric methods €or the titration of weak acids and phenols inseveral solvents and have discussed the relative merits of some electrodesystems.Van Meurs and Darmen 113 have made an extensive study of the conducto-metric and potentiometric titration of nitrogen bases in non-aqueous mediawith, for example, perchloric acid. They have discussed the factors govern-ing the shape of the titration curves, uiz., nature of solvent and titrant,temperature, etc. They present useful conclusions on this method ofde t ei-mination, and prefer pot en tiome t ri c t itration rat her than conducto-metric, especially when dealing with mixtures.A chemically inert mediumof low solvating power, but of sufficient conductivity to permit titration,gives best results and hence nitrobenzene is an excellent solvent. Streuli 114has correlated the potentiometric titration behaviour of different types oforganic bases in nitromethane with their structure. He finds that althoughamines give normal-type titration curves, yet monosubstituted and un-substituted amides and ureas show extremely steep titration curves, probablydue to hydrogen bonding. Equations are presented relating basicity of thevarious compounds in nitromethane and water.Other electrical methods include a continuous process described bylo8 M.N. Das and D. Mukherjee, Analyt. Chem., 1959, 31, 233.lo0 R. H, Cundiff and P. C. Markunas, Analyt. Chim. A d a , 1939, 20, 506.110 I. Shain and G. R. Svoboda, A~zalyt. Chem., 1959, 31, 1857.111 D. H. Mathews and T. R. Welch, J . Appl. Chem., 1958, 8, 701.112 D. H. Mathews and T. R. Welch, J . Appl. Chem., 1958, 8, 710.11s N. Van Meurs and E. A. M. F. Darmen, Analyt. Chim. Acta, 1959, 21, 193.lI4 C. A. Streuli, Arzalyt. Chem., 1959, 81, 1662394 ANALYTICAL CHEMISTRY.Eckfeldt 115 which may have future application in the analysis of flowingsample streams. The procedure introduces a new method of electro-chemical analysis in which the reaction is brought about by allowing thesample to flow through a cell in contact with a large working electrode at apre-determined potential.The potential of this electrode is so chosen as tobring about the required electrochemical reaction excluding as far as possibleside reactions. In measurements of sample solutions containing iodide,iodine, and oxygen the electrode efficiency varied with the solution flow rateand the conditions at the working electrode but was largely independent ofthe concentration of the material being analysed. Hochmann and Bayer 116have developed an interesting method for the determination of oxytetra-cyclin. They rely on the fact that with ferric salts oxytetracyclin reactsin 1 : 1 molecular proportions.Excess of ferric salt is added to the sampleunder test, and the excess of iron determined by high-frequency titrationwith EDTA. Alfonsi 117 has extended his work on controlled electrolysisto the analysis of tin base alloys, leaded bronzes, silver solder, and copper-cadmium alloys.A subject of some interest has been described by Mather and Anson 118who have devised a method for the coulometric generation of hydrogen ionsin anhydrous acetic acid containing sodium perchlorate by anodicallyoxidising a mercury electrode. The method of titration should be applicableto many basic substances normally titrated by volumetric and potentio-metric methods in acetic acid. Accurate results have been obtained forthe titration of sodium acetate and potassium hydrogen phthalate.Po1arography.-Baumgarten and his co-workers 119 have extended thevaluable information on the polarographic characteristics of many metalions in hydroxy-acid supporting electrolytes including ammonium citrate,malonate, and tartrate and also ammoniacal ammonium oxalate. Thepaper also includes data obtained in weakly acidic citrate media.The determination of nitrate in meat and meat-curing brines suffersinterference in many conventional methods because of the presence ofprotein and other organic matter.Dhont l20 has overcome these difficultiesby ensuring that the nitric acid, equivalent to the nitrate, nitrates phenol-disulphonic acid, with the production, in the main, of B-nitrophenol-2,4-di-sulphonic acid.As might be expected from the presence of the nitro-group, this acid is capable of polarographic reduction and determination.By covering the electrodes with a polyethylene membrane, Carritt andKanwisher 121 have perfected a polarographic method for the determinationof dissolved oxygen in fluid systems, which is much more selective to oxygenthan previously described methods. The membrane also prevents electrodepoisoning and the system is temperature-compensated by means of a thermi-stor incorporated in the electrode. The instrument can be used with115 E. E. Eckfeldt, Analyt. Chem., 1959, 31, 1453.116 K. Hochmann and I. Bayer, 2. analyt. Chem., 1959, 166, 88.117 B. Alfonsi, Anulyt. Clzim. Acta, 1958, 19, 569.116 W. B. Mather, jun., and F.C. Anson, Analyt. Chim. Acta, 1959, 21, 468.119 S. Baumgarten, R. E. Cover, H. Hofsass, S. Karp, P. B. Pinches, and I,. Meites,120 J. 13. Dhont, Analyst, 1959, 84, 372.121 n. E. Carritt and J. W. Kanwisher, AnaZyt. Chem., 1959, 31, 6.Analyt. Chim. Acta, 1959, 20, 397HASLAM AND SQUIRRELI. PHYSICAL h1ETHOT)S. 395continuous recording devices or as a portable apparatus with a micrometerscale indicator.It appears that 1,4-benzoquinone and its simple homologues react withsecondary 2-hydroxyethylamines of the general formula R*NH*CH,*CH,*OHto yield substituted benzoquinones of the type C,H,O,*NR*CH,-CH,OH,where R may be aliphatic, arylaliphatic, aromatic, or hydroxyalkyl. Konigand Berg122 show that this reaction, followed by the examination of thepolarographic and fluorescent behaviour of the reaction products, may beused with advantage in the characterisation of secondary 2-hydroxyethyl-amines.A procedure originally put forward by Kemula for the separationof organic nitro-compounds has now been applied with success by Skndi lZ3to the separation of thiophosphoric acid esters used as insecticides and theirbreakdown products. The separation is carried out on a polythene columnand the progress of the separation is followed polarographically.A method has been presented by Keily et aZ.124 for the assay of high-purity chromium metal and chromium oxide. The metal is oxidised to thesexavalent state and a weighed excess of solid ferrous ammonium sulphateis added. Reduction of the chromium occurs and the excess of ferrous ironis then measured by amperometric titration with ceric ammonium sulphatesolution. The method is capable of a precision of 3-45 parts in 10,000.Zittel and his co-workers125 have modified the original method due toHeyrovsky and Berezicky for the amperometric titration of barium.Theyhave altered the titration medium to tetraethylammonium bromide inaqueous ethyl alcohol and use lithium sulphate as titrant. Under theseconditions, and with the dropping-mercury electrode as the indicatorelectrode, they are able to titrate solutions as low as 5 x 1 0 - 5 ~ in bariumwith reasonable accuracy.For the direct titration of potassium with sodium tetraphenylboron,Amos and Sympson 126 use an amperometric method of end-point detectionobtained with a conventional dropping-mercury electrode.The anodicdepolarisation current of the tetraphenylboron a t this electrode is measuredat intervals throughout the titration, and the results are plotted; there isthe usual sharp increase in current when the end-point is passed. Chlorideinterferes at concentrations of 3 0 . 3 2 ~ . Den Herder and Van Pinxteren 127have used a rotating platinum electrode with a saturated calomel referencefor the amperometric titration of fluoride with a standard solution of ferricchloride. Satisfactory current voltage curves are obtained for the titrationof 38-950 pg. of fluoride in a 5-10 ml. volume of aqueous ethanol saturatedwith sodium chloride, and the method is thus most useful for the examinationof water samples.Chromatography .-The last year has seen significant advances in allbranches of chromatography, and under this heading we have selectedpapers which we consider to be of the widest general interest.These papers**2 K. H. Konig and H. Berg, 2. analyt. Chem., 1959, 166, 92.123 E. Sandi, 2. analyt. Chem., 1959, 167, 241.l24 H. J. Keily, A. Edridge, and J. 0. Hibbits, Analyt. Chim. Acta, 1959, 21, 135.H. E. Zittel, F. J. Miller, and P. F. Thomason, AnaZyt. Chem., 1959, 31, 1351.126 W. R. Amos and R. F. Sympson. Analyt. Chem., 1958, 31, 133.I z 7 J . J. Den Herder and J. A. C . Van Pinxteren, Pharm. Weekblad, 1958, 93, 1013396 ANALYTICAL CHEMISTRY.have been grouped together in sections dealing with paper chromatographyand electrophoresis, column chromatography, ion-exchange chromatography,and finally gas-solid and gas-liquid chromatography.disAcusses some of the basic considerations which must be borne in mind indesigning electrophoretic apparatus.He concerns himself with the main-tenance of buffer stability and of stable electrical test conditions and withthe stabilisation and formation of starting boundaries. He makes observ-ations on the matrix, the stabilising media, the selection of buffers, and thejdentification and analysis of separated substances, as well as temperaturecontrol. McDonald and his co-workersla9 have been able to reduce thedevelopment time for paper chromatograms by use of a simple apparatuswhich applies centrifugal force to the paper being developed.The chromato-grams obtained in this apparatus are similar to those obtained by normalmeans. By combinifig the centrifugal force with a high-voltage, direct-current electrical field one is also able to increase the speed of planar electro-phoretic separations.On the theoretical aspect of partition chromatography, Franc andJokl130 have made a study of the R, values given in the literature of alarge number of organic compounds including alcohols, ketones, etc., forminghomologous series. They have proposed what might be a most usefulequation relating R, value [ = log(l/Rf) -11 to the number of carbon atomsin the members of a homologous series.The detection of spots due to organic compounds, e.g., lipids and alkaloids,on paper chromatograms by the iodine vapour method has always had thedisadvantage that, owing to the high background stain, the detection ofweak or tailing spots has been difficult.Pan 131 has shown that if thechromatogram is first sprayed with a solution of aluminium sulphate anddried before being hung in the iodine vapour then the background stainingis much less than by the usual method. After this treatment the chromatodgram can be sprayed with starch solution, and the iodine-stained spotsappear deep blue against a light blue background. Such coloured spotsremain visible for over 1 month. Wegmann la* has also described a usefulidea for spraying chromatograms with marker reagents. He suggests theuse of Aerosol spray bottles, which can be easily manipulated with one handand give a more uniform distribution of spray reagents. The author isaware of the limitations of the method, in that it might be dangerous to useit with caustic alkalis in alcohol and that the aerosol container might suffercorrosion.He still feels, however, that the introduction of aerosol sprayreagents should be promoted by research institutes and industrial labora-tories. It is probable that Miss and Segal 133 have put forward an importantimprovement in Rutter’s well known method of paper chromatography.They thread a small piece of thread through the middle of the filter-paper,825.In a general article on the subject of zone electrophoresis Martin128 N. H, Martin, Artalyst, 1939, 84, 89.120 H. J. McDonald, L.P. Ribeiro, aild L. J. Banaszak, Analyt. Chem., 1W9,180 J. Franc and J. Jokl, J . ChWmdog., 1959, 2, 423.Is1 S. C. Pan, J. Chrornatug., 1969, 2, 433.1sz K. Wegmann, J. Chro+watog., 1959, 8, 321.188 A. Miss and F. Segalk Z . analyt. Chsm., 2959, 165, 1HASLAM AND SQUIRRELL: PHYSICAL METHODS. 397then feed the eluting liquid through this thread in order to develop thechromatogram. The thread can be varied and hence changes may be madein the rate of development of the chromatogram.Interesting observations have been made on the characterisation of fattyacids, resin acids, and naphthenic acids which are used in the soap-makingindustry. The acids are oxidised with chromic-sulphuric acid, and theresulting steam-volatile acids titrated. Acetic, propionic, and butyric acidsare readily identified in the steam-volatile matter by the chromatographicbehaviour of their ethylammonium salts.laAnalytical chemists concerned with the examination of anti-oxidants,whether natural or synthetic, will be well advised to study in detail a veryinteresting report of the vitamin E panel of the Analytical Chemists Com-mittee of the Society for Analytical Chemistry.135 This report is concernedwith the determination of tocopherols which are natural antioxidants inoils, foods, and feeding stuffs, and several useful principles are involved.After preliminary separation from interfering matter the tocopherols areseparated from one another by two-dimensional paper chromatography.The separation in the first dimension is effected on paper impregnated withzinc carbonate, and in the second dimension, the second separation is subse-quently effected on the same paper impregnated with paraffin. The separ-ated tocopherols are determined by taking advantage of the fact that, beingreducing substances, they reduce ferric salts, and the ferrous salts producedreact with bipyridyl to give appropriate colours, suitable for measurement.D e h ~ r i t y , l ~ ~ in a communication on the chromatographic separation of anti-oxidants, describes three basic methods.In two of these, partially acetyl-ated paper is used, and in the third the separation is achieved on papercoated with cotton-seed oil. The developing solvents used are conventional.Toxicologists may be concerned with the analytical separation of sulphon-amide drugs and the examination of alkaloidal residues obtained from suchmaterials as viscera, stomach washes, and urine by application of the Stas-Otto process of preliminary extraction.They will find the circular paper-chromatographic method employed by Tewari and Tripathi137 to be ofinterest. Langford and Vaughan have obtained excellent separationof mixtures of polymers including polyvinyl acetate, polyvinylbutyraldehyde,polystyrene, and polyvinyl chloride, by paper chromatography using isobutylmethyl ketone as developing solvent. When required, even greater separ-ation can be obtained by development in a second direction using a mixtureof this ketone and methanol. The spots are made visible by spraying witha universal indicator solution.Two very simple column chromatographic methods have been devisedby Smith 139 for the separation and determination of adipic, glutaric, andsuccinic acids.A novel feature is the inclusion of an internal indicator inthe silicic acid-water column which permits convenient tracing of the134 M. JureEek and P. Kozkk, 2. andyt. Chem., 1959, 167, 32.135 Analyst, 1959, 84, 356.13' S. N. Tewari and D. N . Tripathi, 2. analyt. €hem., 1959, lM, 356.138 W. J. Langford and D. J. Vaughan, J . Chromatog., 1959, 2, 564.1SB A. I . Smith, Analyt. Chewa., 1959, 31, 1621.B. A. Dehority, J . Chromatog., 1959, 2, 384398 ANALYTICAL CHEMISTRY.separated acid bands. In the first procedure the column is developed witha butanol-chloroforrn solvent and then extruded for separation of thedeveloped bands.In the second procedure the column is developed withthree -butanol-chloroform mixtures, and the acids are collected individuallyas they are eluted from the column. Forstner and Rogers,l40 in work onthe separation and study of 2- and 4-nitroso-l-naphthol, have described theapplication and use of chemisorption in chromatographic separations oforganic isomers and homologues. Their results show that in such caseschemisorbent columns can show greater efficiency than mere physical sorp-tion columns and they point out the particular usefulness of low capacitysalts and impregnated high capacity oxides as chromatographic sorbents.In thedetermination of cobalt in the presence of nickel advantage may be takenof the fact that, from a solution of both the metals containing excess ofpotassium cyanate and ammonium acetate buffer, Dowex 1-X8 ion-exchangeresin selectively holds the c0ba1t.l~~ The cobalt may afterwards be extractedfrom the resin with hydrochloric acid solution and subsequently determinedby the colorimetric cyanate procedure.Wilkins and Hibbs 142 have de-scribed a simple method for the determination of nickel in gold-nickelalloys. The sample is dissolved in aqua regia and, after evaporation to dry-ness to remove nitric acid, the residue is re-dissolved in hydrochloric acid.This acid solution is passed down a Dowex 1-X5 ion-exchange column, andthe gold chloro-complex is strongly absorbed. The nickel is determined inthe eluate by an EDTA titration procedure.has presented a rather novel ion-exchange method for theanalysis of two ions, for example, Na and K present as chlorides in aqueoussolution.An aliquot part of the solution is evaporated to dryness underdefinite conditions, and the residue weighed. A similar aliquot part ispassed through a cation-exchange column saturated with one of the ionsbeing determined. The eluate and washings are then evaporated, dried, andweighed as before. From the two weights obtained the composition of theoriginal mixture can be calculated, to give a result within a 2% error. Themethod may also be used for anions, if an anion-exchanger is used, but in bothcases the salts must be capable of being dried to constant weight.A variationof the method using a cation-exchanger in the hydrogen form with a titrimetricfinish is also described, but by this method the relative error is greater.In analytical work on plating baths, etc., it is often desirable to removelarge amounts of chromic acid before the determination of certain cations.Although ion-exchange resins have been suggested for the purpose, thedifficulty is that most of them are insufficiently stable and produce un-desirable Cr3+ ions. According to the work of Weiner and Schiele,l44 how-ever, Amberlite 1.R.A.-410 ion-exchange resin does not suffer from thesedisadvantages. Prochkzkov5 145 has developed a process which overcomesIon-exchange resins are of increasing service to the analyst.Gabrielson140 J.L. Forstner and L. B. Rogers, Alzalyt. Chew., 1959, 31, 365.141 M. Ziegler and W. Rittner, 2. analyt. Chem., 1959, 165, 197.112 D. H. Wilkins and L. E. Hibbs, AnaZyl. Chim. A d a , 1959, 20, 273.143 G. Gabrielson, AnaZyt. Cltim. Ada, 1959, 20, 146.144 R. Weiner and C. Schiele, 2. analyt. Chem., 1959, 169, 271.145 L. ProchAzkovA,, 2. anaZyt. Chem., 1959, 167, 254HASLAM A4ND SQUIRRELL: PHYSICAL METHODS. 399many of the difficulties previously encountered in the determination ofnitrates in water. Interfering cations are first removed by passage througha suitably prepared active carbon column. The nitrate is reduced withhydrazine in the presence of a definite proportion of copper before colori-metric determination of the nitrite obtained by the sulphanilic acid-wnaphthylamine test.Nitrate, sulphate, and chloride may be determined in the same sampleof water by a simple procedure developed by Ceausescu.1Q6 The water isfirst passed through an ion-exchange resin whereby all the cations are re-placed by hydrogen ions.In the eluate the total acidity due to nitric,sulphuric, and hydrochloric acids is determined by titration with alkali,using sodium alizarinsulphonate as indicator. The titrated solution is nowtreated with barium sulphate suspension, alcohol, and a further amount ofsodium alizarinsulphonate solution. The sulphate is now determined bytitration with standard barium perchlorate solution , the sodium alizarin-sulphonate this time functioning as adsorption indicator.Desorption ofthe sodium alizarinsulphonate is now accomplished by the addition ofsulphuric acid followed by titration of the chloride with mercuric nitratesolution , diphenylcarbazone being used as indicator. The nitric acid isdetermined by difference.ResS and Straka147 have developed a useful method for the determin-ation of sulphur in pyrites concentrates. The sulphur is converted intosulphate by heating with a mixture of manganese dioxide and potassiumhydroxide. The product is leached with water, and the sulphate in theextract determined by passage of an aliquot part of the solution through acation-exchange resin before titration of the resulting sulphuric acid withstandard alkali. The method may be applied to the determination ofsulphur in certain organic compounds containing sulphur, sulphur andnitrogen, or sulphur and chlorine. In the last case allowance has to hemade for the chlorine ionised in the process.On the organic side, difficulties encountered in the determination offluorine in organic compounds also containing phosphorus , by the mercuricnitrate-alizarinsulphonate method, after Parr bomb fusion, have been over-come by Eger and L i ~ k e .l ~ ~ These authors absorb the fluoride and phos-phate on an ion-exchange column and separate them by selective elutionbefore individual determination. Bromine , chlorine, and sulphur can alsobe determined simultaneously with the fluorine and the phosphorus.Fluorine in many fluoro-compounds and chlorine and fluorine in certainchlorofluoro-compounds can often be determined quite readily if the sub-stance is soluble in di-isopropyl ether.149 The solution of the test substancein this ether is treated with a biphenyl sodium dimethoxyethane complexand the resulting sodium salts are converted into the corresponding halogenacids by passage through an ion-exchange resin in the hydrogen form.When chlorine and fluorine are both present, titration of the total acids in146 D.Ceausescu, 2. analyt. Chem., 1959, 165, 424.147 2. fiezbi: and K. Straka, 2. analyt. Chem., 1959, 166, 161.148 C. Eger and J. Lipke, AIzaZyt. Chim. Acta, 1959, 20, 548.149 P. Johncock, W. R. Musgrave, and A. Wiper, Aizalyst, 1059, 84, 245400 ANALYTICAL CHEMISTRY.the eluate gives a measure of both; chloride may be determined inde-pendently in the eluate by application of the mercury oxycyanide method.A combination of ion-exchange chromatography and ultraviolet spectro-scopy enables Shelley and Umberger lm to differentiate and determine acidicaromatic and heterocyclic compounds.A strongly basic resin is used andthe acidic compounds are subsequently eluted with ethyl alcohol or acidifiedalcohol and examined by ultraviolet-spectrophotometry. The method isalso applicable to phenols and such compounds as codeine phosphate.Sherma and Rieman,lsl in further work on solubilisation chromatography,have separated mixtures of aliphatic and aromatic ethers, saturated fattyacids, and substituted benzenes and naphthalenes by elution throughcolumns of ion-exchange resins with aqueous solutions of acetic acid.Ginn and Church lS2 have described two new ion-exchange methodsfor the analysis of surface-active mixtures containing non-ionic and anion-active constituents.In a two-stage method the mixture is passed down astrongly acid cation-exchange column, and the effluent contains the un-changed non-ionic and the anionic component in its acid form. This effluentis now passed through an acid-absorbing, weakly basic, anion-exchangeresin, whereupon the anionic component is absorbed, and the non-ionicpasses through to be recovered from the effluent. The anion-active com-pound is now eluted from the column with alcoholic sodium hydroxide andis recovered from the alkaline eluate. A single-stage mixed-bed method isalso described for the more rapid recovery.of non-ionic surface-active agentsfrom such mixtures.Many review papers on subjects of interest to analytical chemists merelyconsist of very brief descriptions of large numbers of original analyticalpapers. It is refreshing, therefore, to read the critical review by Rose 153on an up-to-date topic, e.g., " Gas Chromatography and its Analytical Applica-tions. "The gas-liquid chromatographic separation of mixtures of compoundshaving a widely varying boiling range has often presented dificulties inchoosing a practicable column temperature. These difficulties have beenovercome by Sullivan and his co-workers 154 and by Nogare and Harden.155The former workers utilise a non-linear temperature programming methodbased very simply on starting the run at room temperature and switchingthe column heater to full heat.This results in a slow increase in temper-ature over the first 10 minutes of run, followed by a rapid increase to say150" in 30 minutes. The reproducibility of the temperature programme a ta fixed heater setting is surprisingly good. Nogare and Harden1% uselinear temperature programming facilitated by a proportional controllerand low heat capacity column and heater. Detector stability is main-tained by the incorporation of a buffer block between the column and thethermal conductivity detectors.150 R. J. Shelley and C . J. Umberger, Analyt. Chem., 1959, 31, 593.151 J. Sherma and Wm. Rieman, tert., Analyt. Chim. Ada, 1959, 20, 357.152 M.E. Ginn and C. L. Church, AnaZyt. Chem., 1959, 31, 551.155 B. A. Rose, Analyst, 1959, 84, 574.154 J. H. Sullivan, J. T. Walsh, and C. Merritt, jun., Analyt. Chem., 1959, 31, 1826.155 S. D. Nogare and J. C. Harden, Analyt. Chem., 1959, 31, 1829HASLAM AND SQUIRRELL: PHYSICAL METHODS. 401A large amount of identification work in gas-liquid chromatography hasbeen based on elution times. It has been inferred that a substance is cor-rectly identified because its corrected relative retention time with referenceto a standard substance is the right one for the substance in question underparticular column conditions or sets of column conditions. This is notalways the case, and the alternative w,ethod of identification which Ander-son 156 has put forward is likely to have far-reaching effects.He describesmethods by which gas-liquid chromatographic fractions issuing from acolumn are collected in cold traps. The material in a given cold trap isthen transferred quantitatively to a previously evacuated infrared gas celland identified by infrared methods.By combining a suitably modified " time of flight " mass spectrometerwhich scans a mass range from m/e = 1 to m/e = 6000 at the rate of 2000times per second, with a gas-liquid partition chromatographic apparatus,Gohlke l57 has produced an apparatus which is capable of separating andpositively characterising organic mixtures boiling below 350". The massspectrometer is connected to the gas-liquid chromatographic apparatusbetween the column exit and the thermal conductivity cell.Such mixturesas acetone, benzene, toluene, ethylbenzene, and styrene can be rapidyseparated and identified.Karchmer 158 has set out the gas-liquid partition characteristics of someeleven sulphur compounds in the boiling range 58-126" on a column ofPP'-iminodipropionitrile on Celite. He finds that, with a helium carrier gasa t 84", this column resolves the compounds on the basis of their electrophiliccharacter. By logarithmic plot of the retention times on this column againstthose obtained on a volatility delineating column (e.g., white oil on Celite), aseries of straight lines corresponding to tertiary thiols, iso-primary thiols,primary normal thiols, aromatics, and thiophens are obtained. Membersof a homologous series tend to lie on their respective straight lines, Usefulgas-liquid chromatographic data have also been published by Chang andKarr 159 on the identification of some 52 aromatic hydrocarbons boiling upto 218" present in a low-temperature bituminous coal tar.The resultsindicate that alkylbenzenes with an equal number of carbon atoms in theiralkyl groups show a linear relationship between the logarithm of the relativeretention time and normal boiling point, whilst C,, C,, C,,, C,,, and C,,alkylbenzenes lie on 5 parallel lines whose separation from each other isrelated to the logarithm of the number of carbon atoms in the alkylgroup.Kratzl and Gruber lrn have developed an ingenious method which islikely to be of interest to analysts concerned with the determination ofalkoxyl groups.By means of hydriodic acid, the alkoxyl groups are con-verted into the corresponding iodides which are quantitatively absorbedon a short column. The iodides are then transferred to a gas-liquidchromatographic column where they are separated on a tritolyl phosphate156 D. M. W. Anderson, Analyst, 1959, 85, 50.157 R. S. Gohlke, Analyt. Chem., 1959, 31, 535.158 J. H. Karchmer, Analyt. Chern., 1959, 31, 1377.159 Ta. Chuang Lo Chang and C. Karr, jun., Analyt. Chim. Acta, 1959, 21, 474.160 K. Kratzl and K. Gruber, Monatsh., 1958, 89, 618403 ANALYTICAL CHEMISTRY.stationary phase. The separated iodides are determined by the conventionalbromination procedure. In addition, it has been shown by Spingler andMarkert that acetyl and formyl groups may be determined and differenti-ated in organic compounds by a rather novel process.The substance isfirst heated with methanol and hydrogen chloride and the methyl acetateand methyl formate produced are separated from the methanol and hydro-chloric acid, etc., by gas chromatography.The selective reactivity of silver nitrate with 2-bromobutane has beenused by Harris and McFadden 162 in a gas-liquid chromatographic methodfor the determination of 2-bromobutane and l-bromo-2-methylpropane.An additional tube packed with crushed firebrick impregnated with silvernitrate is inserted into the feed tube to the chromatographic column. Thisabsorbs the 2-bromobutane at room temperature and the l-bromo-2-methyl-propane is registered on the chromatogram.The analysis can be repeatedwithout the absorption tube, both compounds then being registered andeach component can thus be determined by difference. Brealey et ~ ~ 1 . l ~ have developed a useful method for the gas-liquid chromatographic deter-mination of chloroform in aqueous pharmaceutical preparations. Theessential features of their test are that (a) n-propanol as internal marker isadded to the sample under test, (b) a high molecular-weight polyethyleneglycol is used as stationary phase, and (c) the column is operated at 88";the injection system is designed to avoid fouling of the column. n-Propanol,chloroform, and water are satisfactorily separated and the proportion ofchloroform in a particular preparation is deduced from the peak heights dueto chloroform and n-propanol.A polyethylene glycol of high molecular weight has been found to beparticularly useful for the separation of the products arising from the high-temperature coking of coal,l6* and this has enabled valuable information tobe gained about the benzene, toluene, xylene, styrene, and trimethyl-benzene contents of light oils.The picrate method for the determination ofnaphthalene in coke-oven gas is not particularly satisfactory because thepicrate precipitate is contaminated with the picrates of hydrocarbons otherthan naphthalene. If, however, the impure picrate is decomposed withacetic acid and then extracted with benzene, the benzene extract may thenbe examined by gas-liquid chromatographic test to give a true measure ofthe naphthalene.Vacuum pyrolysis or depolymerisation and gas-liquid chromatographicexamination of the products obtained have for some time been used for theidentification of acrylate and methacrylate polymers.Radell and Strutz 165have designed a method whereby the controlled-temperature pyrolysis iscarried out in an apparatus attached directly to the chromatographiccolumn. This permits the complete analysis to be carried out on about5 mg. of sample and has the advantage that conditions can be made stableand reproducible. By repeating the analysis on two columns with different161 H. Spingler and F. Markert, Mikrochim. Ada, 1959, 122.162 W. E. Harris and W. H. McFadden, Analyt.Chem., 1958, 31, 114.163 L. Brealey, D. A. Elvidge, and K. A. Proctor, Analyst, 1959, 84, 221.164 H. Ritter and H. Schnier, 2. analyt. Chem., 1959, 170, 310.165 E. ,1. Radell and H. C. Strutz, Analyt. Chem., 1959, 31, 1890HASLAM AND SQUIKRELL: PHYSICAL METHODS. 403retention characteristics, qualitative identification of the components of thepyrolysis products can be made.Langer and his co-workers 166 have overcome difficulties in the gas-liquidseparation of phenols by converting them into their trimethylsilyl ethersbefore chromatographic test. Chromatograms showing clear separationswith no tailing of the peaks are obtained, and the method can be applied toaqueous solutions since water is converted into hexamethyldisiloxane andtrimethylsilanol in the conversion reaction and these are eluted initiallyfrom the column.A method, which is also applicable to other anti-oxidants and maskingagents, has been presented by Jennings and his co-workers 167 for the deter-mination of 2,6-di-t-butyl-~-cresol in paperboard. The anti-oxidant isextracted with cyclohexane-propan-2-01 and concentrated, followed bygas-liquid chromatographic test of an aliquot part of the concentrated ex-tract.The column used is propylene glycol on C22 firebrick, with heliumas carrier gas at a temperature of 200". The relative retention times ofvarious anti-oxidants when using the above column and a silicone columnare given, and it is evident that such data can be used for the qualitativeexamination of anti-oxidants.Absorption Spectroscopy.-In this section we have tried to cover as widea range as possible of the large number of excellent papers published in 1959on all branches of absorption spectroscopy.There are very few analysts who have not, a tsome time or other, felt the need of an effective method for the extractionof calcium from solutions in such a way that the calcium may be determinedin the extracted phase.Umland and Meckenstock 168 have shown that, inthe simultaneous presence of both n-butylamine and 8-hydroxyquinoline,calcium may be quantitatively extracted by chloroform from a solution ofpH 11-12. Moreover, the calcium may be determined in the chloroformextract by photometric 'measurement at 370-380 mp. The procedure maybe adapted to the determination of calcium in a whole host of technicalproducts.Copper forms a stable greenish-yellow complex with Tiron (disodiumsalt of 4,5-dihydroxybenzene-1,3-disulphonic acid) and Majumdar and Sava-riar 1G9 have taken advantage of this in a spectrophotometric method forthe determination of small amounts of copper.The complex is formedat a pH of 6.1-6.9 and is measured at its absorption maximum of 375 mp.Jacobs and Yoe 170 have studied the complexes formed by copper, cobalt, andnickel with NN'-bis-(3-dimethylaminopropyl)dithio-oxamide. Cobalt formsa yellow, nickel a reddish-orange, and copper an olive-green complex, andalthough these complexes are themselves insoluble in water, the use of aprotective colloid enables solution to be effected over a required concen-tration.By measurement at 500, 430, and 315 mp of the complexes166 S. H. Langer, P. Pantages, and I. Wender, Chevn. and Ind., 1958, 1664.167 E. C. Jennings, jun., T. D. Curran, and D. G. Edwards, ,4naZyt. Chem., 1958, 30,168 F. Umland and I<. U. Meckenstock, 2. andyyt. Chem., 2959, 165, 161.IG9 A. K. Majumdar and C. P. Savariar, Andyt. Chim. Actn, 1959, 21, 53.170 \V, D. Jacobs and J . H. Yoe, Analyt. Chiin. Ada, 1969, 20, 435.Inorganic applications.1946404 ANALYTICAL CHEMISTRY.formed at pH 9 and application of a spe.ctrophotometricic equation, allthree elements can be determined when present together in the test solution.Small amounts of ferric iron have been titrated at pH 3.5 with ethylene-diamine-(o-hydroxyphenylacetic acid) to a photometric end-point.Themethod 171 can cover a wide range of iron concentrations, for by decreasingthe volume of solution and titrant strength, microgram quantities can betitrated. To decrease the sensitivity for the titration of milligram amountsof iron, the wavelength chosen for photometric measurement is adjustedaccordingly away from 470 mp, at which wavelength the red ferric chelateshows maximum absorption.Ducret and Maurel have carried out much work on the analysis ofminerals, using extraction methods and coloured cations. In the firstmethod 172 for the determination of traces of gold in solution, gold chlorideis complexed with Methyl Violet and the complex is quantitatively extracteda t a low pH with trichloroethylene. The colour of the extract is measuredat 600 mp.In the second method,173 in which Crystal Violet is used ascomplexing agent, traces of tin can be determined by extraction of thecoloured complex with dipropylacetone and measurement at 595 mp. Athird method174 can be used for the determination of traces of phosphatein the form of phosphomolybdate. The phosphomolybdate is complexedwith safranine, and the colour extracted with acetophenone at pH 1-5 beforespectrophotometric measurement at 532.5 mp. Finally, these authors havedescribed a method for the indirect determination of traces of sulphate bymeans of an ion-exchange resin.175 The sulphate ions are exchanged withan equivalent amount of thiocyanate ions, and these are determined byextraction with dichloroethane after forming a complex with MethyleneBlue.Molybdates may be separated from vanadates by taking advantage ofthe fact that, with excess of thioglycollic acid, molybdates produce a molyb-denum(II1) complex of dithioglycollic acid.176 At the appropriate pH thiscompound is selectively absorbed on a Dowex resin, and the vanadium inthe eluate then determined by colorimetric measurement of the blue reactionproduct obtained by the action of excess of thioglycollic acid on the vanadiumcompound.The molybdenum may then be eluted from the column anddetermined as its 8-hydroxyquinoline complex. The determination of smallamounts of magnesium in the presence of large amounts of zinc is carried outby Maurice177 by a method which involves a preliminary removal of thezinc and some other interfering elements by a controlled electrolysis using amercury cathode.Any aluminium is then removed by a chloroform extrac-tion with 8-hydroxyquinoline, and the magnesium finally determined colori-metrically at 505 mp as the complex formed at pH 8.95 with 3-(2,4-dimethyl-phenylcarbamoyl) - 2-hydroxy- 1 - o - hydroxyphenylazonaphthalene. A most171 A. L. Underwood, Analyt. Chim. Acta, 1959, 20, 228.172 L. Ducret and H. Maurel, AnaZyt. Cham. Acta, 1959, 21, 74.173 L. Ducret and H. Maurel, Analyt. Chim. Ada, 1959, 21, 79.174 L. Ducret and M. Drouillas, Analyt. Chim, Ada, 1959, 21, 86.175 L. Ducret and M. Ratouis. Analyt. Chim. Acta, 1959, 21, 91.176 M. Ziegler and W. Rittner, 2.analyt. Chem., 1958, 164, 310.17' hl. J . Maurice, Analyt. Chzm. Ada, 1969, 20, 181HASLAM AND SQUIRRELL: PHYSICAL METHODS. 405useful method has been described by Monnier and Haerdi 178 for the deter-mination of microgram amounts of nickel in the presence of large amountsof other cations. The nickel is precipitated as its nioxime complex andextracted with organic solvent, when, after preliminary procedures toseparate it from foreign cations, it is determined by colorimetric measure-ment in quinoline solution.Sonnenschein’s procedure 179 for the determination of traces of silicon inwater follows fairly conventional lines in the initial production of silico-molybdenum-blue. After that an oxyethyl lauryl amine of this kind offormula is used, where x + y = ca.16:This amine combines with the silicomolybdenum blue to yield a chloroformsoluble complex, suitable for photometric measurement. Ringbom andhis co-workers 180 have also described a method capable of high precision forthe determination of silicon, this time in insoluble silicates, clays, etc. Thesample is fused with sodium hydroxide, and the melt dissolved in watercontaining EDTA. Silicomolybdic acid is now formed by reaction withammonium molybdate in a monochloroacetic acid-ammonium chloroacetatebuffer a t a pH of 3.0-3.7, and the yellow colour produced, which is stablefor almost 2 days, is measured at 390 mp.Everest and Martin181 have developed a useful method for the deter-mination of thorium in medium-grade ores. In the presence of mesotartaricacid, which complexes any zirconium present, the thorium is separated froma nitric acid solution by extraction with a solvent containing tri-n-butylphosphate and ethyl methyl ketone as diluent.Aluminium nitrate is usedas a salting-out agent. The thorium in the organic phase is extracted withwater, followed by absorptiometric determination with l-(o-arsonophenyl-azo)-2-naphthol-3,6-disulphonic acid. Two turbidimetric procedures havebeen devised for the determination of 0.001-@4~0 of tin in copper basealloys.ls2 The first method, applicable in the presence of small amounts ofiron, utilises phenylarsonic acid as reagent. In the examination of samplescontaining large amounts of iron and small amounts of tin the more sensitivereagent 4-hydroxy-3-nitrophenylarsonic acid is recommended, more especiallywhen the tin content is below O .O l ~ o . The methods appear relatively freefrom interference except froin iron.Titanium can be extracted as its thiocyanate complex from sulphate orchloride acidic solutions by tri-n-octylphosphine oxide dissolved in cyclo-hexane. The complex in this medium exhibits a molar absorbance indexof 41,000 at lmX. = 432 mp, and the principle outlined above has beenused in a most simple and sensitive method for the determination of titanium,described by Young and White.183 Neither quadrivalent metal ions nor178 D. Monnier and W. Haerdi, Analyt. Chim. A d a , 1959, 20, 444.179 W. Sonnenschein, 2. analyt. Chem., 1959, 168, 18.180 A.Ringborn, P. E. Ahlers, and S. Siitonen, Analyt. Chim. A d a , 1959, 20, 78.181 D. A. Everest and J. V. Martin, Analyst, 1959, 84, 312.182 H. J. G. Challis and J . T. Jones, Analyt. Chim. Acta, 1969, 21, 58.183 J . P. Young and J. C. White, Analyt. Chem., 1959, 81, 393406 ANALYTICA4L CHEMISTRY.large amounts of Fe(n) or U(VI) interfere in the test. Strocchi and ReboralMhave made strong claims that the dihydroxylamine salt of dihydroxymaleicacid is an extremely sensitive and specific reagent for the colorimetric deter-mination of titanium. The test has to be carried out at a definite pH valueand with a specific time of colour development.Maeck and his co-workers 185 have devised two spectrophotometricmethods specific for uranium. They are based on extraction of the uraniumas tetrapropylammonium uranyl trinitrate with isobutyl methyl ketone, froman acid-deficient aluminium nitrate salting solution.Milligram amounts ofuranium are determined in the extract by direct spectrophotometric measure-ment of the complex at 425 mp. Microgram amounts are determined byadding dibenzoylmethane to the solution in an ethyl alcohol-pyridinemixture and measuring the absorption of the chelate so formed at 415 mp.Vanadium has often been determined in the past by oxidation with hydrogenperoxide in sulphuric acid solution and measurement of the resulting colouredsolution at 460 mp. At this wavelength the concentrations of sulphuric acidand hydrogen peroxide are critical. Harthamp,ls6 however, has shown thatby working at the isosbestic point, vix., 405 mp, the determination may bemade virtually independent of sulphuric acid and hydrogen peroxidecontents.A useful solvent-extraction method for the determination of zinc hasbeen described by Scroggie and Dean.ls7 The zinc is quantitatively ex-tracted from a hydrochloric acid solution of the sample with a 5% (w/v)solution of tri-iso-octylamine in isobutyl methyl ketone.The zinc is thendetermined in situ in the organic phase by using 2-carboxy-2’-hydroxy-5’-sulphoformazylbenzene (Zincon) colorimetric measurement being made at620 mp. o-Carboxyphenylazo-l,8-dihydroxynaphthalene-3,6-disulphonate(sodium salt) prepared by diazotisation of anthranilic acid and couplingwith chromotropic acid, has been shown by Majumdar and Savariar 188 toform soluble coloured complexes with thorium and zirconium.Thesecomplexes obey Beer’s law over convenient concentration ranges and hencecan be used for the determination of traces of these elements. The azo-dyehas also proved to be an excellent complexometric indicator for thesemetals.The coloriinetric determination of halides has received much attention,and a method which may well have other applications has been worked outby Geld and SternmanlS9 for the determination of small amounts ofchloride in hydrogen peroxide. After careful decomposition and evapor-ation of the sample, the residual chloride is treated with mercury thio-cyanate, with consequent liberation of an equivalent amount of thiocyanateions, which form a reddish-orange complex with ferric iron.This colour,which is proportional to the chloride, is suitable for colorimetric measurement.184 P. M. Strocchi and P. Rebora, 2. analyt. Chem., 1959, 169, 1.185 W. J. Maeck, G. L. Booman, M. C. Elliott, and J. E. Rein, Analyt. Clzem., 1959,186 H. Harthamp, 2. analyt. Chem., 1959, 169, 339.187 L. E. Scroggie and J. A. Dean, Analyl. Chim. Acta, 1959, 21, 282.188 A. K. Majumdar and C . P. Savariar, Naturwiss., 1959, 46, 323.189 I. Geld and J. Sternman, Analyt. Chem., 1959, 31, 1662.31, 1130I-IASLAM AND SQUIRRELL : PHYSICAL METHODS. 407Chemists concerned with the analysis of brine will be interested in thework of Collins and Watkins,lgo who have described a rapid and precisemethod for the determination of iodides and bromides in oil-field brines.Iodides are oxidised to iodine with nitrite and extracted with carbon tetra-chloride.The absorbance of this solution at 517 mp is a direct measure ofthe iodide present. After removal of iodides, the bromide is oxidised tobromine with hypochlorite, and the bromine is extracted with carbontetrachloride, and its absorption measured at 417 mp. The method isespecially useful when the concentration ratio of chlorides to the otherhalides is too large to permit determination of bromides and iodides bypotentiometric and other instrumental methods.An improved method for the determination of fluoride in blood serum,which is obviously applicable to other samples, has been presented by Singerand Armstrong.lgl The sample is ashed at a low temperature in the presenceof specially prepared magnesium oxide, and the ash transferred to a micro-distillation apparatus. The perchloric acid distillation of the fluoride iscarried out with a stream of nitrogen passing through the apparatus to sweepthe fluoride from the microcell to the receiver, which markedly reduces thedistillation volume required. The fluoride in the distillate is determined bytreatment with a reagent lake consisting of a mixture of EriochromeCyanine R solution and zirconyl chloride solution under defined conditions,and measurement of the resulting colour at 568 mp.A new colorimetricmethod for the determination of low concentrations of fluoride has beendescribed by Kamada and Onishi.lg2 They use the zirconium lake of theazo-dye, 9-dimethylaminoazophenylarsonic acid, which reacts with fluorideto give the zirconium fluoride complex ion, liberating an equivalent of theazo-dye, which is separated from the unreacted insoluble lake and measuredspectrophotometrically at 500 mp.The reaction of nitrate and nitrite with brucine hydrochloride in thepresence of sulphuric acid has been used by Fischer et dlg3 in two usefulmethods for the colorimetric determination of these ions.For the deter-mination of nitrite alone, even in the presence of nitrate, the reaction iscarried out with a total concentration of 17% sulphuric acid. When theacid concentration is increased to 5oy0, both nitrate and nitrite react andthe total is determined.The colorimetric measurements are made at410 mp. For the assay of sulphuric acid solutions in the concentrationrange 85-99y0 of acid to within &0-3y0, Zimmerman and Brandt 194 havedeveloped a spectrophotometric procedure. The method takes advantageof the fact that quinalizarin when dissolved in various concentrations ofsulphuric acid shows absorption maxima at 537, 575, and 605 mp and anisosbestic point a t 585 mp. The ratio of the absorbance of the solution at535 mp and 630 mp is determined and the concentration of the acid solutionobtained from a previously prepared calibration graph.190 A. G. Collins and J . W. Watkins, Analyt. Chem., 1959, 31, 1182.191 L. Singer and W. D. Armstrong, Analyt. Chem., 1958, 31, 105.192 M. Kamada and T.Onishi, J. Chem. SOC. Japan, 1959, 80, 275.193 F. L. Fisher, E. R. Ibert, and H. F. Reckman, ,4nalyt. C h ~ m . , 1958, 30,1972.194 E. Zimmcrmsn and W. W. Rrandt, Tnlantcz, 1958, 1, 374408 ANALYTICAL CHEMISTRY.Dunstone and Paynelg5 have developed an interesting method for thespectrophotometric determination of zinc, magnesium, cadmium, calcium,strontium, and barium with et hylenediamine-NNN'N'- t e t ra-ace tic acid ;e.g., in the case of zinc the test is based on the fact that, the optical densityof an EDTA solution both in the presence and in the absence of zinc beingknown, the optical density difference may be used as a measure of the zinc.It is necessary, of course, that the zinc must form a chelate with the EDTAand that this chelate has very little absorption at the wavelength used.Chenglg6 has shown that the selectivity of the cupferron method for thedetermination of titanium may be greatly increased by adding EDTA asmasking agent and extracting the complex with 4-methylpentan-Z-one,followed by absorptiometric measurement in the near ultraviolet and theultraviolet region.Under these conditions, titanium, uranium, and ceriumgive yellow complexes, and tin, beryllium, aluminium, iron, hafnium,zirconium, niobium, tantalum, and the rare earths give colourless complexes.The sensitivity of the test to uranium and cerium is not great, and hencetitanium can be determined in the presence of traces of these elementswithout previous separation.A fluorimetric determination which might well be applicable in appro-priate circumstances has been outlined by Rao and A~pa1araju.l~' Itdepends on the blue fluorescence produced by boric acid with resaceto-phenone in sulphuric or phosphoric acid.It may be possible to utilise thisreaction in the determination of boric acid in particular circumstances. Onthe subject of X-ray fluorescence analysis, Brown lQ8 has concluded his mostuseful review with the forecast that the method will find increased applicationto routine and non-routine analytical problems. Advantages are that themethod is rapid, independent of the chemical combination of the element,and non-destructive in that the sample examined is not destroyed during test.The review by Duyckaerts lB9 on the infrared analysis of solid substanceshas set out the physical and chemical factors affecting the spectra.Thelatter include adsorption of substance on particles of dispersing medium,chemical reaction of substance with medium, polymorphism of substance,mixed crystal-formation, distortion of the crystalline structure, and form-ation of complexes between substance and medium.The growing use of infrared spectroscopy in inorganic analysis is demon-strated in a paper by Tuddenham and Lyon,200 who have shown that un-known chlorite minerals can be classified by infrared spectroscopy alone.By relating the infrared data with the chemical analysis of some 21 chloritesand related minerals, both the degree of substitution of aluminium forsilicon and the total iron content of the mineral can be estimated and thestructural type can also be readily deduced.Also in the inorganic fieldNeeb 201 has developed an interesting method of examination of binarylg5 J. R. Dunstone and E. Payne, Analyst, 1959, 84, 110.lu6 K. L. Cheng, Analyt. Chew, 1958, 30, 1941,197 G. Gopala Rao and N. Appalaraju, 2. malyt. Chem., 1969, 167, 325.198 F. Brown, Analyst, 1959, 84, 344.lg9 G. Duyckaerts, Analyst, 1959, 84, 201.200 W. M. Tuddenham and R. J. P. Lyon, Analyt. Chtm., 2959, 81, 377.201 R. Neeb, 2. analyt. Chem., 1959, 170, 95HASLAM AND SQUIRRELL : PHYSICAL METHODS. 409mixtures of aluminium , gallium , and indium. Precipitation with 8-hydroxy-quinoline gives a measure of the total constituents- in the binary mixture,The dried 8-hydroxyquinoline precipitate is mixed with casium bromideand examined as a czesium bromide disc in the infrared regioh of the spec-trum.The individual oxinates have characteristic absorption bands.Particular care is necessary in the preparation of the ccesium bromide discs.A useful method has been devised by Starkeg 202for the colorimetric determination of acetylacetone. This p-diketohe isallowed to react with cupric acetate under specific pH conditions. Theblue chelate thus formed is extracted with chloroform before absorptio-metric measurement at 650 mp. Nicksic and Juddao3 have utilised thegeneral reaction of primary and secondary arylamines with furfuraldehydeto give highly coloured reaction products, in a method for the determinationof $$'-dioctyldiphenylamine in hydraulic fluids.The sample in solution inpropan-2-01 is treated with 18N-sulphuric acid and filtered. The furfur-aldehyde reagent is added to an aliquot part of the filtrate, and the colourmeasured against a similar aliquot part containing no added furfuraldehydeat 385 mp. Degradation products of the amine do not interfere, but adisadvantage of the method is that the reaction does not go to completionand calibration is required with each set of samples tested.A simple method for the determination of small amounts of such per-oxides as benzoyl peroxide , lauroyl peroxide , and cumene hydroperoxidedescribed by Eiss and Giesecke204 takes advantage of the reaction withbenzoyl-leuco-Methylene Blue to form a characteristic Methylene Bluecolour suitable for colorimetric measurement at 662 mp.Zirconiumnaphthenate is used to accelerate the peroxide decomposition in trichloro-acetic acid-benzene solution and thereby increase the leuco-dye reactionrate. The time for complete colour development at 25" varies with theperoxide under test from 30 minutes in the case of t-butyl hydroperoxideto 30 hours for benzoyl peroxide, but once developed, the colours appearstable for several days if kept in the dark at this temperature. Johnsonand Savidge 205 have investigated the use of 4-aminophenazone as a couplingreagent in the presence of an oxidising agent for the determination ofphenols. Suitable conditions of test have been outlined, and the reagentappears useful for the determination of several phenols of pharmaceuticalinterest.A novel test, which may have far-reaching consequences, has beendeveloped by Saville 206 for the colorimetric determination of microgramamounts of thiols.The thiol solution is first treated with nitrous acid toform the S-nitrosothiol. Excess of nitrous acid is now removed by am-monium sulphamate , and an acid solution of sulphanilamide containingmercuric chloride is added. Under these conditions the S-hitmsothiol ishydrolysed to yield nitrous acid, which in its turn diazotises the sulphanil-amide. This diazotised base is coupled with N-l-naphthylethylenediamineOrganic applications.202 R. J. Starkey, Analyst, 1959, $4, 517.203 S. W. Nicksic and S. H. Judd, Analyt. Chem., 1958, 30, 2002.204 M. I.Eiss and P. Giesecke, Analyt. Chew., 1M9, 81, 1558.206 E. Saville, Analyst, 1968, 83, 070.C. A. Johnson and R. A. Savidge, J . Pharm. Pharmacol., 1958, 10, 1713410 ANALYTICAL CHEMISTRY.hydrochloride to yield an intensely coloured azo-dye, suitable for colori-metric measurement and proportionate to the amount of thiol originallysubmitted to the test.Preliminary tests with diazotised dianisidine and Gibbs’s reagent suggestthat these reagents cannot be used very effectively in the separation of thevarious tocopherols. Marcinkiewicz and Green 207 have subsequentlydeveloped a procedure, however, for the separation of the six nitrosotoco-pherols, ie., the two nitrosotocopherols derived from y-tocopherols and theindividual nitroso-derivatives of p-, y-, E-, and q-tocopherol.The separatednitroso-derivatives may then be determined by application of the ferricchloride-bipyridyl reaction. The procedure has been showii to be of valuein the analysis of synthetic mixtures of tocopherols and in the determinationof p- and &-tocopherols in natural oils.Determinations of biuret in commercial samples of urea2W have beenaccomplished by reaction of the biuret with alkaline nickel tartrate solutionand measurement of the absorption of the resulting nickel complex at465 mp. This method seems to suffer much less interference from the pre-sence of ammonium compounds than does the corresponding methodinvolving the preparation of the copper complex.In order to obtain the required accuracy in absorptiometric measure-ments in the far ultraviolet region, Hansen and Buell2Og have developed aspectrophotometer for use in the range 194-225 mp.The instrument has ahalf-intensity band width of 1.5 mp and has good sensitivity. The sameauthors 210 have described the use of the instrument for obtaining absorptionspectra of some biologically important compounds in the far ultravioletregion.A considerable amount of work has been carried out by a joint com-mittee of the Pharmaceutical Society and the Society for AnalyticalChemistry211 which has led to the development of methods for the deter-mination of the capsaicin content of capsicum and its preparations. Afterpreliminary preparation of the sample, the capsaicin is extracted eitherchromatographically or by an ether-alkali partition method.The directspectrophotometric method may then be used to determine the capsaicin.Alternatively, advantage may be taken of the fact that capsaicin, i.e., thevanillylamide of isodecenoic acid, is, in effect, a phenolic substance, and, assuch, couples with a diazotised base. Further, in the preferred method, itproduces a phenoxide when treated with alkali solution. At the same time,this production of phenoxide is accompanied by a precise and definite shiftin the ultraviolet absorption. McKinney and Reynolds 212 have also takenadvantage of the shift in absorption of phenols to longer wavelengths whenconverted into their phenoxide ions in a photometric titration method for theirdetermination.The absorption spectra of both phenol and its ion aremeasured, and a wavelength is selected where only the phenoxide ion shows207 J. Green and S. Marcinkiewicz, Analyst, 1959, 84, 297,208 J. Sverak, 2. analyt. Ckem., 1959, 169, 178.200 R. E. Hansen and M. V. Buell, Analyt. Ckem., 1959, 31, 878.2lO R. E. Hansen, J . Bid. Ckem., in the press.211 Analyst, 1959, 84, 603.212 R. w. McKinney and C. A. Reynolds, Talnnta, 1958, 1, 46JIASLAM AND SQUIRRELL PHYSICAL METIIOI>S. 41 1absorption. The phenol in butylamine solution can now be titrated withalcoholic potash solution, the end-point being determined by plottingabsorbance a t the selected wavelength against the volume of titrant addedand observing intersection of the straight line drawn through the linearportions of the plot.The determination of copolymerised styrene in copolymers containingcarbon black and other fillers, and in insoluble polymers presents greatdifficulty.Hilton et aL213 have overcome this difficulty by nitrating asuitably extracted sample of the polymer with nitric acid under reflusconditions. The styrene yields reproducible amounts of $-nitrobenzoicacid, which is extracted from the nitration products and examined in sodiumhydroxide solution by ultraviolet absorption measurements at 265, 273.75,and 285 my, from which the styrene content can be calculated. The methodhas an accuracy of about 0.2%.Infrared examinations of many organic substances are often made by thepotassium bromide disc method.Quantitative measurements by thisprocedure are not always as accurate as could be wished, and Ileller andWagner 214 claim to have obtained results of better accuracy in the examin-ation of steroid mixtures by melting the mixture between sodium chloride orpotassium bromide plates before the infrared test. For this procedure it isnecessary, of course, that the steroid mixture does not decompose on melt-ing. Chemists concerned with the identification of anionic surface-activeagents will be interested in the paper by Jenkins and K e l l e n b a ~ h . ~ ~ ~ Theseauthors have prepared the barium salts of some 10 organic sulphates andsulphonates and have found that the infrared spectra of these water-insolublesalts serve as an excellent means of identification.They give details of themethod of preparation and ashing of the salts in addition to the procedure forobtaining the infrared spectrum by the potassium bromide disc technique.The use of Alodan, 5,6-bischlorome thyl- 1,2,3,4,7,7-hexachlorobi-cyclo[2,2,l]hept-Z-ene, as a contact insecticide to guard against the ravagesof corn beetle has necessitated the development of a very accurate methodfor its determination in grain. The direct determination cannot be accom-plished, but it is possible by Paulig's method216 to extract the grain withcarbon tetrachloride, to purify this carbon tetrachloride extract by chromato-graphic treatment, then to convert the Alodan in the extract into 5,6-di-met hylene- 1,2,3,4,7,7-hexachlorobicyclohept ene, which is readily deter-mined by infrared measurement.The conversion is accomplished with theaid of alcoholic potash.Lee Smith and McHard 217 have presented much useful infrared spectro-photometric data on organo-silicon compounds. They are able by thismethod satisfactorily to characterise materials whether they be in themonomeric or polymeric state. The method of examination and sometypical spectra of chlorosilanes and silicon polymers are shown, and theinterpretation of these spectra in terms of group frequencies is explained.213 C. L. Hilton, J, E. Newell, and J. Tolsma, Analyt. Chem., 1959, 31, 915.214 I<. Heller and U. Wagner, 2. analyt. Chem., 1959, 16'4, 90.215 J. W. Jenkins and I<. 0. Kellenbach, Andyt. Chem., 1959, 31, 1056.917 A. Lee Smith and J.A. McHard, Analyt. Chem., 1959, 31, 1174.G. Paulig, 2. analyt. Chem., 1959, 168, 401412 ANALYTICAL CHEMISTRY.Lady and his co-workers218 have also used infrared spectroscopy for theanalysis of silicon polymers. They are able to determine the ratio of methylto phenyl groups in such polymers by measuring the intensity of the methyl-silicone and phenylsilicone compounds at 7.92 and 6.97 microns respectively.Most of the standard spectra are prepared from methylphenyldichlorosilaneand methyltrichlorosilane mixed in the appropriate proportions, and in-fluences due to polymeric structure on deviations from this calibration arediscussed.Two useful methods for the identification and analysis of polyurethanerubbers by ihfrared spectroscopy have been detailed by P.J. Corish.219 Inthe first method the rubber is examined as such, in the form of a microtomedsection. The use of crystallinity bands to characterise the acid portion ofthe polyester is discussed, together with the characterisation of di-isocyanatesby their absorption in the skeletal region. In the second method the rubberis hydrolysed in a stainless-steel tube with aqueous sodium hydroxide. Thediamine resulting from the original di-isocyanate is extracted with ether, theaqueous layer then filtered free from disubstituted ureas, and the filtrate dis-tilled substantially to dryness. By drying the distillate in a vacuumdesiccator over phosphoric oxide the glycol resulting from the hydrolysis canbe isolated. The dicarboxglic acids produced are isolated from the distill-ation residue after acidification with hydrochloric acid.The s0dil.mchloride formed in the neutralisation of the excess of alkali, of course, has noeffect in the subsequent infrared examination.In other papers concerned with the infrared examination of plastics,Rohmer 820 has stated that difficulties which arise in the determination ofmethyl groups in polyethylene are often bound up with the method ofstandardisation. He has suggested that many of these difficulties may beavoided by the use of appropriate standards prepared from polyethylene-polypropylene mixtures. Luther, Meyer, and Loew 221 have studied theinfrared spectroscopy of polyvinyl chloride plasticiser films, prepared fromdifferent dialkyl phthalates and different kinds of polyvinyl chloride.Theyconclude that there are two key frequencies, 1430 crn.-l for the polyvinylchloride and 1728 crn.-l for the phthalates, which follow the Beer-Lambertlaw in a concentration range of technical interest, and hence are suitablefor the determination of phthalate plasticiser in polyvinyl chloridefilms.Emission Spectroscopy.-In a most interesting article on Accuracy inSpectrochemical Analysis, Arrak and Mitteldorf 222 have discussed thesubject under six main headings, viz., sampling, spark source, electrodes,spectrograph, photometry, and calcdations. They also mention newtechniques for reducing variables, including special optics for reducing theeffect of arc wander, the packing of electrodes with powder samples, anddevices for mechanically traversing a flat sample during sparking.31, 1100.218 J.H. Lady, G. M. Bower, R. E. Adams, and F. P. Byme, Analyt. Chem., 1959,210 P. J. Corish, Analyt. Chem., 1959, 31, 1298.220 M. Rohmer, 2. analyt. Chem., 1959, 170, 147.221 H. Luther, H. Meyer, and H. Loew, 2. analyt. Chem., 1969, 170, 155.222 A. Arrak and A. J. Mitteldorf, A$$J~. Spectroscopy, 1969, 18, 86HASLAM AND SQUIHRELL : PHYSICAL METHODS. 413Kelley, Fischer, and Jones z23 have described the constructioii and useof 3 high-sensitivity recording flame spectrophotometer which has exceptionalperformance in the red spectral region, Special features and advantages ofthe instrument include high precision and dependability combined withgreat sensitivity.As a result, anion and salt interferences can be minimisedby working at estreme dilution. Reduction of spectral and flame back-ground interferences are achieved by use of a good monochromator. A new" vacuum cup " method has been proposed by Zink 224 for the handling ofsolution samples in spectrochemical analysis. In the method, which avoidstrouble due to boiling over, the sample is contained in a plastic cup surround-ing a centre bored graphite electrode which also has a transverse cut, toallow flow of sample into the centre bore. The sample is sucked into theanalytical gap for excitation by means of the rcduced pressure created inthe spark gap by each discharge pulse.The micro-sampling and -analysis of metals present as tiny specks onthe sample surface has been reviewed by Kunge and Bryan.225 They de-scribe the niethods for the removal of millimicrogram quantities of thesemetallic constituents from the sample by means of special drills as smallas 6.3 microns in diameter. The drilling is performed under a stereoscopicmicroscope, and the drillings obtained are transferred to ultra-pure electrodesfor spectrographic examinat ion.A method has been described by Baird 226 for the spectrochemical analysisof very pure samples of chromium.The chromium is volatilised as chromylchloride and the impurities are collected on a calcium sulphate matrix.This matrix containing the impurities is now burned in a d.c. arc, and theamount of the impurities calculated from measurement of the impurity lineintensities, with indium as an internal standard; Mg, Pb, Fe, Al, Cu, andAg have been satisfactorily detcrmiricd in chromium by this method in therange 0.005-0.0001 yo.A method developed by Radmacher and H e s s l i i ~ g ~ ~ ~ for the spectro-analytical determination of trace elements in coal is really a method for theirdetermination in the carefully prepared ash of the coal.The method isbased on the behaviour on excitation of a mixture of the ash, ammoniumchloride, and carbon powder of very high purity. In the examination ofslags, a preliminary fusion with borax is first effected. Rekus 2% prefersto use indium as the internal standard for the spectrographic determinationof potassium in coal ash. Its advantages are that it is usually absent fromcoal and, spectrographically, it is a compatible partner for potassium, theindium line being approximately 60 A removed from the potassium line, andsuffers no interference from other elements present in coal ash.Indium alsohas the merit that its excitation potcntial is similar to that of potassiumand its ionisation potential is not too far removed from that of potassium.A very useful step which has as its object the preliminary concentration223 31. T. Ketley, I). J . Fischer, and H. C. Jones, AnaZyt. Clzem., 1959, 31, 178.224 T. H. Zink, Appl. Spectroscopy, 1959, la, 94.228 E. F. Kunge and I;. R. Bryan, AppZ. Spectroscopy, 1959, 13, 74.226 C. G. Baird, Appl. Spectroscopy, 1959, $3, 29.227 'CV. Radmacher and H.Hcssling, Z . analyt. Chem., 1959, 167, 172.228 A. F. Rekus, Appl. Spectroscopy, 1958, 18, 141414 ANALYTICAL CHEMISTRY.of small amounts of thallium present in test substances has been proposed.229Advantage is taken of the relatively high vapour pressure of thallium and itscompounds and the thallium is volatilised in a stream of oxygen or hydrogen,the products being collected on a metallic cold finger before spectrographicdetermination of the thallium.It is fairly obvious that there are likely to be important developments inthe use of atomic absorption spectroscopy in the determination of metalsin solution. The principle of the test was outlined in our previous Report(1958) and this principle has now been extended to the determination ofsilver, gold, platinum, rhodium, and palladium in solution.B0 It is probable,however, that the early papers concerned with analytical determinations byatomic absorption spectroscopy stressed the specific character of the testrather too strongly.David,=l in his paper, points out that phosphorus,aluminium, silicon, sodium, and potassium will all interfere in the deter-mination of calcium in the wet digestion products of plant material byatomic absorption spectroscopy. These interferences may be avoided, ie.,that of phosphorus, aluminium, and silicon by the addition of magnesiumand sulphate to both sample and standard, and that of sodium and potassiumby addition of these elements in excess to both sample and standard.Products obtained by the wet digestion of plant material appear to bevery suitable for the determination of zinc and magnesium by atomicabsorption spectroscopy.In a method also due to D a ~ i d , ~ ~ 2 a hollowcathode discharge tube emits intermittent light of the element to be deter-mined at a particular frequency. Between this discharge tube and the slitof a medium quartz spectrograph there is a Lundegiirdh air-acetylene flameassembly into the base of which a fog of the solution under test may beintroduced. The plate holder of the spectrograph is replaced by a slit andphotomultiplier assembly so arranged that this latter slit is placed on theresonance line of the element being determined. The signal from thephotomultiplier is fed to an a.c. amplifier and the rectified output is measuredwith a millivoltmeter.5.MICRO-ANALYSISNEUMAYER~~ has described what might be an important advance in themicro-determination of molecular weights. He has modified Muller andStolten’s apparatus, utilising thermistors as temperature-sensing elements, sothat maximum temperature is registered in only 3 minutes. By using thisapparatus, which operates on the principle that a. solution when exposed tovapours of the same solvent assumes a temperature higher than the solventalone exposed to the same vapour atmosphere, a molecular weight can bedetermined on less than 5 mg. of sample with a relative error of less than 2%.Roth 234 has described some rather interesting methods of determinationz2Q W. Geilmann and K. Heinz Neeb, 2.analyt. Chern., 1959, 165, 251.230 R. Lockyer and G, E. Hames, Analyst, 1959, 84, 385.231 D. J. David, AnaZyst, 1959, 84, 536.232 D. J . David, Analyst, 1958, 83, 655.233 J. J. Neumayer, Analyt. Chim. Acta, 1959, 20. 519.234 H. Roth, Mikrochinz. Actu, 1958, 6, 766HASLAM AND SQUIRRELL : MICRO-ANALYSIS. 415of certain organic functional groups. He details procedures for determiningthe amount of alkali which reacts with acid anhydrides and lactones, aswell as a method for the determination of acid anhydrides by reaction with2,4-dichloroaniline to produce a 2,4-dichloroanilide ; the excess of 2,4-di-chloroaniline is determined by a bromination procedure. Many thiols maybe determined by a method involving reaction with copper(I1) butylphthalate.The excess of copper is determined by reaction with iodide.Disulphides and dialkyl sulphides may be satisfactorily determined byoxidation by bromine to the corresponding sulphones. Isocyanates andisothiocyanates may be readily determined by reaction with amines to yieldsubstituted ureas or thioureas; the excess of amine is determined by titrationwith acid.Filipovic and StefanacS35 have pointed out that some high results ob-tained in the Zeisel method of determination of methoxyl and ethoxylvalues may be due to insufficient purification of the alkyl iodides liberatedby reaction with hydriodic acid. They have overcome this difficulty byreplacing the usual liquid-filled washers with a solid Ascarite purifying tubeand carrying out the reaction in a stream of nitrogen or air.By also in-cluding a layer of " anhydrone '' in the purificatioii tube, the iodides areobtained in a sufficiently pure state to permit direct carbon and hydrogendeterminations to be carried out. The data thus obtained are of obviousqualitative and quantitative use when the organic compound under in-vestigation might contain methoxyl or ethoxyl groups or possibly both.The separation and estimation of methoxyl and ethoxyl groups presenttogether in organic compounds has also been carried out by Makens et aLm6The methyl and ethyl iodides liberated in the conventional way are passedinto a solution of trimethylamine in nitrobenzene, and the ethyltrimethyi-and tetramethyl-ammonium iodides are formed. These iodides have widelydifferent solubilities in this medium and hence can be separated by filtrationand individual determination by a modified Volhard or other methods.A method has been devised by Ashworth 237 for the determination ofvery small amounts of t-butyl alcohol in aqueous solution.He uses amercuric sulphate-sulphuric acid reagent similar to DenigWs reagent and isable to determine concentrations of t-butyl alcohol as low as 1-6 mg. perlitre with about 5% error.Kainzm has developed an interesting method of automatic control ofthe combustion of organic compounds in organic analysis. The apparatusincorporates a flow-meter which is provided with electrodes ; the operationof a relay is the governing factor in controlling the heating of the organicsubstance.Every organic substance is dealt with as an individual andprevious information about its behaviour on combustion is not necessary.A speedy method has been devised for the micro-determination of chlorine,bromine, and fluorine in organic substances.239 The substance is volatilisedin hydrogen, then combusted in an oxy-hydrogen flame. The combustion is235 L. Filipovic and 2. Stefanac, Croat. Chem. A h , 1959, 30, 149.236 R. F. Makens, R. L. Lothringer, and R. A. Donia, Anal;)& Chern., 1959, 31, 1265.237 M. F. R. Ashworth, Mikrochim. Ada, 1959, 506.238 G. Kainz, 2. analyt. Claem., 1959, 188, 427.239 F. Ehrenberger, Mikrochim. A d a , 1959, 192416 ANALYTICAL CHEMISTKY.particularly effective in breaking down organic fluorine compounds.Thetitration methods used for finishing are conventional, i.e., potentiometricfor the halides, and the thorium alizarin-red S method for fluorine.In order to use the Schoniger method of combustion for the determinationof phosphorus in motor oils and additives, Barney and his co-workers2ahave modified the combustion vessel and sample container, so that up to200 mg. of sample can be combusted. They use a one-litre reagent bottleas the combustion vessel and their sample container is fashioned from amicro-extraction thimble held in a simple platinum-wire support. Aftercombustion, the products are absorbed in dilute nitric acid and the phos-phorus is determined colorimetrically as the phosphomolybdovanado-complex. Rogers and Yasuda 241 have used the Schoniger combustionmethod for the determination of fluorine in organic compounds, After thedecomposition of the sample the ionised fluoride is determined by an im-proved ferric salicylate colorimetric method, which is carried out at a con-stant pH of 1.9-2-1.The method appears to give results with an accuracyadequate for the calculation of empirical formulz.have developed a sorting test for the preliminary qualit-ative detection of fluoride in foods and waters. The ash of the food-stuff,or a suitable solution of the substance under test, is treated with tartaricacid and sulphuric acid, and the mixture heated to a temperature sufficientto cause the tartaric acid to turn brown. The volatile products, containinga t this stage only about one third of the total fluoride in the sample, arecollected in a drop of water in a modified Feigl apparatus.The amount offluoride in this drop is determined by application of the reaction withzirconium-alizarin reagent on a spotting plate and comparison with knownstandards.By a combination of solvent extraction and ring-oven methods, West andMakherji 2@ have worked out a scheme for the separation and identificationof 35 metallic ions in a single drop of unknown solution. The unknown isdivided into 4 groups by placing the non-aqueous extract of the metalchlorides, thiocyanates, acetylacetonates, and diethyldithiocarbamates onfilter-paper and depositing them as rings by means of a ring-oven. Anothergroup is obtained by similar treatment of an aqueous solution of residualions.The individual ions are subsequently identified by spot-test methodsapplied to sectors cut from the separated rings of'deposited salts. Budd-hadev Sen 244 has used a reaction of gold(II1) with phenyl2-pyridyl ketoximeto form an orange-yellow chelate as the basis of a new spot test for gold.This coloured chelate is very soluble and can be extracted from aqueoussolutions with chloroform in the pH range 3-9. The limit of identificationis approximately 0-5 pg. of gold. The author details the precautions takenin the detection of gold in the presence of the pIatinum metals, copper,nickel, and cobalt.Quentin et240 J. E. Barney, J . G. Bergmann, and W. G. Tuskan, Analyt. Chem., 1959,31, 1394.241 R. N. Rogers and S.K. Yasuda, Analyt. Chem., 1959, 31, 616.2423 K. E. Quentin, J. Indinger, and S. W. Souci, 2. Lebeizsm.-Untersuch., 1959, 109,249 P. W. West and A. K. Makherji, Analyt. Chern., 1959, 31, 947.244 Buddhadev Sen, Mikrochinz. Acta, 1959, 513.213HASLAM AND SQUTRRET,L : RADIOCHEMICAL METHODS. 4176. RADIOCHEMICAL METHODSIN 1956 the Society for Analytical Chemistry broke new ground byappointing their first Analytical Chemistry Research Scholar in the personof T. T. Gor~uch.2~5 He was given the job of investigating an old problemby a new procedure. In the determination of trace elements in organicmaterials it is usually necessary to effect a preliminary destruction of theorganic matter by wet or dry oxidation processes and, in the past, manycontroversies have arisen about the loss of trace elements in these preliminarytests. GorsuchB5 has brought a new weapon to bear on this problem byadopting a radiochemical approach.In the main, his recovery experimentshave been concerned with the following elements : lead, mercury, zinc,selenium, arsenic, copper, cobalt, silver, cadmium, antimony, chromium,molybdenum, strontium, and iron. Most attention has been paid to lossesof lead and mercury in these preliminary oxidation processes.In radiochemical tracer analysis, Lambie B6 has made a new approachwhich, he claims, results in increased accuracy. He indicates that the errorsinherent in radioactive tracer analysis may be reduced by measuring theunseparated rather than the separated fraction of the radioactivity.Williams 247 has developed a novel method for the determination of verysmall proportions of tin in iron and alloy steels.The sample is first sub-mitted to neutron irradiation in such a way that the product contains thedesirable tin isotope lHSn of convenient half-life and, moreover, long-lived isotopes, l13Sn and 121Sn, are produced in only small quantities. Decayof the irradiated sample for a convenient period enables any 125Sn producedto be converted into 125Sb which is removed in the subsequent chemicaloperations. After this preliminary, tin is added as carrier, and a wholeseries of chemical purifications carried out which have as their purpose thefinal production of a purified stannic oxide containing the active lzlSn andsuitable for counting.Control experiments are carried out on pure tin,The method is capable of determining quite accurately amounts of tindown to 0.0001% in alloy steels and 0-0005% in iron.A radiochemical method described by Morris and Killick248 for thedetermination of small amounts of silver in galena and blendes uses theradionuclides lloMAg and ll0Ag. The silver is separated after the addition ofcarrier, mainly as chloride, sulphide, oxide, and iodate. The final countingis carried out on the silver as iodate, from the weight of which the chemicalyield is determined gravimetrically. Amounts of oxygen of the order of0.01-2% have been determined in beryllium metal by a procedure Zg9 inwhich the metal is first irradiated in a 14.5-Mev neutron flux and the residualactivity is counted with a Geiger counter. The 7.4-second P-activity from16N, which is produced from oxygen in the course of the test, is comparedwith calibration data obtained on known beryllium-beryllium oxide mix-tures.e45 T. T. Gorsuch, Analyst, 1959, 84, 135.e46 D. A. Lambie, AnaZyst, 1959, 84, 173.247 A. I. Williams, Analyst, 1959, 84, 433.248 D. F. C. Morris and R. A. Killick, AIzalyt. Claim. Ada, 1959, 20, 587.249 R. F. Coleman and J. I,. Perkin, Analyst, 1969, 84, 233.REP.-VOL. LVI 418 ANALYTICAL CHEMISTRY.Finally, a method which can be used for the particle-size analysis ofany sub-sieve particles which have a y-ray absorption coefficient significantlydifferent from that of the suspending liquid, has been presented by Ross,=in particular for the analysis of uranium oxide particles. The particles inuniform suspension are allowed to settle and their concentrations at afixed depth in the suspending liquid are continuously determined andrecorded by measuring the transmittance of 7-rays through the solutionfrom an %lAm source. The method can be readily calibrated, and thedata converted to a standard curve of (particle fractions under a certainsize) vmszGs (diameter) obtained from Stokes's law.7. APPARATUSThroughout the year, many excellent pieces of apparatus and manyanalytical instruments have been described. In this short Report, however,we have concentrated largely on general aids to the analyst that can befairly easily constructed in the laboratory.The need for a simple means of indicating and recording the changes inthe composition of the eluate from liquid-solid chromatographic columns hasbeen satisfied in an apparatus due to C l a ~ t o n . ~ ~ ~ This detector depends onthe differences in the heat of absorption of liquids on suitable absorbents.The eluate from the main column is passed through a cold capillary columnsuitably protected from outside temperature changes and fitted with thesame absorbent as the main column. The temperature variation a t a pointin the small cold column is detected by a thermocouple, the output fromwhich can be supplied to a suitable galvanometer or recorder. The detectorcan also be used for separations made on ion-exchange columns, when thedetector is again filled with the resin being used. Peterson and Sober 252have described an apparatus which will be of real value to those engaged ingradient-elution chromatographic separations. The apparatus, whichconsists of a series of identical mixing chambers containing eluant of varyingcomposition in hydrostatic equilibrium , can be adjusted to produce nearlyany concentration gradient without change in the apparatus. The initialconcentration of each eluant and its position in the series control the shapeof the gradient. The authors give details of qualitative relationships andconstruction of the apparatus.The conventional method, originally due to Eschka, for the determinationof mercury by volatilisation and formation of an amalgam with gold, whichis subsequently weighed, has been improved by He has designeda simple apparatus which eliminates errors due to loss of mercury vapour andgives excellent results. The sample is mixed with iron powder and coveredby a layer of zinc oxide in a small silica combustion flask. The flask isfitted by a standard cone joint to a silica tube containing gold foil. Thistube is easily removed complete with gold foil for weighing purposes.A melting point apparatus which is particularly suitable for use with150 C. P. Ross, Analyt. Chem., 1959, 31, 337.261 G. Claxton, J . Chromatog., 1959, 2, 136.s1 E. A. Peterson and H. A. Sober, Analyt. Chem., 1959, 31, 857.'5s J. Lacy, Analyt. Chinz. Actu, 1959, 20. 195HASLAM AND SQUIRRELT. : APPARATUS. 419explosive materials has been designed by Ungnade et aZ.254 The apparatusutilises an electrically-heated copper block, and an optical system is providedwhich projects on to a screen at the rear of the apparatus both transmittedand reflected images of the melting point tube. In this way a completestudy of the phase transition before and during melting is possible.Patterson and Rabouin 255 have devised an all-glass capillary viscometerwhich permits the solution of a polymer sample a t high temperature, filtra-tion, and measurement of the solvent and solution efflux flow times withoutremoval from the vapour heating bath. The advantage of the apparatus isthat it permits safe handling of liquids at high temperatures without thedifficulties of oxidative degradation and precipitation usually encounteredin other methods of examining the viscosity of polymer solutions at elevatedtemperatures.Copies of infrared spectra can be obtained at the same t h e as theoriginal spectrum is being traced by using the mechanical auxiliary recorderdesigned by Watt.256 The apparatus employs a double pen arm by whichone small copy of the spectrum can be made on standard chart for recordfiling and another made on gummed paper, 8" x 24", for sending to theworker initiating the analytical sample. This copy may be easily fixed intoa working notebook opposite the details of the sample tested.J. HASLAM.D. C . M. SQUIRRELL.254 H. E. Ungnade, E. A. Igel, and B. B. Brixner, Analyt. Chem., 1959, 31, 1432.255 G. D. Patterson, jun., and L. H. Rabouin, tert., Rev. Sci. Instr., 1958, 29, 1086.256 P. R. Watt, Chem. and Ind., 1959, 44