ANALYTICAL CHEMISTRY.IN preparing this Report it has been necessary to break with tradition. Thenumber of analytical papers published in one year is so great that it wouldbe quite impossible to record all the papers or even only the most importantones without this Report’s becoming a mere catalogue. We have thereforetried to concentrate our attention on original papers rather than abstractsand to describe as many new principles as possible in the limited space atour disposal.The papers have been collected and divided into the following sections:1. General.2.3.Conventional Qualitative and Quantitative Inorganic and OrganicAnalysis.Physical Methods of Analysis under the Following General Headings :(a) Electrical methods. (b) Polarography. (c) Chromatography.(d) Absorption spectroscopy.(e) Emission spectroscopy.4. Microchemical Methods.5. Miscellaneous Analysis6. Radio-chemical Methods.7. Apparatus.GENERALGeneral papers of particular interest have dealt with a wide range oftopics. Analytical chemists everywhere are likely to profit from the workof the A.B.C.M./S.A.C. Joint Committee on methods for the analysis oftrade effluents. The four panels dealing with organic matter (general),metallic contaminants, non-metallic contaminants, and physical tests havemade great progress and many agreed methods have been published in theAnalyst in the course of the year. Also on the subject of trade effluentsHapp, Stewart, and Cooper2 have devised a very useful test for the deter-mination of volatile hydrocarbons.In this rather novel method the moistvapour above the sample solution containing the volatile solvent in an air-free system is sampled. This moist vapour is then examined directly inthe mass spectrometer and encouraging results have been obtained in thedetermination of, for example, dichloromethane, aliphatic and aromatichydrocarbons, acetone, and methanol in such waters.Those chemists confronted with problems in thermal analysis will finduseful data in the papers presented at the Symposium 3 on Purity Controlby Thermal Analysis, Amsterdam, 1957.The utilisation of new principles in analysis has been a feature of the1 Analyst, 1957, 82.2 G. P. Happ, D. W. Stewart, and H. C . Cooper, Analyt. Chem., 1957, 29, 68.3 Analyt.Chim. Acta, 1957, 17, 1-174.REP.-VOL. LIV 354 ANALYTICAL CHEMISTRY.year. A method of analysis based on observation and measurement ofthe phosphorescent light emitted by appropriately excited molecules hasbeen developed.* The method appears applicable to multiple-bond organicmolecules, each of which exhibits a unique phosphorescence which may becharacterised even in mixtures. For quantitative work very carefullystandardised conditions have to be used. Reflectance measurements havebeen utilised by Rose for the determination of mean particle size of fineblack powders, e.g., carbon black, graphite, etc. A simple reflectometerhead is used and the method is calibrated in terms of powders of knownparticle size. A useful feature of the method is that in the case of pelletsor aggregates, it is the reflectivity of the particle forming the aggregatesand not the aggregate itself that is measured and hence the mean particlesize of the unit particles in an aggregate can be obtained.for the determination of metals in solution.The metal under considerationmust be reactive towards a reagent which is optically active. The opticalrotation of the reagent solution is measured and the solution of the metalion is added to an excess of this reagent solution. Any precipitate is filteredoff and the optical rotation of the filtrate again measured. . Since understandard conditions the optical rotation of a solution is proportional to theconcentration of active ingredient present, the concentration of metal canbe calculated from the change in rotation produced.Silver and iron havebeen thus determined by reaction with D-tartaric acid.Logie 7 has worked out a new method of concentration or removal ofinterfering ions from those being determined. The principle of separationis the electrolysis of the solution in a two-compartment cell separated byan ion-exchange membrane. A cation-exchange membrane being used,the metal ions in the anode compartment pass irreversibly through themembrane into the cathode compartment, leaving the trace element beingstudied, if it is an anion, in the anode compartment. The use of an anion-exchange membrane has of course the opposite effect and use. This methodhas been used with success in the determination of traces of boron in metallicsodium. The sodium is removed by electrolysis of the hydroxide solutionusing a cation-exchange membrane, before isolation of the boron from theanode compartment of the cell and photometric determination of the boronwith curcumin.Analysts requiring a regular supply of diazonium cations for the deter-mination of phenols, etc., or for other purposes may find the proceduredescribed by Lambert and Cates for the storage of such cations dispersedand dried on nuclear sulphonic acid ion-exchange resin of great use.Whenrequired, the cation is released by treatment of the resin with an inert saltsuch as potassium chloride, the pH of the solution adjusted as required, andany coupling reaction carried out. The method of preparation of testpapers with diazonium ions fixed as stable zirconium ions is also described.4 R.J. Keirs, R. D. Britt, jun., and W. E. Wentworth, Analyt. Chem., 1957,29,202.5 H. E. Rose, J. Appl. Chem., 1957, 7, 244.M. Freegarde, Chem. and Ind., 1957, 984.7 D. Logie, Chem. and Ind., 1957, 225.8 J . L. Lambert and V. E. Cates, Analyt. Chem., 1957, 29, 508.A new principle of differential polarimetry has been used by FreegardHASLAM AND SQUIRRELL. 355QUALITATIVE AND QUANTITATIVE INORGANIC AND ORGANIC ANALYSISThe subjects dealt with under this heading tend to be on conventionallines. It should be emphasised, however, that in the inorganic field at anyrate great stress is being laid on complexometric titrations. There arevery few metals indeed which cannot be determined by some form ofcomplexometric procedure.Qualitative.-A procedure for the separation of metals into groups and amore comprehensive scheme of qualitative analysis has been set out bySalaria,g based on the principle of formation and decomposition of thio-salts, This scheme extends that already described by the same author toinclude rhodium, ruthenium, osmium, palladium, iridium, gallium, indium ,rhenium, tantalum, niobium, germanium, scandium, and the rare earthsand alkali metals.Also on the subject of group separation, two authors lo have put forwarda new and very comprehensive scheme of qualitative analysis of anions.The basis of the systematic procedure is the precipitation of difficultlysoluble salts of anions into groups by basic group reagents in sodiumcarbonate solution.Each group precipitate or filtrate is then examinedfor the individual anions in the group.The separation of niobium and tantalum has been achieved by a sublim-ation method.11 The metals as their oxides are caused to react withaluminium chloride, bromide, or iodide and the niobium and tantalumhalides formed are separated by fractional sublimation at controlled tem-perature.A simple and rapid test for arsenic, likely to prove of value in the detectionof arsenic in many organic and inorganic substances, has been devised byClark.12 The solution of the test substance is first reduced with stannouschloride, after which zinc dithiol is added. In the presence of arsenic awhite turbidity is produced in the boiling solution.The principle of thetest may be extended to the detection of germanium. The test solution isboiled with hydrochloric acid and potassium chlorate. The zinc dithioltest is carried out on a sample of the vapour arising from the solution.A delicate test for elementary sulphur13 involves the reaction of abenzene solution of the material with a pyridine solution of lead thiophen-oxide. The lead thiophenoxide polysulphide produced is gradually con-verted, at room temperature, into black lead sulphide.Trace amounts of iron in extreme dilution (1 part in 5 x lo8 in water)and in solutions obtained from alloys containing large amounts of copper,cobalt, nickel, and zinc may be detected by using a reagent containing2 : 2'-dipyridyl or 1 : 10-phenanthroline in thioglycollic acid.l* The com-bined reaction of the mixed reagents avoids preliminary reduction ofthe iron and lengthy separations from traces of other elements.WhereThe products obtained are quite pure.9 G. B. S. Salaria, Analyt. Chim. Acta, 1957, 16, 509.10 I. K. Taimni and L. Manohar, ibzd., 1957, 17, 367.11 M. Chaigneau, Compt. rend, 1957, 244, 900.1 2 R. E. D. Clark, Analyst, 1957, 82, 760.13 H. Krebs, H. Fassbender, and F. Jorgens, 2. analyt. Chem., 1957, 155, 250.14 F. Feigl and A. Caldas, Analyt. Chem., 1957, 29, 680356 ANALYTICAL CHEMISTRY.the iron has to be concentrated or separated a procedure recommendingprecipitation as hydroxide in the presence of an alumina collector isdescribed.In the organic field a very comprehensive scheme for the semimicro-qualitative identification of 21 types of anionic surface-active agent hasbeen presented by Holness and Stone.15 Methods have been worked outfor the isolation of the active agent from the commercial prepxation.One of the features of the method is the use of a mixture of two dyes,Disulphine blue V200 and Dirnidium bromide, which, when used at twodifferent pH values, give coloured chloroform extracts in accordance withthe type of surface-active agent present.Two new spot tests for nitromethane have been described by Feigl andGoldstein.16 The first is based on Nef degradation to yield formaldehydewhich is detected by means of chromotropic acid in concentrated sulphuricacid, and the test can also be used for nitroethane, which yields acetaldehydedetectable by the sodium nitroprusside-piperidine reaction, The secondtest takes advantage of the blue colour formed by nitromethane with 1 : 2-naphthaquinone and calcium oxide.Since nitromethane can be producedfrom monochloroacetic acid, dimethyl sulphate, iodomet bane , and methylhydrogen sulphate, the same reaction can also be used with little modificationas a spot test for these compounds.The reaction of rhodanine with 1 : 2-naphthaquinone-4-sulphonic acidto give a highly coloured product is the basis of Feigl and Gentil’s spottests for monmhloro(or bromo)acetic acid, alkali thiocyanates, thiourea andits derivatives, and cyanamide and its salts.17 All these compounds areconverted into rhodanine before application of the test by the Nenckisynthesis.The oxidative fission of organic substances by fusion with benzoylperoxide and identification of the characteristic gaseous products of cleavagehas been found to be a particular advantage in identification work.18O-Methyl and N-methyl compounds yield formaldehyde, N-ethyl and-propenyl compounds yield acetaldehyde, whilst sliphatic oximes andaliphatic and aromatic hydroxamic acids yield nitrous acid.Quantitative (Gravimetric) .-There have been several interesting develop-ments in gravimetric analysis.Oxygen in titanium and particularly in titanium alloys containingmanganese has been determined by a method due t o ElweU and Peake 19involving chlorination of the sample in the presence of excess of carbon,argon being used as purge gas.The oxygen is converted into carbonmonoxide which is purified, then oxidised to carbon dioxide by passageover heated wpper oxide, and finally weighed.Salicylaldoxime is often used as a reagent for copper. The reactions ofo-hydroxyacetophenone oxime, which may be regarded as the methylderivative of salicylaldoxime, with various metals have been compared with1 5 H. Holness and W. R. Stone, Analyst, 1957,82. 166.16 F. Feigl and D. Goldstein, Analyt. Chcwz., 1957, %I, 1521, 1522.17 F. Feigl and V. Gentil, ibid., p. 1715.1 8 F. Feigl and E. Silva, Analyst, 1957, 02, 582.1@ W. T. Elwell and D. M. Peake, ibid., p. 734HASLAM AND SQUIRRELL. 357those of salicylaldoxime.2* As a result of these investigations, it is suggestedthat the new reagent may find useful application in the gravimetric deter-mination of copper, nickel, palladium, vanadium, and titanium, as well asfor the colorimetric determination of iron, uranium, and vanadium.o-Hydroxyacetophenone oxime has been shown by Poddar21 to haveseveral advantages over salicylaldoxime for the precipitation of copper atpH 2-3 and nickel at pH 5-55.The precipitates possess greater stabilityand are easier to purify. With this new reagent nickel and copper may beseparated from one another and from a large number of other metals.The behaviour of metal diethyldithiocarbamate complexes in chloroformsolution on shaking with solutions of other metallic salts of known pH valuehas led to the preparation of a " displacement series." 22 For example,mercury solutions will displace copper from the chloroform solution of thecopper complex and so on.The use of this principle may lead to interestingdevelopments in the field of metallurgical analysis.Silverman and Trego 23 have devised a method for the separation anddetermination of barium in zirconyl chloride or zirconium metal, basedon a double precipitation of the zirconium as zirconyl chloride from ahydrochloric acid medium followed by a cupferron precipitation-chloroformextraction of any remaining zirconium. The barium is then determinedgravime trically as the sulphat e.of the reductionof quadrivalent and sexavalent selenium solutions to the element by meansof sulphur dioxide in heated but closed flasks.As a result of this work ithas been shown that it is possible to determine quadrivalent and sexavalentselenium in the presence of one another by preliminary reduction of theSeIV to element in weak hydrochloric acid solution followed by filtrationand subsequent reduction of the Sen in the filtrate under more stronglyacid conditions.The difficulties in the determination of molybdenum in titanium byprecipitation as sulphide, such as hydrolysis of the titanium, the need of arapid hydrogen sulphide stream, and the need of a lengthy digestion timebefore the molybdenum sulphide is filterable, have been largely overcomeby the use of thioacetamide; 25 this is added to an appropriately treatedacid solution of the sample, and the solution kept at the temperature ofboiling water for 1 hour.The precipitated molybdenum sulphide in thecooled solution is dense and easily filterable and after combustion is weighedas molybdenum trioxide.The gravimetric determination of beryllium, after separation from iron ,aluminium, and titanium, has been described by Nadkarni, Varde, andAthavale.26 The separation is effected by adsorption of the beryllium onan 1Ft.A-120 ion-exchange resin after complexing the iron and aluminiumA thorough study has been made by Bode and Stemmer20 S. N. Poddar, 2. analyt. Chem., 1967, 154, 254.21 Idem, ibid., 1957, 155, 327.22 G. Eckert, ibid., p. 23.23 L. Silverman and K. Trego, Analyt. Chim. Acta, 1957, 17, 280.24 H. Bode and H.D. Stemmer, 2. anaZyt. Chem., 1967, 155, 96.as W. N. McNerney and W. F. Wagner, Analyt. Chem., 1957, 29, 1177.26 M. N. Nadkarni, M. S. Varde, and V. T. Athavale, Analyt. Chim. Acta, 1967,16,421358 ANALYTICAL CHEMISTRY.with EDTA and the titanium with hydrogen peroxide. The adsorbedberyllium is eluted from the column with hydrochloric acid and determinedby ignition to BeO, after a double precipitation as hydroxide. The method isof particular use in the analysis of beryl.Boron has been determined by a rapid gravimetric procedure whichinvolves conversion into tetrafluoroboric acid and precipitation of thiswith an organic reagent-nitron. The advantages of the method 27 are thatdistillation is unnecessary and fluoride and weak acids and bases do notinterfere.Methods are given to avoid interferences due to bromide,hydriodic acid, nitrous acid, chromic acid, etc.Quantitative (Volumetric) .-In the field of conventional volumetricanalysis further work has been carried out on practical working standards.Some experiments of Easterbrook 28 indicate that working standard sodiumcarbonate is best prepared as follows: Sodium hydrogen carbonate of highquality is first purified, then converted into sodium sesquicarbonate. Thelatter, on heating at 270°, yields sodium carbonate of first-class purity andof high stability at that temperature.Again on the subject of standardisation, Runge et aZ.29 have indicatedthat diaryldisulphimides, (R=SO,) ,NH, in particular 3 : 3’-dinitrodiphenyl-disulphimide, appear to be useful substances for the standardisation ofalkalis by titrimetric procedures.The behaviour of FeIII 1 : 2-dihydroxybenzene-3 : 5-disulphonic acidcomplex to changes in pH has been studied by Sen, Berg, and West30 andshown to be reversible and reproducible.It is useful as a reversible anduniversal indicator in pH titrations, giving colours ranging from light greenat pH 2 through violet to deep orange at pH 13.In the determination of alkali hydroxide in the presence of alkalicarbonate Szekeres and BakB~s-PolgAr,~~ after precipitation of the carbonateas barium carbonate, prefer to titrate the hydroxide with standard zincchloride rather than standard acid, with phenolphthalein as indicator.Phosphorus in many organic compounds, both fluorinated and un-fluorinated, may readily be determined on the semimicro-scale after fusionwith sodium peroxide in a bomb.32 The phosphate in the reaction productsis precipitated as quinoline molybdophosphate before titration.In a method by Pietsch 33 phenarsazinic acid is used for the quantitativeprecipitation of quinquevalent vanadium at pH 2.The precipitate isdissolved in alkali, and the vanadium reduced with oxalate before filtrationfrom phenarsazinic acid. After oxidation with permanganate, the vanadiumis determined by titration with standard ferrous solution. Good resultsare obtained in the presence of magnesium, nickel, zinc, and chromate.Tin in titanium alloys may be detennined, after preliminary solution ofthe sample, by reduction of the tin with hypophosphite in 1 : 1 hydrochloric27 C.A. Lucchesi and D. D. DeFord, Analyt. Chem, 1957, 29, 1169.28 W. C. Easterbrook, Analyst, 1957, 82, 383.29 F. Runge, J. Behrends, and A. Ernst, 2. analyt. Chem., 1957, 158, 266.8 0 B. Sen, E. W. Berg, and P. W. West, Analyt. Chim. Acta, 1957, 17, 355.81 L. Szekeres and E. BakAcs-PolgAr, 2. analyt. Chenz., 1957, 156, 194.32 T. R. F. W. Fennell, M. W. Roberts, and J . R. Webb, Analyst, 1957, 82, 639.33 R. Pietsch, 2. analyt. Chem., 1957, 155, 189HASLAM AND SQUIRRELL. 35 9acid.34 The stannous chloride produced is titrated with iodate-iodidesolution, starch being used as indicator.A method of ferrometric determination of silver, which is particularlysuitable for the examination of silver-copper alloys, is described by Erdeyand Vigh35 and is based on direct titration of the silver solution, in thepresence of acetate buffer and sodium fluoride. The ionised silver is reducedto metal, and Variamine-blue is used as end-point indicator.Barltrop and Morgan36 have presented a new method for the deter-mination of water and alcohols based on titration with acetic anhydridein the presence of perchloric acid, using the ferric hydroxamate colourreaction as a means of external end-point detection.At the end-pointthe red colour of ferric acethydroxamate is formed. The method can beused for the estimation of water in acetic acid, acetonitrile, ethyl acetate,acetone, benzene, and carbon tetrachloride and is said to be both rapid andaccurate.Uranium has been determined in alloy systems37 by precipitation asuranyl ammonium phosphate from a solution of the sample containing anacetate buffer and sufficient EDTA to complex interfering elements.Theacid solution of the separated uranium is passed through a lead reductorand the quadrivalent uranium solution so formed is titrated with standardceric sulphate solution.The interest in, and use of, complexones has been world-wide and this isdemonstrated by the vast amount of publication this subject has receivedthroughout the year. New complexones have been introduced, newindicators used, and many new procedures described. Of the many paperspublished we can review but a few.A new selective complexone for the direct titration of calcium in thepresence of magnesium has been developed and is described by Schmid andR e i l l e ~ .~ ~ This complexone, ethylene glycol bis-(2-aminoethyl ether)-NNN'N'-tetra-acetic acid, gives a good potentiometric end-point with amercury indicator electrode. The total magnesium and calcium is found bydirect titration with EDTA, and the magnesium found by difference.In the titration of complexing agents both in presence and in absence ofindicator, consideration has been given by Flaschka and Soliman 39 to theminimum differences between the stability constants of complexes whichwill permit one metal to be titrated in the presence of another. Moreover,particular consideration has been given to the advantages of triethylene-tetramine as a reagent for this type of titration.The dye Fast-grey FL4 4o has proved a useful indicator in complexometrictitrations using EDTA.In conjunction with other indicators, e.g., Erio-chrome-black T, it can be used for the direct determination of thorium,ferric iron, bismuth, and zinc, or the analysis of binary mixtures. Thorium,34 H. J. G. Challisand J. T. Jones, AnaZyst, 1957, 82, 658.35 L. Erdey and K. Vigh, 2. analyt. Chem., 1957, 157, 184.36 J . A. Barltrop and K. J. Morgan, Analyt. Chim. Acta, 1957, 16, 520.37 G. W. C. Milner and J. W. Edwards, ibid., p. 109.3* R. W. Schmid and C. N. Reilley. Analyt. Chem., 1957, 29, 264.99 H. Flaschka and A. Soliman, Z . analyt. Chem.. 1967, 158, 254.40 H. Khalifa, Analyt. Chim. Ada, 1957, 17, 194360 ANALYTICAL CHEMISTRY.ferric iron, and zinc can also be determined in the presence of many otheranions and cations.A new indicator Calcon (C.I.202), described by Hildebrand and Reilley,41allows the direct titration of calcium in the presence of magnesium withEDTA. The titration is carried out at a pH of 12-13 after initial precipit-ation of the magnesium with diethylamine; the sharp end-point colourchange is from pink to blue.A method first developed by Schwarzenbach in which account is takenof the acid liberated as a result of the interaction of certain bivalent metals,such as copper and zinc, with the disodium salt of ethylenediaminetetra-acetic acid has been shown to be unsatisfactory. An alternative form oftitration is proposed42 in which the bivalent metal is titrated with astandardised solution of the disodium salt of ethylenediaminetetra-aceticacid until further addition of titrant no longer produces a change in thepH of the solution.EDTA has been used by Ueno for the simultaneous complexometricdetermination of mercury and copper.The total metals itre titrated bythe addition of excess of complexone and back-titration with standardcopper solution at pH 10. Potassium iodide is then added which decom-poses the mercury-EDTA complex, liberating an equivalent of EDTA,which is again titrated back with more standard copper solution.The complexometric titration of calcium with EDTA has been achievedby Ramaiah and Vishnu using a photometric end-point with the copper-ammonium complex as an indicator.Copper sulphate solution is added tothe calcium solution under test and the combined solution made greaterthan 1 . 5 ~ with respect to ammonia. The absorption at 630 mp is measuredafter each addition of EDTA, and a sharp fall in absorbance is noticed whenall the calcium has been titrated and the EDTA complex with copper startsto form, causing a decrease in the concentration of coloured cuprammoniumions.Iron, aluminium, and chromium may be determined in the presence ofeach other 45 by procedures based on the different stabilities of their com-plexes with EDTA. Iron is determined by adding excess of EDTA at pH1-5 then warming to 50-60" and back-titrating the excess of EDTApotentiometrically with standard iron solution. Iron and chromium aredetermined by a similar titration after preliminary buffering to pH 5, addi-tion of excess of EDTA, boiling and back-titrating at 50-60" at pH 1.5.Iron, aluminium, and chromium are determined by buffering to pH 5.0then adding excess of EDTA and boiling before back-titration at pH 5.0and 40".Weiner and Ney 46 have shown that the determination of small amountsof chromic ion in the presence of excess of chromate can be accomplished bycomplexing with excess of EDTA at the boiling point; the excess of EDTA41 G.P. Hildebrand and C. N, Reilley, Analyt. Chem., 1957, 29, 258.42 J. Haslam, D. C. M. Squirrell, and M. Heskins, Analyst, 1957, 82, 117.43 K. Ueno, Analyt. Chem., 1957, 29, 1668.44 N. A. Ramaiah and Vishnu, Analyl. Chim.Acta, 1957, 16, 569.45 R. Patzak and G. Doppler, 2. auaalyt. Chem., 1957, 156, 248.46 R. TVeiner and E. Ney, ibid., 1957, 157, 105HASLAM AND SQUIRRELL. 361is then back-titrated, in the presence of buffer, with standard nickel solution,murexide being used as indicator.Indirect use of complexone has been made in several ways, for instance,indirect complexometric methods have been proposed by Sen4' for thedetermination of sodium and potassium. The sodium is precipitated assodium zinc uranyl acetate and the zinc in a solution of the precipitatecontaining ammonia, ammonium chloride and carbonate, is titrated withEDTA using Eriochrome-black T as indicator. Potassium is precipitatedas potassium sodium cobaltinitrite, and the cobalt converted into thiocyanatein the presence of acetone, then titrated with EDTA to absence of bluecolour.The lamp method for the determination of total sulphur in petroleumproducts has been improved.48 The sample is aspirated into an oxy-hydrogen flame and the products of the combustion are absorbed in hydrogenperoxide. The sulphate so formed is then determined by the addition ofexcess of barium acetate, the excess of which is then determined by a back-titration with EDTA.Tantalum, niobium, and titanium can be separated from other coii-stituents of hard metals such as tungsten, iron, and cobalt by precipitationwith ammonia in the presence of glycerol and EDTA as described by Lassnerand W eisser.49The number of papers on organic analysis which can be classified underconventional volumetric analysis is obviously smaller than that on inorganicanalysis.Two useful methods have been described, however, by Fickenand Lane 59 for the titration of the basic functional groups in ion-exchangeresins, perchloric acid being used in glacial acetic acid media. The firstmethod, although time-consuming, appears more reliable and is based onthe direct slow titration of the base in the resin at 100" to an Oracet-blue Bor Crystal-violet indicator. The second, more rapid method, which tendsto give low results, is based on treatment of the resin with excess of perchloricacid in acetic acid solution at loo", followed by filtration and back-titrationof the excess of perchloric acid with sodium acetate in glacial acetic acidsolution.Smith 51 has developed two new titrimetric methods for the quantitativeanalysis of aryloxysilanes.In the first, a bromide-bromate titration iscarried out in glacial acetic acid media, and in the second, the titrant ispotassium methoxide in anhydrous ethylenediamine, o-nitroaniline beingthe indicator. The first method also appears applicable to phenyl ortho-esters of carboxylic acids.Vicinal glycols such as batyl alcohol and cyclohexane-1 : 2-diol may bereadily determined by reaction of the glycol with trimethylammoniumperiodate in a mixed solvent containing ethyl alcohol, ethyl acetate, andacetic acid.524 7 B. Sen, 2. analyt. Chem., 1957, 157. 2.48 0. N. Hinsvark and F. J. O'Hara, Analyt. Chem., 1957, 29, 1318.49 E. Lassner and H.Weisser, 2. analyt. Chem., 1957, 15'7, 343.6 0 G. E. Ficken and E. S. Lane, Analyt. Claim. Acta, 1957, 16, 207.61 B. Smith, Acta Chem. Scand., 1957, 11, 558.b2 R. J. B. Reddaway, Analyst, 1957, 82, 506362 ANALYTICAL CHEMISTRY.PHYICAL METHODSElectrical.-It is apparent from the amount of literature on electro-chemical methods that new potentiometric tests as well as coulometric andhigh-frequency titrations are finding increasing use. Amongst the moreimportant introductions is the method of potentiometric titration in non-aqueous media, by means of alkylammonium hydroxide.53In the field of inorganic electrochemical analysis a method of internalelectrolysis has been developed by Kangro and Pieper st for the precisedetermination of iron.The iron solution with the iron present as ferricchloride is subjected to internal electrolysis with a platinum cathode and asilver anode. The test is carried out in the presence of hydrochloric acidand potassium iodide and in an atmosphere of carbon dioxide. The ter-valent halide is reduced to bivalent halide at the cathode, the third halogenatom being subsequently deposited as silver halide on the anode; theproportion of silver halide is determined by difference. A study has beenmade of the possibility of extension of the principle of the test to the deter-mination of oxidising and reducing agents.Erdey and Siposs 55 have described a method in which copper may bedetermined by direct reductometric titration with ascorbic acid in thepresence of ammonium chloride and sodium acetate.The end-point may bedetermined either visually or potentiometrically and suffers little interferencefrom other ions.A method previously employed with a polarographic finish has beenmodified to determine large proportions of zinc in minerals and foundryproducts.56 The material, with or without additives such as iron or carbon,is heated at 1100" in a stream of hydrogen. The zinc in the solution of thesublimate, with any lead present precipitated as sulphate, is titrated potentio-metrically with standard potassium ferrocyanide solution.A novel method has been developed by Schmidt 57 for the determinationof potassium in potassium salts. The potassium is precipitated with excessof sodium tetraphenylboron, the mixture bulked to volume and filtered, andan aliquot part of the filtrate back-titrated with standard thallous solution,a modified dead-stop end-point being used.The principle of the testmay be extended to the examination of ammonium salts and the salts ofcertain organic bases.On the subject of coulometry, it has been shown by Lingane et aZ.58that the current efficiency in the electro-generation of ceric ion is a functionof current density, falling below 100% at very high and very low densities.Iodide may, however, be accurately titrated to iodine at low currentefficiences owing to direct oxidation of the iodide to iodate a t the anode,at a potential slightly in advance of the cerous-ceric oxidation potential.The iodate so formed in turn oxidises the iodide to iodine. In fact, verylittle of the total current used results in the formation of ceric ion.The53 J. S. Fritz and S. S. Yamamura, Analyt. Chem., 1957, 29. 1079.54 W. Kangro and H. Pieper, 2. analyt. Chem., 1957,155, 169.55 L. Erdey and G. Siposs, ibid., 157, 166.66 W. Geilmann, R. Neeb, and H. Eschnauer, ibid., 154, 418.57 H. J . Schmidt, ibid., 157, 321.5 8 J. J . Lingane, C. H. Langford, and F. C. Anson, Analyl. Chim. Acta, 1957, IS, 166HASLAM AND SQUIRRELL. 363titration of iodide can be satisfactorily carried out, without the presenceof cerous ion at all, at suitable current densities.The use of coulometry has been further extended by Carson et aZ.59to the determination of plutonium. The plutonium is first oxidised to avalency of 6, then, by using electrically generated ferrous ion, titratedback to plutonium(1v).The method, which can be used for samples con-taining 3 y to 10 mg. of plutonium, is subject to very few interferences.In volumetric methods for the chemical determination of sulphur inorganic compounds containing nitrogen, difficulties have often arisen inthe titration because of the presence of nitric and nitrous acids in the Preglcombustion products. Massie 60 has overcome these difficulties by neutralis-ation of the combustion products with ammonium hydroxide and additionof ethanol before conductometric titration of the sulphate with bariumacetate solution.In high-frequency work, one of the disadvantages of most titrimetersis that they only work satisfactorily at comparatively low electrolyteconcentrations, An instrument has been designed by Lane whichoperates at 250 Mc./sec.and enables tests to be carried out a t electrolyteconcentrations up to O-7~-sodium chloride or its equivalent. The newapparatus is particularly suitable for titrations of acids and bases in non-aqueous media.The detection of end-points in high-frequency conductometric titrationsinvolving colloidal electrolytes has been facilitated by Kupka and Slabaugh ,62who have described an instrument operating at a fixed frequency andincorporating an amplitude-stabilised oscillator worked in conjunction witha specially shaped conductance cell. By using this instrument, titrations incolloidal systems can be carried out rapidly even if the conductance changeat the end-point is only a fraction of the total conductance of the solution.Square-wave titrimetry has been successfully employed in titrationsinvolving redox, precipitation , and complex-forming reactions.In themethod by Laitinen and Hall 63 a square-wave alternating signal of constantcurrent or voltage is applied to a pair of micro-electrodes and the currentor voltage output from these electrodes during the titration is measured.By using the procedure, a differential titration curve of equimolar mixturesof chloride, bromide, and iodide can be carried out.In the organic and inorganic field, automatic titrimeters are being usedto an increasing extent in analytical laboratories. In a general paperHaslam and Squirrella describe their use in connection with the deter-mination of: (a) Nitrogen and chlorine in polymers ; (b) iron and aluminium ;(c) water in organic compounds; (a) formaldehyde by the neutral sulphitemethod; (e) Nylon 610 salt in the moist material; (f) aldehydes and ketonesin methyl methacrylate monomer; and (g) the detection of “ Terylene.”59 W.N. Carson, jun., J. W. Vanderwater, and H. S. Gile, Analyt. Chem., 1957,6 0 W. H. S. Massie, Analyst, 1957, 82, 352.61 E. S . Lane, ibid., p. 406.62 F. Kupka and W. H. Slabaugh, Analyt. Chem., 1957, 29, 845.63 H. A. Laitinen and L. C. Hall, ibzd., p. 1390.64 J . Haslam and D. C. M. Squirrell, Analyst, 1957, 82, 511.29, 1417364 ANALYTICAL CHEMISTRY.The direct titration of organic functional groups has been carried outby Jucker 65 using chromium(r1) sulphate.The substance is dissolved in asuitable solvent, e.g., water, dimethylformamide, pyridine, etc., and thesolution brought to an appropriate pH with sulphuric acid. The titrationis carried out potentiometrically using a platinum indicating electrode anda bridged calomel cell as reference. Azo-, nitro-, nitroso-, and quinonoidgroups give sharply defined titration curves and in several cases whereisomers have different redox potentials, with consequent different steps inthe titration curve, they can be determined without separation.Analysts faced with problems involving potentiometric titrations innon-aqueous media will find useful information in a paper by van der Heijdeand Dahmen 66 which describes the practical criteria in the choice of suitablesolvents and conditions.The acidity potential ranges of twelve solventsare given, together with the half-neutralisation of sixteen acids in them.Tetra-alkylammonium bases dissolved in pure pyridine are described asnew titrants for acids in non-aqueous media.The use made by Fritz 53 of tetra-alkylammonium hydroxide in benzene-methanol as a titrant for phenols and organic acids in acetone media hasbeen mentioned previously. The method utilises a glass, modified calomelelectrode system, and under certain conditions a differential titration ispossible. Fritz, Moye, and Richard 67 have extended the use of this titrantto the titration of nitro-aromatic amines and polynitro-aromatic com-pounds a , ~ weak acids, in pyridine solution.A useful application of coulometry to organic analysis has been describedby Miller and DeFord 68 in a method for the spectrophotometric titrationof olefins with electrically generated bromine.The bromine is generatedin an acetic acid-methanol medium from potassium bromide with mercuricchloride present as catalyst for direct titration. The titration vessel isalso a photometric cell, and the progress of the titration can thus be followedspectrophotometrically and a plot made of absorbance against time atconstant current, at a specific wavelength. The stoicheiometric end-pointis determined by finding the point of intersection of the two straightportions of the plot before and after the end-point.Po1arography.-Advances in polarographic and amperometric methodscontinue to be made.A polarographic method for the determination ofgermanium in samples containing from 0.001 to 10% of germanium has beendeveloped by Sauvenier and D~yckaerts.~~ The procedure is based onextraction of the germanium as GeC1, by carbon tetrachloride underappropriate conditions, followed by polarographic estimation of the Ge( IV)in the extract, after re-extraction into a boric acid-KC1 base solution atpH 8.9.Reynolds 7O has described how tin stabiliser, added as sodium stannateto hydrogen peroxide, may be determined by passage of the dilute sulphuric85 H. Jucker, Analyt. Ghim. Acta, 1957, 16, 210.66 H. B. van der Heijde and E.A. M. F. Dahmen, ibid., p. 378.6 7 J. S. Fritz, A. J. Moye, and M. J. Richard, Analyt. Chem., 1957, 29, 1685.68 J. W. Miller and D. D. DeFord, ibid., p. 475.6s G. H. Sauvenier and G. Duyckaerts, Analyt. Chim. Acta, 1957, 16, 692,70 G. F. Reynolds, AnaZyst, 1957, 82, 46HASLAM AND SQUIRBELL. 365acid solution of the peroxide through a cation-exchange resin in the hydrogenform. The tin retained on the resin is eluted with hydrochloric acid fromwhich any traces of hydrogen peroxide are removed by boiling beforepolarographic determination of the tin.A polarographic method of determination of lead has previously beenworked out based on the fact that thorium will displace lead from lead“ complexonate ” solution and the displaced lead may then be determinedpolarographically. It has now been shown by Flaschka and Barakat 71 thatthe principle can be extended to the corresponding amperometric titrationof the thorium.The amperometric titration of microgram and sub-microgram quantitiesof fluoride has been carried out by Johanne~son.’~ The method uses arotating aluminium electrode and a stationary platinum electrode; aconventional current-titre curve is obtained by using N/100-thorium nitratesolution when the titration is carried out in the presence of perchloricacid.On the organic side, antioxidants, e.g., NN‘-di-sec.-butyl-p-phenylene-diamine and $-n-butylaminophenol, have been determined in petrol by apolarographic method due to Gaylor, Conrad, and Landerl 73 using a wax-impregnated graphite electrode, with a solvent-electrolyte of lithiumchloride in propan-2-01.The wax impregnation of the solid electrodereduces residual current and increases sensitivity at lower concentrations.This electrode may find other uses, as it can be used in both aqueous andnon-aqueous media and for both oxidation and reduction reactions.Chromatography.-Although interest in paper and column chromato-graphy is being maintained, the most significant change throughout the yearhas been the increased attention paid to gas-liquid chromatography.Applications of this method of test are being made in most organic analyticallaboratories in this country. It is also probable that high-voltage electro-phoresis, as practised by will prove to be a very useful method ofphysical separation in analysis.A very comprehensive paper by Pfrengle 75 on the paper chromatographyof condensed phosphates such as penta- and hexa-phosphates describestheir separation by appropriate elution on paper and subsequent identific-ation by application of a molybdenum-blue test.The process may be madequantitative by cutting out the paper zones containing the particularpolyphosphates ; these are then hydrolysed to orthophosphate with acidbefore final determination by the molybdenum-blue test.Blasius and Czekay 76 have made a very detailed study of the paper-chromatographic and electrophoretic separation of molybdates and tung-states, of niobium and tantalum as their oxalate complexes, and further,of silicates and phosphates.A very sensitive paper-chromatographic test for the detection andH.Flaschka and M. F. Barakat, 2. analyt. Chem., 1957, 156, 321.72 J . K. Johannesson, Chem. and Ind., 1957, 480.73 V. F. Gaylor, A. L. Conrad, and J. H. Landerl, Analyt. Chem., 1957, 89, 224.74 D. Gross, Nature, 1957, 180, 596.75 0. Pfrengle, 2. analyt. Chem., 1957, 158, 81.76 E. Blasius and A. Czekay, ibid., 1957, UQ, 81366 ANALYTICAL CHEMISTRY.determination of microgram amounts of fluorides by Hall 77 is one inwhich the fluoride solution is added to calcium chloride-thorium nitrateimpregnated paper. A precipitate of calcium fluoride is produced on thestarting line and this precipitated calcium fluoride adsorbs the thoriumsolution very strongly. Interfering impurities in the solution under testare now removed by elution with an acetone-acetic acid solution.Thecalcium fluoride with adsorbed thorium is detected by staining withSolochrome-brilliant-blue BS.Oxycellulose has been found by Elvidge et ~ 1 . ~ 8 to be a very usefulcation-exchange medium in the determination of bacteriostatic agentssuch as phenol and chlorocresol and active ingredients such as atropinesulphate in injection solutions. The preparation is transferred to an oxy-cellulose column and the phenol is eluted with water, then determinedspectrophotometrically in the eluate. The alkaloid is then eluted from thecolumn with acid and determined spectrophotometrically.Some of the principles originally developed by Burstall and his co-workers have been applied successfully to the determination of elementssuch as molybdenum, cobalt , manganese, vanadium, nickel, and chromiumin special steels.79 The solution of the sample is applied to a cellulosecolumn, and, after elution with appropriate solvents, the elements in theeluates are determined colorimetrically.By chromatography on a transparent gel film, in which colloidal silverdichromate has been dispersed, Farlow 8o has been able to separate mixedsoluble chlorides , bromides, and iodides in single microscopic crystals orparticles.The particle in the film is moistened with water vapour where-upon it dissolves and diffuses into the film, forming the respective silverhalides in concentric rings , which separate because of solubility-productdifferences. The bands due to each halide have been developed to distinctivecolours by submitting the film to treatment with a sun lamp, ammonia, andwater vapour at elevated temperatures.The area covered by each bandis semi-quantitatively related to the amount of each halide present. Theprinciple of this method has also been used for the accurate measurementof the chloride-ion content of water-soluble particles of and g.in weight.A simplification of the ion-exchange resin method of extraction of acidsand anions from solution has been made by Moore,81 who uses long-chainamines in chloroform as the extraction medium. He is able to extractfrom aqueous solution, acids, complex metal acids, and some anioniccomplexes of polonium, plutonium, zirconium, and protactinium, by thisliquid-liquid extraction principle.5% Solutions of methyldi-rt-o tylaminesor tri-n-benzylamine in chloroform are suitable extraction solutions.In an improved method by Bkkksy 82 for the preparation of columns usedfor chromatography, the adsorbent is introduced as individual portions of77 R. J. Hall, Analyst, 1957, 82, 663.78 D. A. Elvidge, K. A. Proctor, and C . B. Baines, ibid., p. 367.7 9 G. Venture110 and A. M. Ghe, ibid., p. 343.81 F. L. Moore, ibid., p. 1660.a2 N. BCkesy, 2. analyt. Chem., 1957, 157, 272.N. H. Farlow, Analyt. Chem., 1957, 29, 881, 883HASLAM AND SQUIRRELL. 367slurry which, in the packed column, are separated from one another by piecesof filter paper; the latter are cut very accurately.Analysts faced with identification or purification problems will findvalue in the heavy-paper chromatographic technique which has beendescribed by Brownell et aZ.% for the isolation of pure compounds on thegram scale.The chromatography is carried out by conventional meansbut using a very heavy paper streaked with the mixture to be separated.After development, the resolved bands are located by taking a print fromthe chromatogram on to dry thin paper and spraying or treating with normalreagents. The corresponding band from the heavy papers is then cut outand the compound eluted with solvent.A new method has been developed by Mykolajewycz for thequantitative determination of the amount of separated substance in thedeveloped spots of paper chromatograms. A negative photocopy of thechromatogram is made in which the spots appear as white areas on a blackbackground.The intensity of the light flux through these white areas hasbeen shown to be proportional to the amount of substance in the spot andis independent of the size or form of the spot. Thus by measurement ofthe light flux by means of a suitable photocell arrangement under controlledconditions, and comparison with standard spot measurenients, an accuratemeasure of the substance in a spot can be made.White and Vaughans5 have developed an equation for the design ofliquid-liquid partition chromatographic columns, which relates theseparation factor and column characteristics with the number of theoreticalplates required for a particular separation. The use of this method permitsa more rational approach to the use of column chromatography, and thethree isomeric cresols have been satisfactorily separated in a column thusdesigned.A method has also been described for the determination of phenolin tar-acid mixtures.The method has beenapplied by Bergmann and Gruenwald 86 to the separation of polycyclicaromatic hydrocarbons. Excellent separations have been achieved by usingpaper made less polar and less hydrophilic in character by acetylation or bytreatment with alumina, propylene glycol, Vaseline, or Silicone.A method of identification of nylon and related polymers devised byClasper, Haslam, and Mooney 87 is based on hydrolysis of the sample withacid, after which the product is evaporated to dryness.The residue isdissolved in ethanol and the hydrolysis products are then separated bypaper chromatography, a mixture of .n-propanol, ammonia, and waterbeing used as the developing solvent. The various products are identifiedby observation of the chromatogram under ultraviolet light and by usingninhydrin and methyl red-borate buffer solutions as spray reagents.A chromatographic method for the separation and determination ofadipic and sebacic acids in admixture with phthalic acid, also described byPaper-chromatographic methods are numerous.83 H. H. Brownell, J. G. Hamilton, and A. A. Casselman, Analyt. Chem., 1957,29,550.84 R. Mykolajewycz, ibid., p. 1300.D. White and G. A. Vaughan, Analyt. Chim. Acta, 1957, 16, 439.8 6 E.D. Bergmann and T. Gruenwald, J. Appl. Chem., 1957, 7 , 15.87 M. Clasper, J. Haslam, and E. F. Mooney, Analyst, 1957, 82, 101368 ANALYTICAL CHEMISTRY.Clasper and Haslam,s* gives recoveries of the acids from mixtures oflOOyo & 2%. The separation is effected on a silicic acid column buffered topH 4.30 and the appropriate rc-butanol-chloroform eluates are titrated withstandard alkali. Pimelic, sebacic, and azelaic acids can be eluted approx-imately quantitatively from the column, under the same conditions of test.Valuable information about the purity of amino-acid preparations canbe obtained by paper chromatographic separation of the amino-acidimpurities and determination of the nitrogen content of the spots on the filterpaper corresponding with the individual acidsa9horizontal paper chromatography at elevated tem-peratures has been described in methods for the quantitative determinationof lactose and mannose in lactose hydrolysates, and for separation of theC,-C, volatile fatty acids. The methods are much more rapid than normalchromatographic procedures. By using a developing solvent of butanol-pyridine-water (9 : 5 : 8) galactose and glucose can be separated by twoone-hour developments at 60".Four solvent developments being used,galactoyl oligosaccharides and lactose can be separated. The volatileacids are separated as their ethylamine salts by using water-saturatedbutanol as developing solvent at 50".Ion-exchange resins are finding increased use. Sargent and Rieman 92have effected the separation of glycols by chromatography on a quaternaryammonium based ion-exchange column, using two eluting solvents, (a) asolution of NaBO,, and (b) a solution of borax.Commerical 2 : 4 : 5-trichlorophenol and 2 : 4-dichlorophenol have beenanalysed by Logie g3 using a method which involves the use of the stronglybasic anion-exchange resin De-Acidite FF in a non-aqueous solvent mediumof pure methanol.The constituents are separated either by graded elutionwith glacial acetic acid-methanol mixtures or by the use of triethylamine-acetic acid buffer solutions in methanol of known pH value. The progressof the elution is followed by ultraviolet absorption measurements.Analysts employing zone electrophoretic methods will be interested inthe method employing foam rubber as the supporting material, as describedby Mitchell and I3erzenbe1-g.~~ It has proved satisfactory for thepreparatory separation of small amounts of proteins and other electrolytes,and the samples can be recovered after ionophoresis simply by squeezingthe spongesOn gas-liquid chromatography the use of higher temperature columnshas greatly extended the scope of the method. At a working temperatureof 257" and using a gas density meter, Beerthuis and Keppler 95 havesucceeded in analysing the even-numbered saturated fatty acid methylesters from C,, to C,, in about 90 min.Such stationary phases as ApiezonIn two papers88 M. Clasper and 3. Haslam, J . Afipl. Chem., 1957, 7 , 328.89 E. Schulek and 2.L. Szab6, 2. analyt. Chem., 1957, 157, 405.90 H. R. Roberts, Analyt. Chem., 1957, 29, 1443.91 H. R. Roberts and W. Bucek, ibid. p. 1447.92 R. Sargent and W. Rieman, tert., Analyt. Ghim. Acla, 1967, 16, 144.93 D. Logie, Analyst, 1957, 82, 563.94 H. K. Mitchell and L. A. Herzenberg, Andyt. Chem., 1957, 29, 1229.95 R. K. Beerthuis and S. G. Keppler, Nature, 1957, 179, 731HASLAM AND SQUIRRELL. 369grease, silicone oils, and greases and polythene have been used on a Celitecarrier.James 96 has shown that gas-liquid chromatography is likely to be ofgreat value in helping the analyst to separate both saturated and unsaturatedfatty acids from C, to Czo. C , to C, acids are separated at either 100" or137" on columns containing a silicone oil admixed with 10% of stearic acidas stationary phase, the eluates being titrated with standard alkali.Altern-atively, they may be separated as their methyl esters on columns containingparaffin hydrocarbons or high-boiling esters as stationary phases; a gas-density balance serves as detector. The C,-Czo acids are separated astheir inethyl esters at much higher temperatures, i.e., 200" on columnscontaining an Apiezon oil as stationary phase.A millicoulometer has been described by Liberti 97 for the manual orautomatic titration of the components of a mixture separated by gas-liquidchromatography. The eluted compounds are absorbed in a suitable solutionwhere they are continuously titrated by an electrically generated reagent,using photometric, amperometric, or potentiometric methods of end-pointdetection.Compounds with an active functional group such as volatileacids, bases, thiols, and aldehydes can be titrated directly. In the absenceof active groups the organic vapours are burned and the carbon dioxide soformed titrated coulometrically.Absorption Spectroscopy (Inorganic).-As has been the case for someyears, very many papers have been noted in which analytical determinationshave been described making use of measurements in the visible and theultraviolet region. The tendency throughout seems to be to make measure-ments at specific wavelengths rather than to pursue the use of filterinstruments.Many new colorimetric reagents have been investigated. Lucena-Condeand Prat 98 have described a new reagent for the colorimetric determinationof small amounts of phosphorus, arsenic, and germanium.The reagentcontains MoV1 and MoV in the ratio 3 : 2 in acid medium containingHzSO, and HCl. The colours produced with phosphorus, arsenic, andgermanium have absorption maxima at 840, 850, and 830 mp respectivelyand obey Beer's law over convenient concentration ranges.3-Hydroxy-l-~-sulphonatophenyl-3-phenyltriazen gg has been describedas an excellent colorimetric reagent for palladium. The reagent has aremarkable tolerance for members of the platinum group and can be usedfor the determination of palladium in the presence of Ni, Fe, Co, Ag, and Cu.The reagent is very soluble and forms a stable colour over a wide pH range.Variamine-blue (4-amino-4'-me t hoxydiphen ylamine hydrochloride) hasfound application by Erdey and Szabadv5ry1O0 as a redox indicator involumetric analysis.The substance may also be used for the colorimetricdetermination of such oxidising agents, as iron(m), chromium(vI), man-ganese(vII), vanadium(v), cerium(Iv), silver, iodine, and iodate ; these96 A. T. James, Fette u. Seifele, 1957, 69, 73.9 7 A. Liberti, AnaZyt. China. A d a , 1957, 17, 247.98 F. Lucena-Conde and L. Prat, z'bid., 1957, 16, 473.99 N. C. Sogani and S. C. Bhattacharyya, Analyt. Chem., 1957, 29, 397.100 L. Erdey and F. Szabadvary, 2. analyt. Chern., 1957, la, 90370 ANALYTICAL CHEMISTRY.agents produce with the Variamine-blue a blue meriquinoid molecular com-pound of one molecule each of the oxidised form and of the reduced formof the reagent.The use of hydrazinophthdazines as reagents for the colorimetric deter-mination of iron and vanadium has been described by Ruggieri.lolHydrazinophthalazine and dihydrazinophthalazine yield red-violet com-plexes with ferric ion, in sodium acetate at a pH of 11-2; Beer's law isobeyed in quantitative measurements made at 535 mp with hydrazino-phthalazine.Both reagents yield a straw-yellow colour with vanadiumand the vanadium hydrazinophthalazine complex at pH 5.5 in sodiumacetate buffer gives a colour obeying Beer's law fairly closely at A,,,. = 442mp,Aluminium has been rapidly determined in aluminium brasses andbronzes by Steele and England lo2 using the colorimetric reaction withEriochrome-cyanine RC after separation from interfering elements bysodium hydroxide treatment of an acid solution of the sample.Ferric salts, in buffered solution, form green complexes soluble in zsopentylalcohol with 8-hydroxy-7-iodoquinoline (ferron) and tri-n-butylammoniumacetate.The coloured solutions which are obtained are of high stability-The influence of other metals and of certain masking agents on the test hasbeen studied.lo3The new reagent for phosphorus-o-dianisidine molybdate-has been usedby Welch and West lo4 in the production of sensitive methods for the detectionof small amounts of organic phosphorus compounds containing as little as 0.2 yof combined phosphorus. The procedures described are applicable to acids,esters, acyl halides, and anhydrides together with their thio-analogues.Since its introduction twenty years ago, toluene3 : 4-dithiol has foundgreat favour as a reagent for tin.The general usefulness of the reagent hasnow been extended by a study of its reactions in acetate buffer and alkalinesolution by Clark.lo5 As a result of this it is likely to prove a useful reagentfor copper, cobalt, iron(II), antimony(v), and thallium. The S-dibenzoyland the S-diacetyl derivative are particularly useful in their colour reactionswith palladium(II), rhenium(vII), tellurium(Iv), selenium(Iv), and iridium.The S-diacetyl derivative and the zinc complex of toluene-3 : 4-dithiol arelikely to prove useful sources of the reagent itself which is rather unstable.Fast-grey RA is a very sensitive reagent for copper.Two moles of the acidunite with one mole of copper to form a coloured product which is measuredat 555 mp. The test, due to Khalifa,lo6 is capable of detecting 0.02 p.p.rn.of copper in solution in the presence of many cations: the interference ofiron may be avoided by the addition of ascorbic acid. With appropriaternodification,lo7 the same reagent can be used for the correspondingdetermination of very small amounts of quinquevalent vanadium.Interfering elements have been tabulated.lol R. Ruggieri, Analyt. Chim. Acta, 1957, 16, 242, 246.102 M. C. Steele and L. J. England, ibid., p. 148.103 M. Ziegler, 0. Glemser, and N. Petri, 2. analyt. Chem., 1957, 154, 170.lo* C. M. Welch and P. W. West, Analyt.Chem., 1957, 29, 874.105 R. E. D. Clark, -4nalyst, 1957, 82, 177, 182.loti H. Khalifa, 2. analyt. Chem., 1957, 158, 103.107 H. Khalifa and A. Farag, ibid., p. 109HASLAM AND SQUIRRELL. 37 1Fast-grey RA has also proved to be a very sensitive reagent for zir-conium.lo8 The purple reaction product in 0.2~-hydrochloric acid ismeasured at 580 mp. Metals such as U, Co, Al, Th, Bi, Zn, the alkali metals,and rare earths do not interfere, but nickel and copper do. The interferenceof appreciable quantities of iron may be avoided by the use of ascorbic acid.Methods have also been set out for the use of this dye in the determinationof bismuth log and molybdenum.l1°New methods and techniques in visible absorptiometric analysis havealso been very numerous and cover a wide range of determinations as thefollowing few examples will show.The metal indicator Eriochrome-black T has long been used as an end-point indicator in the titration of metals with EDTA.The reaction ofmicrogram quantities of many metals with Eriochrome-black T and thebehaviour of the reaction products with complexing agents and othersubstances such as potassium cyanide, carbamates, formaldehyde, andmagnesium complexone have been utilised by Berger and Elverslll inproviding a simple scheme of identification of certain cations.Diffculties arise in the visual EDTA titration of calcium with murexideas indicator, and of calcium and magnesium with Eriochrome-black T,particularly when other complexing agents such as potassium cyanide arepresent.These difficulties are avoided in an optical method designed byWallraf,l12 in which a parallel beam of light passes through a metal inter-ference filter of transmission maximum 620 mp, thence through a beakercontaining the solution under test, which is stirred magnetically. Theissuing light then falls on a selenium cell and the resulting current changeswhich take place in the course of the EDTA titration are measured on asensitive galvanometer.When p-phenylenediamine is oxidised by ferric chloride in the presenceof sulphide Lauth’s violet is formed. This reaction is inhibited by smallamounts of thiosulphate and advantage has been taken of this time ofinhibition in the development of a useful method of thiosulphate deter-mination.l13 The times of inhibition caused by known amounts of thio-sulphate under controlled conditions are measured as a calibration, and thesample then examined by a similar clock reaction.Heterometric titrations, Le., titrations to the point of maximum turbidity,have been utilised in several new analytical tests devised by Bobtelsky andRafailoff .l14 The heterometric reaction between lead and sodium diethyl-dithiocarbamate has been studied, and the principle used in a micro-methodfor the determination of lead in the presence of even more than 994% ofmany other cations.A titration takes of the order of 10 minutes and anerror of O-l-O% is reported, if the specially designed “ heterometer ” is used.The determination of bisrnuth1l5 in the presence of many other ions108 H.Khalifa and M. R. Zaki, 2. afialyt. Chem. 1957, 158, 1.100 H. Khalifa, Analyt. Chim. Acta, 1957, 17, 318.110 H. Khalifa and A. Farag, ibid., p. 423.111 W. Berger and H. Elvers, 2. analyt. Chem., 1957, 154, 114.112 M. Wallraf, ibid., 1957, 156, 332.113 J. B. Risk and J . D. H. Strickland, Analyt. Chem., 1957, 29, 434.114 M. Bobtelsky and R. Rafailoff, AnuZyt. Chim. Acta, 1957, 16, 321.115 Idem, ibid., p. 488372 ANALYTICAL CHEMISTRY.has been carried out on the micro-scale by heterometric titration with sodiumdiethyldithiocarbamate in the presence of complexing agents for the intes-fering cations. The end-point of the titration was shown to occur at thernole-ratio Bi : sodium diethyldithiocarbamate = 1 : 2, without dependenceon the complexing agent used.Excellent results were obtained, exceptin the presence of copper and antimony, and a complete titration could becarried out in 15 minutes. This work has also been extended to the deter-mination of cadmium.u6A very sensitive test €or titanium, which is specific in the presence ofmany light and heavy metals, has been suggested by Ziegler and Glern~er.~’Titanium in the presence of sulphosalicyclic acid and tetraphenylarsoniumchloride yields, with chloroform, a yellow chloroform extract.A new method for the separation and determination of traces of boron 118involves extraction of the boron as the rnethylene-blue fluoroborate complexwith dichloroethane and measurement of the colour at 645 my in a spectro-photometer. The method has been applied to the determination of boronin silica after a preliminary decomposition of the sample by means of hydro-fluoric acid, hydrogen peroxide, and ammonium hydrogen difluoride(FNH,,FH) in the presence of a copper(I1) chloride catalyst contained in apolythene reaction bottle.The voluminous work involving absorptiometric measurement in thevisible region has included a method for the determination of tellurium inlead and lead alloys by Fletcher and Wardle 119 involving the precipitationof the tellurium from the solution of the sample in bromine-hydrobromicacid mixture. The tellurium is subsequently dissolved, and finally theabsorption of the bromide is measured at 442 my in the presence of adefinite amount of hydrobromic acid.An adaptation 120 of the principle ofthe test enables bismuth to be determined in lead and lead alloys.A method published by Aldridge and Cremer 121 which is useful for thedetermination of diethyl- and triethyl-tin in mixtures of diethyltin dichlorideand triethyltin sulphate and which may have other applications is basedupon direct reaction of the compounds with dithizone. The aqueoussolution of the mixture is treated with a borate EDTA buffer at pH 8-4 andchloroform; the chlorofonn phase is separated and treated with dithizoneand fresh borate EDTA buffer before measurement of the triethyltincomplex at 610 mp. The aqueous phase is treated with chloroform anddithizone previous to measurement of the diethyltin complex at 510 my.The spectrophotometric determination of trace amounts of zinc as thezinc complex with apy8-tetraphenylporphin complex has been describedby Banks and Bisque.122 The complex is formed in glacial acetic acid andis particularly useful for the determination of zinc in cadmium, magnesium,rare earths, beryllium, iron, yttrium, and the alkali metals.116 M.Bobtelsky and R. Rafailoff, Analyt. Chim. Acta, 1957, 17, 267.117 M. Ziegler and 0. Glemser, 2. analyt. Chem., 1957, 157, 17.11* L. Ducret, Analyt. Chim. Acta, 1967, 17, 213.118 N. W. Fletcher and R. Wardle, Analyst, 1957, 82, 743.lZo Idem, ibid., p . 747.121 W. N. Aldridge and J. E. Cremer, ibid., p. 37.lz2 C. V. Banks and R. E. Bisque, Analyt. Chem., 1957, 29, 622HASLAM AND SQUIRRELL.373A method for the determination of inorganic azides in the presence ofother material, e.g., lead a i d e paint primers, has been developed by Robersonand Austin.123 The principle of the method involves conversion of theazide into hydrazoic acid with acid, followed by distillation into an acidifiedferric nitrate solution and photometric measurement of the reddish-brownferric azide colour formed at 460 my. Thiocyanates interfere in the test.A useful procedure1% for the direct determination of small amountsof copper in fuel oil and petroleum products may well be used for thedetermination of copper in other organic liquids. The liquid under testis treated with propan-2-01 solution of neocuproine (2 : 9-dimethyl-1 : 10-phenanthroline) and quinol and diluted with chloroform.. The absorbanceat 454 mp of the copper-neocuproine complex solution is then measured.The method appears remarkably free from interference.A colorimetric method for the determination of uranium has beensuggested by Blanquetlz5 based on the measurement at 415 mp of thecoloured complex of uranium with dibenzoylmethane formed in aqueouspyridine in the presence of EDTA and tartaric acid. Conditions have beenworked out which avoid interference from other elements and the methodis thus particularly useful for the determination of uranium in mineral ores.One of the disadvantages of many of the methods of colorimetric deter-mination of sexavalent uranium is their lack of sensitivity. A method isput forward by Foreman, Riley, and Smith126 in which many interferingelements are first removed by preliminary treatment of the uranium-con-taining solution with cupferron and extraction in acid medium.Otherinterfering substances are side-tracked by the addition of EDTA beforeextraction of the uranium as its diethyldithiocarbamate complex. Theuranium is recovered from the solution of the complex, then reduced to thequadrivalent condition with lead shot before application of the very sensitiveThoronol test for quadrivalent uranium.Use of tributyl phosphate has been made in the separation of uraniumfrom thorium, bismuth, and a variety of ores.127 Extraction from hydro-chloric acid solution permits separation from thorium, and extraction fromnitric acid solution separation from bismuth and other elements.Conditionshave been worked out which give an extract from nitric acid solution pureenough to enable the uranium to be determined by the 8-hydroxyquinolinespectrophotometric method.Dozinel128 describes how antimony, when present in pure and electrolyticcopper in the range 0~0001-0~003%, may be determined after solution ofthe sample in hydrochloric acid-hydrogen peroxide and removal of theexcess of peroxide.. The solution is reduced with sulphurous acid, then theantimony is oxidised with ceric sulphate to the quinquevalent condition.This antimony is extracted with isopropyl ether and treated with RhodamineB solution ; the coloured reaction product is measured photometrically.123 C. E. Roberson and C. M.Austin, Analyt. Chem., 1957, 29, 854.124 D. M. Zall, Ruth E. McMichael, and D. W. Fisher, ibid., p. 88.126 J. K. Foreman, C. J. Riley, and T. D. Smith, Analyst, 1967, 82, 89.127 A. R. Eberle and M. W. Lerner, Analyt. Chem., 1957, 29, 1134.128 C. M. Dozinel, 2. analyt. Chem., 1957, 157, 401.P. Blanquet, Analyt. Chim. Acta, 1957, 16, 44374 ANALYTICAL CHEMISTRY.The problem of determination of arsenic and phosphorus in copper-basealloys in the ranges 0-0.6% and 0-0.1% respectively has been successfullysolved by Baghurst and N0rman.1~~ The method, which requires nopreliminary separation of the elements, is based on the development of themixed heteropoly-acids with molybdenum and vanadium in acid solutionsof differing strength. The molybdovanadophosphoric acid is first formedin nitric acid solution of sufficient strength to prevent formation of thearsenic complex.Both complexes are then formed at a lower acid concen-tration, measurement of the colours made, and the readings referred to theappropriate calibration curves.A useful method for the rapid colorimetric determination of sulphatein the range 2-400 p.p.m. has been developed by Bertolacini and Barney.13*The method is based on reaction of the slightly soluble barium chloroanilate,with sulphate to liberate the highly coloured acid chloroanilate ion in 50%ethyl alcohol solution, after a preliminary removal of interfering cationswith ion-exchange resin.An important problem is concerned with the determination of mercuryand mercury compounds131 present as vapour, spray, or dust in air inconcentrations around the usually accepted “ toxic limit ” of 100 pg.percubic metre. The vapour of mercury is taken up by iodised active carbonand the mercury-bearing dust is trapped in a mineral wool filter. The activecarbon and mineral wool, in the presence of iron powder, are subsequentlyheated in a stream of carbon monoxide, generated from sodium oxalate, andthe mercury vapour evolved is determined by the colorimetric reactionwith selenium sulphide paper.A very useful procedure has been developed by Chirnside, Cluley, andProffitt 132 for the determination of a few p.p.m. of boron in nickel. Thesample is made the anode of a mercury cathode electrolysis apparatus;this enables the nickel and interfering elements to be removed in the presenceof the minimum amount of sulphuric acid.In its turn this simplifies theapplication of the curcumin-oxalic acid test to boric acid which has beenstudied in considerable detail.Very small amounts of cobalt in a whole host of substances such asnickel, chromium alloys, glasses, iron pyrites, zinc oxide, etc., may bedetermined by a method involving the production of tributylammoniumhexathiocyanatocobaltate(~~).~~~ This substance is extracted with isopentylacetate, and the colour measured at an appropriate wavelength.In a new method for the determination of osmium, Steele and Yoe134have used the naphthylaminesulphonic acids. The osmate(v1)-naphthyl-aminesulpfionic acid complexes show an absorption peak around 560 mpand adhere to Beer’s law from 0.1 to 6.0 p.p.m.of osmium. The osmiumcan be separated from interfering elements by distillation of the tetroxide.Several of the complexes have sensitivities as high as 1 in 20,000,000.H. C. Baghurst and V. J. Norman, Analyt. Ckem., 1957, 29, 778.130 R. J. Bertolacini and J. E. Barney, jun., ibid., p. 281.131 G. A. Sergeant, B. E. Dixon, and R. G. Lidzey, Analyst, 1957, 82, 27.132 R. C. Chirnside, H. J. Cluley, and P. M. C. Proffitt, ibid., p. 18.133 M. Ziegler, 0. Glemser, and E. Preisler, 2. analyt. Chem., 1957, 158, 358.lS4 E. L. Steele and J. H. Yoe, Analyt. Chem., 1957, 29, 1622HASLAM AND SQUIRRELL. 375Ultraviolet spectroscopy has been the basis of many excellent methodspublished throughout the year.The determination of lead in rubber and compounding materials on asemimicro-scale has been facilitated by a method due to Kress 135 involvingthe absorptiometric measurement of the solution of the ash or extract of thematerial in 50% hydrochloric acid.Measurement is made at 250, 270, and289 mp; after correction for the presence of iron and other cations mathematic-ally, the concentration of lead is calculated. The method appears valid in thepresence of copper up to 1/10 of the lead content. A similar spectrophoto-metric method has been developed by Grossman and Haslam136 for therapid determination of lead in PVC compositions. The absorption due tolead chloride is measured at 270 mp in a hydrochloric acid extract of anethylene dichloride solution of the sample.A slight modification of thismethod avoids interference due to any iron present in the composition.The fact that boric acid causes a very marked change in the ultravioletabsorption of chromotropic acid in aqueous solution has been made thebasis of an excellent method for the determination of a few p.p.m. of b0r0n.l~'The addition of boric acid causes a decrease in absorption of a chromo-tropic acid solution in the range 355-380 mp with a point of maximumdecrease at 361.5 mp. A determination of a differential spectrum of asolution of chromotropic acid at 361.5 mp with and without the boric acidsample solution is thus utilised, for the determination of boron, after suitablecalibration experiments have been carried out.Uranium(v1) can be extracted as a complex from sodium nitrate solutionat pH 3.0 into a 25% solution of tributyl phosphate in an inert solvent,138and after being thus separated from interfering elements the uranium canbe determined spectrophotometrically by measurement of the complexsolution at 250 mp.A most useful method for the determination of microgram quantities ofhalide in aqueous solution has been developed by Chapman and Sherwood 139based on direct ultraviolet absorbance measurement of the complexes formedwith palladous sulphate. Mixtures of halides have been separately deter-mined after selective oxidation with manganese dioxide or lead dioxide.Procedures are given for the conversion of organic halogen compounds intowater-soluble inorganic halides by treatment with disodium diphenyl.Finally, a useful application of infrared spectroscopy to inorganicanalysis has been made in the determination of sulphate ion in the range40-80 y in aqueous solution.The solution is freeze-dried with potassiumbromide, and a disc prepared from the resulting powder by the usual vacuum-high pressure technique. The method by Han Tai and isobviously easily calibrated.Ahsorption Spectroscopy (Organic) .-Applications of absorption spectro-scopy to organic analysis have also been numerous. Amongst the many135 K. E. Kress, Analyt. Clzem., 1957, 29, 803.136 S. Grossman and J. Haslam, J . Appl. Chem., 1957, 7, 639.137 D. F. Kuemmel and M. G. Mellon, Analyt. Chem., 1957, 29, 378.138 B.E. Paige, M. C. Elliott, and J. E. Rein, ibid., p. 1029.13p F. W. Chapman, jun., and R. M. Shenvood, ibid., p. 172.140 Han Tai and A. L. Underwood, ibid., p. 1430376 ANALYTICAL CHEMISTRY.useful communications published throughout the year have been thefollowing .New and extremely sensitive colorimetric procedures for the detectionand determination of unreacted isocyanate groups in urethane-basedpolymers have been worked out by Kubitz.lgl In the quantitative methodthe residual isocyanate is treated with an excess of n-butylamine, and theexcess then determined colorimetrically after treatment with malachite-green.For the rapid qualitative detection of isocyanate, a previously preparedcolourless secondary mine derived from malachite-green is used, and when asample containing free isocyanate is treated, a coloured product is produced.A novel method has been put forward by Saville 142 for the determinationof phosphorylating or acylating agents such as phosphorofluoridates, tetra-alkyl pyrophosphates, acetic anhydride, and benzoyl chloride.a-Oxo-aldoximes such as mononitrosoacetone react rapidly in slightly alkalinesolution with the agent, resulting in quantitative production of cyanidewhich is then determined colorirnetrically by the pyridine-pyrazolone test.The colour reaction of o-phthalates and succinates with quinol in thepresence of concentrated sulphuric acid has been put forward by Swann 143as a qualitative and quantitative test for these substances in plasticisers andsynthetic resins blended with alkyds.Quinazarin is formed with phthalatesand dihydronaphthazarin with succinates. For phthalates the reactionis carried out at 145" and the yellow colour, A,,,. = 480 mp, extracted withbenzene. On shaking with aqueous alkali the colour changes to violet,A,,,. = 575 mp. For succinates the reaction temperature is reduced to135" and the benzene extracts obtained are red in acid media and blue aftera,lkali-washing. The strict control of experimental conditions required forquantitative work is described.Organophosphorus compounds have featured in the analytical literature.Diisonitrosoacetone has been used by Sass et aZ.lU for the detection anddetermination of small quantities of organophosphorus halides, acid an-hydrides, and acetylating agents.The reagent forms a coloured complexmeasurable at 486 or 580 mp with as little as 1 y of compound in a 4 ml.portion of sample. A sensitive method also for the determination of organo-phosphorus compounds 145 has been based on the reduction of the phosphorusto phosphine with lithium aluminium hydride, followed by reaction of thephosphine vapours with silver nitrate or gold chloride on paper. Comparisonof the coloured stains produced can be made visually or by photometricmeasurement, and microgram amounts of organophosphorus compoundscan be detected.Hershenson and Hume 1*6 have determined small amounts of aliphaticamines in solution photometrically by taking advantage of the characteristicabsorption band from 750 to 950 mp due to the complex which is formed141 K.A. Kubitz, Analyt. Chem., 1957, 29, 814.142 B. Saville, Analyst, 1957, 82, 269.143 M. H. Swann, Analyt. Chern., 1957, 29, 1352.1*4 S. Sass, W. D. Ludemann, B. Witten, V. Fischer, A. J. Sisti, and J. I. Miller,lP5 F. T. Eggertsen and F. T. Weiss, ibid., p. 453.146 H. M. Hershenson and D. N. Hume, ibid., p. 16.ibid., p. 1346HASLAM AND SQUIRRELL. 377when the amine solution is added to an alcoholic solution of cupric chloride.Should the amine solution be in aqueous media or interfering basic substancesbe present, then the amine may be extracted with chloroform after theaddition of sodium carbonate and the cupric chloride reaction carried outin an alcohol-chloroform medium.Kapur et aZ.147 have noted how the colorimetric determination of vanillinhas been achieved by using absorptiometric measurement at 432434 myof the complex formed with thiobarbituric acid in phosphoric acid media.The method will detect as little as 0.2 pg./ml.of vanillin in 92% phosphoricacid, and may also be applied to the estimation of other aldehydes.A rzaction more specific for propylene glycol than previously publishedmethods for the determination of vicinal glycols has been described byJones and R i d d i ~ k . l ~ ~ The method is based on dehydration with sulphuricacid, which results in rearrangement of the propylene glycol to ally1 alcoholand the enolic form of propionaldehyde. This reaction mixture forms aviolet complex with ninhydrin suitable for quantitative spectrophotometricmeasurement at 595 mp.This coloured complex is specific for propyleneglycol and its polymers in mixtures of glycols.The determination of anthracene in impure anthracene containingcarbazole and phenanthrene has been accomplished by Fauss149 using amethod which involves (1) the preparation of a cell containing a definiteconcentration of pure anthracene in solution and (2) the addition of puresolvent to a second cell containing a known concentration of the impureanthracene until the absorptions of the two liquids are identical at a wave-length of 375 mp. A special cell has been constructed which permits stirringof the solution of the impure anthracene. It is claimed that the methodhas advantages over the differential procedure.o-Phenylphenol (2-hydroxydiphenyl) , after preliminary isolation, mayby determined (a) by taking advantage of the ultraviolet absorption of thephenol at two different wavelengths both before and after treatment withsodium hydroxide, (b) by measurement of the strong blue-violet fluorescenceof the phenol when irradiated in ultraviolet light, and (c) by measurementof the colour obtained on coupling of the phenol with the stabilised diazo-compound Brentamine fast-red GG.150Biggs,151 also on the subject of phenols, has proposed a method whichmay prove to be very useful in the identification of weak acids such ascertain phenolic substances.The ultraviolet absorption of the phenol ismeasured at a particular wavelength in acid and alkaline solutions as wellas in a buffered solution of pH close to the pH of the particular phenolicsubstance.From these data the degree of ionisation of the phenol iscalculated and compared with the values for pure substances.Emission Spectroscopy.-Under this heading Scharrer and Judel 152 haveI*' N. S. Kapur, K. M. Narayanan, G. S. Bains, and D. S. Bhatia, Chem. and Ind.,14* L. R. Jonesand J. A. Riddick, Analyt. Chem., 1957, 29, 1214.149 R. Fauss, 2. analyt. Chem., 1957, 155, 11.l50 D. Harvey and G. E. Penketh, Analyst, 1957, 82, 498.151 A. I. Biggs, ibid., p. 274.152 K. Scharrer and G. K. Judel, 2. analyt. Chem., 1957, 156, 340.1957, 1272378 ANALYTICAL CHEMISTRY.put forward a method for the spectrochemical determination of traceelements such as Ag, Co, Cu, Mn, Mo, Ni, Pb, V, and Zn in soils, fertilisers,and biological material. After suitable preparation of a solution of thesubstance with added iron or cadmium as additional elements, the Ag, Co,etc., are precipitated as their pyrrolidine dithiocarbamates at a definite pHand in the presence of sulphosalicylic acid.The chloroform solution of thedithiocarbamates is evaporated and ashed and the Ag, etc., then determinedspectrographically in the ash by comparison of the intensity of a suitableline of the element under consideration with that of a particular line ofiron or cadmium.The effect of phosphoric acid in depressing the flame emission of calciumcompounds is made use of in a method due to Erdey and Svehla 153 for thevolumetric determination of calcium using a flame photometer.A specialburner restricts the loss of calcium solution in the test. Flame photometricreadings corresponding with known additions of standard phosphoric acidsolution to the calcium solution under test are plotted against volume oftitrant.Also on the subject of flame photometry, in the determination of mag-nesium it has been shown by Knutson l* that it is desirable to use a car-burising flame containing carbon produced from appropriate proportionsof oxygen and acetylene. Under these conditions the sensitivity obtainedwith the 2852A line of magnesium relative to the background is muchincreased. Errors due to the presence of phosphate and sulphate ions arelargely eliminated by the presence of an excess of calcium ions.MICRO-ANALYSISProgress is still being made in the determination of the individualelements in organic compounds by micro-chemical procedures.In viewof the fact, however, that there is a tendency to require the analysis of smallerand smaller amounts of sample, it is likely that Unterzaucher’s newprocedure155 for the determination of carbon and hydrogen in organiccompounds or a modification of it will be of real significance. The abovemethod is capable of determining carbon : hydrogen ratios on as little as0 . 1 4 . 3 mg. of an organic substance, without weighing. The substanceis burnt in a stream of air over copper oxide. The combustion products,containing carbon dioxide and water from the substance and excess ofoxygen, are passed over heated copper to remove this oxygen; the wateris frozen out whilst the carbon dioxide passes on to be determined by passageover heated carbon and application of the volumetric Unterzaucher procedure.After this the water is melted and determined similarly.The interferenceof nitrogen, sulphur, and chlorine is avoided by appropriate arrangementof the combustion and absorption train.In a new combustion method by M&zor156 for the determination ofcarbon, hydrogen, and fluorine in a single sample of organic compound,minium is used to bind the hydrogen fluoride and as the oxidant. ThelS3 L. Erdey and G. Svehla, 2. andyt. Chem., 1957, 154, 406.154 K. E. Knutson, Analyst, 1957, 82, 241.166 J. Unterzaucher, Mikrochim.Acta, 1957, 448.156 L. MBzor, ibid., p. 113HASLAM AND SQUIRRELL. 379minium is employed as a layer on the inner wall of a sintered alundumtube which is placed in the empty glass combustion tube. The pyrolysisproducts from the combustion boat pass through a platinum tube over theminium at a temperature of 550-570", whereat the carbon and hydrogenare completely oxidised and fluorine bound as lead fluoride. The carbondioxide and water formed are determined in the usual way, and the fluorineby dissolving the minium layer from the apparatus and precipitating andweighing as lead chlorofluoride.A very fast and accurate Dumas method for the micro-determinationof nitrogen in solids, aqueous solutions, and biological fluids has been workedout by Kirsten.157 The sample is pyrolysed in carbon dioxide, and theproducts subsequently burned over nickel oxide before collection of thegases in a specially designed nitrometer.A complete analysis takes only16 minutes.Again, whilst retaining the general principles of the micro-Dumas methodfor the determination of nitrogen in organic compounds, changes in the typeof filling and the introduction of automatic traverse methods of combustionand breakdown of the sample have accelerated the test considerably.Nitrogen determinations may now be made in 35 minutes by Charlton'sprocedure.15*A new method15B for the micro-determination of chlorine in organiccompounds involves the preliminary conversion of the chlorine into chlorideand subsequent isolation of this chloride as silver chloride.This is dissolvedin ammonia and reprecipitated in emulsion form with acid before titrationwith standard iodide solution, starch and iodine in chlorobenzene beingused as indicator.Burger160 has presented a new specific and sensitive method for thedetection and quantitative determination of silver which depends on thereaction, at boiling temperature, of an ammoniacal solution of the silversalt with an alcoholic solution of 2 : 4-dinitro-l-thiocyanatobenzene. Underthese conditions an insoluble precipitate of the silver salt of 2 : 4-dinitro-thiophenol is produced.Analysts dealing with bacterial cellulose will be interested in a new testfor its estimation which has beenodevised by Dearing.161 The samples areprepared by treatment with sodium hydroxide, washed, and dried beforetreatment of an aqueous suspension of the dried material with sulphuric acidat the temperature of boiling water under controlled conditions.The pinkcolour produced is measured at 520 mp after centrifuging the suspension, andthe optical density compared with a standard curve prepared by using glucose.The determination of oxygen has received attention during the year.Further work has been carried out on the direct determination of oxygenin organic compounds by reaction with fluorinating agents and measurementof the molecular oxygen released. Sheft and Katz 1 G 2 have used BrF2SbF,,15' W. J. Kirsten, Analyt. Chenz., 1957, 29, 1084.lS8 F. E. Charlton, Analyst, 1957, 82, 643.W. Pilz, 2.analyt. Cheqn., 1957, 155, 423.160 K. Burger, MzRrochim. Acta, 1957, 310.161 G. G. Dearing, Nature, 1957, 179, 579.162 I. Sheft and J. J. Katz, Analyt. Chem., 1957, 29, 1323380 ANALYTICAL CHEMISTRY.a complex which is prepared simply from antimony pentduoride andbromine trifluoride. The organic compound is heated with the BrF2SbF,at 500' with thorough shaking, and the molecular oxygen released measuredtensimetrically. The method appears applicable to solid, liquid, or gaseoussamples.In a series of papers Potter and White163 have critically reviewed anddescribed improvements in the methods for the micro-determination ofdissolved oxygen in water at low concentrations of the order of 0.01 p.p.m.In the first paper the Winkler method with an amperometric finish for theiodometric titration is advised with certain amendments to avoid errorsdue to interfering substances.In the second paper the errors introducedby the use of the McLean sampling vessel are discussed and a new apparatusis described by which a precision of -J=O.O02 p.p.m. can be obtained. Amodification for use with warm water is also described. Paper 3 containsa description of a sensitive electrical circuit for use in the amperometrictitration of iodine with a sensitivity of 0.01 pg. of iodine per 100 ml. solution,no interference being caused by 2 p.p.m. of ferrous, ferric, or cupric ions.The titration of 10-7~-thiosulphate with lO-%-iodate is practicable. Paper4 describes a test of the efficiency of the Winkler method at concentrationsin the range 0.0007-0.0544 mg.of 02/litre. In paper 5 an ion-exchangemethod for the effective removal of interfering ferrous ions in the Winklerreaction is described, together with a referee method for the determinationof dissolved oxygen in water, with a precision of &04015 p.p.m.Booth, Bryant, and Parker1@ have successfully extended the well-known vacuum fusion method to the micro-determination of oxygen andhydrogen in sample weights of the order of 20 mg. of boron, beryllium,copper, chromium, iron , silicon, tantalum, thorium, titanium, uranium, andzirconium. The metal is brought into contact with platinum containingdissolved carbon at 1880" and the resulting carbon monoxide, hydrogen,and nitrogen, with small amounts of carbon dioxide, are pumped away andisolated, before analysis by a low-pressure method. The carbon monoxideis converted into carbon dioxide over Hopcalite, the carbon dioxide frozenout, then the carbon monoxide, and hence the oxygen, determined by takingaccount of the pressure change before and after this treatment. Hydrogenis determined by a similar process involving its removal by passage overheated palladium at 350400'.In general, the results for nitrogen do notappear to be particularly trustworthy.Several micro-qualitative tests worthy of note have been recorded.A spot test for micro-amounts of P5+ has been developed by Zechner165based on the reaction of phosphorus with quinoline molybdate impregnatedfilter-paper to form quinoline phosphomolybdate. The reagent paper iseasily prepared and 1 pg.of phosphorus can be detected.Two substituted naphthylamines 166 have been successfully used asspot-test reagents, viz. , 4-nitro-l-naphthylamine for mercuric mercury in163 E. C. Potter, J . A$@. Chem., 1957,7,285,297; E. C. Potter and J. F. White, ibid.,pp. 309, 317, 459.164 E. Booth, F. J. Bryant, and A. Parker, AnaZyst, 1957, 82, 60.166 S. Zechner, Mikrochim. Acta, 1957, 159.166 J. L. Garnett and L. C. Lock, Amulyt. C h h . Acts, 1957, 17, 351HASLAM AND SQUIRRELL. 381which CeIV i s the only other element known to interfere, and l-nitroso-2-naphthylamine for CeIv for which ion the test appears to be specific.The reaction between nitrate and chromotropic acid in the presence ofexcess of sulphuric acid has been utilised in the development of a usefulspot test for nitrate by West and Sa,rrnay167 At a dilution of 1 : 200,000as little as 0.2 pg.of nitrate ion gives a yellow colour, and interference fromnitrites and oxidising agents is eliminated by a preliminary treatment ofthe sample with sodium sulphite, sulphuric acid, and sulphamic acid.Finally, a very specific spot test for vanadium has been developedla8which is based on the production of a turquoise-blue colour with sodiumsalicylate in syrupy phosphoric acid solution.MISCELLANEOUS ANALYSISA method has been described for the determination of carbon and carboncompounds in br0mine.1~~ The bromine sample is passed in a stream ofoxygen through a combustion tube at 1000" to effect conversion of thecarbon into earbon dioxide.The bromine is then frozen out and the carbondioxide purified by passing through copper sulphate, manganese dioxide,and anhydrone, followed by absorption on Ascarite.By a rather novel procedure put forward by Jennings and Osborn170carbon dioxide in water in the range 0.01--0-10 mg. per litre may be deter-mined by aspiration of the acidified water with carbon dioxide-free air.The carbon dioxide evolved is absorbed in sodium hydroxide solution,which is subsequently titrated with N/lOO-acid. The acid used betweenpH 8.3 and 5.0 is a measure of the carbon dioxide in the water under test.The commercial product chlorbenside, an acaricide for red spider, consistsessentially of a mixture of p-chlorobenzyl $-chlorophenyl sulphide with asmaller proportion of o-chlorobenzyl @-chlorophenyl sulphide.In itsassay 171 the isomeric sulphides are oxidised to the corresponding sulphonesand weighed. The melting point of the product is determined, and theproportion of active para-para-sulphide compound deduced by referenceto appropriate melting point curves of mixtures of the pure sulphones.Fluorbenside is examined similarly.A method has been described 172 whereby the photometric titration dataobtained after the end-point of acid-base titrations can be platted to givea stoicheiometric end-point by extrapolation. The method is of particularuse in the titration of weak bases in water and the titration of essentiallynon-basic compounds like urea or amides in acetic acid.Great accuracyis claimed for the method owing to the sensitivity of the photometricmeasurements on which the plot is based.RADIO-CHEMISTRYThe pioneer work in radio-chemical analysis, a considerable proportionof which has been carried out in this country, is now bearing fruit and there16' P. W. West and P. L. Sarma, Mihrochinz. Acta, 1957, 506.lB8 V. P. R. Rao and G. G. Rao, 2. azzaEyt. Ghem., 1957,156, 100.lB0 M. Codelland G. N~rwitz, Analyf. Chem., 1957, B, 967.170 P. P. Jennings and E. M. Osborn, AnaZyst. 1957, 82, 671.1'1 D. J. Higgans and W. H. Stephenson, ibid., p. 435.172 C. Rehm and T. Higuchi, Analyt. Chem., 1957, 29, 367382 ANALYTICAL CHEMISTRY.is no doubt that with the introduction of more simplified equipment radio-chemical methods will in the near future become well-established proceduresin many analytical laboratories.The problem of preparing thin deposits of a-emitting elements fromorganic solvents has been largely overcome in a method described byThe solution in an organic solvent is evaporated on a tray the periphery ofwhich is heated so as to give a suitable temperature gradient across the tray,causing smooth evaporation of the solvent within the boundary of theheated periphery.In addition, a method has been described by Wagner, Pollack, andDonahoe 174 for the measurement of radioactive precipitates on filter paperby examination of both sides of the paper.Consideration must be givento thickness of paper and precipitate and close geometry conditions ofcounting must be used.A recording apparatus designed by Schram and Lombaert 175 facilitatesthe determination of soft radiations (14C,35S) in aqueous medium, for example,in chromatographic eluates.The solution is spread in a thin layer incontact with a plastic scintillator coupled to a coincidence circuit. Theefficiency of the instrument is stated to be comparable to that of a thinend-window G.M. counter in the absence of auto-absorption,Amongst the many useful applications of radiochemical analysis is amethod for particle-size determination by Abraham et aZ.176 capable ofbeing placed on an automatic basis and making use of a sedimentationprocedure in conjunction with radio-activation. The powder is neutron-bombarded and the activity which radiates from a thin laminate is used as ameasure of the weight of material in the laminate.The advantages of themethod are its speed and reliability and the fact that it can be used withreactive fluids such as liquid metals, water, and organic liquids.In the separation of small amounts of magnesium from iron withammonium sulphide, the question has been raised as to whether correctresults for magnesium have been obtained owing to compensating errors,i.e., a certain amount of co-precipitation of magnesium with the ironsulphide having been compensated for by titration of foreign ions withEDTA in the magnesium test. This is not the case as experiments byGamsjager and R e i ~ h e r t , l ~ ~ using active magnesium, have proved.In connection with the analysis of barium [14C]carbonate and 14C-labelled cyanide prepared from it, methods of general applicability to14C-labelled compounds have been worked out by Moyer and Isbell.178Total reactivity is taken by a direct count and by count measurement ofthe carbon dioxide liberated by wet oxidation after absorption in alkalineethylene glycol. A count of carbon dioxide evolved by acid treatmentof the carbonate after similar absorption gives a basis for its evaluation.The specific count for 14C-labelled cyanide .is taken by reaction with a173 D.G. Tuck, Analyt. Chim. Acta, 1957, 1'4, 271.174 P. T. Wagner, L. R. Pollack,and C. G. Donahoe, jun., Analyt. Chem., 1957,29,405.1 7 5 E. Schram and R. Lombaert, Analyt.CJzim. Acta, 1957, 17, 417.176 B. M. Abraham, H. E. Flotow, and R. D. Carlson, Analyt. Chem., 1957,29,1058.177 H. Gamsjager and R. Reichert, 2. analyt. Chem., 1957, 158, 356.178 J. D. Moyer and H. S. Isbell, Analyt. Chem., 1957, 29, 393HASLAM AND SQUIRRELL. 383reducing sugar and measurement of fixed 14C in either formamide or alkalineethyleneglycol.Two papers 179,180 describe the use which has been made of the radio-nuclides 114In and llsIn in the determination of traces of indium in rocksand minerals by neutron-activation analysis. The same radionuclideswere used in the determination of indium in the mineral cylindrite. Thefigures obtained were also confirmed by a method which involved analysisof the decay curve of a sample of cylindrite which had been irradiated withneutrons and also by a method involving y-ray spectrometry.The application of new radiochemical methods to the verification orotherwise of old data is of particular significance in the redetermination ofcertain trace metals in sea-water.HummelIsl has determined gold byneutron irradiation of the sea-water in the Harwell pile. The product istreated with inactive gold. After purification and isolation of the mixtureof inactive gold and the active product lg8Au, the latter is measuredin an end-window Geiger tube. Comparison is made with known goldsoh tions.A procedure requiring the minimum of chemical separation has beendeveloped by Cosgrove and Morrisonls2 for the determination of traceimpurities in tungsten.The use of y-scintillation spectrometry for identific-ation and measurement of the impurities present after neutron activationgives a sensitivity of 0.001 to 1 y for many elements.The important determinations of nickel, cobalt, and copper, oftenpresent in only a few p.p.m. in oceanic rocks, marine sediments, andmeteorites, have been tackled successfully by Smales, Mapper, and W0od.18~After neutron activation of the samples in the Harwell pile and subsequentaddition of nickel, cobalt, and copper carriers, the products are dissolvedand the nickel precipitated as the nickel dimethylglyoxime complex beforeprecipitation of copper as its thionalide derivative. The cobalt in thefiltrate from these precipitations is purified, then precipitated as potassiumcobaltinitrite and counted.The nickel dimethylglyoxime is purified,reprecipitated as nickel dimethylglyoxime, and counted, whilst the copperthionalide is purified and the copper finally precipitated as cuprous thio-cyanate and counted.Cabell and Smales Is4 have determined small amounts of rubidium andczsium in rocks, minerals, and meteorites by a method which again involvesneutron bombardment of the sample. The product is sintered with sodiumperoxide and brought into solution, and carrier added before precipitationof rubidium, caesium, and potassium as cobaltinitrites. The rubidium andcaesium are separated from one another and from potassium by passagethrough a cation-exchange column, and the corresponding rubidium andczesium eluates converted into chloroplatinates, then counted in a conven-tional Geiger f+counting assembly.1 7 ~ A.A. Smales, J. van R. Smit, and H. Irving, Analyst, 1957, 82, 539.180 H. Irving, J. van R. Smit, and (in part) L. Salmon, ibid., p. 549.181 R. W. Hummel, ibid., p. 483.lS2 J. F. Cosgrove and G. H. Morrison, Analyt. Chem., 1957, 29, 1017.183 A. A. Smales, D. Mapper, and A. J. Wood, Analyst, 1957, 82, 75.184 M. J. Cabelland A. A. Smales, ibid., p. 390384 ANALYTICAL CHEMISTRY.APPARATUSA few of the more interesting pieces of apparatus which have beennoted in the course of the year are described below.For use in volumetric analysis a new burette of high accuracy has beendesigned by Smith 185 and tests have shown it to be a great improvementon the ordinary burette.The burette is made of precision-bore tubingand contains a free-moving piston which is graduated with a single orvernier scale. Use of the piston avoids drainage errors and reading theburette is simple and extremely accurate, all meniscus errors being avoided.Automatic stopping devices for the piston can be easily fitted, facilitatingready automatic " zeroing " of the burette or automatic pipetting of a fixedquantity of reagent for routine analysis.An apparatus has been devised by Call l86 for the rapid micro-samplingand determination of vapours particularly halogenated hydrocarbons inair. The air sample is taken through hypodermic tubing by suction andpassed through a heated silica tube, the issuing gases being then passedthrough a reagent solution and the concentration of halogen compoundmeasured colorimetrically.In the case of ethylene &bromide, the reagentfor the bromine produced in the combustion is phenol-red, in a phosphatebuffer at pH 610, which by reaction with bromine produces bromophenol-blue. Once calibrated, the method appears rapid and is particularlyuseful when only small samples are available, e.g., in the case of deter-mination of the concentration of fumigants in the air spaces in soil.On the subject of weighing, a sensitive quartz-beam microbalanceoperating on the principle of the normal gas density balance is preferredby Czanderna and Honig.ls7 With proper temperature control the stabilityis good over long periods of time and the instrument will detect mass changesto a precision of 5 x 10-8 g.with an accuracy of It is said to beextremely rugged in relation to its sensitivity and can be constructed,maintained, and operated without unusual experimental skill.Chemists using chromatographic methods will be interested in a devicedue to B 0 v 6 1 ~ ~ which greatly improves the functioning of the float siphonof automatic fraction collectors when used in the fractional separation ofnon-conducting liquids. A small float in the siphon tube completes anelectrical circuit immediately before the siphon is emptied and causes thecollecting table to rotate. Failures are reported to be less than one in athousand.A simple device for concentrating and eluting spots from chromatogramshas been described by Reith.189 Should a large number of similar spotsbe required to be concentrated, the sections of the papers holding the spotsare pressed together between " Perspex " sheets with a wick in one end ofthe compressed sheets and a pointed, thin, collecting paper at the other.The material is concentrated on the point of the collecting paper by ascendingg.185 I.C . P . Smith, Chem. and Ind., 1957, 1117.186 F. Call, J . AppZ. Chern., 1957, 7 , 210.187 A. W. Czanderna and J. M. Honig, AnaZyt. Chem., 1967, 29, 1206.188 1. Bov6, AnaZyt. Chim. Ada, 1957, 16, 364.180 W. S . Reith, Nature, 1957, 179, 580HASLAM AND SQUIRRELL. 385elution with a solvent which evaporates at the point of the collecting paper.The concentrated spot can then be eluted by a small volume of solvent byreversing the apparatus and using descending elution.The applicationof large amounts of test solution to the paper in chromatographic work hasalways been a problem. A neat device developed by Merz,lgo with whichthe test solution is applied as a uniform streak from a micro-burette drivenby a motor, has largely solved this problem.A useful piece of apparatus has also been designed for the qualitativetransfer of samples to the absorbent column of a gas-liquid chromatographicapparatus. This design by McCreadie and Williams 191 facilitates breakinga capillary containing the weighed sample, at the top of the sealed column,thus avoiding any disturbance of equilibrium. This method is particularlyuseful where the gas inlet pressure is above atmospheric and where the useof an internal standard is not practicable, e.g., when the sample is corrosive,etc.Cummingsand RedfearnIg2 have presented an assembly for the preparation of lowconcentrations of sulphur dioxide in air, for use in the calibration of auto-matic recording instruments.The apparatus, which avoids troubles dueto adsorption and desorption on to the glass walls of the apparatus by usingcontinuously flowing gas streams, could well find application in thepreparation of other gas-air mixtures.A diffusion cell has been described by McKelvey and Hoelscher lg3 alsofor the preparation of very dilute gas mixtures, where the minor componentof the mixture can be liquefied in the laboratory.The liquefied componentof the desired mixture diffuses from a reservoir through a glass tube to themixing chamber through which the diluent gas is passed at constant pressure.For a given cell and liquid component the rate of diffusion is dependentonly on temperature at a constant pressure, Thus the final compositionof the mixture can be quantitatively varied by accurate regulation of thetemperature oi the liquid-component reservoir.A wide-bore dropping-niercury electrode and zinc reference electrodehave been used with success by Briggs et a.l.19.' for the continuous polaro-graphic determination of dissolved oxygen in sewage effluents. Theelectrodes have greater reproducibility in continuous use than the con-ventional dropping-mercury electrode, and the wide-bore electrode has acurrent output about fifteen times greater than the usual type, facilitatingthe use of a more robust pointer-type microammeter, after only a smallamplification.A polarographic cell incorporating a mercury thread electrode has beendesigned and used by Nikelley and Cooke lQ5 for polarographic detectionof metallic ions at concentrations as low as lo4? per ml. by the anodicstripping technique. The method, which involves the deposition of theThe preparation of gas mixtures has received attention.lgO IV. Merz, Mikrochiot. Ada, 1957, 474.l g l S. IV. S. XIcCreadie and A. I;. Williams, J. Appl. Chein., 1957, 7, 47.I g 2 \V. G. Cummings and N. W. Redfearn, Chevn. and I n d . , 1957, 809.lg3 J. M. McKelvey and H. E. HoeIscher, Analyt. Chem., 1957, 29, 123.lg4 R. Bnggs, I?. S. Davies, G. V. Dyke, and G. Knowles, Chetn. and Tnd., 1957, 223.l g 5 J. G. NlkeIly and W. D. Cooke, Analyt. Chem., 1957, 29, 933.REP.-VOL. LIV 386 .A N .I LY TI CAI, CHEMISTRY.metal at the surface of the mercury electrode and then the anodic removalof it under controlled conditions, has been used for the determination ofthe lead and cadmium in spectrographically pure zinc. The calibrationvalues are constant over long periods, and the half-peak potentials agreeclosely with those obtained at a dropping-mercury electrode.which is said to be superiorto the A.S.T.M. lamp used for the determination of sulphur in petroleumdistillates, the latter giving inaccuracies when solutions containing elementalsulphur or some types of volatile sulphur compounds are present. Thisnew lamp gives greater precision at low sulphur contents, uses less sample,and has the advantage of speed, better flame control, and safety.A very simple and easily constructed microscope hot stage has beendescribed by Jennings lg7 for the micro-determination of melting pointsusing only a single crystal. Melting on the hot stage is convenientlyobserved with a polarising microscope or by inserting Polaroid discs in thelight source and eyepiece of a standard microscope.Fluorescence emission spectra of liquids have been measured by usinglaboratory-made accessories in conjunction with a small monochromator,photomultiplier tube, and commercially available a.c. amplifier. Theapparatus of Parker and Barnes lg8 can also be used for the measurementof fluorescence " excitation " spectra. The apparatus has proved to beparticularly useful in studies of fluorescence emission and " excitation "spectra of the two N-phenylnaphthylamines which are used as rubberantioxidants.Automatic spectrophotometric titrations have been convenientlycarried out using the simply designed cell and titration unit of Malmstadtand Vassallo 199 in conjunction with a commercially available secondderivative control unit. A large variety of colour-change titrations canbe carried out with little, if any, modification to the usual titrimetricprocedure.A useful contribution to infrared analysis 2oo is a small evacuable diewhich also serves as the pellet holder and can be used for the qualitativeand quantitative infrared analysis of fraction-milligram size solid samplesin potassium bromide. The die is rectangular and only slightly larger thanthe minimum external dimensions of the sample beam area. The samplemixture with potassium bromide can be prepared by freeze-drying andvibrator grinding in the normal way.A thread wick lamp has been designedJ. HASLAM.D. C. M. SQUIRHELL.Isti W. I<. Battles, ,-liiuZ?t. Ckeni., 1957, 29, 1338.' 9 7 W. G. Jennings, J . Chern. Edztc., 1957, 34, 95.IY* C. A. Parker and W. J. Barnes, A?zalyst, 1957, 82, 606.* 0 9 H. V. Malmstadt and D. A. Vassallo, Analyt. Chipn. Acta, 1957, 16, 465.I. J. Kirkland, Analyf. Chenz., 1957, 29, 1127