ANALYTICAL CHEMISTRY.THE transition stage from war to peace during the past year hasbeen indicated in analytical chemistry by the appearance ofnumerous papers, the previous publication of which had been with-held on national grounds. Most of these communications, how-ever, are concerned with matters of more purely technicalimport4ance, and are therefore more suitably dealt with in theAnnual Reports of the Society of Chemical Industry. There hasalso been a number of belated abstracts of papers published twoor thre'e years previously in German journals, which, until a fewmonths ago, were not accessible to English readers.The scarcity of platinum, which was one of the immediate con-sequences of the war, has been intensified by the continuance ofunsettled conditions in Russia.Increasing attention has thereforebeen given to the preparat.ion of platinum substitutes for analyticalapparatus.l Comparative tests with alloys containing from 70 t o90 per cent. of gold and 10 to 30 per cent. of palladium (palath and?*hofaniz~??t) have shown that in some respects these are superior t oplatinum for analytical work, but are less suitable for fusions withalkali hydroxides.2 I n such cases, silver vessels are preferable evento platinum.3 An alloy of nine parts of gold with one part ofcopper is recommended in place of platinum for cathodes, whilst foranodes the alloy is coated with platinum.* Good results have alsobeen obtained in the electrolysis of gold by the use of an ironanode1 in place of platinum, whilst' platinum gauze is used as thecathode.6Physical Methods.Solutions of sucrose and mixtures of ethyl alcohol and waterhave been recommended as suitable standard substances for cali-Compare Ann. Report, 1918, 118.L. J. Gurevich and E. Wichers, J. I n d . Eng. Chem., 1919, 11, 570 ; A.,L. Quennessen, Bull. SOC. chim., 1919, [iv], 25, 237 ; A., ii, 292.P. Nicolardot and J. Boudet, ibid., 84 ; A., ii, 166.J. Guzmhn, Ana7. Fis. Quim., 1919, 17, 115 ; A,, ii, 300.ii, 347.12128 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.brating viscosimeters. The method of expressing the results in“ centipoises ” has the advantage thatl the absolute and specific.viscosities thus expressed are the same when compared with watera t 20° as the standard.7The “viscosity value” of an oil, 2, may be calculated by meansof the formula Z = 4.0723 + 3-518/E, where E represents Englcrdegrees.By plotting this value in relation to the temperatures, aseries of nearly straight lines is obtained, which cut one anotherapproximatlely at’ one point, Z = 1 and t=185”. This is applicableto numerous oils. The viscosity of mixtures of oils is not propor-tional to the ratio of the constituents, but may be calculated bymeans of the formula El + = (rtlE, + kn,E2) (nl + kn,), where E ,and E, represent the respective viscosities of the oils, E, being thatof the more fluid, nl and ng their respective proportions, andA gas pyknometer has been devised consisting of a cylindricalvessel with capillary openings a t the ends, closed by meaiis ofrubber fittings and screw clips.The vessel is first charged withclean, dry mercury, and gas then drawn into it) and weighed. Thedensity is calculated by means of t’het formulak = .I/E,E,.*1 +0*00367t d = --+1 (’i: ) 1 +0*003~7ttg’in which 9 represents the weight, of the, pyknometer, 9-11 theweight of pyknometer+air, IT t’he volume1 of the pyknometer, tthe temperature at the time of filling, and t’ the temperature atthe time of weighing, s the density of air in the vessel at t , and t?the relative, density of the gas (air=1).9A method of measuring the size of ultramicroscopic particles,such as smoke in air, has been based on the photography of t<heirpath in the field of an ultramicroscope, which lies in an alternatingelectrostatic field.The degree of oscillation gives the data for.calculating the diameter of the particles.l*The following formula may be used for estimating the amountof finely divided material suspended in a liquid from the absorptionof light, 1 -Z/Io= e - B / n @ , where Z/I(, represents the coefficient ofthe transmission of light, the mass of suspended particles, aiiclAnn. Report, 1916, 166.7 E. C. Bingham and R. F. Jackson, Bull. Burmu of Standards, 1918, 14* E. Oelschlager, Zeitsch. Ver. Deutsch. Ing., 1918, 422.69 ; A., ii, 268.K. Kling and L. Suchowiak, Metan, 1917, 1, 37 ; -4., 1920, ii, 15.lo P. V. Wells and R. H. Gerke, J. Amw. Che712. SOC., 1919, 41, 312; A.,ii, 187ANALYTICAL CHEMISTRY. 129B and fi constants which vary with the nature of the particles andwave-length of the light .I1The accuracy of observations in ultra-violet absorption spectro-scopy is increased by the use of a new form of spectrophotometerin which four sector-shaped openings are arranged diagonally aboutthe optical axis.The result of this is that all parts of a circularbeam of light are utilised in their proper proport!ion independentlyof the size of the aperture.12Attention may also be directed to a series of papers on the con-struction and technical applications of the refractometer.13I n a study of the freezing points of solutions, it has been shownthat the weight of solvent, W , may be replaced by the expremionw+bw, where w represents the solute and b a constant varyingwith the experimental conditions.I n the case of a solvent con-taining several solutes, the observed total depression of the freez-ing point was found to differ but little from the sum of the calcu-lated depressions for the individual solutes.14 The limitations ofthe method as applied t o quantitative analysis are discussed.Although under f avourable conditions the method will give resultsaccurate within about 2 per cent., previous experience with thesame class of substance is necessary.15A new method of analysis has been based on the behaviour ofsubstancea towards X-rays. A beam of the monochromatic raysis made to pass through a glass tube containing the powderedmaterial, and the resulting diffraction patterns are photographed.The method can be used for the qualitative analysis of mixtures,and in some casw for the approximate estimation of their con-stituents .I6Gas Analysis.Certain precautions should be taken when using cupric oxide forcombustions in gas analysis.The temperature must not ba allowedto fall below red heat, or the activity of the reduced copper will bediminished. Nitrogen prepared from air by deoxidation withphosphorus invariably contains some phosphorus vapour, and there-fore when great accuracy is required, pyrogallate should be usedfor absorbing the oxygen.1711 C. Cheneveau and R. Audubert, Compt. rend., 1919,168, 766 ; A., ii, 205.12 S. J. Lewis, T., 1919, 115, 312.18 J. C. Philip, F. Stanley, F. Twyman and F. Simeon, H. Main, A. Homer,14 C. E.Famitt, T., 1919, 115, 790.l6 Ibid., 801.16 A. W. Hall, J . Amer. Chern. SOC., 1919, 41, 1168; A., ii, 470.1 7 E. Ott, J. GmbebucTbt., 1919, 62, 89; A., 1920, ii, 62.REP.-VOL. XVI. PA. E. Berry, J . SOC. Chem. Id., 1919,38,139-146 T130 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.The use of soda-asbestos as an absorbent for carbon dioxide hasthe advantage that it acts as its own drying agent, whilst it enablesa more simple form of apparatus to be used. The mixture willabsorb upwards of 10 per cent. of its weight of carbon dioxide, andis particularly suitable for the estimation of carbon in steel.l*A study of the conditions of absorption of oxygen by sodiumpyrogallate has shown that the rate of absorption increases withthe dilution of the sodium hydroxide solution, but is always pro-portional t o the concentration of pyrogallol in the solution.Carbonmonoxide is evolved from all sodium pyrogallate solutions of lowerspecific gravity than 1.30, and in all cases when the concentrationof the oxygen under examination exceeds 95 per cent. A formulais given for the preparation of a rapid absorbent evolving theminimum amount of carbon rnonoxide.19Oxygen in the upper atmosphere may be estimated by means ofa simple form of apparatus in which the difference of pressure ismeasured, with the aid of a barometer tube and micrometer screw,before and after deoxidising the air with phosphorus.20A sensitive t w t for ozone is based on the fact that a trace ofit immediately destroys the fluorescence of an extremely dilutesolution of fluorescein, whereas much larger amountij of nitrousvapour, chlorine, or carbon monoxide are required. As little as10-9 gram of ozone may thus be detected and estimated, so thatthe reaction is much more sensitive than the starch iodide test.21Carbon monoxide in hydrogen may be estimated by selectiveoxidation in the presence of a suitable catalyst, and an instrumentbased on this principle has been devised.22 The reaction is notquite complete between 150° and 400°, whilst the preferentialoxidation is reduced by increasing the temperature.Above 400°,the combustion of the hydrogen is more rapid than that of thecarbon monoxide.23Carbon monoxide may also be estimated by oxidation t o carbondioxide by means of iodine pentoxide under specified conditions.In the case of gases containing more than 0.2 per cent.of carbonmonoxide, and where the accuracy need not exceed 0.2 per cent., amodification of the apparatus previously described 24 may be used.2618 L. J. Rogers, Canadian Chem. J., 1919, 3, 122.1* GI. W. Jones and M. H. Meighan, J. I&. Eng. Chem., 1919, 11, 311;20 F. W. Aston, P., 1919, 115, 472.22 E. K. Rideal and H. 8. Taylor, ArzaZy&, 1919, 44, 89 ; A., ii, 200.23 E. I(. Rideal, IT., 1919, 115, 993.24 T., 1914, 105, 1996.26 J. I. Graham, 3. Soo. Ohem. Ind., 1919, 88, lor; A., ii, 117.A., ii, 240.L. Bonoist, Compt. rend., 1919, 168, 012 ; A., ii, 198ANALYTICAL CHEMISTRY. 131Titration with potassium iodate in the presence of hydrochloricacid affords an accurate method of estimating sulphites and sulphurdioxide in gaseous mixtures.An addition of glycerol prevents lossfrom oxidation of the sulphite by dissolved air, and does notinterfere with the subsequent titration.26A reaction capable of detecting 1 part of carbonyl chloride in10,000 parts of air depends on the separation of diphenylcarbamidewhen the air is passed through an aqueous solution of aniline,COC1, + 4C,H,*NH, = CO(NH*C6H5)2 + 2C6H5*NH,,Hc1.The precipitate may be dissolved off the filter with alcohol, thesolution evaporat?ed, and the residue dried a t 60° and weighed, orammonia may be separated, as in Kjeldahl’s process, and Btimatedcolorimetrically.27For the estimation of gasoline in natural gas, a measuredquantity of the gas is passed through drying tubes and then throughan absorption vessel immersed in a mixture of ether and solidcarbon dioxide in a drying tube.The vessel is then sealed and thecondensed liquid weighed.28 I n another method, a solid material,such as charcoal, is used as the absorbent for the gasoline vapours.29A method of estimating acetylene in admixture with ethylene o rother hydrocarbons has been based on the observation ofChavastelon,30 that when acetylene is passed into a neutral solutionof silver nitrate, the liquid becomes acid in accordance with theequation : C,H, + SAgNO, = C,Rg,,AgNO, + 2HNO,, so that bytitrating the liberated nitrio acid, a measure of the acetylene isobtained.31A gricultural Analysis.Few new analytical processes have been published in connexionwith agricultural chemisbry during the past year, and .most of thecommunications have dealt with methods previously known.In estimating carbon in soils by the wet combustion method,absorption of the carbon dioxide by barium hydroxide, as inSchollenberger’s method,32 has the drawback that carbon dioxide isreadily absorbed from the air, whilst absorption in potassium hydr-26 P.Haller, J . SOC. Chem. Ind., 1919, 38, 5 2 ~ ; A., ii, 198.27 A. Illing and R. Schtnutz, Compt. rend., 1919, 168, 773, 891 ; A.. ii, 244.28 K. Kling, Metan, 1917, 1, 3.49 G. G. Oberfell, S. D. Shinkle, and S. B. Meserve, J. Ind. Eng. Chem.,8o Oompt. Tend., 1897, 124, 1364; A., 1897, i, 545.1919, 11, 197.W.H.Ross and H. L. Trumbull, J . Amer. Chem. SOC., 1919, 41, 1180 ;A., ii, 482.8a J. Ind. Eng. Chem., 1916, 8, 427: A., 1916, ii, 395.s 132 AJYNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.oxide solution is tedious. A simple modification, in which thecarbon dioxide is absorbed in a soda-lime tube, is rapid and givesaccurate results.%The total nitrogen in soil extracts cannot be accurately estimatedby the direct application of the Kjeldahl process when as mucha.s 10 per cent. of the nitrogen is in t.he form of nitrates, and insuch cases a process of reduction must be used.34 For example, theextract may be rendered slightly alkaline with sodium hydroxidea d treated with Devada's alloy prior to the digestion withsulphuric acid in the Kjeldahl process.35 I n another method, thedifferent forms of nitrogen are estimated by using Kjeldahl'smethod for the total nitrogen other than nitric nitrogen, distillingthe ammoniacal nitrogen from the original extract with magnesiumoxide, and reducing the residual liquid with magnesium chlorideand copper-magnesium alloy to obtain nitric and nitrous nitrogen.Finally, the ammonia and nitrous nitrogen are removed fromanother portion by boiling with dextrose, ferrous sulphate, andsodium carbonate, and the solution is again reduced with t'he alloyto obtain the nitrio nitrogen.36Nitrates in soil may be quantitatively extracted with cold waterunder specified conditions, and may then be accurately estimatedin the extract by the phenoldisulphonic acid method, provided thetemperature be kept below that at which nitrates and chloridesreact with the dilute sulphuric acid.An addition of calciumhydroxide to the soil prior to the extraction will prevent soilscontaining organic matter from yielding coloured extracts.37For the estimation of organic phoBphorus in soils, i t is recom-mended that calcium should first be extracted with 1 per cent.hydrochloric acid, which is subsequently removed by means ofaqueous carbon dioxide solution, after which the organic phosphorusis extracted with 4 to 6 per centl. ammonium hydroxide solutionand the extract filtered through a layer of the soil. No advantageis gained by the use of potassium or sodium hydroxide for theex t r actqi on .3*The solubility of rock phosphates in 0.2 per cent.citric acidsolution is about the same as the solubility in ammonium citratesolution, and although the latter does not extract the whole of the88 D. D. Waynick, J . Ind. Eng. Chem., 1919, 11; 634; A., c, 371.'4 R. S . Snyder, Soil Sci., 1918, 6, 487; A,, ii, 296.8 5 B. S. Davisson and J. T. Parsons, J. Ind. Eng. Chem., 1919, 11, 306 ;86 T. Pfeiffer and W. Simmermacher, Landw. Versuchs-Stat, 1918, 93, 66 ;8 7 H. A. Noyes, J . Ind. Eng. Chem., 1919,11, 213; A., ii, 199.88 C. J. Schollenberger, Soil Sci., 1918, 6, 366 ; A., 3, 168.A., ii, 242.A,, ii, 296ANALYTICAL CHEMISTRY. 133available phosphorus, it is preferable to citric acid as a method ofjudging the effect of any special treatment of the phosphat'e.Thesolubility increases with the strength of the citric acid, whilstdilute nitric acid is still less suitable for the extraction.39An experimental study of the methods of preparing superphos-phates has shown that in the case of commercial products contain-ing about 1 2 to 20 per cent. of phosphoria oxide and 10 to 20 percent. of water there is a system with a fairly high proportion ofphosphoric oxide and a very low proportion of water. I n estdm-ating frele phosphoric acid in such products, it is necessary t o useanhydrous ether for the extraction, since water, alcohol, or ordinaryether causm more or less hydrolysis of the monocalcium phosphate,according t'o the amount of water originally present .40The value of agricultural lime, has been shown by practical teststo depend rather on its power of neutralising acids than on theproportions of calcium oxide, magneBium oxide, o r carbon dioxidepresent.The neutralisation power may be estimated by boilingthe lime with standard acid, titrating the excess of acid with alkali,and expressing the results in terms of calcium carbonate.41 Anelectrical method of estimating the lime requirement of soils hasalso been devised. The soil is shaken with distilled water and(another portion) with calcium hydrogen carbonate sdution forthree hours, and the electrical resistance of each liquid determinedbefore and after shaking with the soil. The ratio between the tworesults affords a measure of the acidity or alkalinity of the ~0il.42Organic Analysis.Qzm?itatiue.-A new method of separating and identifyingalcohols has been based on their conversion into allophanates, bymeans of the action of cyanic acid gas.The alcohol is thenidentified by the melting point of the recrystallised precipitate, andfurther tests are applied by hydrolysing the allophanate and deter-mining the physical characters of the alcohol. Normal allophanatesare produced by alcohols containing an ethinoid group, terpenicalcohols, except linalool, and cyclic alcohols, except terpifieol. Thepresence of the phenolic group in cyclic alcohols interferes withthe reaxtion, and in such case3 a preliminary esterification is neces-sary before applying the test.43Ann. Report, 1917, 161.am J. A. Stenius, J . Ind. Eng. Chem., 1919, 11, 224; A., ii, 199; compareA.Aita, Anndi Chim. App?., 1919, 10, 46 ; A., ii, 25.S . D. Comer, J . Ind. Eng. Chem., 1918, 10, 996.0. J. Lynde, Tram. Roy.80~. Canada, 1918, [iii], 12, 111, 21 ; A , , ii, 376.43 A. mhal, Compt. rend., 1919,168, 946 ; A., ii, 301134 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.The detection of methyl alcohol in ethyl alcohol by oxidation bformaldehyde is untrustworthy in the presence of higher alcohols,but the oxidation products of the latter may be distinguished bythe fact that they give yellow to reddish-brown colorations withapomorphine and sulphuric acid, whereas formaldehyde gives aviolet coloration with that reagent.44A specific reaction for oxalates has been described, according towhich a red coloration is obtained when the oxalate solution istreated with manganese sulphate solution, acetic acid, and potassiumdichromate or alkali hypochlorite solution.The presence of phos-phoric or hydrofluoric acid does not interfere with the tmt.45The distinctive blue coloration given by thiophen in the indo-phenine reaction is not obtained unless a trace of an oxidisingagent, preferably nitric acid, is present ; otherwise the coloration isgreen.46Compounds containing arsenotungstic and arsenomolybdic com-plexes have been recommended as reagenb for phenolic amineg.They give an intense blue coloration with phenols, purine deriv-atives, and phenolic amines. The arsenotungstic reagents also reactwith hydroxylamine and hydraxine, whilst the arsenotungsto-molybdic reagents also give a coloration with substances, such asaniline, conkaining one amino-group.*'A qualitative test for morphine capable of detecting 1 part in10,000 has been based on its property of yielding dyes on treat-ment with diazonium compounds, such as diazobenzenesulphonicacid. On adding this compound t o an alkaline solution of themorphine salt, colorations ranging from pale to deep red, andchanging to orange on acidification, are obtained.The reactionwill detect morphine in the presence of other alkaloids.48A comparative study of the sensitiveness of different tests forquinine49 has shown that' the fluorescence test with sulphuric acidis capable of detecting 1 part in 100,000, whilst the thalleioquininereaction is ten times less sensitive.In the latter te&, it isadvantageous t o replace chlorine by bromine. Reference is madeto a sensitive reaction which has been based on the turbidity givenby a solution containing as little as 1 part of quinine in 200,000with a reagent consisting of potassium iodide and mercuric chloridein acetic acid.5044 H. Wolff, Chern. Zeit., 1919, 43, 5 5 8 ; A., ii, 482.45 H. Caron and D. Requet, Ann. Chim. anal., 1919, [ii), 1, 26; A,, ii,413 E. wray, J . SOC. Chem. Ind., 1919, 88, 83r ; A., ii, 204.47 I,. Guglialmelli, Anal. Soc. Quim. Argentina, 1918, 6, 186 ; A,, ii, 87.48 L. Lautenschlager, Arch. Pharm., 1919, 257, 13 ; A., i, 344.4 9 H. Salomon, Ber. Deut. p h m . Get?., 1918, 28, 273; A, ii, 87.5 0 G. Giemsa and J.Halberkann, Deutsch. Ned. Woch., 1917, No, 48.438ANALYTICAL CHEMISTRY. 135Aconitine, both crystalline and amorphous, givm a violet color-ation with phosphoric acid solution containing 4 per cent. of sodiummolybdate. Aspidospermine and veratrine also give violet color-ations with the reagent, but may be distinguished from aconitineby other tests. The coloration is not given by other alkaloids.The deep red coloration given by digitalin on treatment withpicric acid and potasshm hydroxide serves to distinguish it fromcertain closely allied glucosides, some of which give an orangecoloration, whilst others do not give any coloration in the test.Peptones also give a similar red coloration. It is suggested thatthe reaction may be due to the presence of a carbonyl group linkeddirectly to a carbon atom.51Quantitative.-In estimating halogens in organic compounds bycatalytic reduction in the presence of palladium, the use of hydr-azine is suggested as being preferable to purified hydrogen, beingdecomposed by the catalyst into nitrogen and hydrogen.Afterthe decomposition, the catalyst is separated by filtration, and thehalogen estimated in the filtrate.52A modification of Young and Swain's method of eatimating nitro-groups by means of stannous chloride53 givea trustworthy resultswith numerous nitro-aromatic compounds. The substance is mixedwith alcohol, the air in the flask displaced with carbon dioxide, anexcess of standard stannous chloride solution added, and the flaskheated on the water-bath while a current of carbon dioxide ispassed through it.Finally, the excess of stannous chloride istitrated with standard iodine solution.64A rapid method of estimating methoxyl groups by the methyliodide process embodies the same principle as that of Kirpal andBuhn,55 but instead of evaporating the excess of pyridine, the liquidis diluted with water, acidified with nitric acid, a measured quantityof silver nitrate added, and the excess titrated with thiocyanabPAn analogous method has been devised for estimating methoxylgroups containing sulphur, in which the methyl iodide and hydrogensulphide are absorbed by pyridine containing silver nitrate, andthe silver sulphide separated before. completing the estimation.57The presence of water interferes with the accurate estimation ofether in alcohol from the specific gravity of the liquid. This isobviated by fractional distillation and determining the specificH. Baljet, Pharm.Weekblad, 1918, 55, 457; A., ii, 438.aa M. Busch, Zeitsch. angew. Chem., 1918, 31, 232.53 J . Amer. Chem. SOC., 1897, 19, 812; A., 1898, ii, 186.J. G. F . Druce, Chem. News, 1919,118, 133; A., ii, 199.55 Ber., 1914, 47, 1084; A., 1914, ii, 497.66 J. T. Hewitt and W. J. Jones, T., 1919,115, 193.6' M. Hijnig, Monatsh., 1919, 39, 871 ; A., ii, 171136 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.gravity of the alcohol before and after distillation of a first fractioncontaining all the et’her. The amount of the latter is then obtainedby means of a formula.68The possibilities and limitations of Duclaux’s method of estim-ating homologous acids by distillation with steam have been studiedand the results compared with those previously obtained.69 Thedegree of concentration does not have any pronounced influence onthe results, except to some extent in the case of butyric acid, Thegeneral conclusion drawn from test distillations was that DucIaux’smethod will enable the amounts of two fatty acids in a mixture tobe estimated within about L per cent.of the true quantity, or, inthe case of three acids, within about 5 per cent. by a single dis-tillat.ion, or about 1 per cent. by fractional distillation.60 I n thisconnexion, mention may be made of a new type of still-head ofspecial construction, by the use of which the distillation slows downwhen the limit for each pure constituent in a mixture is reached,so that it is possible with the aid of this appliance to separatebenzene, toluene, and xylem by direlct distillation.61Cyanides, cyanates, and bromides may be estimated when insolution together by titrating the liquid with silver nitrate. Titra-tion in alkaline solution gives the amount of cyanide, whilst thethree compounds together are obtained by titration in the solutionneutralised with acetic acid, and the cyanide and bromide togetherby titration in the solution acidified with nitric acid.62A new method of estimating oxalic acid is based on the fact that,when heated with acetic anhydride, it is quantitatively decomposed,so that the volume of carbon dioxide liberated affords a measureof the oxalic acid originally present.Formic acid is the only otherorganic acid of common occurrence which undergoes a similardecomposition.63For the estimation of soluble starch in the presence of starchand the products of its hydrolysis, advantage has been taken of thefact that the blue iodine compound with soluble starch is insolublein a semi-saturated solution of ammonium sulphate. The pre-cipitate is separated and washed with the aid of centrifugal form,dissolved in water and, after removal of the iodine, saccharifid,and the resulting dextrose estimated polarimetrically.64There have been a few additions to the methods of analysingH. E. Cox, Analyst, 1919, M, 26; A., ii, 83.s9 H.D. Richmond, ibh?, 1917, 42, 125; A., 1917, i, 316.6o Ibid., 1919, a, 255; A,, ii, 435.61 S. F. Dufton, J . SOC. Ohem. Ind., 1919, 38, 4 5 ~ ; A., ii, 136.6a G. Velardi, Boll. chim. .farm., 1919, 58, 241 ; A., ii, 483.6J H. Krause, Ber., 1919, 52, 426 ; A., ii, 203.64 J. C. Small, J . Amer. Chem. SOC., 1919, 41, 107; A., ii, 172ANALYTICAL CHEMISTRY. 137sugars. It has been shown that a cupric sodium hydroxide reagentcan replace Fehling’s solution, over which it has the advantage ofnot becoming turbid when boiled .65I n order t o obtain concordant results in the method of titratingsugars with copper phosphate solution, the exact details of pre-paring the salt mixture must be followed. The possibility of thereduction of the copper sulphate in the method of Folin andMcEllroy66 may be prevented by rendering the solution alkalinebefore adding the thiocyanate, and a modified process embodyingthis precaution is described.67For the estimation of thiophen in benzene, good results areobtained by a modification of a method in which Denighs’ reagent(basic mercuric sulphate) is shaken with the benzene, and the pre-cipitated compound of thiophen dried and weighed.The use ofPaolini and Silbermann’s reagent (basic mercuric acetate) is alsotrustworthy, the rmulting precipitate, SC4(HgC,H,0,),, beingwashed with cold water, dried, and weighed.68Sulphonyl chlorides of aromatic substances may be estimated bymixing them with water, neutralising free acids with sodium hydr-oxide, boiling them under a reflux condenser with excess of sodiumhydroxide solution, and titrating the excess.The amount ofsulphonyl chloride corresponds with the quantity of alkali used forthe hydrolysis.69A convenient method of estimating phenacetin and otherpaminophenol derivatives has been based on their reaction withhydrochloric acid and sodium hypochlorite t o form p-benzoquinone-chloroimide, HO*C,H,*NH,,HCl+ 4Cl= 4HC1+ O:C,H,:NCl. Afterremoving the excess of chlorine by a current of air, potassium iodideis added, and the liberated iodine titrated. Four atoms of iodineare liberated in this reaction, and the paminophenol isregenerated -70A general method of estimating alkaloids is to precipitate thealkaloid from an acidified aqueous solution with alkali, to mix itinto a soft paste with plaster of Paris, and t,o extract the mass withchloroform.The alkaloid is then removed from the extract bymeans of standard acid, the excess of which is subsequentlytitrated .7166 E. Justin-Mueller, J . Pharm. Chim., 1919, [vii], 19, 18; A., ii, 202.66 J . BioZ. Chem., 1918, 33, 513 ; A., 1918, ii, 207.67 0. Folin and E. C. Peck, ibid., 1919, 38, 287 ; A., ii, 354.68 P, E. Spielmann and S. P. Schotz, J. SOC. Chem. Id., 1919, 38, 1 8 8 ~ ;A., ii, 433.F. Neitzel, Chem. Zeit., 1919, 43, 500 ; A., ii, 482.‘O A. D. Powell, Analyst, 1919, 44, 2 2 ; A., ii, 86.Rapp, Apoth. Zeit., 1918, 33, 463.P138 BNNUAL REPORTS ON THE PROQRESS OF CHEMISTRY.From a. comparative study of the methods of estimatingmorphine, a.method has been devised in which the alkaloid isextracted by means of a mixture of two parts of chloroform andone part of alcohol. Modifications for use in the cases of prepara-tions of morphine and of opium are also given.72Experimenh have been made which show that berberine may beaccurately estimated in an alcoholic extract of Hydrastis canadensisby precipitation with Mayer’s reagent (mercuric chloride andpotassium iodide), and subsequent conversion into berberinepicrolonate, which is dried at looo and weighe(d.73Znorganic Analysis.&ualitative.-Several new indicators have been described in thecourse of the year. Magenta and other colouring matters of thetriphenylmethane group when decolorised with sulphur dioxidemay be used as sensitive indicators for the detection of alkalinity,especially in water.74 An aqueous decoction of red beetroot is asensitive indicator for both weak and strong acids.The colour ischanged to yellow by alkalis, but is restored by sulphuric acid in adilution of 1 : lO,OOO.75The red iodotannio reaction76 is much more sensitive than thestarch-iodine reaction, but there must be no excem of either iodineor tannin, or the red coloration will not appear. On the otherhand, it has the drawback that potassium iodide interferes withit.?7 The presence of salts, and especially of potassium iodide,increases the sensitiveness of the starch-iodine reaction, whilstraising the temperature, or the presence of organic substances, suchm alcohol, renders it less sensitive.78 A convenient method of pre-paring starch indicator has been based on the property of starch todissolve in 1 per cent.salicylic acid solution. The preparationkeeps well, remains clear, and when diluted gives a deep bluecoloration with iodine.79The influence of the quality of, and previous treatment of, thepaper on the reactions obtained with coloured test papers has beenA. Tingle, Amer. J . Pharm., 1918, 90, 689, 788, 851 ; A., ii, 87, 88, 175.78 R. Wasicky and M. Joachimowitz, Arch. Pharm., 1919, 255, 497 ; A.,74 I. Guareschi, Buzzetta, 1919, 49, i, 115 ; A., ii, 348.7 5 M. Chauvierre, Bull. SOC. chim., 1919, [iv], 25, 118 ; A., ii, 196.78 D. E. Tsakdotos and D. Dalmas, ibid., 1918, [iv], 23, 391 ; A., 1918,7 7 Ibid., 1919, [iv], 25, 80; A., ii, 169.78 I.M. Kolthoff, Pharm. Weekblud, 1919, 56, 391 ; A., ii, 259.5s G. J. Hough, J . Id. Eng. Chem., 1919, 11, 767.i , 564.ii, 454 ; Ann. Report, 1918, 132ANALYTICAL CHEMISTRY. 139studied, and it has been shown that sized papers are less sensitivethan unsized, although they give a sharper reaction.80A new systematic scheme for the detection and approximateestimation of the acids of Group I has been devised, and has beenshown by test analyses to be trustworthy.81Turning t o the reactions for individual substances, it has beenfound that o-tolidine is a delicate reagent f o r gold, being capableof detecting 1 part in 20 millions. Ferric salts, ruthenium, osmicacid, and vanadium salts also give a yellow coloration, but mostother common metals do not give this reaction.In the presence1of copper, the coloration is green instead of yellow.82Mercury in organic or inorganic compounds may be detected bytreating the solution or suspension of the substance with nitricacid, exceas of ferrous sulphate, and concentrated sulphuric acid sothat the liquids do not mix. I n the presence of mercury, a reddish-violet ring is formed, and the usual brown ring produced by thenitric acid does not develop until later.83A sensitive reaction for manganese is based on the red colorationproduced when the solution is treated with potassium oxalate,acetic acid, and potassium hypochlorite,s* but this test is not sosensitive as that with lead peroxide and nitric acid, although i tmay be used conversely for detecting traces of oxalic acid.85The difference in behaviour on treatment, with excws of mercuricchloride solution affords a means of distinguishing between thesodium salts of different sulphur acids.No precipitate is given bythe sulphate, sulphite, or hydrogen sulphite, whereas the sulphide,thiosulphate, and polythionates yield precipitates. Further differ-entiation is based on the reactions towards methyl-orange and onthe behaviour towards iodine.86Several new reagents for micro-chemical analysis have beendescribed. For example, quinosol (the potassium salt of 8-hydroxy-quinoline-5-sulphonic acid) and superol (2-hydroxyquinolinesulphate) yield distinctive crystalline precipitates with arsenates,barium, mercurous salts, lead, tin, iron (ferrous), and silver.87Characteristic crystals of lead iodide are obtained by treatingsoluble lead salts with a drop of potassium bromide and of80 I .M. Kolthoff, Pharm. WeekbZad, 1919, 56, 175; A., ii, 518.81 L. J. Curtman and D. Hart, Chem. News, 1919,119, 25, 37 ; A., ii, 425.82 W. B. Pollard, Analyst, 1919, 44, 94; A., ii, 201.8s A. Abelmam, Pharm. Zentr.-h., 1919, 60, 247; A., ii, 428.84 H. Caron and D. Raquet, Ann. Chim. anal., 1919, [ii], 1, 174 ; A., ii,85 D. H. Wester, Phrm. Weekblad, 1919, 56, 1289; A., ii, 479.86 A. Sander, Chem. Zeit., 1919, 43, 173; A., ii, 241.87 N. Schoorl, Phamn. Weekblad, 1919, 56, 325; 'A., ii, 201.351.I?* 140 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.potassium iodide solution .88 A microscopic reaction, which is givenby most bismuth compounds, is the formation of colourless, crystal-line salts on treatment with dilute hydrochloric acid and hexa-methylenetetramine solution.*g&mntitative.-Arsenious oxide may be used as a t'rustworthystandard for iodometry.90 The purity of the arsenious oxide maybe conveniently estimated by measuring the electrical conductivityof a saturated solution. The most common impurity is arsenicoxide, which may be estimated by determining the reaction of thesolution t o methyl-orange and methyl-retd.91 I n the idiometricestimation of arsenic acid, the re'action,AqO, + 4HI = As2O3 + 21, + 2H20,proceeds from left to right only in strongly acid solution.92Attention has been drawn to several sources of error, such asatmospheric oxidation, in the estimation of sulphurous acid andsulphites by means of iodine.I n order to obtain accurate results,the sulphurous acid solution should be added to the iodine solu-tion.93 The reaction between iodine and thiosulphates varies withthe acidity or alkalinity of the solution. I n slightly alkaline solu-tion, part of the thiosulphate is converted directly to sulphate, andin strongly alkaline solution the whole of i t is thus converted.94For the direct iodometric estimation of hydrogen peroxide, afew drops of ammonium molybdate should be added with thepotassium iodide and acid to act as catalyst, and the liberatediodine immediately titrated.95Hypophosphites in sulphuric acid solution are oxidised to phos-phorous acid by iodine, and on then adding excess of sodiumhydrogen carbonate, the oxidation is continued to phosphoric acid.A method of estimating hypophosphites and phosphites is basedon these reactions.96 A chromate may be directly estimated by aniodometric method, but it is necessary to have sufficient acid pre-sent to inhibit a side reaction.97 I n using potassium dichromatefor iodometric estimations, precautions must be taken to eliminateerrors due to impurities in the dichromate and to atmosphericoxidation.9888 G.Denigbs, J . Pha~m. Chim., 1919, [vii], 20, 159 ; A., ii, 523.89 Idem, Ann. Chim. anal., 1919, [ii], 1, 213; A., ii, 431.90 R. M. Chapin, J . Amer. Chem. Soc., 1919, 41, 351 ; A., ii, 196.91 I.M. Kolthoff, Pltam. Weekblad, 1919, 56, 621 ; A., ii, 522.92 Ibid., 1322 ; A., ii, 427. 9a Ibid., 1366; A,, ii. 473.94 Ibid., 572 ; A . , ii, 365. 95 Ibid., 949 ; A., ii, 370.96 Boyer and Bauzil, J . Pharm. Chim., 1918, [vii], 18, 321 ; A., ii, 77.97 I. M. Kolthoff and E. H. Vogelenzang, Pharm. Weekblad, 1919, 56. 514;D* C. R. McCrosky, J . Amer. Chem. Xoc., 1918,40, 1662 ; A., ii, 31.A., ii, 300ANALYTICAL CHEMISTRY. 141The abnormally high results obtained when sodium arsenate isused for titrating potassium permanganate in the presence of nitricacid are probably due to the occurrence of complicated reactions inthe course of. the titration.99A volumetric method of estimating sulphurous acid has beenbased on the oxidation of the sulphur dioxide by means of hydrogenperoxide, and titration of the excess of hydrogen peroxide by meansof potassium permanganate solution, standardised against purehydrogen peroxide under similar conditions.1For the volumetric estimatJon of sulphates, a method sufficientlyaccurate for technical purposes has been based on the reactionbetween certain soluble sulphates and freshly precipitated bariumoxalate, and titration of the resulting soluble oxalate with per-manganate solution.2An oxidimetric method has been devised to obviate the sourcesof error in the ordinary methods of estimating nitrous acid andnitrites.The nitrite solution is run into excess of acidified perman-ganate solution, the excess reduced by means of ferrous sulphate,and the excess of the latter titrated with standard permanganatesolution.Chlorides or bromides in small quantity do not interferewith the process.3 The influence of fluorides on the oxidimetricestimation of nitrites may be eliminated by combining an iodo-metric method with the oxidimetric method.4A cyanometric method of estimating silver and halogens has beenbased on the fact that silver iodide in cold, very dilute ammoniacalsolution forms only a turbidity unless a large excess of potassiumiodide was added. On adding potassium cyanide, the turbiditydisappe'ars when sufficient CN' has been added to form Ag(CN),'.Halogens are estimated indirectly by adding excess of silver nitrate,removing the precipitate, and titrating the excess of silver.5The behaviour of various metallic f errocyanides towards chlorineand bromine has been studied, and it has been shown that nickeland bismuth are quantitatively precipitated as f errocyanide.6The conditions under which zirconium is quantitatively precipit'atedas phosphate have been investigated; the separation is com-plete in the presence of 2 to 20 per cent.of sulphuric acid.The addition of a small quantit'y of ammonium nitrate to the09 A. Bose, Chem. News, 1918, 117, 369 : A., ii, 36.1 T, J. I. Craig, J . SOC. Chem. Ind., 1919, 38, 9 6 ~ ; A., ii, 241.a A. C. D. Rivet& Chem. News, 1919, 118, 253; A., ii, 295.J. S . Laird and T. C. Simpson, J . Amer. Chem. SOC., 191 9, 41, 624 ; A , ,I. Rellucci, Uazzetla, 1919, 49, i, 209 : A., ii, 476.6 J.Eggert and L. Zepfel, Ber., 1919, 52, [B], 1177 ; A., ii, 351. ' I?. F. Werner, Zeit8ch. anal. Chem., 1919, 58, 23; A., i, 313.ii, 242142 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.washing water prevents hydrolysis of the precipihb, which willthen, on ignition, yield zirconium pyrophosphate.7 The composi-tion of the precipitate approximates more closely to the normalphosphate as the acidity of the solution increases.8 The methodeffech a separation of zirconium from aluminium, iron, andchromium.9A simple method of estimating carbon dioxide in carbonates isto treat the substance with acid in a tmtrtube placed in a suctionflask, and to absorb the carbon dioxide in standard barium hydr-oxide solution. The resulting barium carbonab is separated, andthe excess of alkali in the filtrate titrated.10Perchlorates may be estimated in the presence of &lorate by amethod based on the fact that only the perchlorates are reduced bya hot acid solution of titanium chloride, the excess of which issubsequently titrated with ferric chloride solution .I1An accurate method of estimating arsenic acid is by reductionwith potassium thiocyanate, and gravimetric estimation of thearsenic as sulphide.12A combination of the Roee-Finkener and Eschka methods affordsa rapid and accurate means of estimating mercury in most of itscompounds.The powdered substance is heated with iron powderin a porcelain crucible covered with a gold or silver crucible,through which circulatm cold water, and the condensed mercury.iswashed with alcohol and weighed.l3The fact that gallium chloride volatilises at a relatively lowtemperature enables gallium to be separated from other metals thechlorides of which are less ~o1atile.l~Molybdenum may be estimated by precipitation as sulphide, andconversion of the sulphide into molybdenum trioxide, but thetemperature should not be allowed to exceed about 425O, or themolybdenum trioxidei will ~ub1ime.l~A study of the methods of estimating calcium has shown thatprecipitation as oxalate from a solution acidified with acetic acidin the presence of excess of ammonium chloride gives accurate' G. E. F. Lundell and H. B. Knowles, J. Arner. Chem. Soc., 1919, 41,a G. Steiger, J . Wmhington Acad. Sci., 1918, 8, 637 ; A., ii, 82.1801 ; A., 1920, ii, 60.P. Nicolardot and A.Reglade, Compt. rend., 1919,168, 348 ; A,, ii, 171.J. G. Williams, Chem. News, 1919, 119, 8 ; A., ii, 348.lo D. D. van Slyke, J . Biol. Chem., 1918, 36, 351 ; A., ii, 78.l2 L. W. Winkler, Zeitsch. acngew. Chem., 1919,32, I, 122 ; A,, ii, 243.l8 S. Pica de Rubies, Awl. Pis. Quim, 1918, 16, 661 ; A., ii, 80.'l4 T. W. Richa.rds, W. M. Craig, and J. Sameshirna, J . Amer. Chem. Soc.,Is K. Wolf, Zeitsch. angew. Chem., 1918, 31, I, 140; A., ii, 121.1919, 41, 131 ; A., ii, 157ANALYTICAL UHEMISTRY. 143results. The precipitate is best weighed as oxalate.16 Good resultsmay also be obtained by precipitating the calcium from anammoniacal solution and weighing it as oxide.17Electrochemical Analysis.There have been several important contributions to the methodsof electrometric titration during the year.A special form ofpotentiometer has been devised for determining the end-pointsharply in such titrations, a calomel electrode being used.18 Bymeans of this instrument, ferrous iron may be accurately estimatedby .titration with potassium dichromate or permanganate, andferrio iron and potassium dichromate by titration with stannouschloride. Advantages of the method are that extremely dilutesolutions may be used, that the time is greatly reduced, and thatsome of the conditions may vary within fairly wide limits.19It has been shown in titrating ferrous salts with potassium per-manganate solution in acid solution that the conductivity remainsfairly constant throughout the titration, but that i f insufficientacid is present, the conductivity steadily falls until the oxidationis complete before becoming constant, the end-point being indicatedby a sharp change in the direction of the curve.On the otherhand, in titrating manganous salts with permanganate, theelectrical conductivity increases until the oxidation is complete, andthen becomes constant.20When potassium dichromate is used for titrating ferrous ironin acid solution, the E.M.F. increases rapidly towards the end-point, which may be obtained from the middle point of the curvesection. Titration with potassium bromate solution also givesgood results. When potassium permanganate is used, the E.M.F.is increased by stirring the solution during the titration.21From a study of the methods of estimating sulphates, chlorides,calcium, and magnesium in relatively weak solution by measure-ment of the electrical conductivity, it has been found that downto a certain limit of dilution the results are accurate to withinabout 1 per cent., but that beyond that limit smooth curves areobtained, and the results are no longer trustworthy.22Ferrocyanides may be estimated by slow titration with potassiuml6 L.W. Winkler, Zea'tsch. angew. Chern., 1918, 31, I, 187, 203 ; A., E, 34.l7 E. Canals, Bull. SOC. chim., 1918, [iv], 23, 422 ; A., ii, 34.l9 J. C. Hostetter and H. S. Roberts, ibid., 1337 ; A,, ii, 480.2o V. Villumbrales, Anal. Fh. Quim., 1919, 17, 100; A., ii, 299.I.M. Kolthoff, Ohem. Weekblad, 1919, 16, 460 ; A., ii, 362.z2 G. A. Freak, T., 1919, 115, 66.H. S. Roberts, J . Amer. Chem. SOC., 1919, 41, 1358; A,, ii, 471144 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.permanganate in acid solution, the end-point being taken as thegreatest change in potential corresponding with the addition ofequal amounts of potassium pelrmanganate solution. Ferricyanidesor chlorida in moderate amount do not interfere with the estim-ation, but salts which yield precipit'ates with either ferro- or ferri-cyanides must not be present.%A method of estimating iodides by measurement of the con-ductivity depends on the oxidation of the iodide by means ofpotassium iodate solution :51' + 10,' + 6H' = 3H20 + 31,.The mixture is titrated with hydrochloric acid, the conductivitybeing measured after each addition, until a rapid increase is shown,the end-point being found by reference to the curve.The methodis applicable in the presence of bromides, for the oxidation ofwhich a higher temperature and concentration is required.24Small quantities of vanadium in steel may be estimated bydissolving the sample in nitrio acid and oxidising the vanadiumwith nitric acid under specified conditions, which leave chromiccompounds unaltered. The solution is then cooled and titratedby the elelctrometrio method.25 By a modification of the methodthe chromium may also be estimated.26A rapid method of estimating carbon in steel has been based onthe absorption of the carbon dioxide, obtained by direct combus-tion, in barium hydroxide solution and measuring the change inthe electrical conductivity of the solution caused by the precipita-tion of barium ions.The construction of a nomographic chart isdescribed, by means of which the percentages of carbon may beread with an error of less than 0-005.27Experiments have shown that Pb" may be separated fromCr"' by electrolytic precipitation as lead peroxide under certainspecifia conditions as to the proportions of the two metals in thesolution, etc.28Chlorine, bromine, or iodine may be electrolytically estimatedby an indirect method in which the halogen is precipitated it5 asilver salt, which is dissolved in alkaline potassium cyanide solu-G. L. Kelley and R.T. Bohn, J . Amer. Chem. SOC., 1919,41, 1776.a4 I. M. Kolthoff, Chem. Weekblad, 1919, 16, 926 ; A., ii, 370.85 G. L. Kelley, J. R. Adams, and J. A. Wiley, J . Ind. Eng. Chem., 1917,9,a6 G. L. Kelley, J. A. Wiley, R. T. Bohn, and W. C. Wright, ibid., 1919,27 J . R. Cain and L. Q. Maxwell, ibid., 852 ; A., ii, 476.2* J. Milbauer and J. Setlik, J . pr. Chem., 1919, [ii], 99, 86; A., ii, 372,780 ; A., 1917, ii, 512.11, 632; A., ii, 431ANALYTICAL CHEMISTRY. 145tion, and the latter electrolysed with a nickel-plated oopperelectrode and a rotating iron anode.29Water Analysis.A rapid method of estimating the total solids in water, based ona determination of the electrical conductivity, is frequentlyemployed, but when a mean equivalent weight aad conductivity areassumed in the calculations, the results may be very erroneous inthe case of different waters. It is only when the; composition ofthe solution is known that the equivalent conductaivity may becalculated, and tables for reference under such conditions havebeen drawn up.30For extracting and estimating dissolved gases in water, a methodhas been described in which a bulb, from which the air has beenexhausted, is fitted to a large bottle of the water.On turning thetap below the bulb, the gases are extracted from the water, and byplacing the bottle in water a t about 40°, are completely removed.31Attention has been directed to the fact that pure sodiumcarbonate is acid towards a small amount of phenolphthalein andalkaline towards a larger amount. Hence, in titrating carbondioxide in water with sodium carbonate solution, the amount ofindicator used must be proportional to the quantity of sodiumcarbonate. Directions are given for a method embodying thisprecaution.32 I n order to eliminate the influence of ferrous saltswhich may be present, Rochelle salt may be added before titratingthe water with sodium carbonate in the presence of a definitequantity of phenolphthalein.33The interference of chlorides in the edirnation of nitrates inwater by the phenolsulphonic acid method may be eliminated byusing a more dilute solution of the reagent and adding it to thewater prior to evaporation, which is carried out under specifiedconditions."A source of error in the estimation of albuminoid ammonia inwater is the presence of nitrogenous impurities in the potassiumpermanganate, which are only very slowly eliminated on boilingLn E. Lasala, Anal. Fis. Quim., 1919, 17, 86 ; A., ii, 239.I . M . Kolthoff, Chem. Weekblad, 1918, 15, 1160; A,, ii, 76.F. W. Richardson, J . SOC. Chern. Ind., 1919,38, 3 2 ~ ; A., ii, 167.sa R. Czenmy, Zeitsch. anal. Chem., 1919, 58, 1 ; A,, ii, 297.3s H. a u f , Ber. Deut. pham. Qea., 1919, 29, 344 ; A., ii, 297.s4 R. C. Frederick, Analyst, 1919, a, 281 ; A., ii, 371146 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.the permanganate solution with alkali. This may cause the resultsfor albuminoid ammonia to be much too high.35A series of experiments to ascertain the velocity of absorptionof chlorine by the same water in varying intervals of time hasshown that the velocity constant usually increases with the timeof contact. The use of colour readings as an index of chlorineabsorption is only trustworthy with a given water under knownconditions. The chlorine absorption does not increase in directproportion with the increase in pollution (as indicated by theoxygen absorption), but shows decreasing acceleration. Experi-ments have indicated that absorption for five minutes would be aseffective for the routine control of chlorination as the use of alonger time interval .36 C. A. MITCHELL.36 E. A. Cooper and J. A. Heward, Biochem. J . , 1919, 13, 25 ; A., ii,'_296.86 A. Wolman and L. H. Endow, J . Ind. Eng. Chem., 1919, ~11, 209 A.,ii, 197