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(1)Application of Phosphomolybdenum BIue Reaction in Spectrophotometric Analysis*. :. By ' '' HiroshiNAMIKI .,-. '. - ' DePartmentofChemistry (Received June 2, 1965). The studies reported in the previous paper2) were carried out mainly- on problems con.cerning with the procedute of color development. the fu' ndamental. ef phosphomolybdenum' blue. The optimum procedure for the spectrophotoimetric determination of phosphorus was explained from the results obtained. In this paper the method was further investigated in order to develope a -new analytical procedure for determining phosphorus in various samples. Effects of various ions on phosphomolybdenum blue method for determining phosphorus Were studied. The difficulties are encountered with this method in 'the presence of oxidizing ions such as iron (III), nitrate and nitrite often con-. Jtained in samples or in reagents used through the run of digestion. A simple `and rapid procedure for eliminating the interferences caused by those i6ns was restablished and applied to determinatfon-of-iihosPhorus' in several'kinds of isamples containing iron or large amounts of di,Verse 61ements.'', '/ ･･ I･ L'･y... ' -..,,", njlLY,Si.S,g,`. ' gfq p.ouu. i,",d.",?.g/ia' aCety'ene･ orgapi{ .pbos?hgf.y,g. .f.grf}.pgy, n...d.g. tttted. Phosphomolybdenum blue method was further utilized 'for d'etermining t. esmall amount of tin. A suitab!e method was recommended based on;the, dis'cussions of hitherto knoWn niethod. tt t/ /-.lt ...t ,..,,t'h .....'.'.'-,,11././ tt ' tt e.ttt '. tt t･. t t tt. t tt t. t-t and Procedure ' ''' ''' -' ' t '.' Reagents. Preparation of the solutions''of reagents and basic procedure of color de-. rvelopment were done by the method recommended in the previous paper2) Reagents.-Ammonium molybdate (1.5%) in szalfztric acid (6.5N).-Prepare Ldilute sulfuric acid by pouring 182 ml. of sulfuric acid (sp. gr. 1.84) into 400 ml.. -of water. Dissolv.e 15 g. of ammotiium molybdate, (NH,)6Mo7024.4H20 in 400.ml･. ･of water. Then, poures the solution into the prepared dilute sulfuric acid while stirred well, and make up to 1000 ml. with water. Stannous chloride solution.-Dissolve 5 g. of stannous chloride, SnC12.2H20, 'in 25 ml. of concentrated hydrochloric acid with gentle warming, then dilute * Some parts of this paper were already reported in Ref. 1..

(2) 52 H. NAMIKI. to 250 ml. with water. Store in a dark place with a small piece of tin in the solution.. Standard PhosPhate solution.-Dissolve 7.164g. of potassium dihydrogen phosphate, KH2P04, previously dihydrated at 1100C, in water and dilute to; 1000ml, Take 10 ml. aliquot and makeup to 1000ml. with water. One ml. of. '. this solution contains 50 ptg. of phosphate ion.. Procedure.-Take a solution containing 5 to 200 ptg of phosphate in a 50 ml.. ･A. of volumetric fiask and neutralize, if not neutral, with either dilute sulfuric acid or with dilute ammonium hydrexide using P-nitrophenol as an indicator. Add 5 ml. of ammonium molybdate-sulfuric acid solution and dilute the solution. with water to about 40ml. and mix well. Add O.25 to O.3ml. of stannous chloride solution, and make up to the mark with water. Mix. throughly and ioUOmWmtcl el?t,aunsidngfOwratleOrtaOs la5 rvefi' enrUetne cS 6.. Measure its absorbance at 7oo mpt in a. The measurement of absorbance was made by use of a Shimadz's photoelectric spectrophotometer Type-QB 50. tt '. tt. '. tt /. '. .' Effects of Diverse lons. '. Effect of diverse ions.-Maximum permissible amounts of 20 diverse'ions for the determination -with less than 5% error is-given in Table 1. Silicate and arsenate produce the blue color. Effect of silicate,'however, is so small that only 5%:error is resulted with presence of 500 times the amount of phosphate., Arsenate needs separation ' from phosphate before color development. iaebPlael,9YiOn MethOdS SUCh aS by hydrogen sulfide or by distillation are appli-. An increase or a decrease of color intensity, caused by the presences of halide or sulfate, may be corrected if the amounts of these ions are known.. Figure'1 shows the effects of sulfate and chloride obtairied by use of 1 p.p.m., of phospha.te solution.. .. More than 5 p.p.m. of nitrite, more than 3% of nitrate and more than 40 p.p.m. of iron (III) causethefading of blue color. An experimental result obtained on the effect of nitrate is shown in Figure 2. Elimination of the interferences due to oxidizing ions.-Following reagent solution a'nd procedure are proposed to rem6ve the interferences of above ox-. idizingions. ' . ' '. sodiuM maSsipuiinfi{eiOiUtiOn'-A SOiution containing 2% patassium iodide and io% Procedure in Presence of iron (JIJ).-Take a solution, usually acidic, to be analyzed into a 50 ml. volumetfic flask and neutralize with dilute ammonium hydroxide (1+10) until the solution shows slight brown color. If the precipitate of fe'rric hydroxide appeared here, dissolve it with 1-2 ml. of dilute nitric acid. (1+50). Then, add 2 ml. of above masking solution (color of solution will turn. 4.

(3) Application of Phosphomolybdenum Blue Reaction. 53. tt. Table 1. Effects of diverse ions.. Ions investigated v. b. Maximum parmissible. Error. Clr .. O-5%. -20%/1% of Cl-. O.15%. I-. O-500 p. p. m.. 120 p. p. m.. Br-. O-500 p.p.,m.. -10%/100 p.p. m. of I-O.8%/100 p.p. m. of I". S042-. O-5%. +1%11% of SO,2-. 1%. S032-. O-O. 8%. +2%/O.1% of SO,2- '. O.3%. NQ3-. O-3% ,. Fade the blue color. NO,nt. O-18 p.p. m.. SiO,2--. O-O. 1%. As043-. O-5 p. p. m.. As033-･. 5,20 p.p.m.. Fe3-e. O-200 p. p. m.. Ca2+'. Mg2+. O-O. 2% O-O. 2%. A13+. 500 p. p. m.-. Mn2+. 25 p.p. m.. Zn2+. Vs+. 30 p.p.m. O.23 p.p.m.. Ti4+. 7. 5, 15 p. p. m.. Cu2÷. O-1 p. p. m.. F-. 5, 25 p,p.m.. ". Produce blue color. )) -No interference. Fade the blue color No interference. )) J) )) )) J7 )7 )) )). 3% -. 5p.p:m: ''. 500 times of PO,3r 1/20 of P043--. .. ---7 ,' 40 p. p. m.. ny. >O.23 p.p. m. >15 p. p. m. >1 p. p. m. >25 p, p. m.. op 05. 500 p.p.m.. ..:2:--D.-o-.o. /-"x. ".×..×bo.. q4. t'. 'Q4. e g. ,. O.3 1. O.3. ￡. g. * s q2. 1. e. 2. <A ol. 3. g. .A. Q2. o.{. o. 1.0 2.0 3.0 4.0 5.0. concentration,ofcl-orSq3", `va. Fig. 1. Effect of chloride and sulfate.. o. o. 5 IO Tirne, l5 20 rnin.25 Fig. 2. Effect of nitrate.. PO,3-; 2.0 p. p. m.. PO,3-･; 2.0 p. p. m.. 1; Effect of chloride 2; Effect of sulfate. Concentration of N03'". 1;1.0%, 2;2.0%, 3;3.0%. 30.

(4) 54 ･･ H.NAIxtllKI to strong brown, forming a ferric sulfite complex.). Allow to stand the solu-. tion at room temperature, until the brown eolor disappears. If more than. 10 mg. of iron (III) is present, place the fiask in a boiling water bath for a few'. minutes. Develope and measure the blue color in accordance with the proce-dure recommended in first section of the this paper. Prepare a calibration curve for O-4 p.p.m. of phosphate concentration. with addition of masking solution as used in'the procedure. If the precipitate is formed on standing or heating for reducing iron (III),-. ". a. dissolve it again with a small portion of nitric acid (1+50). If more than. 50 mg. of iron (III) is present, add enough amount o,f 10% sodium sulfite solu-tion to reduce it.. Presence of nitrate or nitrite.-Operate as described'for iron (III) excluding. the prQcessi for standing or heating of the solution. . Rt'"sults.-Satisfactory results were obtained using 1 ml. of masking soiution,. in the presence of various amounts of iron (III), as shown in Table 2. Iron (III) up to 10 mg. was rapidly and completely reduced to iron (II) and. only 5 minutes were enough at room temperature. The heating of solution Table 2. Masking of iron (III). Absorbance. 10% Na2S03 soln. added mL. Fe (III) added mg.. o 5. o. O. 440. o. O. 442. 10 25. o. O. 442. o' '. O. 432. 50. 1. O. 432. 100. 2. O. 445. 250. 5. O. 450. 500. 10. O. 447. P043" 2.0 p.p.m., masking solution 1ml.. `. Table 3. Masking of nitrate and nitrite.. Absorbance. N02- or N03- added. 30 minutes. 10 minutes. NO,- p. p. m.. NO,- %. '. o. O. 440. O. 440. 200. O. 437. O. 435. 500. O.438. O. 445. 1000. O. 447. o. 443. 3 5 10. O. 440. O. 438. O. 441. O. 443. O. 439. O. 440. P043- 2.0 p.p. m. masking solution 1ml. ,.

(5) Application of Phosphomolybdenum Blue Reaction 55･ was required to reduce iron (III) of the amount more than 10 mg., and addition. of sodium sulfite solution was required only when more than 50 mg. of iron (III)d. v,. b. was present. Table 3 shows the results obtained with the presences of nitrite or nitrate. Sulfamic acid, reported by Greenberg3' for prevention of nitrite interference. was also tried for nitrite and nitrate with. good results. . " oO,5 Asadditionofmaskingsolutioncauses g. change in color intensity (,Figure 3), a cali-. brationcurve.wasmadeusingthesame. ￡ 8o4 e'.. amount of masking solution as used in the. analyticalprocedure.Whensodiumsulfite Q3 was required for the reduction of large. amountsofiron(III),considerableamounts Fig'3.. o Masking 2.o 4.o 6p solutiony mL Effect of masking solution.. 3-; 2.0 p. p. m. ofsodiumsulfitewasconvertedtosulfatePO 4 Final volume of solution. as a result of reduction. In this case changes. in color intensities occured because the effect of. 50 ml.. sulfate on color intensity was. different from that of sulfite. Therefore, the calibration curve is necessary with use of the same amounts of iron (III) and reagents as in the procedure for sample.. GeneralApplications By use of masking solution described above, phosphomolybdenum blue method is applicable for determining phosphorus in the samples containing iron or large amounts of other elements. Nitric acid was used inmost of the cases to dissolve samples without loss of phosphorus as phosphine, andpermanganate solution was used for complete. ,oxidationofphosphorustophosphate. For some samples not attacked by nitric acid, a mixture of hydrochloric acid and ' nitric acid was used, and then phos'. E･. phate was coprecipitatedwith ferric hydroxide from slightly acidic or neutral solution, thus separatingfromchloride. Forsamples containing phosphorus in exide forms, sulfuric acid may also be used. Coprecipitation technique deScribed above was also applicable for separating phosphate from large amounts of diverse elements or for obtaining a higher concentration of phosphate from a dilute solution4). General procedures studied for the sample treatment were described as follows;. Procedure A.-Dissolve 1g. of sample with about 50ml. of nitric acid (1+3) and boilthe solution for a few ' minutes to expel nitrogen dioxide. Add of 3% potassium permanganate solution until precipitate of mangaa few drops nese dioxide appears. After cooling,dissolve the precipitate by adding 10% sodium sulfite solution dropwise. Transferthe solution into a 100 ml. volumetric flask and dilute to the mark with water..

(6) H. NAMIKI. 56. Procedure B.-Dissolve the sample with mixture of equal parts of hydro･chloric acid and nitric acid. Cool and dilute to 50-100 ml. with water. Add 1 ml. of 2.5% ferric nitrate solution if no iron is contained in sample. Precif pitate ferric hydroxide by adding dilute ammonium hydroxide (1+5), keeping 'the pH of solution at between 5 and 10. Separate the precipitate either by a Tcentrifuge or by filtration and wash with 2or3 times of water. Dissolve the precipitate with sma!1 portion of nitric acid (1+5), then, transfer the solution. st. 4. rinto a 100 ml. volumetric fiask and･make up to 100 ml. with water.. Procedure C.-Take the,sample into a platinum dish and add 10ml. of sulfuric acid (1+1). Add 10 ml. of hydrofluoric acid, if needed, to decompos.e. the sample. Evaporate gently on a hot plate until white fumes of sUlfur trioxide appear. After cooling, dissolve the residue in hot water and finally ･dilute to 100 ml. into a volumetric flask.. Re'sults.-An aliquot of solution containing 3-70ptg. of phosphorus was .pipetted from the solution obtained above and phosphorus was determined Table 4. Determination of phosphorus in steel and copper alloy.. Sample. Phosphorus. Kinds N. B. S.-14b. Steel. N B. S.-15b. 1. 00 × 10/100*. O. OIOO. 1. 00 × 20/100. O. O092. 1. 00 × 10/100. O. 0318. N. B. S.-30b N. B. S,-No. 63. O. O08. O. 032. O. 0423 O. 044. O. 0420. O. 0255 O. 024. O. 0260 O. 590. O. 100 × 5/100. O. 62. O. 580. s) * 101100 shows that ･10 ml.. Certified value %. O. 0307. Js JJ sJ sJ eJ. N. B. S.-20c. Bronz. Found %. Taken g.. .. was pipetted from the solution made up to 100 ml.. Table 5. Determination of phosphorus in rock. g. Samples Kinds. Phosphorus Taken, g. Oshima. 1. 00 × 5/250 1. 00 × 25/250 1. 00 × 10/250. Oshima. 1. 00 × 10/250 1. 00 × 25/250 1. 00 × 10/250. Lava, A Lava, B Sakurazima-. Lava. 1. 1. 1. 1.. 00 00 00 00. × × × ×. 5/250 5/250 10/250 5/250. added, ptg.. Phosphorus found ptg･. % in sample. 16. 3. 5. 5 25. 5 27. 0. O. 028 O. o26 O. 027. 16. 3. 5. 5 14. 3 23. 3. O. O14 O. O14 O. O17. 16. 3. 17. 17. 34. 32.. O. O. O. 0.. 5 3 5 8. 088 087 086. 083.

(7) Application of Phosphomolybdenum Blue Reaction 5.7 aPPi li,",g,tdh.e,,MK?kg".g.tdeCch""9,. q. rock, respectively, and results obtained were listed in Table 4 and 5. Known amounts of phosphate were added to samples for rock, because suitable samples were not available.. ' ". 2 .Pie,Vli",Od"Slg .P.r29,O,S,･e,d6f ,teei, copper aiioy and. ' ' Determination of Phosphine in Acetylene. ' ' Phosphine in acetylene Was oxidized to phosphate by passing the gas through bromine solution and determined as the phosphomolybdenum blue after "excessive bromine was reduced to bromide with sodium sulfite solution. The. method required only 25-50 ml. of sample and 15 minutes. ' Reagents.-A O.3% bromine solution used in this experiment was prepared by pfoperly diluting a saturated bromine solution titrated with a standard sodium hyposulfite solution. For additional supply of the reagent, an approximate dilution of stock saturated bromine solution, visually compared with the color of the initial diluted reagent, may suffice.. For- preparing a calibration curve, standard phosphate solution contaifiing 50 ptg.. of phosphate in lml. as prepared in first section was used. One ml. of the standard. A. solution is equivalent to O.O18 ml. of phos-. phine at･ normal temperature and pressure. For more convenient use, a standard solution, lml. equivalent to O.Olml. of phosphine at normal temperature and pressure,. 1 1. can be prepared as follows; Dissolve 6.075 g.. of potassium dihydrogen phosphate in water rand,dilute to 1000･ml.. Dilute 10ml. ofthis '. soiutiontolOOOml.withwater. Apparatus.-A 50 or 100 ml. capacity injector and a large diameter test tube were. b. usedforthesamplingandalsofortheox- ･. e.. gyo. Oo. o. B. oo. g o. D. Do. n o. ･o. g. oo. idationofphosphine.ApparatuswaSCOn- Fig.4.Apparatusforabsorpt･ion. structed simply as shown in Figure 4. of phosphine. Procedure.-Place20ml.ofO.3%bro- A;Injector(100ml.) mine solution and some glass beads into theB; Large diameter test tube plac' inginto20ml.ofO.3%bromine glass tube.. Takea25-50ml.ofsamplegasintothe SOIUtiOnandsomeglassbeads.. injector and pass the gas through the glass tube for about 1 minute. Then, transfer the bromine solution into a 50 ml. volumetric fiask. Add 10% sodium sulfite solution dropwise until yellow color of bromine disappeares, and add 1. or 2 drops in excess. Develope and measure the blue color according to the. '. '. ,.

(8) 58 H. NAMIKI. procedure recommended in Part 1. Determine the volume (milliliter) of phosphine at OOC, 1 atm. from the absorbance refering to the calibration curve and calculate the phosphine contents in acetylene from a fQllowing equation.. of sample OC) PH,(%)- 760×(273+temperature 273xatomospheric pressure (mm Hg). ×. measured phosphine (ml. at OOC, 1 atm.) × 100 . sample (ml.) .. ts. n. Calibration curve.-Take various;. 1 standardphosphatesolutionand20ml.･. o.6 of O･3% bromi.ne solution into a series of' 50 ml.volumetric flasks,then, develope. E'so･4 ･''･-･ bh,Z,3,':e,,.COBr,,a:,Cgrgie,S,,gg.gge.8.bP.gei. ;t milliliters of phosphine at OOC,1 atm. <O.2 and also at 180C,latm. (Figure 5)･ A calibration curve obtained at 180C,. OO qol o.o2.Qo3 qo4 1atM･iSCOnVenientforapproximatedepH, ,mi. terminationofphosphinecontentwithout Fig.5.calibrationcurve PreCiSeCalculations,becauseitiscalcufor phosphine. Iated that a change of 2.70C m tempera1; For ooc,1atm. ture or 7.6mm Hg. in atmospheric pres-. 2; For 18oC,1atm. sure is equivalent to only 1% volume change of sample gas. Results.-Phosphine was completely absorbed in bromine solution by pas-･ sing the sample acetylene for 1 minute. Bromine solution was a convement oxidizing agent because the control of acidity is not required before the blue:. color development. However, final color intensity was affected by bromide derived from the reduction of bromine. As shown in Figure 6, this may be corrected with a calibration curve prepared by ues of approximatelythe same. ij. amountofbrominesolutionasintheactualanalysis. ' It is noted that phosphine is unstable5) and tends to vary its content while. acetylene gas sample is handled in the experiment. Therefore, an apparatus was constracted as shown in Figure 7 for enabling comparison of the test. resultswiththatobtainedbyJIS6)method. , ･. About 9 1. of sample gas was passed through the system for 4 hrs. and phosphine was determined by JIS method. Test samples for this method were intermittently taken into the injector every 30 minutes and phosphine content was determined. The results obtained using 5 acetylene gas samples evolved from different calcium carbide lots were listed in Table 6. Table 6 shows･ constancy of phosphine content in gas samples obtained during this experimental gas flow and agreement of results with JIS method. An attempt to use a powdered calcium carbide as a standard sample for. `.

(9) 59. Application of Phosphomolybdenum Blue Reaction. ' s Qs v" O.4. a L. o co e o.s. }. Q2o. '. IO. 5. 15 20 25 30. O.3 % Brominsolution, ml.. Fig.. 6.. Effect of bromine solution.. P043- ;2.0 p.p.m.. T. l. p. o. o: 8 oi '. e'. CB. A Fig. 7. Apparatus used forthis experimentals.. A;Unitbyauthor B;UnitbyJISmethod C;Gasholder p;Paraffinelayer T; Thermometer Table 6. Determination of phosphine in acetylene. ,. ir.. Sampling. time pfter startlng, rpln.. Phosphine found, %. Sample A. Sample B. Sample C. Sample D. Sample E. o 30 60 90. O. 0258. O.0326. O. 0352. O. 0872. O. 0236. O. 0258. O. 0332. O.0352. O. 0884. O. 0230. O. 0260. O. 0330. O. 0358. O. 0888. O. 0240. O. 0254. O. 0332. O. 0884. O. 0240. 120 150 180 210 240. O. 0262. O. 0332. O. 0888. O. 0238. O. 0892. O. 0240. O. 0888. O. 0238. O. 0888. O. 0243. O. 0352. O. 0260. O. 0258. O. 0334. O.0258. O. 0332 O. 0330. O. 0352. O. 0243. O.0356. .O. 0238. 270,. Average By JIS method. O. 0259. O. 0276. O. 0331. O. 0354. O. 0886. O. 0239. O. 0334. O. 0371. O. 0866. O. 0245.

(10) 60. H. NAMIKI･. the phosphine q.etermination was unsuccessful. Variable phosphine con-. y*. c" oos. e'. o. o. tents were obtained each time for. o. -.--. g o o. the acetylene evolved from the same calcium carbide. This variation of phosphine contents may be due to a fractional decomposition at a high temperature during the gas evolution ' ' p'rocess. Figure 8 shows the results. e OP7 ..s .s. ga. = Q06. a. .. a. ' oo % tHOeOatingtem2pOeOr'ature,3eOcO'obtainedfotthedecompositionof. Fig･8･Decompositionofphosphine PhOSPhinebyheatingsamplegasin in acetylene by heating. an aPparatus constructed especially for.this study.7) In an analysis of. Sample gas was heated for 10 minutes.. t lumpy calcium carbide, high tem-. perature was not observed and therefore no variable phosphine contents ob-. served. Table 7 shows the analytical results obtained for the acetylene evolved. from the powdered and the lumpy samples, taking the sample gases intermit'Ltently every 15 minutes during gas evolution. T.able 7. Variation of phosphine content during gas evolution.. Phosphine found, % 1. I I. 2. 3. 4. 5 O. 029. Powdered CaC2. Q. 027. O. 043. O. 030. O. 038. Lampy CaC2. O. 085. O. 090. O. 088. O. 092. Determination of Phosphorus in Organic Phosphorus Compounds One of the prob!ems in analysis of organic phosphorus compounds, such :as dipterex, parathion and meta systox, is how to oxidize the sample without. .. ･a lpss of phosphorus due to volatalization.. Organic compounds, either dissolved or suspended in water or other sbl-. vents, were decomposed by ignition after the solvents were evaporated to tdryness from alkaline medium, and phosphorus was finally determined as phos-. .phomolybdenum blue. Procedure.-Take the sample containing 2-50ptg of phosphorus into a platinum crucible. Add 1ml. of 1N sodiumhydroxide solution. Evaporate the .solution to dryness and ignite for a few minutes. After cooling, add 1.5-2.0 ml. ･of 1 N sulfuric acid and heat slightly until the solution becomes clear. Transfer 'the solution into a 50 ml. volumetric flask. Wash the crucibie several times. with hot water. Determine phosphorus by the same procedure described in 'the first section.. Results.-Parathion and meta systox, used for the experiment, were deter-. aj.

(11) Application of Phosphomolybdenum Blue Reaction 61 Mined for phosphorus contents by titration of a large amount of phospho--. mo!ybdicacidprecipitate.Dipterexwaspurifiedby･recrystalization.' ge. Experimental re$ult in Table 8 shows that, more than O.05N ･of sodium hydroxide concentration was enough to prevent the loss of phosphorus during. the evaporation. Ignition was necessary to complete the oxidation of samples.. The analytical results were shown in Table 9.. b. '. '. Table8.Decompositionofdip- Table9.Determinationofphosphorus. terexbysodiumhydroxide, ' indipterex,ethylparathion ' 6oncentration phosphorus andmetasystox. of NaOH. used*, N. found,** pt g･. o. Phosphorus in. sample. calculated, "g.. 4. 0. O. 1. 31. 5. O. 2. 32. 0. O. 5. 31. 8. 1. 32. 0. 2. 5. 31. 5. 5. 31. 8. * 1ml. of sodium hydroxide solgtion was always added. ** Calculated value of P is 31.0 ptg.. tt. Samples. Phosphorus founq{ ptg･. Dipterex. 15. 31. 46. 62.. Ethyl parathjdn. IL 6. IL 2. 23. 1 34. 8 46. 1. 27. 6 39. 4. 14. 27. 41. 55.. 0 9. 16. 4 30. 2.. 9 8. 45. 8 59. 4. Meta. systox. 5 0 5 0. 15. 2 30, 4 43..5 57. 0.. 53. 2'. '. Determination of Phosphate in Polluted Water by the Extraction of PhosphomolybdenumBlue '. To determine phosphate in water polluted by sewage and waste, the colored. interfering substances wereextracted with n-butyl alcohol, and phosphomolybdenum blue was developed in aqueous solution and subsequently extracted into-. n-butyl a!cohol. , ". k･. Phosphate more than O,02 p. p. m.was determined without the interferences of polluting substances. The method is suitable for analysis of water containing various amounts of chloride since the method was not affected by the presence. of chloride up to 3%. . ' ' Procedure.-Take 50 ml. of sample water into a 100 ml. separatory funnel and add dilute sulfuricacid (1+50) to slight acidic reaction. Add 15-20 ml. of n-butyl alcohol and extract the interfering substances, shaking the solution for. 30-60 seconds. Transfer the aqueouslayer into an another 100 ml. separatory funnel. Add 6.5ml. of sulfuric acid (6.5 N)-ammonium molybdate (1.5%) solu-･ tion, described in the first section and O.25 ml. of 2% stannous chloride solution. Allow to stand the solution for about 15 minutes to develope the color completely. Add exactly 10 ml.(or a certain definite voiume) of n-butyl alcohol and. extract the blue color complex With shaking for 1-2 minutes. Descard the･ aqueous layer and pour the organiclayer into 10-mm. cell through a dry filter.

(12) 62 H. NAMIKI. paper or a dry cotton plug. Measure the absorbance at 830mpt against. n-butylalcohol. ' '. Make a calibration curve by the same procedure using standard phosphate. rsolutioncontaining5-40ptgofphosphate. ･ Results.-The volume change of organic phase du.e to dissolving each portion of water and n-butyl alcohol was minimized' by saturating the aqueous phase with n-butyl alcohol in first extraction for the interfering substances. The concentration of acid and ammonium molybdate adjusted in the color development were different fromthat recommended in first section. The absorb:ance of organic phase for blank solution slightly increased with shaking time when concentrations were controlled. pt T'. a. Q4 ' ' asinfirstsection.Themaximum ' absorption was observed at 830 mpt. Q3 when the blue complex was extracted. ,o with suMcient shaking time, theredeuum blue complex was extracted go ao･ 2p,,'..3'p., Xp t.go ?,Y,,g8ff2,eg.ltg,a,,CglhOig.}.ie,e,,xy,a.s,d:IIIIe,gzn,E. Fig. 9. Effect of chloride on phosphornolybdenum blue extraction method.. Figure 9 shows that, when the blue complex was extracted with suMBlue color for 20 yg of phosphate was ex'tracted with 10ml. of n-buty! alcohol, cient shaking time, the same color. ･shaking for 1 minute. intensities were obtained without the. . . interference of chloride up to 3%.. Effect of polluting substances on analysis was studied in the presences of several. lkinds of organic matters. The results were shown in Table 10. Samples of polluted water were taken from two rivers, Ooka-gawa and 'Tsurumi-gawa in Yokohama city, at intervals of about 2km. Phosphate in these water samples were determined with and without the addition of known :amounts of phosphate. The results were listed in Table 11. '. '. DeterminationofTinbyPhosphomolybdenumBlue . The blue color formation by the reduction of phosphomolybdate with tin <II) was employed to the determination of small amount of tin. Method hitherto reported8) was first tested, but no reproducible color inten-. sities was obtained. It was found that both phosphate and molybdate 1000 times more than the amount ca!culated for tin were necessary for complete reaction of tin.. Aluminum foil was used to reduce tin (IV) to tin (II) and several precau-. . i. ti.

(13) Appl･ication gf Phosphomolybdenum Blue Reaction. 63. Table 10. Determination of phosphate in the presence of diverse organic substances (P043-':. 10 ptg. added).. Organic matter. Kinds. :. Phosphate found, ptg.. Added, g.. Palmitic icid. O. 1 O. 5 1. 0. 10. 4 10. 6 10. 4. Sodium steatat'e. O. 1 O. 5 1. 0. 10. 3 10. 4. Cellulose. 'O. 1. 10. 3 10. 6 11. 8. k. s. 10. 0.. O. 5 1. 0. tt. Starch Starch*. O. 1 O. 5 1. 0. 10. 1. O. 1. 10. 3 10. 3 10. 2. 9. 5 8. 8. gig. Saccharose. 1. 0. 10. 0 10. 1 9. 8. Humic acid. O. Ol O. 02 O. 04. 9. 8 10. 1 9. 5. Petroleum. O.. 5. O.1 . 0. 5. LO 2. 0. Formalin. O. 1. O. 5 1. 0. (mL). 10. 4 10. 3 10. 4. (ml.). (mL) (mL). 9. 8 10. 0 9. 6. (ml.) (ml.). * Treated with not water. Table 11. Determination of P043- in polluted water.. SaMple '. Recovery test with. No.. Taken. O-1. 50. O-2. 25. P043- fourid pg･. mL. an addition of 5.0 ptg PO,34. P043- found ptg. P043-' in sample. found p.p.m.. (.. ;･. 1. v. O-3 O-4. T-1. 28. 2 27. 5. 33. 2. O. 564 O. 550. 11. 4. 16. 1. O. 456 O. 448. IL 2 10. 25 25 50.. 50. 10. 5 26. 2. 30. 3. 1. 05 1. 05. 40. 0 79. 8*. 86. 0. 1. 60 1. 60. 10. 3. 14. 9. T-2. 50. T-3. 50. T-4. 50. O. 206 O.' 206. 10.. 3. ol. 3o2. 15. 1 15. 3. 19. 9. 12. 8 13. 1. 17. 1. O. 256 O. 262. 13. 1 13. 2. O. 164 O. 160. 8･. 2'. 8. 0. O. 306. O: Ooka gawa. T:Tsurumi gawa. * Extracted with. 20 ml. of n-butyl alcohol..

(14) 64 H. NAMIKI '. ' tions for the process were noted. Tin in several kinds of samples were determined by this method, after tin was separated from･interfering ions by the coprecipitation with manganese dioxide. Reagents.-Potassium dihydrogen phosphate solution.-10% in water. Ammonium molybdate solution.-10/a./ in water. Standard tin solution.-Dissolve O.500g. of tin in 50ml. of concentrated. hydrochloric acid and dilute to 500 ml. with"water. Take 50 ml. of this solution and dilute to 500ml. with diluted hydrochloric acid (1+9). One ml. of this solution contains 100ptg of tin. (For discussion of the reduction process of tin (IV) by aluminum foil, standard tin (IV) solution, which was prepared by oxidizing tin (II) to tin (IV) with hydrogen peroxide, were used in this. eXPefiilllllthe.￡S.)in. it. s 4. i. foil.-Abo.t gg.s% .f purity is suitable･. Procedure.-Take the sample solution containing 100-700 ptg. of tin in a 100ml. Erleqmyer flask. Add 10 ml. of 18N sulfuricacid and{3:5ml. of'･concentratedhydrochloricacid. Dilute to about 40ml. with water. Prepare O.2g. of aluminum foil and add one-third of it into solution. Heat the solution slightly and dissolve the aluminum. If the･･ precipitate of metal such'as cOpper. and antimonyappeared here, filter the solution into an another 100 ml. Erlenmyer flask. Add the remaining aluminum foil into the solution and dissolve. itwithheating.Boilthesolutionfor3-5minutes. ･ ''' Cool rapidly to room temperature in a running water, passing nitrogen or carbon dioxide gas from a top of flask in order to prevent a contact of air. with the solution. Immediatelyaftercooling, add and mix 2ml. of 10% potassium dihydrogen phosphate solution. Add 2ml. of 10.% ammonium molybdate solution without the mixing of solution. Then, mix well the solution and transfer into a 50ml. volumetriG fiask. Dilute to the mark with water and. mix welL ･. Measure the absorbance at 800 mpt with 10-mm. cell against water. Make a calibration curve using standard tin solution as the same procedure as described above. Results.-A standard tin (II) solution, which was prepared from stannous chloride and titrated with a standard iodine solution, was used te investigate the suitable condition for the formation of blue color. Comparably high acidity of 3.6 N was first chosen as the final sulfuric acid concentration of solution, because the method required some acid to dissolve aluminum in the process of reduction of tin (IV).. At this acidity, the amount of phosphate and molybdate required for the complete'development of blue color were investigated. The result was shown in Figure 10. The peaks of absorbances in each curves given interestmg information as to the fundamental property of phosphomolybdenum blue complex. However the flat level of the absorbance curve is selected for designating reagents concentrations. The concentrations of O.4% for both of potassium. y't. l '. 9.

(15) i. Application of Phosphomolybdenum Blue Reaction. o･9. O.4. /A. o x O.4. }i-. 6. s <. e oe 8 a Q2 <t. ･ 2o.3. 5. ]t. k.. 2 02.. 'i. i. o. 65. o. O.4. Q8. Ol. 'O 2･468 10 KH2P04 % ConceptrqtieftofH2SCI4,N. T.2. l.6. 2.0. - Fig.10. Effect of concentration of Ffg.11. Effectofacidity. Sn (II);6.2 p.p.m. Ammonium molybdate;O.4%. Potassium Sn (II),,; 6.16 p.p.m. H2S04;3.6N.' Con- hydrogen phosphate; O.4% (Measured centration of ammonium molybdata. 1; at700mpt) ･- ･' ' ' 2;O.32%, 3;O.16%. (Measured at O.64%, phosphate and molybdate for determina-. tionofSn. ' ･. 700 mpt). -1 wrd,r,o,g,el"',?hezp,R･.aj,e.2",8,,i,m,illsn,`s,gl,?･l.2i,lb,g･,a,te.w.sr,z,sgilgcg･zd"?･Ei,hg's,iil.eth.os,'. peak of curve in Figure 11 may show the formation of product as that indicated by Figure 10. Figure 12 shows that two different absorption spectra of blue color obtained (1) with the reagent concentration corresPonding to the peak in Figure 12 and (2) with the reagent concentration by.author. Maximum color intensity was reached after 4 minutes and was stable for 20 minutes if,the interfering ion was absent. The reducing process of tin (IV). O,3 ' ' '. '. '. 2. l 1. 06. 1-. 8 q2 g. l r. e. 2 k. 8. 3. *. S O.4 ￡. a <O1 -/. .o .. o. o. A. ･< O,2. }. 400･ 500 600 700 800 900 . Wevelength,rnN. O 5 10Sn,-15 p.p.m. Fig. 13. Calibration curve for. 20. Fig. 12. Absorption spectra of phosphomolybdenum blue for .determination. 1;. Sn (II) ; 6.16 p. p. m.. 2; Al foii for cocking was used. 3; Standard Sn (II) solution was used.. oftin.I･ ' '. tin.. 99.93% Al was used.. ' Conditionofsolution. ' O.4%, 1; H,SO,3.6N,KH,PO, ammonium molybdate O.4%. 2; H,SO,8.IN,KH,PO, O.4% ammonium molybdate O.4%. '. '.

(16) 66 H. NAMIKI '. was studied. Tin (II) was rapidly oxidized to tin (IV) when the solution was exposed to air at an elevated temperature. Therefore, the solution must be kept free from air during the reducing process. Usual water containing small. amount of oxygen should not be used. About 99.8% purity of a!uminum was suitable to reduce tin (IV) because of easy dissolution in acid, but the blue. colorforblanksolutionincreasedwiththedecreaseofaluminumpurity. , Calibration curves obtained by use of aluminum were shown in Figure 13.' ' The method was examined using standard tin solution, and the result was. ¥ r. listedinTable12. ･ -'. Effects of diverse ions were investigated and no interferences were observed. wh'm･following ions were present; more than 100mg. of chloride, more than 10w mg. of sulfate, O.5mg. of nitrate, O.5mg. of sulfite, 2mg. of iron, O.1 mg. '. ' Table12.Determinationoftininstandardsolution. ' ･ ' Sn found. Sn taken p. p. m.. Error p. p. m.. p. p. m.. 2. 5. 2. 2. -O. 3. 2. 5. 2. 7. 5. 0. 5. 2. 7. 5. 7. 7. +O.2 +O.2 +Q.1 +O.2. 7. 5. 7. 2. -- O. 3. 10. 0. .10.2. 10. 0. 10. 1 12. 7. +O.2 +O.1 +O.2. 12. 5. 12. 3. -r'O･2. 15. 0. 15. 3. 15, O. 15. 4. +O.3 +O.4. 5, O. r. 12. 5. 5. 1. I. Table 13. Determination of tin.. Sample Kinds. Water. Taken 1000 mL. Sn (II) contained or added, ptg. 250 250 500 500. a. Sn (II) found, ptg.. Error ptg. ￡. 263 270 490 485. + 13 + 20 - 10 --- 15. -12. .Brass A. 50 mg. 410 410. Brass B. 50 mg. 495-. 495. 398 405 465 475. Steel. sod mg. o. 35'. 100 100 200 200. 120 1!5 210 220. 400. 425. --- 5. -30. - 20. + + + + + +. 35 20 15 10 20 25.

(17) Application of Phosphomolybdenum Blue Reaction 67 of titanium, 10mg. of arsenic and more than 500 mg. of manganese. Copper and antimony caused the increase-of b!ue color intensity in the presence of milligram amount, but these ions were reduced to metallic state and separated. ) i$'. prior･todevelopingthebluecolor.' '- ' -' ' To apply this method for analysis of several kinds of samples, the copreci-. pitating technique with manganese dioxide was employed for collecting tin. Tin in copper alloy, steel and water was determined. Results were shown in Table'13. For steel and water analysis, a known amount of tin was added,. becausesamplesofpropertincontentwerenotavailable. ' ･ Miscellaneous Phosphate was determined in calcium pyrophosphate and also in toothpaste consisting mainly of calcium pyrophosphate. No interference by the large amounts of pyrophosphate was encountered. Pyrophosphate was a-lso determined after converting it to phosphate by boiling with acid. A reagent starch showed presence of O.O08% of phosphate when analyzed after boiled in water. Phosphate in calcium sulfate was analyzed after extracting with dilute sulfuric acid. Fading of blue color by nitrite was utilyzed for ana!ysis. Determination of small amount of nitrite was made by the comparison of fading color with a. series of standard solutions. ･ Summary A simple and rapid method for eliminating the interferences of oxidizing ions, such as iron (III), nitrite and nitrate on coloration of phosphomolybdenum. blue, was established. Phosphorus in steel, rock and copper alloy were deter-. mined by phosphomolybdenum blue method applying above eliminating tech' . ' ). ; }. p. Phosphorus or its compounds in several kinds of samples were also determined colorimetrically by phosphomolybdenum blue. Phosphine in acetylene was oxidized to phosphate by passing the sample gas through bromine solution and determined. Organic phosphorus coMpounds such as parachion, dipterex. and meta systox were destroyed after the solvents were evaporated from alkaline medium, and phosphorusin these samples were determined. To determine phosphate･in polluted water, interfecing substances were extracte,d with n-butyl alcohol. Phosphomolybdenum blue was developed in aqueous solution and extracted with n-butyl alcohol.. The formation of blue color was applyed to the determination of small amount of tin and a suitable procedure was proposed.. t.

(18) 68 ･- - ･- ･ -H.NAMIK･I Acknowledgement ' Tokyo Institute The author is much indebted to Professor Iwajilwasaki of of Technology, and Professor Isao Kayama of Tokai University for their invaluable advice and discussion throughout this work.. -A' "'t. ･.,,,J. xf. '. References. ,A. ' ' Analyst (Bunseki Kagaku), 7, 691 (1958); 1) F. KAWAMuRA and H. NAMiKi: JaPan H. NAMiKi, ibid. 10, 945 (1961); Ibid. 10, 895 (1961); Ibid. 10, 900 (1961). F. KAwAMuRA and H. NAMiKi, Industrial Water (Kogyo Yosui), No. 20, 19 (1960). 2) H. NAMiKi: Bzttt. Chem. Soc. JaPan, 37, 484 (1964).. 3) A.E. GREENBERG, L.W. WEiNBERGER and C.N. SAwyER: Anal. Chem. 22, 499. . (1950). .. 4) M. ,IsHiBAsHi and M. TABusHi: JaPan Analyst (Bunseki Kagaleu), 8, 588 (1959).. 5) J.W. MELLoR: "Comprehensive Treaties on Inorganic Theoretical Chemistry". 6) Jis.¥:L',ij.iil'ndPlis8tOrZ'-a8iigt5'n9d2i2d') K. igoi (igso). ' 7) H. NAMiKi and F. KAwAeviuRA, Report of Laboratory of Carbide Chemistry, Yoko-. '8) hamaNationalUniv.No.1,1(1962). . E.B. SNADELL: "Colorimetric Determi,nation of Traces of Metals" 2nd Ed. p. 567 (1950) (Interscience Publishers).. t. SP '1,. i. 1. ･s. be. '.

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