V O L U M E 28, NO. 8, A U G U S T 1 9 5 6
1273
Table 111. Interplanar Spacings and Line Intensities d , 8.
1.
a, A.
1/11
T N T (from Melt) 9.94 1 7.08 7 5.99 1 5.61 8 5.18 2 5.01 3 4.62 2 4.28 5 4.00 2 3.87 10 3.71 3 4 3.49 1 3.31 1 3.16 6 3.06 3.00 3 2.92 2 1 2.89 2.72 4 4 2.68 2 2.59 1 2.55 2.44 3 2 2.37 2 2.30 1 2.24 1 2 20 3 2.13 1 2.06 1 2.03 1.49 1 1.92 1
1.
2.
a, A.
1/11
T N T (from (Contd.) 1.88 1.83 1.78 1.75 1.68 1.64 1.58 1.53 1.46
Melt) 2 1
1 1
1 1 1 1 1
T N T (from Ethyl .4lcohol) 9.88 2 7.02 6 6.66 1 6.02 1 5 5.63 5.44 4 5.22 1 4.97 4 4.29 7 3.87 10 3.73 2 3.53 2 3.43 3 1 3.34 3.27 4 3.16 2 3.06 4 3.01 4
2.
1/11
T N T (from Ethyl Alcohol) (Conid.) 2.93 1 2.87 4 2.79 L 2.72 ? 2.67 2.60 3 1 2.52 2.43 3 2.36 2 2.30 3 1 2.23 2.18 1 2.14 3 1 2.10 2.04 2 2.01 2 1 1.97 1.93 1 1.88 3 1. 8 3 1 1.81 1 1 1.78 1.76 1 L73 1 1.70 1 1.67 1 1.64 1 1 61 1 1.58 2 1.53 2 1 1.43 1.39 1
standard flat-specimen sample holders. Patterns were recorded n-ith a Norelco diffractometer using copper radiation filtered through nickel foil (A = 1.5418 A ) . Powder patterns of 2,4,6-trinitrotoluene samples vere also obtained using a rotated capillary in a 114.6-mm. diameter camera with copper radiation filtered through nickel foil. EXPERIMENTAL DATA
Table I lists the compound, source, or method of preparation and molar ratio in the case of the complexes. Interplanar spacings are given in Table I1 for the range 22.09 to 1.54 8. Intensities are given as peak height above the background level, with the most intense reflection given a value of 1.00. Interplanar spacings and intensities for 2,4,6-trinitrotoluene obtained from the rotated capillary samples are given in Table 111. Intensities y e r e visually estimated and are given on a basis of 10 to 1, 13-here 10 represents the most intense line. LITERATURE CITED
(1) ;Im. SOC. T e s t i n g M a t e r i a l s , X - r a y diffraction d a t a cards ( 2 ) B u r k a r d t , L. A , .ISAL. CHEX 26, 1255 (1954). (3) B u r k a r d t , L. A , , B r y d e n , J. H., Acta Crust. 7, 135 (1954) (4) SIcCrone, ITr. C . . .I~YAL. CHEM.21, 1583 (1949). (5) Soldate, A . SI., S o y e s , 1%.lI.,Ibid.,19, 442 (1947). ( 8 ) T a y l o r . P a t r i c i a , p r i v a t e communication. RECEIVED for review J u n e 4 , 1955.
Accepted February 24, 1956.
Photometric Determination of Germanium with Phenylfluorone C. L. LUKE and M A R Y
E. CAMPBELL
Bell Telephone Laboratories, Inc., Murray Hill,
N. 1.
In an improved photonietric phenylfluorone method for the determination of microgram quantities of germanium, interference from other metals is eliminated by isolating the germanium with a carbon tetrachloride extraction previous to the photometric determination. Very rapid color development is achieved by adjusting the solution to pH 3.1 before adding the phenylfluorone. A study has been made on the use of complexing reagents to eliminate metallic interference.
minutes is required for full color development. Ernst ( 2 ) hns shown that the time can be reduced to 1 or 2 minutes by adjusting the pH of the solution t o 4.5 with the aid of a sodium acetateacetic acid buffer before adding the phenylfluorone. It appeared possible to develop a very rapid photometric method for germanium based on the extraction technique of Schneider arid Sandell, followed by the color-forming technique of Ernst. This paper describes the authors’ n-ork in developing such a method. APPARATUS
A
RELIABLE method for the determination of microgram
quantities of germanium in the presence of milligram quantities of other metals is needed in certain phases of semiconductor research and development. A photometric method, based on the phenylfluorone spot test of Gillis, Hoste, and Claeys (S),was developed by Zischkau ( 9 ) , who was able to eliminate the interference of antimony and tin by complexing with fluoboric and phosphoric acids, but found no simple method for the elimination of interference due to molybdenum. Cluley ( I ) , working independently, presented a similar method in which the germanium is first isolated from all interfering elements by distillation as chloride. This method is very satisfactory for most analyses, but is time-consuming. Schneider and Sandell ( 7 ) reduced the time of analysis by replacing the distillation with a carbon tetrachloride extraction of the germanium from 9.Y hydrochloric acid solution (8). The only metal that accompanies the germanium, in more than trace quantities, into the carbon tetrachloride layer is trivalent arsenic, which causes no interference in the phenylfluorone method. I n the photometric methods mentioned the acidity of the solution a t color development is high. and as much as 30 t o 60
A Beckman Model B spectrophotometer, with absorption cells having a light path of 1 em., was used. REAGEKTS
SODILXHYDROXIDE SOLUTION(570). Dissolve 5 grams of sodium hydroxide in 100 ml. of water in a polyethylene bottle. STASDARD GERMANIUM SOLUTIOZ. (10 y of germanium per ml.). Transfer 0.1441 gram of pure germanium dioxide to a 100-ml. platinum dish. Add 3 ml. of (57c) sodium hyroxide solution, and stir and rub Kith a polyethylene rod until all the oxide has dissolved. Add about 75 ml. of water. Neutralize to Congo red paper by adding sulfuric acid (1 9 ) dropwise. ildd 3 or 4 drops in excess after the paper has turned blue. Remove the Congo red paper and transfer the solution to a 1-liter volumetric flask. Dilute t o the mark with water and mix. Transfer 50.0 ml. of the solution to a 500-nil. volumetric flask, dilute to the mark with water, and mix. HYDROCHLORIC ACID( 9 s ) . Transfer 385 ml. of hydrochloric acid t o a 500-ml. volumetiic flask, dilute nearly t o the mark n-ith water, cool, dilute t o the mark with water, and mix. BUFFERSOLUTIOZ. ( p H 5 ) . Dissolve 900 grams of hydrated or 540 grams of the anhydrous sodium acetate, SaC2H3O2.3H?O, salt, in about TOO ml. of water by narming on a hot plate. Filter with suction through a R h a t m a n S o . 40 paper and transfer to a 2-liter volumetric flask containing 480 nil. of acrtic acid. Cool, dilute to the mark with water, and mi\.
+
ANALYTICAL CHEMISTRY
1274 Guar ARABICSOLUTION.Dissolve 0.5 gram of powdered gum arabic (gum acacia) in 50 ml. of hot water by stirring. Filter n-ith suction through a K h a t m a n KO.42 paper on a platinum cone. Prepare fresh each day as needed. PHENYLFLL-ORONE SOLUTION.Transfer 0.0500 gram of phenylobtainable from fluorone (2,3,7-trihydroxy-9-phenyl-6-fluorone, Jasonols Chemical Corp., Brooklyn, N. Y.) to a 100-nil. beaker. .Add 50 ml. of methanol and 1 ml. of hydrochloric acid, and stir until dissolved. Transfer t o a dry 500-ml. volumetric flask, dilute t o the mark with methanol, and mix. This solution is stable for a t least a month. D o not store in a polyethylene bottle. PROCEDURE
Preparation of Calibration Curve. Transfer 0, 0.5, 1.0, 2.0, 3.0, and 4.0 ml. of standard germanium solution (10 y of germanium per ml.) to 60-ml. Squihh-type separatory funnels. .Add 2 ml. of sulfuric acid (1 l ) , dilute to 7 ml. with water, and add 19 nil. of hydrochloric acid. Add 20 nil. of carbon tetrachloride, stopper, and shake vigorously for 1 minute. ~ 4 1 1 0 the ~ layers to sgparate and run the carbon tetrachloride la?-er into a second 60-ml. separatory funnel xhich is dry or has been rinsed nith 9 N hydrochloric acid. Add 2 ml. of carbon tetrachloride to the acid solution in the first funnel, shake for 10 seconds, allow to settle, and run the lower layer into the second funnel. JT-ash the combined carbon tetrachloride solutions by shaking for 10 seconds n-ith 2 ml. of 9 N hydrochloric acid. .Allow the layers to separate and transfer the lower layer to a third 60-ml. separatory funnel which has been dried in an oven or with an air jet. Add from a buret 12.0 ml. of water to the carbon tetrachloride solution in the third funnel. Stopper and shake vigorously for 1 minute. .illow the layers to separate and discard the lower layer. Filter the aqueous layer through a small dry \Thatman S o . 40 filter paper and collect the filtrate in a dry 50-ml. conical flask. Pipet 10.0 ml. of the filtrate into a 50-ml. volumetric flask. .Add 1.5 nil. of sulfuric acid (1 l ) ,then 10 ml. of buffer solution, and then 1 ml. of gum arabic solution from measuring pipets, swirling after each addition. A4dd 10.0 ml. of phenylfluorone solution, stopper, and mix. Ignore any precipitation of sodium acetate, as the precipitate will dissolve upon subsequent acidification. Let stand 5 minutes. Dilute to the mark with hydrochloric acid (1 9). and mix. Transfer a portion of the solution t o a 1-em. absorption cell and make the photometric measurement immediately a t 510 mp, using water as the reference solution. Prepare a calibration curve. Analysis of Sample. Dissolve the sample (containing no more than 40 y of germanium) in a small excess of a suitable acid or alkali in a 50-ml. conical flask. Halogen acids or their salts must not be used a t any stage in the preparation of the sample solution. Organic matter, if present, must be destroyed by n e t oxidation. Finally add 2 ml. of sulfuric acid and evaporate on a lleker-type flame t o about 1.25-ml. volume. Carry a reagent blank through all steps of the analysis. If the sample is known to contain less than about 0.25 mg. of antimony, add 5 drops of perchloric acid and evaporate on the flame t o a volume of 0.75 to 1 ml. Otherwise add 2 ml. of sulfuric acid plus about 0.1 gram of hydrazine sulfate and evaporate on a flame to a volume of 0.75 to 1 ml. Cool. If a precipitate of iron or chromium Eulfate is present, add 1 ml. of water and heat uncovered on a low temperature hot plate until fumes of acid just appear in the flask; if necessary, repeat the addition of Rater and heating just, to fumes one or more times to dissolve the precipitate completely. Cool. Ignore insoluble sulfates of lead, barium, or calcium. .4dd 6 ml. of water, pour into a 60-ml. se aratorv funnel, and wash in with 19 ml. of h>-drochloric acid! a d d - 2 0 ml. of carbon tetrachloride and continue as in preparation of calibration curve.
the photometric determination, for fear of changing the intensity of the germanium color produced or of obtaining cloudy solutions. I n order to est.ablish the optimum pH for rapid color derelopment, -io-:. portions of germanium, in the form of aliquots of a standard germanium solution, plus various amounts of sulfuric acid were diluted t o 10 nil.; a 10-m1. aliquot of p H 5 acetate buffer solution was added; the pH of the mixture was measured; and the germanium was then determined photometrically as directed above. Reagent blanks for each Eample were carried through the photometric analysis (see Table I).
+
+
Table I.
Optiniuni pII for Color Development Absorbance
So.
Sulfuric .-icid Present, MI.
pH of Mixture
Reagent
blank
Germanium
Difference
1 >
0.25
4.3 4.0 3.1 1.8
0.29
0.96 0.91
0.67 0.83 0.89 0.90 0.77
0.50 0.75
3
1
1.00 1.25
1.0
0.08 0.06 0.04
0.03
0.95
0.94 0.80
Talde 11. Determination of Germanium by Carbon Tetrachloride Extraction-Photometric hlethod Yo. 1 2 3 1
Germanium €ound, y
Otliri I l c t d l s Added
Li. S a . IT. R b , Ca,, B, Be, IIg, Ba, Sr, C a C r , I I n . Re, Co, Si
Pd,Pt,ll Ir. Os. Rli
41 40 40 41
+
DISCLSSION
Most of the conclusions of Schneider and Sandell regarding the germanium extraction have been confirmed. Quantitative tests have shown that the recoverj of germanium is only about 957, complete when a single carbon tetrachloride extraction is used. .4s additional extractions do not improve the recovery, it is necessary to compensate for the loss of germanium by including the extraction in the preparation of the calibration curve. Considerable difficulty ryas experienced in establishing suitable conditions for rapid color development in bnffei ed solutions. Cloudy solutions were frequently obtained upon dilution to volume after color development. However, optimum reagent concentrations xere eventually found that made it possible t o overrome this difficulty. I t is desirable to avoid altering the aliioiutc or relative concentintion of any of the reagrnts used in
39 40
The optimum p H for color development is 3.1, as the sensitivity of the germanium determination is high and does not vary appreciably with change in pH. Complete color development occurs in less than 2 minutes x h e n the solution is more alkaline than pH 1.8. Xeverthelem, as a precautionary measure, the time has been extended to 5 minutes in the method described. Color development a t pH 1.8 is attractive from the standpoint of decreasing the interference of other metals, but completely clear solutions and more stable colors are obtained when color development is made a t p H 3.1. Even a t this pH, however, there is a tendency toward a fading of the germanium-phenylfluorone color after 10 or 15 minutes of standing, following the dilution to volume with hydrochloric acid (1 9). Some difficulties are presented by samples that contain appreciable amounts of chromium, antimony, or titanium. I n order to prepare a sample for the carbon tetrachloride extraction it is necessary t o fume it n-ith sulfuric acid. ]Then this is done, chromium, regardless of its 01 iginal valence state, precipitates as a basic sulfate. Severe loss of germanium by occlusion occurs if this precipitate is not redissolved before proceeding. The precipitate from small amoinits of chromium-i.e., less than 100 ;-can be redissolved by digesting in hot sulfuric acid (1 1))but solution of laiger amounts is often virtually impossible. To date no completely satisfactory method for the analysis of Eamples containing more than traces of chromium has been found. Iron behaves in the same way as chromium, but the iron sulfate is much more easily dissolved. If more than about 0.25 nig. of quinquevalent antimony is pieaent after fiiining TI ith 4 f i n ic acid, the antimony is hy-
+
+
V O L U M E 28, NO. 8, A U G U S T 1 9 5 6 drolyzed on dilution with water previous to the carbon tetrachloride extraction, and germanium is lost through coprecipitation. When more than t,races of antimony are present in the sample to be analyzed, the antimony must be reduced t o the trivalent state with hydrazine sulfate before dilution with water. Iron and titanium cause no trouble when present separately. When present together, no difficulty is encountered if the sample is fumed with perchloric acid before the carbon tetrachloride extraction. On the other hand, if the sample is fumed with hydrazine sulfate before the extraction, a black precipitate appears which is insoluble in cool gAV hydrochloric acid. It dissolves if heat is applied, but the results obtained for germanium are invariably low. Use of Complexing Reagents. I t seemed prohable that in certain instances, where the concentration of interfering metals is known to be low, interference might be eliminated by the use of complesing reagents rather than by preliminary isolation of the germanium by carbon tetrachloride extraction. I n order to investigate the possibilities of such a method, it \vas necessary first to determine nhich metals interfere. Phen>-lfluorone reacts with several metals in ac.id solution to forni colored compounds, which vary in their stability tom-ards acid. The compounds of germanium and tin a ~ ' eparticularly st:il)le and can be formed in highlJ- acid solution. Others are produced slowly or not at :ill in strongly acid solution. Zisrhkaii and Cluley have been able to minimize interference in the photometric determination of germanium by maintaining a high acidity at color development. In the method described above, where the c,olor is developed a t pH 3.1, the solution is made highly acid just before the photometric measurement in order to destroy, :ts completely as possible, interfering metal-phenylfluorone caompounds. Some of the compounds are completely destroyed Iiy the acidificntion, n-hile others are only partially destroyed. I n order t o determine which metals ?-ield stable colored phenylfluoi.one conipounds, specifivity testa were made on 0.1-mg. portions of each of the 59 metals listed in Table 11. Each metal aliquot plus 1.5 ml. of sulfui,ic acid ( 1 1) TTas diluted t o 10 ml.; 10 ml. of p H 5 buffer plus 1 nil. of gum solution plus 10.0 nil. of phenylfluorone solution were added; the solutions were then alloived to stand 5 minutes, diluted to volume with hydro9), and measured photometi~ically. The only chloi,ic acid (1 metals that produced colored compounds a t pH 3.1 that were not completely destroyed upon snhequent acidification before photometric measurement were tin, antiniony(III), titanium, zirconium, hafnium, vanadium(J?), niobium, tantalumj molybdenum, tungsten, iron(III), nnd gnlliiim. The colors were of vai,ious intensities and hues, but a11 absorbed to some extent a t 510 mp. Iron(II), vanadiiini(IV), nnd antiniony(V) produced no cwlor with the phen,vlfliioronra. Sevei,al metals other thnn
+
+
Table 111. Determination of Germaniuni by Carbon Tetrachloride Extraction-Photometric JIethod No. 1 20 3 4a
Other Metals Added AS
AJ Sb
Sh __ Sn
Se, Te Z r , Ti, Ga Fe, V, Hi N o , ICii, Zn, Xi. Bi. C': Cr Fe. Ti Fe. Ti Fe Ti
Germanium Found. 5 41 40
IS
:?.i. ) 41 41 40
38 39 40
2 42 19 42 41
1275
those listed would probably interfere, if more than 0.1 mg. was used-for example, 0.2 mg. of bismuth reacts with the phenylfluorone to form an orange-pink color. Of the twelve interfering metals listed above, all but three cause high results in a germanium determination when color i3 developed a t pH 3.1. Zirconium, gallium, and ferric iron cause low results. Apparently, when appreciable amounts of metals that react with phenylfluorone are present, full color development is prevented, because germanium has to compete with the other metals for the limited amount of phenylfluorone available. As the colors due to zirconium, gallium, and ferric iron are appre9) ciably bleached upon dilution with hydrochloric acid (1 previous to the photometric measurement, the incompleteness of the germanium color development becomes apparent. (On the other hand, a t p H 1.3, the colors due to these three metals are not sufficiently bleached on addition of the hydrochloric acid, and results for germanium are high; a t p H 1.8, the reaction of the three metals with phenylfluorone is so suppressed that full color development of t,he germanium is permitted and the results obtained are again high.) Investigation of various complesing reagents has shown that the interference of 0.1-mg. portions of all but three of the interfering metals mentioned above can be completely suppressed, without appreciably reducing the color due to germanium itself, by adding 2 ml. of a loci, solution of ethylenediaminetetraacetic acid (EDT.l) just before addition of the phenylfluorone. The interference due to antimony(IIIj, molybdenum, arid niobium is reduced but not eliminated. However, the interference of antimony can be eliminated by oxidizing it to the quinquevalent state previous to color drvdopment. The most convenient method for performing this oxidation is to fume with perchloric acid. The oxidation is not complete ( J ) , but the slight amount of antiniony(II1) that remains is sufficiently complesed by the EDT.4 to prcvent interference. The interference of mol\,bdenuni and niobium can be prevented by adding 2 ml. of a 3% solution of hydrogen peroxide prior to addition of the buffer, gum, EDTh, and phenylfluorone. The perchloric acidE D T A method yields very satisfactorj- resul the presence of 0.1 mg. of any of the metals listed in Table 11. However: the method is of limited applicabilitJ-, because not much more than a few tenths of a milligram of interfering metals ran be complet,ely complexed lrith the recommended amounts of hydrogen peroxide and EDTA. During the present investigation, it was noted that all the metals that interfere in the photometric determination c m he precipitated from strong acid solution with cupferron ( 5 ) . Attempts to make this the basis of a new method of isolating the germanium were not successful. Removal of the interference by gravimetric separation with cnpferron or by solvent extraction of precipitated cupferrates into chloroform was tested. Several of the. interfering metali !Yere incompletely removed, and in the estraction procedure, difficult?- due to the insolubility of tantalum cupferrate in chloroform was encountered (6). I t is evident that the cupferron separation method cannot compete with the distillation or carbon tetrachloride extraction methods for the isolation of the germanium. However, the cupferron estraction method has proved to he usrful for removing most of the interference previous to a determination in which hydrogen peroxide and EDTA are used as complesing agents. I n this manner the range of applicability of the complexing method is appreciably increased. I n certain instances, where appreciable amounts of interfering metals are present in the sample to be analyzed, it may be desirable to use hydrogen peroxide and E D T A in the color development, following the separation of the germmimi by carbon tet rachloride est ract ion.
+
EXPERIMENT.. L a Sample fumed Ir-ith hydrazine sulfate rather t h a n peichloric acid before carbon tetrachloride extraction.
I n order to test the proposed method, synthetic sample solutions were prepared and analyzed as dirwtrd. Each sample solu-
ANALYTICAL CHEMISTRY
1276 tion was made up to contain 40 y of germanium plus 100 y of more Of j9 Of the more encountered All samples were fumed with perchloric acid before the carbon tetrachloride extraction. T h e results are shown in Table 11. order to investigate the effectof larger amountsof impurities, the experiment was repeated using 40 y of germanium, plus 10 mg. of one or more of the most commonly encountered metals (Table 111). All but five of the samples were fumed with perchloric acid before the carbon tetrachloride extraction. The low results for germanium shown in Nos. 3, 11, and 13 are caused by precipitation of the antimony, chromium, or titanium. I n No. the precipitated chromium sulfate was successfully disPolved and germanium quantitatively recovered.
One Or
LITERATURE CITED
(1) Cluley, H. J., Analyst 76, 523 (1951). (2) Ernst, R. G., U. S.Metals Refining Co., Carteret, N. J., private
communication.
(3) Gillis, J., Hoste, J., Claeys, A., Anal. Chim. Acta 1, 302 (1947). (4) Luke, c. L., Campbell, E.,ASAL. CHEW25, 1588 (1953). (5) Lundell, G. E. F., Hoffman, J. I., “Outlines of Methods of
Chemical Analysis,” p. 118, Table 71, Wiley, New York, 1951.
(6) Milner, G. W. C., Barnett, G. A., Smales, A. A., Analyst 80, 380
(1955). (7) Schneider, W. A , Sandell, E. B., Milikrochim. Acta 1954, 263. (8) StricMand, E. H,, ~~~l~~~ 80, 548 (1985).
(9) Zischkau, C., American Smelting and Refining Co , South Plain-
field, N. J., private communication, May 1948.
RECEIVED for review January 14, 1966. Accepted M a y 9,1956. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh. P a . , February 1956.
Photometric Determination of Tin with Phenylfluorone Determination of Tin in lead and 1% Antimony-lead Alloys C . L. LUKE Bell Telephone Laboratories, Inc., Murray Hill, N. J. A photometric phenylfluorone method for the determination of microgram quantities of tin in organic and inorganic samples has been developed. Interference from other metals is eliminated by separating the tin from the bulk of the sample and then isolating i t by means of carbamate-chloroform extractions before making the photometric determination. The new method has been adapted to the determination of tin in lead and 1% antimony-lead cable sheath alloys.
B
ECAUSE available photometric methods for the determination of tin lack specificity and sensitivity ( 6 ) , a new method was needed. The fact that tin interferes seriously in the determination of germanium with phenylfluorone ( 4 ) made it probable that this reagent could be used for the determination of tin This proved to be true. Sensitivity is high, and by employing suitable separations before the photometric determination, complete specificity can be achieved. Tin can be determined in most metals and alloys, if it can be isolated sufficiently for the photometric determination. Thus, the method has been adapted to the determination of tin in lead and in 1% antimony-lead alloys used in the manufacture of telephone cables. The method should also be useful in the determination of tin in organic samples. APPARATUS
A Beckman Model B spectrophotometer, with absorption cells having a light path of 1 cm., n-as used. REAGEIVTS
STANDARD TIN SOLETION (20 y of tin per ml.). Transfer 0.2000 gram of pure tin metal to a 250-ml. Vycor conical flask, add 10 ml. of sulfuric acid, and heat on a Meker-type flame to dissolve the metal. When solution is complete, heat t o copious fumes to expel sulfur dioxide. Add 30 ml. of sulfuric acid, cool, and then add about 125 ml. of n-ater. Cool to room temperature, transfer to a 200-ml. volumetric flask, dilute to the mark, and mix. Ignore the presence of the globule of sulfur. Transfer 20.0 ml. of the solution to a 1-liter volumetric flask. Add 300 ml. of cool sulfuric acid (1 2), dilute to 950 ml., cool to room temperature, dilute to the mark, and mix.
+
CARBAMATE SOLUTION.Dissolve 2 grams of Eastman‘s diethylammonium diethyldithiocarbamate in 200 ml. of chloroform. Prepare fresh each day as needed. THIOGLYCOLIC ACID SOLUTION. Dilute 20 ml. of thioglycolic acid to 200 ml. with water and mix. POTASSIUM IODIDE-ASCORBICACID SOLUTION. Dissolve 6 grams of potassium iodide lus 1 gram of ascorbic acid in 40 ml. of water and mix. Prepare 8 e s h each day as needed. HYDROGEN PEROXIDE (3y0). Dilute 5 ml. of hydrogen peroxide (30%) to 50 ml. with water. BUFFERSOLUTIOX ( p H 5 ) . Dissolve 900 grams of hydrated sodium acetate, NaC2H302 3H20, or 540 grams of the anhydrous salt in about 700 ml. of water by warming on a hot plate. Filter with suction through a Whatman No. 40 paper and transfer to a 2-liter volumetric flask containing 480 ml. of acetic acid. Cool, dilute to the mark with water, and mix. GUMARABICSOLUTIOK.Dissolve 0.5 gram of powdered gum arabic (gum acacia) in 50 ml. of hot water by stirring. Filter with suction through a Whatman No. 42 paper on a platinum cone. Prepare fresh each day as needed. PHENYLFLUOROKE SOLUTION.Transfer 0.0300 gram of phenylfluorone (2,3,7-trihydroxy-9-phenyl-6-fluorone, obtainable from Jasonols Chemical Corp., Brooklyn, N. Y.) to a 100-ml. beaker. Add 50 ml. of methanol and 1 ml. of hydrochloric acid. Stir until dissolved. Transfer to a dry 500-ml. volumetric flask, dilute to the mark with methanol, and mix. This solution is stable for a t least a month. Do not store in a polyethylene bottle. CUPFERRON SOLUTION.Dissolve 1 gram of cupferron in 100 ml. of water. Prepare fresh each day as needed. COPPERSULFATE SOLUTIOX.Dissolve 0.5 gram of copper sulfate, CuSO4 5H20, in 100 ml. of water. TARTARIC ACIDSOLUTION. Dissolve 1 gram of tartaric acid in 100 ml. of water. LEADNITRATESOLUTIOS. Dissolve 15 grams of lead nitrate in 500 ml. of water. PERCHLORIC ACID-NITRIC ACID MIXTURE. Mix 50 ml. of perchloric acid (70y0)with 10 ml. of nitric acid. POTASSIUM PERMANGANATE SOLUTION.Dissolve 1 gram of potassium permanganate in 100 ml. of water. MASGASESENITRATESOLUTION.Mix 5 ml. of manganese nitrate (50% solution) with 50 ml. of water. GENERAL PROCEDURE
Preparation of Calibration Curve. Transfer 0, 1.0, 2.0, 3.0, and 4.0 ml. of standard tin solution (20 y of tin per ml.) to 125-ml. conical flasks. Bdd enough sulfuric acid so that each flask contains 5 ml. of the acid, dilute to 50 ml. with water, and cool t o room temperature. Transfer the sample to a 125-ml. Squibb-type separatory funnel. Add 25 ml. of carbamate solution, shake momentarily, relieve the pressure in the funnel, and then shake vigorously for
