of Ciz or more. Results should be expressed in terms of micromols.
Chemical Co., and the Procter and Gamble CO.
ACKNOWLEDGMENT
LITERATURE CITED
This work is a direct outgrowth of the long range cutaneous permeability studies conducted by Irvin H. Blank, without whose invaluable advice and encouragement this paper would not have been written. Pure anionic surfactants were obtained through the courtesy of the Colgate-Palmolive Co., the Lever Brothers Co., the hionsanto
(1) Conn, H. J., “Biological Stains,” 5th ed., p. 137, Biotech Publications, Geneva, N. Y . , ( 1946). (2) Faust. S. D.. Wute;r & Sewage Works 100, 242 (1953’). (3) Jones, J. H., J. Assoc. O$c. Agr. Chemists 28, 398 (1945). (4) Longwell, J., Maniece, W. D., Bnalyst
.,
80, 167 (1955). (5) Lundgren, H. P., Teztile Research 15,
J. Am. Chem. SOC.63.2854 (i941). (6) Moore, W. A., Kolbeson, R. A., ANAL. CHEM.28, 161 (1956). (7) Palmer, K. J., Galvin, J. A., J. Am. Chem. SOC.65,2187 (1943). (8) Task Group Report, JL Am. Water Works Assoc. 50*, 1343 (1958). RECEIVEDfor review July 13, 1961. Accepted January 26, 1962. Investigation supported by grants from the U. S. Army Chemical Corps (Contract DA 18108-405-CML-672) and from the Division of Medical Sciences of the De artment of Health, Education, and Wel?are, U. S. Public Health Service, National Institutes of Health (Grant RG-4760). 335 (1945): ,,
Spectrophotometric Determination of Microgram Quantities of Manganese in Uranium and Aluminum with 8-H yd roxyquinaldine KENJI MOTOJIMA, HlROSHl HASHITANI, and TSUYOSHI IMAHASHI Division o f Chemistry, Japan Atomic Energy Research Institute, Ibaraki-ken, lapan
b Microgram quantities of manganese are determined using the extraction of the 8-hydroxyquinaldine (2-methyl8-quinolinol) complex with chloroform and the spectrophotometric measurement of the extract. The method is applied successfully to traces of manganese in uranium after most of the uranium is removed b y tributyl phosphate extraction. This method, without preliminary separation of the metal, is used also for the determination of microgram quantities of manganese in aluminum. With both metals, the procedure is more sensitive, precise, and accurate than the usual permanganate method, and is useful for determining manganese down to the 1 -p.p.m. level.
S
PECTROPHOTOMETRIC
METHODS,
widely used for the determination of small amounts of manganese in many materials, are based on the permanganate ion formed 17ith a suitable oxidizing agent. This method has been applied to the determination of manganese in uranium (1, 3, 11 , l a ) . However, a t higher uranium concentrations, uranium interferes; therefore, solvent estraction methods have been used to separate uranium from manganese prior to the color development (6, IS). The present authors felt that the results of the determination of microgram quantities of manganese by these methods would not be accurate because of their low sensitivity and poor reproducibility. Therefore, a more sensitive and accurate method for application to reactor grade
uranium was desired. X sensitive extraction-spectrophotometric method using 8-quinolinol (‘7) was not suitable because of the difficulties in eliminating the interference of the other metals, especially aluminum, which occur as impurities in the reagents. HolTever, 8-hydroxyquinaldine (Zmethyl-8-quinolinol) has similar analytical properties (4, 10) to the parent compound escept that it does not form an aluminum complex ( 4 , 5, ‘7-9). I n this investigation, a method was developed for the extraction of the manganese 8-hydroxyquinaldine complex. It is thought that the extractionspectrophotometric method with 8hydroxyquinaldine for the determination of manganese may be of value in other applications. This method, without preliminary separation, was used for the determination of microgram quantities of manganese in aluminum. APPARATUS A N D REAGENTS
Apparatus. A Shimadzu, QR-50 spectrophotometer with a 1-cm. glass cell was used for all absorbance measurements. A glass electrode p H meter (Horiba, Model M-3) was used for p H measurements. An Iwaki Model KM shaker, Squibbtype 200-ml. separatory funnels graduated a t 10, 50, and 100 ml., a special pipet for taking exactly 10 ml. of chloroform, and 30-ml. glass-stoppered Erlenmeyer flasks were used for the extraction. Reagents. Standard Manganese Solution. A stock solution containing 1.00 mg. of manganese per ml. was
prepared by dissolving pure manganese metal in hydrochloric acid. Solutions containing 5 and 1 pg. per ml. were obtained by dilution. Uranium Solution. A solution containing 0.1 gram of uranium per ml. was obtained by dissolving the corresponding amount of U02C12.3H20 (Yokosawa Chemical Co., Ltd., reagent grade) in water. Aluminum Metal. Pure metal, 99.99% grade (Osaka Aluminum Co., Ltd.) was used. 8-Hydroxyquinaldine Solution (2y0). Two grams of the reagent (Tokyo Chemical Industry Co., Ltd.), which had been purified by steam distillation, was dissolved in 5 ml. of glacial acetic acid by heating, and this solution was diluted to 100 ml. with water. This solution is stable for a week or longer. Chloroform. Chloroform was purified by washing several times with sulfuric acid, aqueous alkaline solution, and then water, drying over anhydrous calcium chloride, and then distilling. The chloroform used was also recovered by this method. TBP-Chloroform Mixture, 60% v./v. About 600 ml. of tributyl phosphate (TBP) was mixed with 400 ml. of chloroform. The mixture was shaken with a 5% solution of sodium carbonate to remove mono- and dibutyl phosphate, and washed several times with water. This was equilibrated by shaking with 6 M hydrochloric acid before use. The mixture used was recovered in the same way. EDTA Washing Solution. Fifty milliliters of 1% disodium hvdrorren (ethylenedinitrilojtetraacetate (EDTA) solution was diluted to 600 ml., and the pH of the solution was adjusted to 11 to 12 with sodium hydroxide solution before use. VOL 34, NO. 4, APRIL 1962
571
06
\
02
W A V E .EhGTH
-
Figure 1. Absorption spectra of 8hydroxyquinaldine complex of manganese and iron extracted with 10 mi. of chloroform 1. 2. 3. 4.
20 p g , of manganese 40 pg. of manganese 5 0 p g . of iron Reagent blank against chloroform
All other reagents were prepared from reagent grade chemicals. PROCEDURE
General Procedure and Preparation of Calibration Curve. About 50 ml. of slightly acid solution containing 2 to 60 pg. of manganese is treated with 3 ml. of 2% 8-hydroxyquinaldine, and the pII of the solution is adjusted to 11.0 to 12.4 with sodium hydroxide solution. The resulting solution is transferred to a separatory funnel and the volume is brought to 100 ml. An extraction is made with exactly 10 ml. of chloroform by vigorous shaking for 1 minute. The chloroform layer is drawn off into an Erlenmeyer flask containing 1 gram of anhydrous sodium sulfate and shaken to remove droplets of water. The absorbance of the extract is measured a t 395 mp, using a blank as reference. The calibration curve is prepared by taking 4 to 100 p g . of manganese and by treating as mentioned above. The relationship between concentration and the absorbance is linear for up to 60 pg. of manganese. Determination of Manganese in Uranium. Not more than 3 grams of uranium metal is weighed into a 100ml. beaker and treated with hydrochloric acid. After decomposition is complete, potassium chlorate solution is added to obtain a clear solution. In this case, 20 ml. of 6M hydrochloric acid and 5 ml. of 4% potassium chlorate solution are suitable for each gram of uranium. Heating is continued for a few minutes to expel excess chlorine. When the sample is a uranyl salt such as nitrate, chloride, or sulfate, the weighed sample is dissolved in about 30 ml. of 6 M hydrochloric acid. In the case of the oxides, the sample is dissolved with a necessary amount of nitric acid and then diluted to about 30 ml. with 6 M hydrochloric acid. 572
ANALYTICAL CHEMISTRY
The dissolved sample solution is transferred to a separatory funnel and shaken with three 20-ml. portions of the TBP-chloroform mixture t o remove most of the uranium. After being washed with chloroform to remove the remaining TBP, the aqueous solution is transferred to a beaker and heated gently t o expel the droplets of chloroform, and the volume is reduced t o about 5 ml. by evaporation t o expel most of the hydrochloric acid. ilfter being diluted to about 50 ml., the resulting solution is treated with 5 nil. of 30% ammonium citrate solution and 3 ml. of 2% 8-hydroxyquinaldine solution, and the pH is adjusted to 11.4 t o 12.4 with sodium hydroxide solution. After 1 ml. of 5% potassium cyanide solution is added, the resulting solution is transferred to a separatory funnel and the volume is brought t o 100 ml. Then the extraction is made by adding exactly 10 ml. of chloroform and shaking vigorously for 1 minute. The chloroform layer is transferred to another separatory funnel containing about 10 ml. of EDTA washing solution, and is washed by shaking for 1 minute. Manganese is determined by measuring the absorbances of the extract a t 395 and 580 mp, using a blank as reference. In this case it may be necessary to make a correction for the iron most of which seems to be present in the citrate and in the sodium hydroxide solution used. This correction can be made by using the following formula:
where, C M n is micrograms of the manganese present, A395 and Asso are absorbances measured a t 395 and 580 mp respectively, and a%:, a:&, a,”,:, and a::: are absorbances per microgram of manganese and iron a t 395 and 580 mp, respectively. The values obtained from the experiments were: a!:; = 0.0195
a!% = 0.0007
afo = 0.00820
aE5 = 0.00861
Determination of Manganese in Aluminum. Not more than 2 grams of aluminum metal is taken in a beaker containing 10 ml. of 20% tartaric acid solution and 4 ml. of 5y0potassium cyanide solution. After 10 ml. of 25% sodium hydroxide solution is added, the beaker is heated to dissolve the sample. When dissolution is complete, the volume of the solution is brought to about 50 ml., and 3 ml. of 2% 8-hydroxyquinaldine solution is added, and the pH is adjusted to 11.4 to 12.4 with ammonium chloride solution. The resulting solution is transferred to a separatory funnel and the volume is adjusted to 100 ml. The extraction is made with 10 ml. of chloroform as given in the general procedure. The chloroform layer is transferred to another separatory funnel containing about 10 ml. of EDTA washing solution, and the extract is washed by shaking for 1 minute. The absorbances of the extract are measured as described in the procedure for uranium.
9
I3
, I
12
13
PH
Figure 2. Effect of pH on extractability of manganese-8-hydroxyquinaldine complex Each contained 2 0 pg. of manganese 1. Nouranium 2. In presence of 5 0 mg. of uranium and 5 ml. of 30% ammonium citrate solution
In this case, it niay be necessary to make a correction for the iron. The formula as given in the procedure for manganese in uranium is used. EXTRACTION OF MANGANESE-S-HYDROXYQUINALDINE COMPLEX
Wavelength. The manganese complex of 8-hydroxyquinaldine extracted with chloroform has an absorption maximum at 395 mp as seen in Figure 1, and this wavelength has been adopted in the present investigation. Effect of Variables. PH. -4series of several solutions, each containing 30 pg. of manganese, xas treated with 3 ml. of 8-hydroxyquinaldine solution and enough ammonium hydroxide or sodium hydroxide to give the pH range from 4 to 13. Then extractions were made and the absorbance of the extracts was measured by the above procedure. The measurements of pH were made on the aqueous layers after ex%raction and the results are shorrn in Figure 2. Extraction is quantitative a t the pH range from 11.0 to 12.4 AMOUNT OF REAGEST. When more than 2.0 ml. of 2% 8-hydroxyquinaldine solution was used, the absorbances were reasonably constant. Therefore, 3 ml. of the reagent solution was sufficient. SHAKING PERIOD.The quantitative extraction of the manganese complex with chloroform seems to be attained by vigorous shaking for 30 seconds. STABILITY.The absorbance of the dried chloroform extract of the manganese complex of 8-hydroxyquinaldine was unchanged for a t least a week. OTHERSUBSTANCES. The influence of some of the anions was investigated. Relatively large amounts of nitrate, chloride, sulfate, tartrate, and cyanide ions do not interfere with the extraction of manganese (Table I). As the amount
than 70% (v./v.) of TBP, however, Table 11. Effect of Hydrochloric Acid the separation of two layers, the Concentration on TBP Extraction. aqueous solution and the TBP-chloroform mixture, is inadequate and 60% ManHydro(v./v.) of TBP was used. Leaving ganese chloric Added, Found, Acid the hydrochloric acid concentration Substance M1. pg. Concentraconstant, uranium was extracted in the tion Kumbers HC1 (ea. 12-11) 5 30.5" presence of nitric acid. The results of Aq. of hlanganese 10 30.3" showed that the uranium and iron exSoln., A1 Extraction Found, pg. 30.4a HKOs (ca. l5M) 5 tractabilities and the manganese de10 29. 8a 4 4 20.0 HzS04 (ca. 18J2) termination were not affected. 5 30.1a 5 3 20.0 10 30. 4a 6r 3 20.7 OTHER IKTERFEREKCES.Table I11 Tartaric acid (2OC,4,) 5 2 20 0 s h o w the effect of foreign metals on the manganese determination, when the recommended 8-hydroxyquinaldine extraction procedure is used, Some of these metals may be removed in T B P a Each contained 2 grams of uranium and 20 pg. of manganese. Each extraction extraction. Aluminum does not form a made from 30 ml. of aq. soln. with 20 ml. complex with 8-hydroxyquinaldine (4). of TBP-chloroform mixture. 6 20.6b Cadmium, chromium, gallium, molyb8 20.23 denum, niobium, strontium, tantalum, 10 19.0b titanium, vanadium, tungsten, zinc, a Thirty pg. of manganese tested. of manganese, hence tlie correction and zirconium are not extracted in this Twenty pg. of manganese tested. as given in the procedure may iiot be p H range. Copper and some of nickel practical. Honei-er, as noted, TBP and cobalt are extracted, but these extraction 1% as carried out from hymetals can be masked easily by the drochloric acid medium to extract the addition of potassium cyanide. Magof citrate is increased, the p H range for iron together rrith uranium. Then nesium, thorium, and lead are partly the quantitative extraction of manthe formula should be applied to corextracted as 8-hydroxyquinaldine comganese complex becomes slightly limited, rect for the microgram quantities of plexes. The interferences of these as shov-n in Figure 2. When 5 ml. of iron which may be present in the metals can be completely eliminated 30y0 ammonium citrate solution is ammonium citrate and sodium hyby washing the extract with EDTA added, the p H range is betneen 11.4 droxide. washing solution. The selectivity of to 12.4. RESULTS.Recovery tests mere carthe proposed method is very high, as iilthough EDTA completely preried out by analyzing Kew Brutiswick the interference due to the foreign ions vents the extraction of manganese, Laboratory (SBL) uranium oaide samis negligible, ivith the exception of the extracted manganese complex in ple KO.65-1 with added manganese. indium and iron. The interference of chloroform is not affected by shaking I n this experiment, the sample was indium does not seem to be important, with EDTA solution (pH 11to 12). dissolved in concentrated nitric acid because reactor grade uranium conand hydrochloric acid ivas added to the tains a negligible amount of this elesolution to adjust the acid concentrament. DISCUSSION AND RESULTS tion range t o 5 to 6111. The TUP exELIhIIKATIOK O F ISTERFERESCC OF Manganese in Uranium. REMOVAL IRON. The amount of iron, present traction and manganese determination OF URAXIUM.Since uranium forms a nere carried out according to the recas an impurity in the reactor grade diuranate precipitate in alkaline ommended procedure. The results uranium, is usually greater than that medium, a suitable complexing agent for uranium is desirable for the separation of manganese by the %hydroxyquinaldine extraction method. Citrate Table 111. Effect of Foreign Metals on Manganese Determinationa does not interfere with manganese Foreign Added,b Manganese Relative extraction but it is not effective in Metal lg. Source Found, l g . Error, 70 complexing a t high uranium concentra+0.5 AI 20.1 200 tions. Five milliliters of 30% am+1.5 Bi 20.3 200 monium citrate prevents only 50 mg. +1 .o Cd 20.2 200 of uranium from precipitating as the -0.5 19.9 co 200 +1.5 Cr(II1) 20 3 200 diuranate in this p H range. There-1.0 cu 19.8 200 fore, a preliminary separation of ura-1.0 Ga 20.0 130 nium is necessary. 42.0 $110 In 90 4 T B P extraction method was Mg 19.9 -0.5 200 +l,O Mo(V1) 20.2 adopted to remove uranium. The 200 -1.0 Ni 19.8 200 extraction was carried out from hydro-1.0 200 19.8 WV) chloric acid medium to remove iron a t -2.0 Pb 200 19.6 the same time. As the hydrochloric $2.0 Sr 20.4 100 acid concentration is increased, the +o.o 200 20.0 Ta(V) Th +2.0 2 00 20.4 extractability of uranium becomes much +l.O Ti(IV) 200 20.2 greater. However, when the acid +0.5 200 20.1 V(V) concentration is increased by more +2.0 200 a(VI) 20.4 than 711, manganese is partly extracted Zn +1.0 200 20.1 Zr(1V) -0.5 200 19.9 with uranium (Table 11). When the concentration of T B P in TBP-chloroa Each solution contained 20 l g . of manganese. form mixture becomes larger, uranium is * Each quantity does not represent the maximum permissible amount. extracted more effectively. With more Table I. Effect of Anionic Substances on Determination of Manganese
VOL. 34, N O . 4, APRIL 1962
573
Table IV. Recovery of Manganese from Uranium Sample Solution.
Re-
Manganese, fig.
Recovery, covered %
Added
Found 10.2* 2.5 12.9 2.7 108 5.0 15.2 5.0 100 10.0 20.4 10.2 102 15.0 25.8 15.6 104 20.0 31 .O 20.8 104 0 Each contained 0.476 gram of uranium (4/25 aliquot of 3.500 grams of UaOa, NBL, NO.65-1). b Mean value of 14 determinations shown in Table V.
Table V.
Comparative Analyses of Manganese in NBL U308 Spectrographic Standard Samples
Sample No. 65-1
-4ddedo
65-2
10
65-3
5
65-4
2
65-5
0
a
indicate that the method provides reasonably reproducible figures and is very reliable (Table IV). A number of the above mentioned uranium oxide samples were analyzed (Table V). The values obtained for manganese were essentially in agreement with those furnished by NBL (2), with the exception of sample 65-1. The standard deviation obtained (0.3 p.p.m.) confirmed the suitability of this method. The proposed method is more sensitive than the permanganate method (6, IS), Finally, the results of the analysis of
Manganese in Uranium, P.P.M. Permanganate Method Proposed Method Founda Found 24, 22, 26 22.0,21.4,21.1, 21.1,21.4,21.1, 21.2, 21.8, 21.8, 21.8, 21.2, 20.9, 21.5, 21.6 Av. 24 21.4 f 0.3 12, 12, 13 11.3, 11.0, 10.8, 10.7, 10.7, 10.4, 10.7 AV. 12 10.8 f 0 . 3 7, 7, 5 6.1, 6.1, 5.9, 5.6, 6.0, 5.7 Av. 6 5.9 f 0.2 4, 3 , 2 3.2, 3.0, 3.1, 2 . 8 Av. 3 3.0 f 0.2 0 , 0.5, 0.9 1.3, 1.2, 0.8, 0 . 9 Av. 0.5 1.1 f 0.2
20
From (4). Table VI.
Determination of Manganese in Uranium Metal
Absorbance Measured Found At At Sample 395 mp 580 mp pg. P.P.M. .4 0.244 0,090 8.0 5.0 0.260 0.103 8.1 5.1 0 147 B 1.60 0.240 4.6 2.9 0 115 3.1 0.214 5.0 0 123 1.5 1.60 0.174 2.4 C 0.140 0.190 2.3 1.4 2.0 D 0.103 1.60 0.170 3.2 2.1 0.105 0.174 3.4 1.60 E 0.245 6.6 4.1 0.115 1.2 0,099 0.229 6.7 2.00 0.317 NBL-KO. 16 9.5 4.8 0.135 0.133 4.7 0.314 9.4 0.132 9.4 4.7 0.313 4.8 0.203 0.393 9.6 Samples il to E nere produced at Atomic Fuel Corp., Ibaraki-ken, Japan. They contain other impurities (p.p.m.): A1 4 12, B < 0.1, Cd < 0.1, C 280 N 390, Co < 1, Cr 5, Cu 1 -3, Fe 103 109, Mg 4 " 8 , Mo < 1, Xi 32 ~ 3 8 Si, 20 N 43, V < 0.1. Certified value for manganese of NBL standard uranium metal sample No. 16 is 6 p.p.m. Taken, Grams 1.60
-
-
Table VII.
Added
Recovery of Manganese from Aluminum Sample Solution.
Manganese, pg. Found
2.0 5.0 10.0 15.0 20.0 30.0
Recovery, Recovered*
%
2.3
115 112 103 104 102 101 100
5.6
10.3 15.6 20.3 30.4 30.1; 30.9; 30.2 41.0 42.0, 40.8, 40.2 40.0 a One gram of aluminum metal taken in each experiment. * Mean value of 3 determinations.
574
0
ANALYTICAL CHEMISTRY
some uranium metals are shown in Table VI. This method can be used for the determination of manganese in uranium down to the 1-p.p.m. level and should be useful in uranium oxides and other uranium salts. Manganese in
Aluminum.
DIS-
Pure aluminum is not easily dissolved in hydrochloric acid, but is rapidly dissolved in sodium hydroxide solution. I n this work, tartaric acid was used t o prevent the hydrolysis of manganese. Two grams of tartaric acid is sufficient to mask 5 mg. of manganese, which mas ascertained by the treatment of an alloy sample containing 1% of manganese. SOLUTION.
ELIMINATION OF INTERFEREWE OF IRON.As with uranium metal, the amount of iron present as an impurity in aluminum metal is usually greater than that of manganese. By adding potassium cyanide, iron can be masked as ferrocyanide immediately on dissolution of the sample, and correction for iron in the reagents made by the formula. In this case, 4 ml. of 5% potassium cyanide solution is sufficient to mask 2 mg. of iron. OTHERINTERFERENCES. The interference of other metals and their elimination, as discussed in relation to the determination of maganese in uranium, are also pertinent to the procedure for aluminum. With the exception of indium, the effect of their presence is made negligible, and the proposed method is shown to be highly selective The effects of tartrate, cyanide, and ferrocyanide on the manganese determination were examined. These substances are added or produced when the sample is dissolved. Tartrate and ferrocyanide ion, and potassium cyanide do not interfere with the determination of manganese, when present in relatively large amounts or less than 0.5 gram, respectively (Table I). RESULTS. Recovery tests were carried out by analyzing aluminum metal both with and without the addition of manganese. -4 known amount of manganese solution was taken into a beaker and evaporated almost to dryness, and the aluminum metal was dissolved in the beaker according to the recommended procedure. The results indicate that the method provides reasonably reproducible figures and is very reliable (Table VII). -4number of aluminum metals were analyzed using the proposed method. The values obtained for manganese were essentially in agreement with those furnished by the producing companies (Table VIII). In the determination of aluminum, the proposed method is more sensitive and rapid than the ordinary permanganate method, and the results are precise and accurate. Time for a
single analysis of the metal sample is 40 minutes, including approximately -_ dissolution ofthe sample. . This method can be used for the determination of manganese in aluminum down to the 1-P-P.m- level when 2 grams of aluminum are taken. It should also be useful for the determination Of manganese in Other aluminum compounds. LITERATURE CITED
(1) Bane, R. IT.,U. S. Atomic Energy Comm. Rept. AECD-3130 (1951). (2) Clinckner, M, R., u. Atomic Energy Comm. Rept. NBL-143, 77 (1958). (3) Haslm, J., Russel, F. R., Analyst 77,464 (1952). (4) Hollingshead, R. G. W., “Oxine and its Derivatives,” Vol. 111, p. 757, Butterwyorths Scientific Publications, London, 1956. (5) Hynek, R. J., Wrangell, L. J., AXAL. CHEM.28,1520 (1956). (6) Ishii, D., Bunseki Kagaku 9, 698 (1960). (7) Merritt, L. L., Jr., Walker, J. IC.,
Table VIII.
Determination of Manganese in Aluminum Metal
Sample, Manganese Found, P.P.M. 2.00 7.8, 7 . 9 Av. 7.9 2 1.00 36.4, 35.5, 35.3 Av. 35.7 3 0.500 76.4, 74.4, 76.4 Av. 75.7 4 1.00 15.6, 15.9 Av. 15.8 5 Si 0.18, Fe 0.46, Cu 0.01, Mn 0.01 0.300 111, 107, 111 A V . 110 4 Analyzed at each producing company by the permanganate-colorimetricmethod or
No. 1
Impurities,” % Si0.052, Fe0.057, Cu0.0015, Ti0.0071, V 0.002, Mn 0.0008 S i 0 . 2 3 , FeO.156, Cu0.0048, Ti0.0075, V 0.003, Mn 0.0034 Si 0.863, Fe 0.688, Cu 0,0085, Ti 0.0113, V 0.005, Mn 0.0069 Si 0.06, Fe 0.15, Cu 0.01, Mn 0.001
Taken, grams
spectrographic method-
IND. ENG.CHEM., ANAL. ED. 16, 387 (1944). (8) Motojima, K., Bull. Chem. SOC.Japan 29,71,455 (1956). (9) Motojima, K., Hashitani, H., Ibid., 29,458 (1956). (10) Motojima, K., Hashitani, H., Bunseki Kagaku 9, 151 (1960). (11) Rodden, C. J., U. S. Atomic Energy
Comm. Rept. TID-7555, 24 (1958).
(12) Rodden, C. J., “Analytical Chemistry
of the Manhattan Project,” McGrawHill New York, 1950. (13) d. S. Atomic Energy Comm. Rept. IGO-AM/S-I 19 (1958).
RECEIVEDfor review June 14, 1961. Accepted January 2,1962.
Removal of Sulfur Fumes by Lead Dioxide in the Combustion Method for Carbon in Iron and Steel WESLEY M. PETERSON The A. H. Pufnam Co., Rock Island, 111.
b The use of lead dioxide for the removal of sulfur dioxide in the combustion method for carbon in iron and steel is described. The properties of the lead dioxide must be such that the temporary retention of carbon dioxide for an excessive length of time is prevented. This is accomplished by depositing thin films of the material upon chemically inert bodies such as quartz sand grains. In this surface form, a single charge will function for more than 1000 cast iron carbon determinations without loss of accuracy.
A
for the sulfur dioxideremoving agents which are used in the determination of carbon in iron and steel by the direct combustion method is desirable. Solutions of potassium permanganate or potassium dichromate which contain sulfuric acid convert sulfur dioxide into this acid completely in an oxidationreduction reaction. The bulk of moisture absorbed by the gaseous stream is subsequently removed with concentrated sulfuric acid, while acid mists are retained in an asbestos column. SUBSTITUTE
The special apparatus required by this method, the difficulty in obtaining blank-free carbon determinations using these corrosive liquids, and the necessity of renewing the drier frequently are marked disadvantages. Oxidized copper cloth, granular cupric oxide, and platinized silica jel are efficient substitutes, although these require specific elevated temperatures for their activity. This necessitates a specially designed heating unit. Dry absorption a t room temperatures is desirable from the point of simple and inexpensive combustion train design. Two absorbents have been advanced for this method. They are granular zinc (1) and granular hydrated manganese dioxide (6). A charge of 20-mesh zinc in a Fleming zinc jar will effect the complete removal of SO2 for approximately 100 low sulfur steel, 12 cast iron, or 3 sulfurized steel determinations. While the opinion is held that zinc does not remove SO2 ( 2 ) , it is evident that absorption capacity falls rapidly during use. Attempts to lengthen the service life of a charge with increased size lead to difficulties with perme-
ability. Thus the use of this material is limited to low sulfur steel carbon determinations. Freshly prepared granular hydrated manganese dioxide removes SO2 through a vigorous adsorption of the gas followed by chemical reaction. The removal is complete for cast iron and sulfurized steel determinations in continuous operation. Temporary retention of C02 is small enough to be satisfactory for high speed gravimetric determinations of carbon in steel. Because of these properties, hydrated manganese dioxide has largely replaced the materials described for the removal of SOz. No satisfactory substitute has been found for the high oxygen flow rates and short flushing times used in the eudiometric (gasometer) method for the determination of carbon in iron and steel. These advantages, however, are limited to carbon determinations with fresh charges of freshly prepared material. Although the adsorptive capacity for SO2 appears t o be little affected during use, the chemical activity diminishes rapidly, so that the entire charge is soon functional as a chemical reagent. ConVOL. 34, NO. 4, APRIL 1962
* 575
