V O L U M E 2 5 , N O . 9, S E P T E M B E R 1 9 5 3 chromatographic analysis after preliminary fractionation by other techniques. However, it serves well the purpose of illustration. Chromatographing an iso-octane solution of this fraction through a column prepared with 7.25 ml. of water yielded four distinct zones (Figure 10, A ) . When a column prepared with 5.8 ml. of water was used (Figure 10, B ) , it was found that the zones with peaks a t tubes 17, 26, and 29 in Figure 10, A , have been pushed out of the picture (peak tube 17, Fipurp 10, A , is altogether different spectrophotometrically from peak tube 23, Figure 10, B ) and the zone of tubes 4 to 7 has nox been separated into four new zones. The identity of the zones was determined by running their ultraviolet spectrum. When the column w a s prepared with only 2 ml. of water (Figure 10, C), it was found that the peak a t tube 12 (Figure 10, B ) had shifted to tube 48 and that their spectra were practically identical. Furthermore, the peak a t tube 4 (Figure 10, B ) had shifted only to tube 5 , while the peaks at tubes 8 and 23 did not materialize. When the sample was chromatographed with no m-ater added to the silicic acid (Figure 10, D),it was found that the band with the peak of tube 5 (Figure 10, C ) was separated into three distinct bands which represented about 73% of the material in the original band. An additive spectral curve obtained from the three zones (Figure 10, D ) was
1363
very similar but not identical with that of the m:ttr.ri:il t,ube 5 (Figure 10, C).
ill
peak
From the separations discussed it is seen that the sample has been srparated into nine distinct parts in thc, c~ffluc~nt rractiona. ACUNOWLEDGMENT
The authors wish to thank Harold J. E. Segrave for his assistance and interest in this work and (‘arl J. Wessel, National Reseal c:h C‘ounoil, for furnishing sonic of the phenols. LITERATURE CITED (1) Craig, L. C . , a n d Craig, D., “Technique of Organic C h e m i s t r y , ” Vol. 111,p. 171, New York, Interscience Publishers, 19.50. (2) M a r t i n , A. J. P., a n d Synge, R. I.. hl., Biochem. J., 35, 1358 (1941). (3) Stillson, G. H., Sawyer, D. IT.,arid H u n t , c‘. K., J . A m . Chem. Soc., 67, 303 (1945). (4) Koolfolk, E. O., et al., B u r . Mines, Bull. 487, 7 (1950). (5) Zahncr, R. J., a n d Swann, W. B., As.tr.. CHEN.,23, 1093 (1951). Aprils, 1953. Acccptcd
.I\iiie %,
1853.
Colorimetric Determination of Molybdenum with Mercaptoacetic AcidFRITZ WILL 1111, AND JOIlN EX. YOE Pratt Trace .inulysis Lmboratory, D e p a r t m e n t os C h e m i s t r y , Cinirersity of Virginia, CharlottesvilIe, Va.
The purpose of this investigation was to study the reactivity of mercaptoacetic acid with inorganic ions, in particular the molybdate ion, and to develop a colorimetric method for determining molybdenum, especially in materials containing large amounts of iron. Procedures have been developed for the colorimetric determination of molybdenum in the presence or absence of iron and also for the determination of both molybdenum and iron in the same aliquot. The method is simple and accurate and should be useful for the determination of molybdenum in steels, molybdates, and other materials, especially those containing large amounts of iron.
S
POT-PLATE studies showed that acetylmercaptoacetic acid gives a yellow color with molybdenum in acid solution; iron praduces a blue color in acid solution but the color fades immediately to colorless. In alkaline solution the iron complex is purplish-red. These color reactions were found to be revereible both in acid and in alkaline media. Mercaptoacetic acid (HS.CHI.COOH, also called thioglycolic acid, thioethanoic acid, and thiolacetic acid) gives color reactions similar to those of the acetyl derivative. However, since mercaptoacetic acid has a sensitivity of about 0.1 p.p.m. of molybdenum and is readily available in the pure state, it was preferable to investigate it rather than its acetyl derivative, Because the molybdenum complex is yellow and the iron complex colorless in acid solution, it appeared that mercaptoacetic acid might be used for the determination of molybdenum, even in the presence of iron. In fact, investigation has shown that both molybdenum and iron may be determined, the molybdenum being determined in an acid solution, where the iron complex is colorless, and the iron in an alkaline solution, where the molybdenum complex is colorless. Lyons ( 3 ) and Swank and Mellon ( 7 ) reported mercaptoacetic acid as a colorimetric reagent for total iron; the latter mentioned that molybdenum gives a yellow or orange color a t high con-
’ Present address, dluminum Co. of America, New Kensington, Pa.
centrations. Hamence ( 1 ) showed that mercaptoacetic acid could be used for the detection of molybdenum by the production of a yellow eolor in acid solution. Richter (6) and Xleyer ( 4 ) reported the use of the reagent for the determination of molybdenum but also used hydrazine sulfate in the process. Miller and Lowe (6) employed mercaptoacetic acid, but only as a reducing agent for molybdenum(V1) in the classical thiocyanate determination of the latter. In the investigation, detailed studies were made to determine the effect of a number of variables on the molybdenum-mercaptoacetic colored complex and to develop procedures for the colorimetric determination of molybdenum, in either the presence or absence of iron, and for the determination of both molybdenum and iron in the same aliquot. APPARATUS .4NI) REAGENTS
Instruments. Absorbancy measurements were made with a Beckman spectrophotometer, Model DU, using 1.00-cm. cells. All pH measurements were made with a Beckman glass electrode pH meter, Model G. Visual color comparisons were made in 50-ml. Nessler cylinders (tall-form). Reagent Solutions. Mercaptoacetic acid is a water-soluble, colorless liquid. A 5% solution (volume) of mercaptoacetic acid, neutralized with ammonium hydroxide, was used for most of the work. If impurities are present in the reagent, a slightly turbid
ANALYTICAL CHEMISTRY
1364 solution results after dissolving it in water. This turbidity usually disappears on neutralization. A freshly prepared reagent solution should be allowed to stand overnight and then any resulting precipitate should be filtered off before use. STANDARD MOLYBDENUM SOLUTION.A 1000-p.p.m. molybdenum solution was prepared by dissolving 1.8401 grams of dry ammonium molybdate tetrahydrate in water and diluting to 1 liter. It was standardized by precipitation with a-benzoinoxime, igniting the precipitate, and weighing as the oxide (2). The 1000-p.p.m. molybdenum stock solution was diluted to any desired concentration.
10 p.p.m. Mo-merwptoacetate pH*&O Ccm cell
seen in Figure 1 that absorption occurs only below about 330 mp. This curve is typical for those at the different pH values, showing that acidity has no pronounced effect upon the absorption characteristics of the reagent solution. Spot-plate tests showed that mercaptoacetic acid gives a yellow color with molybdenum in acid solution. Figure 1 shows that the molybdenum complex has a maximum absorption at 365 mp. The effect of pH on the color reaction was studied by taking absorbancy measurements a t 365 mp of solutions containing 10 p.p.m. of molybdenum and 0.4% (volume) of reagent a t various pH values, ranging from pH 1.25 to 8.50. The highest absorbancy occurs between pH 3 and 5 (Figure 2). REAGENT CONCENTRATION
The effect of reagent concentration on the colored complex was studied by taking absorbancy measurements a t 365 mp on solutions containing 10 p.p.m. of molybdenum, buffer solution (pH 4), and varying amounts of mercaptoacetic acid. The reagent concentration that produces the highest absorbancy was found to be 0.4% (volume) of reagent solution for each 25 ml. of solution. For a IO-p.p.m. molybdenum solution, this corresponds to a mole ratio of reagent to molybdenum of about 500 to 1, demonstrating that a large excess of reagent must be present for full color intensity of the complex. With much higher reagent concentrations, the color intensity decreases. This may be due to partial reduction of the molybdenum to a colorless complex by the excess reagent. RATE O F REACTION AND STABILITY O F THE COMPLEX
Figure 1. Absorption Curve for Molybdenum Mercaptoacetate
STANDARD IRON SOLUTION.A solution of ferrous ammonium sulfate was prepared by dissolving 7.022 grams of reagentgrade ferrous ammonium sulfate hexahydrate in about 300 ml. of distilled water containing 5 ml. of concentrated sulfuric acid, diluting to 1 liter, and mixing. The solution contained 1000 p.p.m. of iron and was diluted to any desired concentration as needed, several drops of concentrated sulfuric acid being added to prevent hydrolysis. No oxidation of the iron is necessary because the reagent determines total iron, iron(II1) being reduced by the reagent to iron(I1). BUFFERSOLUTIOK.A sodium acetate-hydrochloric acid buffer solution was found to be satisfactory. A buffer solution of p H 4 was prepared by mixing 50 ml. of 1 N sodium acetate solution with 35 ml. of 1 N hvdrochloric acid solution and diluting to 250 ml.
The formation of the molybdenum mercaptoacetate yellow complex is instantaneous and its intensity is stable for at least 30 minutes; only a 2% decrease in absorbancy occurs after 1 hour. The color may be stabilized by the addition of a few tenths of 1% of potassium chlorate. BUFFER SOLUTION
Absorbancies of solutions containing 10 p.p.m. of molybdenum and 0.4% (volume) of reagent were measured a t 365 mp, after varying amounts of the sodium acetate-hydrochloric acid buffer solution (pH 4) were added. Xeither 1, 3, or 5 ml. of the buffer per 25 ml. of solution showed variation in the absorbancy, but a volume of 5 ml. was chosen. BEER’S LAW
The molybdenum mercaptoacetate complex obeys Beer’s law over a concentration range of 4 to 15 p.p.m. of molybdenum at 365 mp; this is within the absorbancy range of about 0.2 to 0.7. SENSITIVITY O F REACTION
3.4C
;0.30
z0.2-
IO p,pm Mo I-cm. cell 365 mu
0.11
‘
1
2
3
4
5
k .I 6
7
8
PH
Figure 2.
Effect of pH on the Color Reaction
SOLUTIOSS OF DIVERSE IONS.Reagent-grade salts were used to prepare the solutions of the various ions. The stock solutions generally contained 1 mg. of the element per milliliter of solution. EFFECT OF pH
Aqueous solutions of mercaptoacetic acid are clear and colorless, whether basic or acid. This observation was confirmed by taking absorption curves from 220 to 700 mp at pH values of 2.66, 4.65, and 8.20 for a 0.4% (volume) reagent solution. It is
Fifty-milliliter solutions containing 0.4% (volume) of reagent, 5 ml. of buffer, and 0.10, 0.15, and 0.20 p.p.m. of molybdenum were prepared. These solutions were observed against a blank in both K’essler cylinders and with the Beckman spectrophotometer, The 0.10-p.p.m. molybdenum solution could not be distinguished from the blank in Nessler tubes. However, the 0.15p.p.m. molybdenum solution was readily distinguishable visually and gave an absorbancy measurement of O.OOF at 3G5 mp. Thus, as a conservative value, the practical sensitivity of the color reaction was taken to be 1 part of molybdenum in 7,000,000 parts of solution-Le., 0.15 p.p.m. of molybdenum. Spot-plate sensitivity tests were made by transferring 0.05 ml. of a standard molybdenum solution to a depression in a white porcelain spot plate, adding 0.05 ml. of the sodium acetatehydrochloric acid buffer (pH 4), and finally 0.05 ml. of a 5% (volume) reagent solution. The lowest concentration of test solution to give a color distinguishable from the blank was 10 p.p.m. of molybdenum. Thus, 0.57 of molybdenum in 0.05 ml. of solution may be detected on a spot plate.
1365
V O L U M E 25, N O . 9, S E P T E M B E R 1 9 5 3 Table I.
Tolerance to Diverse Ions Added as A1 (Nos)a AsCla Na2HAsO4 AuCls HsB03 BeClz Bi(N0s)a Cd ( Nos) z Cez(SOa)a Ce(SO4)z
KClOa
CO(N03)z
0.5 10 400
8
>zoo0 8 2 100 2
2 > 1400 (as ClOa -1 4
Cr(N0a)s Cu(N0dz FeSOI. (?rTHa)aS01 HgNOa HgClz hlgC12 MnClz Xi( Z J 0 a ) z Pb(SOs)? SbCls KazSiOs SnClz SnClr Tl(SO4) 2
Must be absent
NazWO4 Zn (SOa) z Xitrates Potassium salts Potassium acid phthalate Citric acid Oxalic acid Tartaric acid
1 >2000
uoz(~o3)2 voc12
Citrate Oxalate Tartrate
Limiting Concn., P.P.M.
1
2 hlust-be absent 1
10 300 20 2
4 6 8 10
2 2
2
>ZOO0 (each)
>SO00 (each) >5000
200 200 200
EFFECT O F TEMPERATURE ON THE REACTION
Twenty-five milliliters of the colored complex containing 10 p.p.m. of molybdenum, 0.4% (volume) of reagent, and 5 ml. of buffer showed no change in the color intensity over a temperature range of 15" to 35" C. EFFECT O F DIVERSE IONS
Reactions with Various Ions. Tests were made on spot plates with mereaptoacetic acid and the following 78 inorganic ions, in neutral, acid, and ammoniacal qolutions, wherever possible: d g + , A l + + + , AU(>la-, .Ss-+-, As04---, BOs---, Ba++, Ber-. BI+'T, Br-, COS--, Ca+-, C d - + , C e - + - , Ce+++', C1-, Co+-, C r + - + , Cs+, C u + + , D y + + + , E r - + T , Eu++', F-, Fe-+, Fe++-, Ga'-', G d + -+, Ge++++H f + + - + H g + Hg- -, I-, I n + + T ,IICIS--, K + , L a + + + , Li+, l I g + + , ' N n ' + , iIoOai-, S a - , Xb-++'+, N d + + , Si+", KO2-, Os*-+-, HPOIC-, P b + + , PdCla--, PtCla--, P r + + - , Rb+, ReOa-, R h + + + ,Ru'++, S--,Sb+-+,S c + + + ,SeOs--, Sios--, Sm+T+,Snf', S n + + + +Sr+?, , TaOa---, TeOl--, T h + + + - ,Ti+-+', TI+, Tm'++, E O 2 + + ,VO-+, WO4--, Y + + + ,Y b + - + , Zn+-, Z r + + - +
One drop of a 0.05% reaqent solution was added to 0.05 ml. of a 1000-p.p.m solution of the element, and any color formation or precipitate was noted. The following observations were made: Fe+++ and Fe++, unstable blue color in acid solution, purplishred color in alkaline solution; Cu++, dark brown precipitate in acidic and alkaline media. PdCI,--, yellow color in acidic and alkaline media: -4uCll-, UOa++, and Ce++-+, decolorized in acid; Hg+, black precipitate in acid; Se++++,orange color in alkaline solution; Xi++, dark green precipitate in alkaline medium; Ag+, light yellow color in alkaline and nitric acid media; Moo4--, yellow color in acid. Tolerance to Diverse Ions. Into a 23-ml. volumetric flask, 10 ml. of a 25-p.p.m. molybdenum solution were pipetted; t o this nas added the diverse ion. The pH was adjusted to 4, 5 ml. of buffer and 2 ml. of 5% (volume) reagent were added, and the solution was diluted to 25 m]. The final solution contained 10 p.p.m. of molybdenum and 0.4% (volume) of reagent. The p H was checked with the p H meter to ensure the optimum range of 3.5 to 4.5 and the color intensity was measured a t 365 mp,
An ion was considered to interfere with the molybdenum colored complex if the resulting solution differed by 0.005 in absorbancy from that containing molybdenum and no diverse ion. Table I summarizes the tolerances of the diverse ions as p.p.m. of the respective ion. Since S a + , K+, NOs-, SO4--, and C2HIOZ-were in the buffer and test solutions, these ions were not studied separately. ELI\IINATION OF IRON INTERFERENCE
Only 2 p.p.m. of iron can be tolerated under the set experimental conditions (Table I). Higher iron concentrations give low results for molybdenum, evidently because of the lack of sufficientexcess reagent to react with both molybdenum and iron. Accordingly, an excess of the reagent was added greater than that necessary for full color intensity of the molybdenum complex. In this case, for concentrations of 10 p.p.m. molybdenum, 10 p.p.m. iron, and 1% reagent (instead of 0.4%) no interference of iron was noted, but the color of the molybdenum complex faded rapidly. This confirms earlier experiments which showed that if a very large excess of reagent is present, the molybdenum complex fades, although a considerable excess must be present to obtain full color intensity. Since mercaptoacetic acid is a reducing agent, a large excess probably causes partial reduction of the molybdenum to a colorless complex and hence fading. The problem then was to find an oxidizing agent which would keep the molybdenum in the oxidation state for full color intensity but not consume the mercaptoacetic acid as a reducing agent. Potassium chlorate was found to be a satisfactory stabilizing agent for this purpose. With 10 p.p.m. of molybdenum and 0.4% (volume) of reagent, full color intensity is obtained immediately and undergoes only a slight fading (about 2%) after 30 minutes. When 0.2% of a potassium chlorate solution was present, fading was not observed until after 1.5 hours. Potassium chlorate appears to keep the molybdenum in the oxidized state for full color intensity but does not consume the reagent to such an extent as to cause fading because of the lack of excess reagent. On increasing the reagent concentration from 0.4 to 1% (volume) with 10 p.p.m. of molydenum and 0.2% of potassium chlorate, fading was not apparent until after 20 minutes. However, with no chlorate present, fading was instantaneous with such a large excess of mercaptoacetic acid. With 20 p.p.m. of iron, 10 p.p.m. of molybdenum, 1% (volume) of reagent, and 0.2% of potassium chlorate a t pH 4, no interference of iron resulted, and no appreciable fading occurred until after 20 minutes. On increasing the potassium chlorate concentration to 0.4%, the fading did not occur until after approximately 30 minutes. Increasing the iron to 50 p.p.m.. a solution containing 0.4% of potassium chlorate, 10 p.p,m of molybdenum, and 1% (volume) of reagent resultedinonly a slight iron interference; fading did not occur until after approximately 20 minutes. The latter solution had a molybdenum to iron ratio of 1 to 5 . Using the same reagent concentration but with a molybdenum to iron ratio of 1 to 60 (10 p.p.m. of molybdenum and 600 p.p.m. of iron), a 20% error in the molybdenum determination resulted. However, by increasing the mercaptoacetic acid from 1 to 1.4% (volume), the error was reduced to 3%. Hence, the mercaptoacetic acid procedure for molybdenum can be applied with a stabilizing agent (potassium chlorate) in the presence of appreciable amounts of iron, provided an excess is present-i.e., an amount sufficient to react with both the molybdenum and iron. IRON MERCAPTOACETATE
The color of the iron mercaptoacetate complex is due to a ferrous complex. Any ferric iron present is reduced to the ferrous state by the reagent; hence, a measure of total iron is obtained.
1366
ANALYTICAL CHEMISTRY
Spotplate tests showed that below pH 6 the iron coniplex is colorless and that above pH 6 it is purplish-red. The optimum pH range for the iron colored complex is 6 to 11. The maximum absorption occurs a t 535 mfi. Conformity to Beer’s law was tested by measuring the absorbancies of solutions at 535 mfi containing varying amounts of iron, 2 ml. of 5% (volume) reagent solution, and 2.5 ml. of 3 N ammonium hydroxide in a total of 25 ml. The solutions had a p H of 10. The optimum iron concentration was found to be 3 to 10 p.p.m. Potassium chlorate had no effect on the iron complex.
Table 11.
Salt Solutions rvf 0 Taken, .Mg.
Mo Found, Mg.
Mg.
5.00
4.95 4.90 5.00
-0.05 -0.10 0.00
5.00
5.05 4.95 5.00
tO.05 -0.05 0.00
M n , 150 Xi. 10
5.00
4.95 4.90 5.05
-0.05 -0.10 +0.05
Fe. 300
5.00
4.90 5.00 5.05 4.95 4.95 5.00 4.90 5.05 4.95 5.00
-0.10 0.00 f0.05 -0.05 -0.05 0.00 -0.10 +0.05 -0.05 0.00
Metals Present, Mg. Ca, Sr, Ba, 1000 each Zn, 1000 Cd, 50 ME. 5
1)iffereni:e.
In determining molybdenum with mercaptoacetic acid, as much as 600 p.p.m. of iron can be tolerated under the set experimental conditions. The tolerance of molybdenum on the iron complex was studied. S s much as 500 p.p.m. of molybdenum may be present in a solution containing 5 p.p.m. of iron without interference. This corresponds to a molybdenum to iron ratio of 100 to 1. As seen in Figure 2, the molybdenum mercaptoacetate complex has no appreciable absorption above p H 8 in the optimum range for the iron complex. RECOMMENDED PROCEDURES O F A 3 %LYSIS
Molybdenum. The final solution, whose absorbancy is to be measul.ed, should contain the optimum concentration of 4 to 15 p.p.m. of molybdenum. Add a 5-ml. aliquot of the solution being analyzed (20 to 75 p.p.m. of molybdenum) to a 25-ml. volumetric flask. Adjust the pH to within 3.5 to 4.5. Add 5 ml. of a sodium acetate-hydrochloric acid buffer of pH 4 and 2 ml. of 5% (volume) reagent. Dilute the solution to 25 ml. and mix. Measure the absorbancy a t 365 mp and check the pH of the solution to be sure it is within the optimum range of 3.5 to 4.5. If more than 25 ml. of solution is required, add sufficient reagent to make the concentration 0.4% (volume). Observations must he made within 30 minutes, unless potassium chlorate has been added as a stabilizer. Five milliliters of a 2% potassium chlorate solution per 25 ml. will stabilize the color for at least 1.5 hours. Molybdenum in the Presence of Iron. When iron is present a t a ratio of iron to molybdenum of not greater than 60 to 1, the procedure given in the preceding paragraph is followed, except that the reagent concentration should be 1.4% (volume)-Le., 7 ml. of 5% (volume) reagent solution per 25 ml. of solution, and 5 ml. of 2Y0 potassium chlorate solution added per 25 ml. of solution. Determination of Molybdenum and Iron. The final solution containing the molybdenum complex should contain the optimum concentration of 4 to 15 p.p.m. of molybdenum. The concentration of the iron complex should be 3 to 10 p.p.m. in its final solution. Add a 5-ml. aliquot of the solution being analyzed to a 25-m1. volumetric flask. Adjust the pH to within 3.5 to 4.5. -4dd 5 ml. of a sodium acetate-hydrochloric acid buffer of pH 4,7 ml. of 5% (volume) reagent, and 5 ml. of 2Q/, potassium chlorate. Dilute
the solution to 25 ml. and mix. Measure the absorbancy at 365 mM for the molybdenum determination. Transfer the 25 ml. of solution to a volumetric flask, the volume of which will give a n iron concentration of 3 to 10 p.p.m. Adjust the pH to within 8 to 11 with ammonium hydroxide, dilute the solution to the mark, and mix. Measure the absorbancy of the purplishred iron complex a t 535 mp. APPLICATION OF THE PROCEDURES
Salt Solutions. These solutions were analyzed according to the recommended procedure given in the preceding sections. The results are summarized in Table 11. National Bureau of Standards Samples. The NBS steel samples were dissolved in about 100 ml. of 1 to 3 hydrochloric acid by heating. The hot solution was treated with nitric acid to oxidize the molybdenum and decompose the carbides. The solution was boiled to expel oxides of nitrogen and diluted to a convenient volume. Molybdenum was separated from the large amount of iron in the steel by precipitation of the molybdenum in an aliquot of the steel solution with a-benzoinoxime according to the procedure by Knowles (b).
‘rahle 111. NBS Sample Steel 72a
Standard Samples
Mo
XBS,
JIO
Found.
Difference,
0 202
0.210 0,205
+0.008 +0.003
Steel 36
1 01
1. 0 3 0.98
f0.02 -0.03
Steel 160
2.95
2.97 2.94
f0.02 -0.01
CalloO4 71
%
35.3
Fe
35.1 35 4 35.1
NBS,
Fe Found,
1.92
1.97 1.99
%
CaMoOl 71
%
%
-0.2
to.l -0.2
r/c
4-0.05 f0.07
The precipitate was dissolved directly on the filter paper with about 50 ml. of hot 1.5 N ammonium hydroxide and finally with enough acetone to dissolve the reagent residue and prevent the precipitation of the reagent in the filtrate of the dissolved precipitate. The dissolved precipitate was allowed to pass through the filter paper into a volumetric flask of convenient size, the solution diluted to the mark, and mixed. A suitable aliquot was analyzed for molybdenum with mercaptoacetic acid according to the recommended procedure. The calcium molybdate sample was dissolved according to the directions on the National Bureau of Standards certificate of analysis. Both molybdenum and iron were determined, but it was not necessary to separate molybdenum by a-benzoinoxime. Table I11 summarizes the results. LITERATURE CITED Hamence, J. H., A n a l y s t , 65, 1 5 2 3 (1940). Knowles, H. B., Bur. Standards J . Research, 9, 1 (1932). Lyons, E.. J . Am. Chem. Soc., 49, 1916 (1927). Meyer, E’. 0. W., Pharm. Zentralhalle, 89, 3-8 (1950). (5) Miller, C. C., and Lowe, A. J., J . Cham. SOC.,143, 1 2 5 8 4 6 11940) 1 6 ) Richiei, F.,Chem. Tech., 1, 31 ‘1949). 17) Swank, H. W., and Mellon, M , G., IXD.EXG.CHEM.,ANAL.ED., 10,7-9 (1938)
(1) (2) (3) 14)
RECEWEDfor roview -4pril 15, 1953. Accepted June 15, 1953. Abstracted from a dissertation presented by Fritz Will, 111, t o the graduate faculty of the University of Virginia in partial fulfillment of the requirements for the degree of doctor of philosophy, January 1953.
