616 ,
ANALYTICAL CHEMISTRY
It is apparent that as much as %yoferric oxide can be tolerated with little loss of precision, provided the tungsten concentration is a t least O.Ol%, although 50% ferric oxide partially obscures the tungsten line and leads to high results. Fortunately, with the exception of pyrite concentrates, when the iron is high, the tungsten is also high, and dilution with silica is effective in decreasing the concentration of both elements to a point where the tungsten can be determined. CONCLUSIONS
The silver chloride volatilization technique has several advantages over other methods for the determination of tungsten in ores. The method is very sensitive and can determine concentrations as low as 0.0005~0tungstic oxide without difficulty. By increasing the size of sample, it should be possible to increase this sensitivity still further. The method is reasonably precise even in the absence of an internal standard. A probable error of 5% can be obtained routinely. The method is rapid and is readily adaptable to routine operation. Burning time per sample is only 30 to 40 seconds. The method is almost independent of changes in matrix compositidn. The presence of a large amount of silver chloride ensures that the volatilization conditions will be controlled by this compound. The method can be employed over a wide range of concen-
tration. I n actual practice it has given satisfactory results with tungsten concentrations between 0.3 and 0.0005%. ACKNOWLEDGMENTS
The authors wish to acknowledge the assistance of A. -M. Gaudin, Department of Metallurgy, Massachusetts Institute of Technology, who first presented the problem and H. Rush Spedden, Department of Metallurgy, Massachusetts Institute of Technology, who provided the samples for analysis. They also wish to thank Thomas R. P. Gibb, Jr., Metal Hydrides Incorporated, for his helpful suggestions in the preparation of the manuscript. LITERATURE CITED
(1) Ahrens, L. H., J. S.African Chem.Inst., 23,21-6 (1943). (2) Harrison, G. R., “M.I.T. Wavelength Tables,” New York, John Wiley & Sons, 1946. (3) Kaufman, David, unpublished investigations. (4) Meggers, W. F., and Scribner, B. F., “Index to the Literature on Spectrochemical Analysis 1920-1939,”2nd ed., Philadelphia, Pa., American Society for Testing Materials. (5) Ibid.,Part 11,1940-45. (6) Nedler, V. V., Bull. acad. sci. U.R.S.S., Ser. phys., 4, 142-4 (1940). (7)Scobie, A.G., IND.ENQ.CHEM.,ANAL.ED.,15,79 (1943). (8) Scribner, B. F., and Mullin, H. R., J. Optical SOC.Am., 36, 357 (June 1946). (9) Willard and Furman, “Elementary Quantitative Analysis,” 3rd ed., p. 67,New York, D.Van Nostrand Go., 1940. and Fieldes, M a Analyst, , 69, 12-14 (1944). (10) Wilson, 9. H., RECEIVED July 19, 1948.
Determination of .Isopropyl Alcohol, Diacetone Alcohol, and Z=Methyl=2,4=pentanedioI In the Presence of Each Other F. J. FRERE
AND
J. J. BUSZ, Publicker Industries, Inc., Philadelphia, Pa.
A rapid method, based on the work of Barbaudy, has been developed for the determination of isopropyl alcohol, 4-hydroxy-4-methyl-2-pentanone,and 2methyl-2,4-pentanediol in the presence of each other. Results with a reasonably high degree of accuracy can be obtained in 15 minutes.
I
N T H E process of hydrogenating diacetone alcohol (4-hydroxy-
4methyl-Zpentanone) there is formed in addition to the main product, Z-methyl-2,4-pentanediol, a small amount of isopropyl alcohol (%propanol). This results from the degradation of diacetone alcohol to acetone, which in turn is reduced to isopropyl alcohol. I n order to follow the rate of hydrogenation and ascertain the activity of the catalyst, it is essential to know the composition of the reaction mixture a t any given instant. Fractional distillation is time-consuming and cannot be used for the rapid analysis of spot samples. A rapid method has been developed which requires an expenditure of time not exceeding 15 minutes. I t s principle is not new, but rather is based on the work of Bsrbaudy (1), who first applied it t o the analysis of the mixture: benzene-ethyl alcohol-water. More recently, Campbell and Miller (2) applied the method to the analysis of the mixture: benzene-ethyl alcohol-carbon tetrachloride. Both authors claim an accuracy of approximately 0.25%.
PRINCIPLE OF THE METHOD
A survey of the literature reveals that the method has found only limited use among analytical chemists, although undoubtedly there are many systems to which it may be successfully applied. One of the great advantages to be gained by its use is that of time. Just as one physical or chemical property is sufficient to fix the composition of a binary system, two will fix the composition of a ternary system. Therefore, the composition of a ternary liquid system may be determined if any combination of two pairs of components possesses some chemical or physical property that is nearly identical for members of a given pair but is not possessed by, or is different from, that for members of the other pair. I n many cases it is necessary to consider only a single pair of components, providing one member of the pair possesses some chemical property that is not common to the other t x o components. T o illustrate the principle more specifically, let us consider a system composed of components A , B, and C. Now, the compc-
V O L U M E 21, NO. 5, M A Y 1 9 4 9 sition may be ascertained if A and B possess some nearly identical physical or chemical property that differs from that of C, or if A and C or B and C possess some other nearly identical physical or chemical property that differs from that of components B and A , respectively. When only one pair of components such as A and B is under consideration, it is only necessary that either A or B possess some chemical property that is not common to the other two components. I n each of the above cases of component pairs it is assumed that the third component is present without materially altering the relative values of the properties common to the pair.
A method of obtaining data in ternary systems, afforded by the use of pseudobinary curves, consists simply of adding to a fixed binary mixture varying amounts of the third component. If the binary mixture is treated as unicomponent, it is possible to plot any property against composition on rectangular coordinate?. From several such plots one is able to select ternary solutions of variable composition but with fixed chemical or physical property. The values of these properties may be plotted on triangular coordinates, with the result that there are formed two series of nearly parallel lines intersecting a t an angle approximating 60 '. The accuracy of the method depends to a very great extent on the similarity of properties exhibited by the component pairs. Any physical property which is, or is approximately, a linear function of composition may be used. I n general, specific gravity and refractive index satisfy this requirement. Chemical properties appear to be somewhat more numerous: bromine, hydroxyl, carbonyl, and acid number, and oxidation value. Oxidation reaction offers a choice of reagents which may be selective for certain types of compounds, in which case it can be used in conjunction ir-ith an osidant that is capable of completely oxidizing all the components. The method fails when the system is composed of more than three Components. However, if these extraneous materials are present in low concentration, one may obtain a reasonably good approximation as to the composition of a given system.
617 Table I. Specific Gravities in Ternary System: Isopropyl Alcohol-Diacetone Alcohol-2-Methyl-2,4-pentanediol Sp. Gr., 25"/ Iso25OC. PrOH 0.7900 0.8000 0,8100 0.8200 0,8300 0.8400 0.8500 0.8600 0.8700 0.8800 0.8900 0.9000 0.9100 0,9200 0.9300 a
93.6 86.0 78.7 71.1 63.7 55.0
48.4 41.5 34.4 27.4 20.5 13.6 6 , .5 4.1 1.2
IsoPrOH D A 4 Weight Per Cent 5 . 8 93.5 3.2 12.6 86.3 6.8 19.2 79.1 10.4 26.0 71.9 14.0 32.7 64.7 17.6 40.5 57.5 21.2 46.4 50.5 24.7 52.6 43.6 28.2 59.0 36.9 31.5 65.3 30.0 38.0 71.5 23.5 38.2 77.8 16.9 41.5 84.1 10.1 44.9 48.0 5.7 64.3 1.9 88.3 20.0
D d S " Diol
0.6 1.4 2.1 2.9 3.6 4.5 5.2 5.9 6.6
7.3 8.0 8.6 9.4 47.9 78.8
Iso-
Diol
PrOH
DAA Diol
3.3 6.9 10.5 14.1 17.7 21.3 24.8 28.2 31.6 35.0 38.3 41.6 45.0 30.0 9.8
93.4 86.6 79.6 72.8 65.7 59.0 52.5 45.7 39.2 32.6 26.4 20.0 13.7 7.9 2.3
5.9 12.1 18.4 24.5 30.9 36.9 42.7 48.9 54.7 60.7 66.2 72.0 77.7 82.9 92.7
0.7 1.3 2.0 2.7 3.4 4.1 4.8 5.4 6.1 6.7 7.4 8.0 8.6 9.2 5.0
DAA, diacetone alcohol; diol, 2-methyl-2,4-pentanediol.
Isopropyl Alcohol. A reagent grade material was refluxed for several hours with freshly calcined calcium oxide, after which it was fractionated a t atmospheric pressure on a Podbielniak column. The center cut was selected for use. 2-Methyl-2,4-pentanediol. Every grade of diol tested was found t o contain varying amounts of a carbonyl compound which could not be removed by repeated fractionation, but could be removed by first azeotroping with benzene a t atmospheric pressure. The diol was then fractionated under reduced pressure on a Podbielniak column. The center cut was selected for use. 2 N Solution of Hydroxylamine Hydrochloride, made by dissolving 139 grams of the salt in distilled water and diluting to 1 liter. 0.5 N Sodium Hydroxide. Twenty grams of carbonate-free sodium hydroxide are dissolved in freshly boiled distilled water, diluted to 1 liter, and standardized against pure diacetone alcohol as described in procedure. Bromophenol Blue, 0.1 gram dissolved in 100 ml. of water. PROCEDURE
MATERIALS AND REAGENTS
Diacetone Alcohol. il reagent grade material was fractionated under reduced pressure on a Podbielniak column. The center cut was selected for use. i-PrOH
Diacetone Alcohol. Add 20 ml. of 2 ,V hydroxylamine hydrochloride and 2 to 3 drops of bromophenol blue to 150 ml. of distilled water contained in a 250-ml. Erlenmeyer flask and neutralize with 0.5 N sodium hydroxide to the appearance of a faint greenish blue coloration. Weigh out 1 to 2 grams of sample in a weighing pipet and transfer to the flask containing the solution. Thorouehlv mix and allow to stand for several minute; "Titrate with 0.5 N sodium hydroxide, comparing the color change with that of a blank containing the same volume of solution, indicator, and hydroxylamine hydrochloride. The color change is from yellow t o greenish blue. Specific Gravity. Determine the specific gravity of the sample a t 25" C. using a 25-ml. pycnometer, Locate, on the diagram, the point of intersection of the diacetone alcohol and specific gravity lines. Determine the composition of the solution, corresponding to this point, according to the method of Gibbs or Roozeboom as outlined in Findlay's text on the phase rule ( 3 ) . RESULTS AND DISCUSSION
DAA
DlOl
Figure 1. Gravities (23/25) in System : Isopropyl Alcohol-Diacetone Alcohol-2-~Iethyl-2,4-pentanediol
Lines of constant specific gravity were constructed as outlined under Principle of the Method. The resdts shown in Table I are plotted in Figure 1. Solutions containing known varying amounts of diacetone alcohol, isopropyl alcohol, and 2niethyl-2,4-pentanediol were prepared and analyzed according to the above procedure. The gravities were determined in duplicate and the diacetone alcohol in triplicate. These results are shown in Tahle 11.
ANALYTICAL CHEMISTRY
618
up of errors on one or more of the components. This is especially true in the case of diacetone alcohol because of its large equivalent weight. Hen-ever, despite these shortcomings, results of sufficient accuracy may be obtained to permit one to follow the course of the hydrogenation reaction and to evaluate the activities of various types of catalysts. When reasonably purr diacetone alcohol is used as a starting material, nothing will be gained by resorting t o the more lengthy procedure of fractional distillation. An examination of the hydrogenated products shoxed negligible amounts of acetone.
Table 11. Analysis of Synthetic Mixtures
__ Iso-
Added
PrOH
DAA Diol Weight Per Cent 49.7 50.3 0.0 0.0 52.2 47.8 50.0 0.0 50.0 5.0 5.0 90.0 90.1 5.3 4.6 10.0 5.3 84.7 50.9 23.3 25.8 25.1 25,l 49.8 25.2 49.8 25.0 10.0 45.0 45.0 9.7 42.3 48.0
Found IsoPrOH DhA Diol Weight Per Cent 49.8 0.0 50.3 4.8 90.1 9.8 51 . o 25.2 25.0 9.8 42.1
50.2 47.6 0.0 90.1 5.4 5.2 23.4 49.6 25.1 44.8 48.2
0.0 52.4 49.7 5.1 4.5 85.0 25.6 25.4 49.9 45.4 9.7
LITERATURE CITED (1) Barbaudy, M. J., Bull. S O C . chim., 39, 371 (1926).
I t is seen that the method is capable of giving results with a reasonably high degree of accuracy, but that an error in one determination, gravity or diacetone alcohol, will cause a piling
(2) Campbell, A. N., and Miller, S. I., Can. J . Research, 25B,No. 3 . 228 (1947). (3) Findlay, Alexander, “The Phase R g e and Its Applications,” NPW York, Longmans, Green and Co., 1939.
RECEIVED May
20, 1948
MAGNESIUM Rapid Alkalimetric Determination in Calcium and Magnesium Carbonate Ores S. C. S-ISE AND 12. S. TELANG, Laxminurayan Institute of Technology, >Vagpur I*niaersity. V a g p u r , India
S”
ME uf the voluriietric methods employed for determining the magnesium content of. carbonates have been reviewed by Williams ( 5 ) . Kolthoff and Stenger ( 2 ) have discussed the application of acid-base displacement titration methods for magnesium salts. Some of the existing methods are applicable in the presence of calcium salts under appropriate limiting conditions. An acid-alkali method employing calcium hydroxide (lime water) in place of sodium hydroxide for the volmetric determination of magnesium in the presence of calcium ( 4 ) is of particular interest on account of its extreme simplicity, rapidity, arid accuracy. Although this method usually has been employed for water analysis, it could be safely utilized for the determination of magnesium in hydrochloric acid solution of calciun~and magnesium carbonates, provided iron and aluminum, i\-hich are likely to be precipitated in alkaline medium, are not present. Table I. Alkalimetric Determination of Magnesium in Prepared Mixtures of Carbonates of Calcium and Magnesium Mixture
XgCO3 in
12‘0.
Alixtiirr
MgCOs Present
%
Gram
I 2 3 4 5 6 7 8 9
1.98 4.74 9.09 13.04 16.67 2 5 . on 33.34
0.02 0.05 n.in 0 15 0.20 0.15 0.10 0 02 0.20 0.20
10
5 0 , oo
66.67
so.on
IIgCOa Found Gram 0.0204
n. 0502
0 1012 0.1.521 0.2014 0.152.5 0.1200 0,0202 0.2031 0.2042 ~~~~
~
The authors’ principal objective was to develop a rapid method for the determination of magnesium in the presence of interfering elements like iron and aluminum without sacrificing accuracy, and at the same time to employ easily available and less expensive reagents. The calcium hydroxide method ( 4 ) appeared very promising in these respects, provided due modifications could be made, so that it could be applied in the presence of iron and aluminum. Experience showed that the method outlined in the prrsrnt paprr fills the requirriiientb.
Killiarns ( 5 ) used sulfuric acid to dissolve. the carbonate ore, with the obvious intention of preventing calcium from going into solution. It is likely that the digestion may not bc complete unless a vigorous agitation is carried out during the digestion, as the calcium sulfate formed produces a resistant coating on the undigested particles, and prevents the inner core of the carbonate ore from coming into contact with the acid. Furthermore, on account of the slight solubility of calcium sulfate, the solution will contain a little calcium which will be precipitated as the carbonate if the sodium hydroxide used contains carbonate. This point appears to have been overlooked by Williams. PREPARATION OF SAMPLES .AND REAGENTS
The purity of Merck’s precipitated calcium carbonate ( p r o analysi) and magnesium carbonate was established by analysis ill this laboratory. I n order to check the reliability of the proposed method, three sets of experiments were carried out as illustrated in t,he tables. Errors may arise from incfficiency of mixing, saiiipling, etc., if a large quantity of a mixture of calcium carhoiiatr and magnesium carbonate is prepared and if a representative saniple of the mixture for further analysis is then chosen. I t \va,s. therefore, thought advisable to prepare the required mixtures by directly weighing out actual quantities of calcium carbonate a n d magnesium carbonate. To obtain a 1-gram mixture containing 20% magnesium carbonate, 0.2 gram of magnesium carbonate and 0.8 gram of calcium carbonate were weighed out separately and mixed, and the whole mixture of 1-gram weight was employed for analysis. Similarly, to determine the accuracy of the method in the presence of iron and aluminum, the mixtures of calcium and magnesium carbonates were prepared by actual weighing and then a few milliliters of solutions of aluminum chloride and ferric chloride, the iron and aluminum contents of which per millilit,er were determined by previous analysis, were added. Sodium hydroxide solution was standardized against pure succinic acid (analytical reagent quality, British Drug Houses) and checked by titrating with hydrochloric acid standardized against a known weight of a carefully selected piece of calcite crystal; both methods gave concordant values of the strength of the sodium hydroxide solution Calcium hydroxide was also standardized against the same hydrnchloric acid.
