Cha racte riz a t io n of Hy d roxyI Co mpound s Identification of Their 3,5-Dinitrobenzoate Esters by X-Ray Diffraction KENNETH J. GARSKA, ROBERT C. DOUTHIT, and VICTOR A. YARBOROUGH Development Department, Union Carbide Chemicals Co., South Charlesfon, W. Va.
b An x-ray diffraction technique has been used for identification of hydroxyl technique often compounds. This makes possible the identification of hydroxyl compounds which cannot b e examined readily b y other techniques such as gas chromatography and mass spectrometry. Reference x-ray diffraction patterns have been obtained for the 3,5-dinitrobenzoate esters of 24 alcohols containing from one to 2 2 carbon atoms. Detailed descriptions are given for obtaining and qualitatively using the x-ray diffraction patterns of these esters. In the qualitative analysis of single or multicomponent hydroxyl-containing mixtures, this x-ray diffraction technique is used either alone or with infrared spectrometric techniques. The studies also indicate that semiquantitative x-ray and infrared spectrometric techniques can b e developed for examining mixtures of alcohols.
(6, 7, 11). Small amounts (0.002%) of alcohols in aqueous solutions have been converted to the 3,5niques
dinitrobenzoates, which then have been separated chromatographically using petroleum ether as the developer. The resulting fractions are detected by their ultraviolet absorption at a wave length of 240 mfi, The titration of dinitrobenzoates refluxed in pyridine gives consistently accurate and precise results (8). However, phenolic derivatives do not titrate quantitatively, and the method of titration is nonselective. Mixtures of aldehydes and ketones have been successfully identified from the infrared spectra of their 2,4-dinitrophenylhydrazone derivatives (9). Therefore, the possibility of developing a similar technique for hydrosyl-con-
Table I.
N
derivatives have been used for the identification of organic hydroxyl-containing compounds. Most of these techniques involve the formation of chloro- or nitrosubstituted aromatic acids, or reaction with a n isocyanate to form a urethane. Various physical techniques which have been used to examine the derivatives include: determination of melting point, x-ray diffraction, chemical microscopy. chromatography, infrared spectroscopy, and titrimetric analysis. The melting point, the technique most frequently used, is satisfactory only if the derivative is pure, because traces of impurities lower the melting point ( 2 ) . X-ray diffraction patterns have been used to identify the xanthate derivatives of about 20 alcohols (IO). This latter technique also has been applied to mixtures of alcohols. Dunbar and Ferrin have obtained photomicrographs for the 3,bdinitrobenzoate esters of approximately 40 related compounds (4). They found the crystal form to be unique and were able to identify as many as three alcohol derivatives in various mixtures. I n addition, the resolution of the 3,5-dinitrobenzoate esters of various alcohols has been carried out on a micro scale by chromatographic tech-
392
UMEROUS
ANALYTICAL CHEMISTRY
Melting Point Data on 3,5Dinitrobenzoate Esters
Alcohol
Melting Point, O C. Lit. Measured value (2)
Methanol 108 108 Ethanol 93 91-93 1-Propanol 74 72-73.5 1-Butanol 64 (62.5) 63 42-43" 1-Pentanol 46.5 1-Hexanol 60 58.4 BHeptanol 48.5 49 3-Heptanol 53 61-62 1-Octanol 61 1-Octadecanol 72-73 1-Docosanol 84-85 124 123 2-Propanol %Methyl-1-pro87 87 panol 76 76-77 2-Butanol 1,l-Dimethyl142-143 142 ethanol 66-68 70 2-Methylbutanol 87-88 50.5 ZEthoxypropanol 50-51 2-Ethylbutanol 2-Methylpentanol 51.5 45-47 2,2-Dimethyl51 butanol 51 2-Ethyl-4methyl5 pentanol 4-Methyl-2-pentanol 62-63 65 Cyclopentylmethanol 92-93 1,l-Dimethylocta54-55 decanol a Contaminated with diisopropyl ether.
taining compounds, based on the identification of their 3,5-dinitrobenzoate esters, seemed worth investigating. X-ray diffraction as well as infrared spectroscopy appeared adaptable to this purpose. To develop the x-ray diffraction technique, diffraction patterns of the 3,S-dinitrobenzoate esters of 24 alcohols have been prepared, four examples of which are shown in Figure 1. 9 compilation of these x-ray diffraction patterns, with qualitative and quantitative methods of analysis, is included in this paper. The number of hydroxyl compounds is so numerous that to include them all is beyond the scope of this investigation. Therefore, the 24 alcohols selected include closely related substances to illustrate the unique diffraction patterns produced by their 3,5-dinitrobenzoate esters. Several other alcohols investigated give only oils upon the formation of their 3,5-dinitrobenzoate esters, and they have been identified only by infrared techniques. -4paper (3) describing the infrared study of the 3,5-dinitrobenzoate esters of these same alcohols is being written. EXPERIMENTAL
Apparatus. The x-ray diffraction d a t a were obtained with a standard Philips Korelco x-ray diffractometer. A half-degree divergence slit, a 0.006inch receiving slit, and a 1' scatter slit Ii-ere used. The source was a copper-target x-ray tube operated at 35 k v . and 15 ma. A nickel filter was used to provide essentially monochromatic copper K , radiation. A rotating specimen holder was used to eliminate orientation in the horizontal plane of the pon-dered sample. The detector 11-as an argon-filled Geiger tube and the signal was fed through a ratemeter to a Bro\\n stripchart recorder. The recorder was operated a t a speed coincident to l o ,28, per 0.5 inch of chart paper. Sample Preparation. Most of the derivatives were prepared by a standa r d method outlined by McElvain (6), where the alcohol is reacted with 3,5-dinitrobenzoyl chloride in the presence of pyridine. The other derivatives were prepared by a modified procedure of the standard method of Cheronis and
~~~~~~~
Entrikin ( 2 ) lvhere the derivative is extracted with hexane from an acidified pyridine solution and washed with a dilute solution of sodium carbonate. The derivative was then recovered by evaporation of the hexane. Recrystallization was carried out in a methanolwater mixture. The derivative then n as vacuum-dried for 24 hours a t room temperature. Diffraction Patterns. The diffraction patterns of the 3,5-dinitrobenzoa t e esters mere obtained using the standard powder technique (1). The sample was ground with a mortar and pestle and sieved to 325 mesh. The ground specimen 11 as deposited in the rrxcessed portion of the specimen holder and a microscope slide was used to produce a smooth surface on the poader, level with the rim of the specimen holder. Diffraction patterns obtained on the same specimen for repetitive mountings gave little or no indication of preferred orientation. The diffraction pattern of the derivative n-as obtained by scanning a t a rate of 1' per minute from 0" to 50', 20. -4 2-second time constant n-as used for the ratemeter, and the scale factor Tvas adjusted to give a recorder deflection of 25 to 75% of full scale for most of the lines in the diffraction patterns.
Table II. Methanol do
I/Ilb
9.40 80 5 7.14 4 5.46 5.25 5 4.72 100 4.51 6 4.36 7 19 4.06 9 3.84 3.65 5 2 3.57 14 3.40 3.19 59 3.145 34 9 3.028 2 2.880 2.844 3 2.731 3 2.698 3 2.645 7 2.582 3 2.419 7 2.360 3 2 2.303 2.213 2 3 2.165 2.094 3 2.061 6 1.919 2 5 1.888 1.849 5 1.590 2
RESULTS AND DISCUSSION
Melting Points. For convenience, Table I lists the melting points of the 3,5-dinitrobenzoate esters in order of increasing number of carbon atoms for straight-chain alcohols and then for branched alcohols. I n only two cases do the melting points of the derivatives differ by more than 2' from the literature value ( 2 ) . These discrepancies can be attributed to contamination of the original alcohol by other hydroxyl-containing compounds. However, the presence of these impurities had little or no effect upon the diffraction patterns obtained. Diffraction Data. The diffraction patterns for the 3,5-dinitrobenxoate derivatives of methanol, ethanol, octadecanol, and docosanol are shown in Figure 1 t o demonstrate the unique character of the diffraction patterns produced by derivatives formed from similar hydroxyl compounds. Several strong lines characteristic of the respective derivative are evident in each of the four diffraction patterns. Therefore, an unknown ester can be identified by comparison of its diffraction pattern with reference diffraction patterns. Furthermore, the presence of another alcohol (in excess of 1%) in the original hydroxyl compound also can be determined readily. The diffraction data for all the derivatives are given in Table 11. Although a large number of lines are common to srveral of the diffraction patterns be-
2-Heptanol
~
~~
~~
~
Diffraction Data for 3,5Dinitrobenzoate Esters of Alcohols Ethanol 1-Propanol 1-Butanol 1-Pentanol 1-Hexanol d 1/11 d 1/11 d I/Il d IJi d 1/11 12.01 100 11.71 100 10.95 100 16.07 100 16.38 100 3 4 14.98 76 8.85 50 10.16 95 8.82 9.02 3 11 8.19 2 5.91 15 8.87 8.01 18 7.41 3 14 7.35 20 7.94 37 5.83 6.03 28 5.89 7 4 7.63 36 6.96 5.52 17 5.33 15 5.52 2 4.90 23 16 5.93 15 5.55 4.62 90 5.10 26 57 5.26 7 5.12 6 4.54 4.51 30 4.85 6 19 4.70 18 4.66 16 4.45 4.22 25 4.62 5 12 4.48 29 4.59 10 4.40 4.00 40 4.46 4 11 4.24 18 4.45 18 4.15 3.96 30 4.17 3 13 4.32 36 4.11 37 4.05 9 3.93 3.75 22 27 4.19 14 3.74 37 3.97 3.56 50 3.80 16 4.13 34 20 3.71 9 3.69 7 3.83 3.43 4 24 3.98 13 3.71 3.33 25 3.68 3 3.56 11 3.90 12 3.56 5 8 3.32 3.28 30 3.60 17 19 3.68 7 3.44 17 3.51 3 3.20 3.06 10 13 3.54 2 3.26 14 3.44 16 3.08 3.01 4 16 3.42 2.91 5 2.96 3 3.19 7 2.831 4 3 2.94 19 3.35 4 3.07 2.852 14 2.768 5 5 2.816 11 2.94 7 3.29 4 2.707 2.707 4 7 2.754 7 2.831 5 3.25 2.667 3 2.607 2 2.751 5 4 3.20 3 2.675 2.585 5 2.398 9 5 3.13 1 2.667 6 2.501 2.557 5 1.976 3 2.418 6 3.06 2.494 2 5 2.600 8 2.90 6 2.557 7 2.401 2.411 8 2 2.337 5 2.77 6 2.298 2.312 10 3 2.191 12 2.751 6 2.207 2.275 5 2 2 2.112 2.164 9 2.707 2.216 4 2 8 2.600 2 2.023 .... 2.132 2.067 4 2 4 2.542 2.097 3 1.985 2.016 4 2 9 1.874 4 2.482 2.045 1.997 5 4 2 2.358 1.888 1.977 10 2 2.194 2 2.161 2.062 8 2 1.845 3 1.834 3-Heptanol
14.26 100 13.55 100 2 9.21 3 7.97 4 6.67 2 8.08 4 5.80 7.14 7 14 5.76 7 4.98 14 4.77 31 4.77 4.61 6 4.57 15 6 4.41 5 4.55 42 4.32 4.28 5 17 4.13 4.03 35 11 3.95 6 4.03 3.72 36 3.77 30 14 3.74 24 3.62 3.54 7 3.65 16 3.41 3 3.40 6 3.21 3 3.31 3 3.02 3 3.23 3 2.831 5 8 2.857 2.747 5 2.801 4 2.667 2 2.644 3 4 2.585 1 2.301 2 2.227 2 2.488 2.380 3 2.083 2 2.304 4 1.985 2 2.154 3 1.955 2 4 1.947
1-Octanol 18.04 100 17.67 97 9.01 11 27 7.87 10 7.45 19 6.01 35 5.72 10 4.97 4.87 19 50 4.70 10 4.53 31 4.27 22 4.14 14 3.95 16 3.87 45 3.75 3.58 14 23 3.51 13 3.46 3.29 19 3.24 12 24 3.12 7 3.02 10 2.92 7 2.78 5 2.715 9 2.636 7 2.600 4 2.560 5 2.411 5 2.338 6 2.264 2.202 4 2.106 12 7 2.014 5 1.957 1.905 6 4 1.838 3 1.759
1-Docosanol 36.8 100 33.0 94 23.0 39 16.99 67 15.50 27 11.45 25 9 9.41 18 7.82 8 7.56 6.87 11 6.65 9 5.80 8 5.26 13 13 4.68 4.53 11 4.35 25 4.32 24 50 4.15 3.94 15 3.80 20 3.70 22 3.63 24 3.45 8 3.43 7 3.34 8 3.19 9 3.12 9 3.04 7 2.92 5 2.868 5 2.735 4 2.652 4 2.578 5 2.327 6 2.243 6 2.212 6 2.111 6 2.076 5 1.957 5 1.877 4
1-Octadecanol __2-Propanol 98 10.16 100 29.1 26.2 100 9.18 8 3 55 8.47 14.79 18 13.48 60 5.90 64 9.98 10 5.33 12 9.03 15 4.97 12 7.50 8 4.90 42 8 4.61 6.97 14 7 4.40 6.76 5.99 10 4.24 55 10 5.44 17 4.13 27 4.93 8 3.93 4.53 24 3.73 70 14 4.44 22 3.62 4.37 16 22 3.43 12 4.28 21 3.28 4.22 24 3.17 19 4 4.13 34 3.08 4.02 14 2.853 22 3.98 14 2.83i io 3.82 34 2.813 10 3.62 15 2.723 11 3.43 11 2.585 3 2 3.36 6 2.462 4 3.23 9 2.443 3.19 9 2.219 5 3.10 8 2.173 4 3.01 7 2.118 3 2.748 5 2.038 5 2.622 6 1.866 4 2.515 5 1.704 4 2.501 5 2.443 5 2.392 5 2.344 6 2.333 6 2.176 7 2.111 6 (Continued on page S94)
VOL. 33, NO. 3, MARCH 1961
a
393
Table
II.
Diffraction Data for 3,5Dinitrobenzoate Esters
2-Methyl-1propanol
%Butanol
1,l-Dimethylethanol
%Methylbutanol
of
Alcohols (continued)
%Ethoxypropanol
2-Ethylbutanol
cause of the similarity in the structure of the 3,bdinitrobenZoate esters, no two derivatives conceivably would have identical crystalline structures, thereby eivine identical diffraction Datterns. No such case has been noted in this study to date. There are several lines having an 1/11 value greater than 10 unique to each diffraction pattern. These unique x-ray lines easily identify pure derivatives or mixtures of derivatives. Each of the 24 alcohols investigated can be identified in an unknown mixture by comparison of the three most intense lines in the x-ray diffraction pattern of their 3,bdinitrobenzoate esters with the data shown in Table 11. The intensity of each line (1/11)is compared with a value of 100 for the strongest reflection in each pattern. The ratio of degrees, 28, per Angstrom unit is very large for small d spacings giving a proportionately greater angular separation per Angstrom unit a t the higher 28 values. Therefore, the angular separation is sufficient to distinguish among most of the reflections. An apparent correlation exists between the length of the carbon chain attached to the 3,5dinitrobenzoate radical and the size of the largest d spacing in the diffraction pattern of the ester. Furthermore, as chains of about 20 carbon atoms in length are studied, a trend toward the formation of extremely large d spacings is noted. This tendency is evident when the diffraction patterns shown in Figure 1 for the 1- and 2-carbon chains and the 18and 2Zcarbon chains are compared. Diffraction patterns for crystalline alcohols such as those obtained for octadecanol, 1,l-dimethyloctadecanol, and docosanol provide a means of direct examination of high molecular weight alcohols by x-ray diffraction. However, the diffraction patterns of the 3 , s dinitrobenzoate esters of these three solid alcohols are more unique than the patterns of the alcohols themselves; and, in addition, the derivatives can be obtained and identified more readily from mixtures than can the pure alcohols. Quantitative Analyses. After proper identification of the hydroxyl components present in a mixture of 3,5-dinitrobenzoate esters, quantitative estimations of the relative amounts present in the original sample can be made. A series of standard samples containing known ratios of the identified hydroxyl derivatives is prepared and diffraction data are obtained on these various samples. Using the strongest reflection for each derivative in the several diffraction patterns. a calibration can be DreDared by * Plotting the intensity ratios against the concentration ratios. The lower concentration limit for reliable results is V
d
1/11
d
1/11
d
1/11
13.48 100 11.60 100 11.18 100 11.87 100 15.50 100 13.05 100 6 5.72 9.50 10 6.07 9 6.30 17 9.30 5 8.08 3 2 5.63 7.82 14 5.83 11 5.38 14 5.54 3 7.84 37 24 6.80 6.83 23 5.64 8 5.17 20 5.12 8 5 5.29 42 5.04 2 4.79 5 5.55 30 5.18 3 4.88 3 5.44 44 4.79 4.76 30 5.01 8 4.82 3 4.56 6 5 5.21 4.55 14 4.85 4 5 5.05 17 4.52 13 4.68 5 4.37 4.49 32 4.67 16 4.46 9 4.65 11 4.34 15 4.25 9 14 4.21 4.25 14 4.48 4 4.04 26 19 4.34 8 4.16 4.11 5 3.79 87 4.11 10 4.05 8 4.31 8 3.91 10 69 3.75 11 3.90 17 3.89 6 4.13 7 3.68 59 3.97 11 3.79 12 3.77 10 3.72 7 3.55 18 4.03 15 3.78 21 3.94 14 3.61 3.62 24 3.40 9 3.67 6 5 3.74 4 3.61 8 3.42 3 3.53 10 3.26 5 3.86 39 3.62 4 3.08 4 3.29 4 3.48 26 3.55 10 3.75 6 3.33 4 3.17 7 2.82 6 3.41 7 3.57 23 3.13 15 3.42 2 3.40 13 2.90 4 3.10 7 3.36 3 2.798 15 3.30 2 2.787 13 3.20 3.02 16 3.14 3 3.23 ii 2.850 7 7 2.514 2 2.96 9 3.09 2 3.15 11 2.92 8 2.743 2.831 9 2.97 9 2.805 10 2.732 3 3.02 10 2.380 2 10 2.196 2 2.780 6 2.656 6 2.91 3 2.92 3 2.449 2.735 6 2.755 3 2.150 4 3 2.90 5 2.514 5 2.405 2.667 6 2.690 1 2.362 3 2.086 2 3 2.420 3 2.847 2 2.637 2 2.607 2 2.259 I.999 9 2.301 2 2.546 4 2.600 1 2.380 6 2.173 1.899 5 2.523 5 2.221 2.327 4 2.132 1 2 2.142 1.874 3 2.235 3 2.196 4 2.207 2 2.287 11 2.085 2.156 2 2.122 1 2.201 2.028 3 2.027 2 2.083 2.058 11 1.981 1.993 3 2 1.991 1.967 2 1.807 3 1.957 1.859
2-Methylpentanol
2,ZDimethyl- 2-Ethyl-44Methyl-2butanol methylpentsnol pentanol
16.04 100 21.28 100 14 6 16.52 9.31 32 8.04 7 10.80 16 5.80 13 6.80 6 5.50 9 5.11 21 5.15 4.64 40 4.41 12 5.10 38 4.28 46 5.01 30 4.11 25 4.93 8 21 4.77 19 4.03 12 4.35 46 3.92 12 8.27 16 3.80 3.61 33 4.13 25 12 4.06 28 3.38 12 3.85 53 3.29 13 17 3.62 3.25 11 3.10 6 3.59 6 3.04 10 3.40 2.92 10 3.31 7 4 3.18 13 2.768 34 2.708 5 3.08 9 6 2.96 2.683 7 3 2.92 2.607 2.508 5 3 2.866 2.292 5 2.840 5 2,242 3 2.801 5 1.910 7 3 2.756 2.667 5 2.630 5 2.579 6 2.568 6 2.508 6 4 2.230 4 2.272 4 1.981
CvcloDentvl- 1.1-Dimethvl metlianol" octadecanol"
9.31 91 12.55 100 14.94 100 23.4 100 14 7.97 7 9.36 7.19 13 11.86 63 12 6.35 13 8.59 5.40 3 8.10 13 14 5.67 12 7.97 24 5.21 19 7.51 11 5.76 4.68 100 5.39 34 7.31 13 41 6.42 22 5.16 4.50 25 4.70 13 21 4.51 24 4.80 4.33 71 5.99 32 4.03 16 5.34 26 36 4.47 11 4.43 22 5.04 19 4.23 3.82 12 19 4.25 3.65 78 17 4.20 18 4.62 23 4.18 11 4.53 3.39 28 37 4.07 25 3.92 49 7 4.19 3.19 48 3.80 54 3.82 6 4.11 13 3.72 18 3.15 33 3.56 11 3.55 3.02 32 3.88 15 3.49 17 17 3.75 79 7 3.36 2.88 8 3.33 19 3.65 2 3.28 32 2.853 8 3.18 24 2.719 5 3.50 9 3.04 7 3.20 21 2.695 11 2.93 8 3.36 15 3.13 2.644 10 2.796 11 3.05 17 3.30 13 2.572 10 3.20 10 8 2.600 3 2.95 2.414 14 2,521 3 2.868 7 3.12 15 20 7 2.475 2.356 3 2.826 12 3.02 11 7 2.89 2.298 3 2.719 5 2.410 4 2.564 2.212 8 2.292 5 2.748 11 2.161 7 2.585 9 8 2.137 3 2.515 9 6 2.462 2.087 8 2.099 3 2.468 9 1 2.374 3 2.344 2.056 10 1.934 6 2.278 9 2.267 1.918 6 6 2.137 11 2.227 1.888 8 2.161 5 2.058 7 9 1.848 1.993 11
d spaoings given in Angstrom units. Represents intensity of each reflection compared with 100 for I1, the strongest reflection in each pattern. a
394
ANALYTICAL CHEMISTRY
"
1 0 0 ~ 3 , 5 - D I N I T B O B E N Z C ~ ~OF E OCTADECANCL i
80 [ 60
1
o , , , , , , , , 48
I
40
,
, , , 24
,
32
,
,
,
,
16
,
,
,
, u
8
0
I 60
401
o , , , , , , , , , , 48
Figure 1.
40
32
,
,
,
,
, , , , , , , ,u 8 0
,
24 16 DEGREES, 2 8
X-ray diffraction patterns for 3,5-dinitrobenzoate esters of four typical alcohols
about 1% for a minor component. this procedure n’orks for mixtures of the 3,5-dinitrobenzoate esters, fractional crystallization or preferential reaction becomes a problem when the derivatives are prepared from a mixture of hydroxyl compounds. LITERATURE CITED
(1) A Z a r O f f , L. V., Buerger, M. J., “The
Powder Method,” p. 181, McGraw-Hill, New York, 1958.
(2) Cheronis, N. D., Entrikin, J. B., “Semimicro Qualitative Organic Analysis,” p. 368, Interscience, New York, 1957. (3) Dout&t, R. c., Gar&, K. J., yarborough, V. A., Development Department, Union Carbide Chemicals Co., South Charleston, W. Va., unpublished data. (4) Dunbar, R. E,, Ferrin, F. J., Mimechem. J. 3, 65 (1959). (5) McElvain, S. M., ‘‘Characterization of Organic Compounds,” P. 199, Macmillan, New York, 1953. (6) Meigh, D. F., Nature 169, 706 (1952).
(7) Rice, R. G., Leller, G. J., Kirchner, J. G., ANAL.CHEM.23, 195 (1951). (8) Robinson, W. T., Jr., Cundiff, R. H., Sensabaugh, A. J., Markunas, P. C., Talanta 3,307 (1959). (9) ROSS, J. H.9 ANAL* CHEM. 25, l288 (1953). (lo) Warren, G. G., Matthew% F. IVY Ibid., 26, 1986 (1954). (11) White, J. W., Jr., Dryden, E* c*, Zbid., 20, 853 (1948). RECEIVED for review September 29, 1960. Accepted November 22, 1960. 3rd Annual Rocky Mountain Spectroscopy Conference, August 1960.
Flame Photometric Determination of Phosphorus in the Presence of Sodium, Potassium, and Other Cations D. N. BERNHART, W. 6. CHESS, and DAVID ROY Research laboratories, Victor Chemical Works, Division of Sfauffer Chemical Co., Chicago Heights, 111.
b Phosphorus content in an aqueous solution can be determined b y its interference on the flame emission of strontium at 660 mp. At this wave length there i s no interference due to sodium, potassium, or many other cations. The same interference holds whether the phosphate i s present as ortho, cyclic, or condensed. However, with lower oxidation states of phosphorus, the interference decreases and requires the use of calibration curves containing the same oxidation state of phosphorus as in the samples to be analyzed. In either case, the samples may merely be dissolved in water and determined in this manner, eliminating the lengthy hydrolysis to orthophosphate. The calibration curve may be set up differentially, using a reference
standard containing phosphorus. Thus, samples may be run very rapidly with a good degree of accuracy.
A
FLAME PHOTOMETRIC DETERMINATION of phosphorus by its inter-
ference of the emission of the calcium flame a t 422 mp was reported by Dippel et al. (2). I n 1955, a year later, Brite (1) reported the flame photometric determination of organic phosphorus compounds by their continuous emission at 540 mp. Although both of these procedures are good, neither will work in the presence of cations such as sodium or potassium. I n 1958, Moore and coworkers (3) reported the flame emission of strontium at 660 mp with little interference from cations, but with a large interference due to phosphates. This
appeared to be the basis of a modification of Dippel’s method which might work in the presence of sodium and potassium. The following experimental work was carried out and resulted in a very rapid control procedure for accurately determining the phosphorus content of sodium and potassium ortho- and polyphosphates. EXPERIMENTAL
The source of strontium was made by dissolving SrClz.6I&O in 0.7N HC1. All of the phosphate solutions were acidified in the same manner to prevent precipitation of strontium phosphate. A Beckman D U spectrophotometer with an oxygen-hydrogen burner was used with the photomultiplier set at full and a ratio of 10 pounds of oxygen to 21/2 pounds of fuel. This ratio gave optimum VOL. 33, NO. 3, MARCH 1961
395
