-0OCCH2CH2COKHCHCOO I
hydroxylamine is impeded by bulky and electron-donating groups, which is in agreement with a nucleophilic mechanism for the reaction.
The inhibitory influence of the methyl or alkyl group mag be attributed to their greater electron-releasing properties over that of hydrogen. Conversely, the inductive effect of the fluorine atom in fluoracetamide accelerates nucleophilic attack by hydroxylamine. The influence of the methyl and phenyl groups on the acid strengths of formic acid, and the influence of fluorine on the acid strength of acetic acid, run parallel to their effects on the velocities of the hydroxylamine reactions of the respective amides. I n the case of bulky neighboring groups, inhibition due to steric hindrance must also be noted. The reaction between monocarboxylic acid amides and alkaline
LITERATURE CITED
.4schan, O., Ber. 19, 1402 (1886). Bergmann, F., A N ~ LCHEM. . 24, 1367 (1952). Boxer, G. E., Everett, P. M., Ibid., 21, GTO(1949). Feigl, F., Anger, V., Xikrochemie 15, 23 (1934). Feigl, F., -knger, V., Frehden, O., Ibid., 15, 9 (1934). Ford, J. H., A s . 4 ~ . CHEM.19, 1004 (1947). Goldenberg, V., Ph.D. thesis, Polytechnic Institute of Brooklyn, 1957; microfilm or other copies obtainable from University hlicrofilms, 313 North First St., Ann Arbor, Mich. Goldenberg, H., Goldenberg, V., McLaren, A. D., Biochim. et Biophys. Acta 7, 110 (1951).
(9) Goldenberg, V., Goldenberg, H., McLaren 4. D., J. Am. Chem. Soc. 72, 5$l? (1950). 10) Hestrin, S., J . Bid. Clam. 180, 249 (1949). 11) Hill, L,, aN.4L. CHEM.19,932 (1947). 12) Hill, U., IND.ENG.CHEM.,ANAL. ED. 18, 317 (1946). 13) Jeffery, G. H., Vogel, A. I., J . Chem. soc. 1934, 1101. 14) Lipmann, F., Tuttle, L. C., J . Biol. Chem. 159, 21 (1945). 15) Rohmann, F.,Be?. 30, 1978 (1897). 16) Walker, J.. J . Chem. SOC.61, 696 (1892). (17) \Tallish, E.G., Schmall, M. S., ANAL. CHEM.22, 1033 (1950). RECEIVED for review September 10, 1957 Accepted March 10, 1958. Meeting-in hliniature, Metropolitan Long Island Subsection, Xew Tork Section, ACS, BrookFebruary 15, 1957. Based on a lyn, ii.T., thesis submitted by Vivian Goldenberg in February 1957, in partial fulfillment of the requirements for the degree of doctor of philosophy in the Polytechnic Institute of Brooklyn.
SpectrochemicaI Determinution of Fluorine in Porcelain Enamel Frits DONALD C. SPINDLER and M O N A FRANCK SMITH' Technical Center, Ferro Corp., Cleveland, Ohio
b
Rapid comparison of porcelain enamel frits is facilitated by a spectrochemical determination of fluorine. Calcium carbonate and graphite are mixed with the sample to produce calcium fluoride bands. The intensities of the band head a t 5291.00 A,, corrected for background, are compared with those of chemically analyzed standards. The range of fluorine covered is from a few tenths to 6% in frits. Some factors considered are the emulsion, amperage, time of exposure, and band components. Various amounts and kinds of additives are evaluated.
N
uhtmous articles indicate the inadequacy of many methods for determining fluorine. Classical wet and photometric methods are time-consuming. An attractive approach t o fluorine determination is by emission spectroscopy. Frits containing fluorine from a few tenths to 6% can be analyzed by this fast, convenient method. The spectrographic method is based on the emission of calcium fluoride bands in the direct current arc. Ahrens (d), Harrison, Lord, and Loofbourow 1 Present address, Chemzcal dbstracts. Ohio State University, Columbus, Ohio. 1330
ANALYTICAL CHEMISTRY
(6), and many others, show these molecules as diatomic with no indication of valence. The molecular bands of calcium fluoride (CaF) have many heads, including ones a t 5291.00, 6036.92, 6064.40, and 6086.91 A. The individual components of these bands are often distinct enough for densitometry. I n the spectrochemical determination of fluorine, the emphasis has been on water, rock, and slag samples (1-3, 6, r), using the calcium fluoride bands and the bands of barium fluoride (BaF) and strontium fluoride (SrF) to a lesser extent (2). Suitable methods for fluorine determination in enamel frits may be established after considering the important variables. Porcelain enamel frits, which are the basic material for porcelain enameling, are selected glasses of widely varying composition. These molten glasses are fritted by air or water quenching to form brittle flakes or granules. One of these frits has the composition shown in Table I. Fluorine may be added to a glass batch as an alkali silicofluoride or fluorspar. Fluoride aids in smelting the raw batch. I n zircon enamels, it increases the opacity. The firing temperature of porcelain enamel is sometimes lowered by using glasses high in
Table
I.
Typical Frit Composition, Zircon Cover Coat
70 Si02 B20a Na20 AlzOa BaO Zr02
26.6 22.2 10.1 5.7 0.4 16.8
% ZnO CaO FD K20 PzO,
3.0 7.7 6.0 1.9 2 0
fluorine. Fluorine losses occur during smelting as silicon tetrafluoride, boron trifluoride. and alkali fluorides. PHOTOGRAPHIC EMULSIONS AND APPARATUS
Because the bands of calcium fluoride are in the visible region, the usual ultraviolet emulsions m-ere not used. The Eastman I-L emulsion (Eastman Kodak Co., Rochester, N. Y.) was preferred oyer the slo\ver but finer-grained IV-L plate and the faster 103-F plate, which has a background too high for densitometry. A4Bausch & Lomb dual-grating spectrograph TT-as used with the standard optics. As the primary aperture setting was 2.5 mm., the entire analytical gap is used. The grating of 15,000 lines per inch with a reciprocal dispersion of 8 A . per mm. (blazed a t 6000 A.) WEIS considerably more sensitive than the grab
ing of 30,000 lines per inch with a reciprocal dispersion of 4 A. per mm. (blazed at 3000 A,). Generally the dispersion of the 4 A. per mm. was preferred; the intensities were sufficient. Neither dispersion mas appreciably better in regard to the ratio of line t o background. Second order spectra were very weak. Either a 20- or 50-micron slit may be used. The calcium fluoride band head at 6036.91 A. is the strongest and is useful for identifying fluorine in low amounts. but it is poor for densitometry because of the calcium oxide bands in this region. Of all the calcium fluoride bands, the 5291.00-A. head had the lowest background and was used in subsequent analytical work. A Wratten 2B filter or glass plate was added t o the optical path t o cut out second-order ultraviolet radiation. Electrodes, inch in diameter, were used. The anodes were the deep undercut preforms, such as United Carbon 105-D (United Carbon Products Co., Bay City, Mich.). Electrodes, ‘/4 inch in diameter, required excessive arcing time. Hemispherically tipped counter electrodes were used despite considerable wandering of the arc on the sides. When buffering with calcium carbonate and graphite, the exposures were 10 to 30% darker than with flat counters. With certain sample-ammonium chloride-calcium carbonate combinations (1 to 4 t o 1 and 1 t o 5 to l), the flat counter electrodes produced equally darker exposures. The arc source used was a SpecPower 110-2, furnishing power to a Spec-Stand (National Spectrographic Laboratories, Inc., Cleveland, Ohio) with water-cooled electrodes and fume c\;haust. FINAL METHOD
Graphite powder is purchased as spectroscopically pure. Calcium carbonate is the usual reagent quality powder, dried before use. Frit samples are ground to pass a 100-mesh sieve. Portions of sample, calcium carbonate, and graphite in the proportion 1 t o 1 t o 2 are nixed in disposable gelatin capeulw in a dental amalgamator. Then 40 mg. of the mixture are placed in a decp electrode, United 105-D, which is inch in diameter. It is firmly tamped with a hemispherically tipped metal tamp. The samples are run in duplicate. The electrodes are arced a t 8 amperes for 3 minutes, using a hemispherically tipped counter electrode, standard grade. A 3-mm. analytical gap is maintained. A series of iron lines from 5200 to 5400 A. Kith intensities reported by Crosswhite (4) is used to calibrate the I-L emulsion. Transmittance values of the 5291.00-.4. band head are corrected for background. Fluorine percentages (Table 11) are plotted against fluorine intensities for a series of wet analyzed samples and the one available certified standard, National Bureau of Standards KO. 91, opal glass. The performance of the method and the validity of the wet analyses are indicated b y the straight-
line calibration curve which results. The average deviation of duplicate spectrochemical values from the corresponding wet value is 0.11%. A smaller set of these samples is selected for subsequent fluorine determinations. To cover more effectively the range from 0.3 to 3% fluorine, a separate curve has been used, employing a 50-micron slit to improve intensities and a 30second exposure to improve the background. ADDITIVES
Fluoride bands might be expected Table II.
Sample 1302C NBS91 862 1240B 1302A 863 1349A 1302B 1349B 1240C
Analytical Data
Analysis, 70Fluorine SpectroWet chemical 6.02 6.0 5.72 5.7 3.20 3.1 2.94 2.87 2 61 2 58 2 10 18 2 00 2 28 1 70 1 7’7 1.43 1.40 1.13 1.65
vi-
ation,
9%
0.02 0.02 0.10 0.07 0 03
0 3 0 28
0 07
0.03 0.52
Table Ill.
Ratio0 1010
Slit, Filter, Microns % Trans. 20 35
from strontium, barium, or calcium in frits. Fortunately, strontium is rarely used. The barium fluoride bands at 4950.5 A. are weak, and the presence of barium oxide up to 10% has not seriously affected the calcium fluoride emission. S o evidence was found of bands of fluorine with silicon, sodium, potassium, or boron. Calcium carbonate is added to produce the calcium fluoride bands. The correct amount of calcium carbonate results in the maximum formation of calcium fluoride. As more calcium carbonate is added, the time required for the consumption of the sample increases. Equal parts of sample and calcium carbonate are adequate. This makes the calcium content of the sample n minor factor. Various combinations of sample, ammonium chloride, calcium carbonate, and graphite have been tried. Table I11 indicates features of each combination. Some required oven drying of the filled electrodes. Globule formation is avoided by adding graphite or ammonium chloride. hIoderate t o high proportions of ammonium chloride (ratio notations 1410 and 1810) caused a dry
Principal Mixtures Tested
Time,
Counter Preferredb H or F
Notee Irregular arcing with globule formation 180 H or F 10 to 2070 precision 2120 20 35 Similar to 2120 180 H or F 20 35 2012 180 H Preferred 20 100 1012 Requires 180 seconds 1014 50 100 180 H or F 1018 50 100 180 H or F Requires 180 seconds 180 H or F No advantages 1210 20 100 loo 40 F Low background 1410 50 Tendency for sample ejection, low F 1810 50 100 30 background 150 F High background 1410 50 100 High background 150 F 1810 50 100 Slow burn 180 H or F 1180 50 100 Slow burn 180 H or F 1440 50 100 For low fluorine 30 H 50 100 1012 Ratio of sample t o ammonium chloride to calcium carbonate to graphite. b F, flat; H, hemispherically tipped counter electrode. 8ec. 180
Table IV.
Data on Sample 862 (3,2y0 fluorine) Time CaF at BackInterval. 5291.00 A., ground, L30/ Mixture SeC. ?& Trans. 70 Trans. La L3O-15Ob 0.45 1.41 1018 0-30 74.7 94 30-150 28.2 53 0.32 0.90 2.43 1014 0-30 28.2 89 29.9 58 0.3i 30-150 4.6 90 1.90 6.35 1012 0-30 30-150 30.8 55 0.30 7.1 83 1.59 0.94 1210 0-30 1.8 33 1.7 30-150 22.9 79 0.82 4.32 1410 0-30 30-150 31.5 45 0.19 48.0 82 0.52 10.4 1810 0-30 30-150 35.0 40 0.05 Per cent transmittance is read of the calcium fluoride line at 5291.00 A. and the background just below band head. Setting 50y0 transmittance at an intensity of 1.00, relative intensities of line (including background) and background are read. L is corrected line intensity. 6 Ratio of intensity of first 30 seconds to next 2 minutes. 0
VOL. 30, NO. 8, AUGUST 1958
1331
thermal expansion, partial sample ejection, and occasional interruption of the arc. Ammonium chloride and graphite have dissimilar effects as shown by Table IV; relatively smaller proportions of graphite cause early volatilization. The slow calcium fluoride emission is pronounced in the 1018 mixture; the larger sample available with the 1012 mixture produces a better ratio. With ammonium chloride present, the best ratio is 1810, indicating an advantage of ammonium chloride if the required sensitivity permits such a drastic sample dilution. The inadequacy of a 30-second exposure is due to nonquantitative calcium fluoride emission during this time. The background improvement counteracts this for some analytical applications. The 1012 mixture arced for 3 minutes is the most dependable arrangement, as shown b y Tables I11 and IV. The steadiness of the arc is a strong argument in its favor. Moderate variations in sodium, potassium, or barium content did not affect the fluorine results. Wainer and Dubois (8) presented briefly a method for enamel frits. They placed a calcium carbonate-sample mixture on the broken top of a flat electrode. This reduces the globule difficulties, but results in low sensitivity and high background. Additives for internal standardixation impose additional complications. Monnot ( 7 ) uses the unusual device of
reading a second-order silicon line, 2435.16 or 2987.65 A., against calcium fluoride 5291.00 A. Gillis, Eeckhout, and Kemp (6) use copper 5105.54 A. for slag analysis. Both claim better accuracy than when calcium fluoride is read against background, but this has not been studied to any extent for frits. AVERAGE-TIME SETTINGS
Ahrens ( I ) found that an exposure time of 1.5 seconds a t 7 amperes was adequate for phosphate rock containing a few tenths per cent fluorine. This is definitely misleading in the solution of the frit problem. For frits, the calcium fluoride emission occurred throughout a 3-minute exposure period, but this time can be altered considerably by changing the ratio of additives to sample. By burning to completion several sample and additive combinations, 8 or 10 amperes produced a favorable burn. S o serious attempt was made to increase the amperage, and a t a lower amperage the burning is too slow. With the more favorable mixtures, the calcium fluoride 5291.00-A. band in the second 30-second period is only 10 to 20% of the intensity of the first 30-seeond exposure period. This effect was studied with several mixtures. -4sample is arced a t 8 aniperes, jogged after 30 seconds, and burned an additional 2 minutes (approximately to completion for the mixtures studied). Table I V shows for
six sample mixtures the per cent transmittance of the calcium fluoride 5291.00-4.band head and background, and a corrected line intensity. The ratios of the lines for the first 30 seconds to the next 2 minutes are tabulated. Background is appreciable in the interval from 30 to 150 seconds, which makes it desirable to complete the arcing in 30 seconds. However, considerable fluorine is observed after the first 30 seconds. With the 1210 mixture, the major part comes over later, as shown by the line ratio of 0.94. LITERATURE CITED
.ihrens, L. H., “Quantitative Spectrochemical Analysis of Silicates,” pp. 93-8, .Iddison-Wesley, Cambridge,
Mass., 1955. 12j Ahrens, L. H., “Spectrochemical .\rialvsis,” pp. 145-51, 173-6, Addisonh-esley, Cambridge, Mass., 1950. (3) Castro, R., Loude, R., Spectrochint. Acta 4, 496 (1952). Crosswhite, H. M ,Zbid., 4,122 (1950).
Gillis, J., Eeckhout, J., Kemp, S . , Rev. universelle mines 8 , 284 (1952). Harrison, G. R . , Lord, R. C., Loofbourow, ,J R., “Practical Spectroscopy, p. 446, Prentice-Hall, Sew York, 1948. IIonnot, G. A , Spectrochim. dcta 6, 153 (1954).
Kainer, E., Dubois, E. M., Bull. Am. Ceram. SOC.20, 4 (1941).
RECEIVEDfor review March 25, 1957. -4ccepted March 24, 1958. Pittsburgh Conference on -4nalytical Chemistry and -4pplied Spectroscopy, March 1957.
Determination of Simple Aliphatic Nitriles by Reaction with Alkaline Hydrogen Peroxide DOROTHY H. WHITEHURST and JAMES E. JOHNSON Development Deportment, Union Carbide Chemicals Co., Division o f Union Carbide Corp., South Charleston, W. Va.
b A chemical method for the determination of nitriles is based on the reaction of nitriles with alkaline peroxide. By concentrating the reaction mixture, the nitrile is completely saponified to the salt of the corresponding acid. One mole of base is consumed in the over-all reaction. The method has been applied to the determination of a number of simple aliphatic amines. Where it is applicable, concentrations ranging from a few parts per million to 100% can be determined. The standard deviation of the method is 0.5% for high purity samples and 0.15 p.p.m. in the range of 5 p.p.m. of the nitriles in water. 1332
ANALYTICAL CHEMISTRY
M
OST of the analytical methods reported for nitriles depend on a determination of nitrogen content. These methods are of little value for mixtures of nitrogen-bearing compounds. Siggia and Stahl (a) were able to reduce certain nitriles to amines Land t o determine the amine formed. This method has its limitations because the reduction of a number of important nitriles, such as acetonitrile and succinonitrile, is not complete. I n the method presented here, the reaction of a nitrile Kith alkaline hydrogen peroxide to form the amide (1) has been used as the basis of a n analytical procedure. I n the initial reaction of nitrile with
excess hydrogen peroxide and potassium hydroxide some of the amide is simultaneously converted to the corresponding acid salt. By concentrating the alkaline reagent the remaining amide can be converted completely to the acid salt. The excess potassium hydroxide is theh titrated with standard sulfuric acid using phenolphthalein indicator. The difference between a blank and sample titration is a measure of the nitrile present, APPARATUS A N D REAGENTS
Potassium hydroxide, 0.2N and 1.ON squeous solutions.
