from a National Bureau of Standards solution standard) were as follows: 3.8 i 0.2 c.p.m.; Em-222, 3.9 i 0.2 c.p.m.; Po-218,3.7 0.2 c.p.m.; 3.8 i 0.2 c.p.m. Based upon. the initial activity of the radium used, the overall efficiency including chemical recovery and counting geometry was an average of 17.2% for each peak for this detector. Because this is within 5oj, (relative) of that
obtained with a source of known alpha activity with a similar counting geometry, the chemical recovery of the radium is assumed to be approximately 95%. Following some improvements in the source-detector geometry and using a 450 sq. mm., silicon-surface-barrier detector (Oak Ridge Technical Enterprises Corp., Oak Ridge, Tenn.), the overall efficiency for radium-226 measurement has consistently been on the
order of 85% with a typical background activity level of approximately 0.01 c.p.m. for the four peaks combined. LITERATURE CITED
(1) Yavin, A. I., de Pasquili, G., Baron, P., Nature 205, 899 (1965). WORKsupported by a grant from the National Gallery of Art, Washington,
D. C., in association with the National Gallery of. Art Research Project at Mellon Institute.
Decomposition of Organic Fluorine Compounds Using Sodium-Biphenyl Reagent Phyllis P. Wheeler and M a e I. Fauth, Research and Development Dept., U. S. Naval Propellant Plant, Indian Head, Md.
decomposition Of Organic fluorine compounds is often extremely difficult. Fusion with metallic sodium or potassium in a nickel bomb is often recommended as the most universally effective method (6). The oxygen flask combustion has also been applied successfully (3). Carbonbonded halogen may be converted to halide by treatment with a solution of the diphenyl-sodium-dimethoxyethane complex (sodium-biphenyl reagent) (1, 4). Because both the fusion and the oxygen flask methods require heating the sample, the sodium-biphenyl method is more convenient and less hazardous. Chambers et al. (8) found that there is a limiting vapor pressure above which this technique cannot be used without modification. UAKTITATIVE
EXPERIMENTAL
Materials and Reagents. Sodiumbiphenyl reagent (Southwestern Analytical Chemicals) was purchased (ts the premixed solution in 15-ml. vials. Toluene and isopropyl ether (Rlatheson, Coleman and Bell) were used without further purification. 1,2=-Dibromoperfluoropropane, perfluorodimethylcyclobutane, and 3,6dioxa - 2 - hydryl . perfluoro - 5methylnonane were obtained from the DuPont Co.
Procedure. A weighed sample of a size expected t o yield 1 to 10 mg. of fluorine was dissolved in an inert solvent in a 125-ml. separatory funnel. Solid and high-boiling liquid samples were weighed in gelatin capsules. Low-boiling liquids presented some difficulty. Weighing the sample in a glass capillary with the open end drawn to a fine tip proved successful with some substances. The capillary was then broken under the surface of the solvent. A vial containing 15-ml. of the sodium-biphenyl reagent is emptied into the separatory funnel containing the sample dissolved in toluene or isopropyl ether. After two minutes, excess reagent is destroyed by 2 ml. of isopropyl alcohol. The fluoride is then extracted with four 20-ml. portions of water and titrated with 0.04N thorium nitrate using sodium alizarin sulfonate as the indicator (6). RESULTS AND DISCUSSION
Several types of fluorine-containing organic compounds were analyzed. These include organic acids, halocarbons containing bromine, ring compounds, phenylmethane derivatives, and one compound, 1,l-difluorourea, in which N-F bonds occur. Data for these compounds are given in Table I. Results for research compounds which have not been completely characterized are presented in Table 11.
20640
Table 11. Results Obtained for Research Compounds
Formula
Fluorine, % , Calcd. Found
The method is applicable to a wide variety of organic compounds and may be used for compounds containing elements other than carbon, hydrogen, and fluorine, such as other halogens, nitrogen, sulfur, and oxygen. The fact that the method is suitable for the decomposition of 1,l-difluorourea indicates that it may be used for classes of fluorine compounds other than those containing only C-F bonds. The principal limitations of the method are low solubility of some compounds in the types of solvent required and handling problems arising from high volatility of sample. For those compounds which are free from the above limitations, the sodium-biphenyl decomposition of organic fluorine compounds is a rapid, convenient, and safe method of preparing the sample for subsequent determination of fluorine. LITERATURE CITED
(1) Bennett, C. E., Debbrecht! E. J.,
Table 1.
Fluorine Analysis of Various Classes of Organic Compounds
Compound p-Fluorobenzoic acid 1,l-Difluorourea 1,2-Dibromoperfluoropropane
Perfluoropropanoic acid
Formula CeHdFCOOH NH2CONF2 CF&FBrCFzBr CFsCFzCOOH
CFsCF&F( CFs)Ck( CFa) C&?&HZC~E Trisrpent afluoropheny1)-methane ( C~FS)&H Phenylpentafluoro henylmethane C ~ H ~ C H ~ C B F ~ Perf3uorodimethylcyclobutane Bis( entafluoropheny1)-methane
3,6-Dioxa-Z-hydry~perAuoro-j-
methylnonane
1970
ANALYTICAL CHEMISTRY
Fluorine, 70 Calcd. Fourid 13.56 13.68 39.57 38.38 36.79 37.01 57.91 57.87 56.87 56.61 75.98 54.57 55.43 36.80
75.64 53.96 55.65 37.03
CFsCF&F*OCF(CFs)CFzOCHFCFa 71.45 71.27
131st Meeting ACS, Miami, Fla., April 1957, Abstracts, 24B. (2) Chambers, R. D., Musgrave, W. K. R.,Savory, J., Analyst 86, 356 (1961). (3) Fernandopulle, M. E., Macdonald, A. Rf. G., Microchem. J . 11, 41 (1966). (4) Johncock, P., Xusgrave, W. I(. R., Wiper, A., Analyst 84, 245 (1959). (5) Ma, T. S., ANAL. CHEW30, 1557 (1958). (6) Steyermark, A., "Quantitative Qrganic Microanalysis," 326-32, 2nd ed. Academic Press, New York, 1961. Division of Analytical Chemistr 152nd Meeting, ACS, New York, N. %!,1966. Research supported by the Foundatlonal Research Program of the Naval Ordnance Systems Command.
