MAY 15, 1940
ANALYTICAL EDITIOS
TABLE v. MISCELLANEOUS COMPOUNDs (Equivalent millimoles of CHI. Temperature 100' C.) Grignard Evolved Grianard Added Substance Found Theory Found Theory n-Butanol over0 CaO 0.100 0.006 o.ons n-Butanol overb activated AlzOa 0.173 0.172 Nil Benzophenoneb aa received 0.006 0.114 0.115 Benzophenonec recrystallized from pentane Nil 0.126 0 123 Ethyl benzoateb distilled 0,004 ..... 0. I62 0.162 (2 moles) Benzoyl peroxidec 0 , 0 6 0 O.OS3 (1 mole) 0.287 0 249 (3 moles) a Added in capillary t o cell 1 and distilled into reagent in cell 2. b Substance dissolved in isoamyl ether and added by syringe t o reagent i n cell 2. 0 Added to cell 1 and siphoned hack reagent from cell 2.
.....
.....
tions of time and temperature can be set to include all compounds containing active hydrogen. The presence of acids renders the measurement of the quantity of reacting reagent without evolution of methane extremely inaccurate. It was concluded that the method showed promise for the determination of Grignard evolved of oil and oil-impregnated paper samples but that no correlation between known groups with the Grignard added could be expected.
..... .....
Conclusion A microgravimetric Zerewitinoff method is described which has numerous advantages over the volumetric procedure. The preliminary tests show that theoretical results may be obtained for the active hydrogen content of a typical organic compound at 25' C. in the absence of certain types of peroxides. It appcars unlikely, however, that arbitrary condi-
303
Acknowledgment T h e authors wish to express their appreciation of the interest taken in this work by W. F. Davidson, director of research.
Literature Cited Assaf and Gladding. IND.ENG.CHEM., Anal. Ed., 11, 164 (1939). Balsbaugh and Onclcy, TND. EKO.CHEM.,31, 315 (1939). Evans, Davenport, and Revukas, Ibid., Anal. Ed., 11, 553 (1939). Larsen, Ibid., 10, 196 (1938). Master, Ibid.. 11, 452 (1939). Niederl, J. B., and Niederl, V., "Micromethods of Quantitative Organic Elementary Analysis", New York, John Wiley &Sons, 1938.
Wood, J. SOC.Chem. Id., 50, 257 (1931). Zerewitinoff, Ber., 40, 2023 (1907). PRESENTED before t h e Division of Microchemistry at the 99th Meeting of t h e American Chemical Society, Cincinnati, Ohio.
A Semimicro-Dumas Method for Difficult Compounds ANTHONY R. RONZIO, University of Colorado, Boulder, Colo.
A procedure is given for the determination of nitrogen in carbon compounds which form methane and tars upon pyrolysis. A special nitrometer for use in this procedure is described.
0
RGANIC compounds which form tars, graphitic carbon, or methane upon pyrolysis, present difficulties when analysis is attempted by the standard Dumas method. T h e following modification of the mcthod previously published by the author (6) has given satisfactory results on this class of compoiinds for the past 2 years, in the hands of both the author and others. Spies and Harris (6) and Hayman and Adler (3) have proposed methods for burning tar- and graphite-forming compounds. T h e large amounts of copper acetate required by the procedure of Hayman and Adler for the larger seminiicrosample introduces difficulties in burning the sample a t a slow and uniform rate, and for this reason preference is given to the method of Spies. The greater quantity of potassium chlorate necessary to burn the larger sample makes the use of boats out of the question. Mixing the potassium chlorate with cupric oxide gives satisfactory combustions. Precipitated manganese dioxide made according to the method of ter Meulen (7), after having been heated to 500" to 600" C. in a stream of purest carbon dioxide. will quantitatively burn methane to carbon dioxide and water a t 500" to 600" C. Although ter hleulen uses manganese dioxide in place of copper oxide for the Dumas nitrogen, he seems to be unaware of the oxidizing power of manganese dioxide toward
methane at a higher temperature than he recommends (400" to 450' C.). The combustion tube is made of Supremax glass. Figure 1 shows the arrangement of the burners and the dimensions of the various fillings. Sections a, h, and 1 are copper spirals, and b is a section of iodine pentoxide (60-mesh). Section c is 10-mesh pumice, which serves to insulate the hot copper oxide (gO-mesh), d, from the iodine pentoxide. Section e is 40-mesh copper reduced by hydrogen, which is followed by section.{, platinized asbestos, and sect.ion g, manganese dioxide pretreated in the following manner: The freshly precipitated and washed manganese dioxide is allowed to dry in Petri dishes, the lunips are broken up with a razor blade and screened, and the product, >20- to
