A kinetic study has been made of the decomposition of benzoyl peroxide in benzene. Kinetic data for this study have been obtained from three separate sets of measurements. Rate measurements from evolved carbon dioxide and direct iodometric measurements of peroxide are in good agreement. Alkali-metric determinations of the product, benzoic acid, have also been made during the course of the reaction.Gravimetric determinations show that the total evolved carbon dioxide from the reaction is a function of the temperature, and indicate that the mechanism involves two parallel fast reactions, one of which evolves one mole of carbon dioxide per mole of peroxide and the other two moles of carbon dioxide per mole of peroxide. The latter reaction predominates at higher temperatures.A kinetic analysis is included and provides for a slow reaction involving the rupture of the peroxide bond, followed by free radical reactions.[Formula: see text]The secondary free radical reactions would probably form hydrogen radicals, but there is evidence to support the view that these hydrogen radicals are not eliminated by mutual termination.The reaction is first order and the energy of activation was found to be 31,000 cal. per mole.
The use of ultraviolet spectrophotometry for quantitative inorganic analytical purposes has long remained unexploited. An extremely large number of complexes of metals have characteristic absorption properties in the visible portion of the spectrum and many colorimetric methods of analysis depend upon this fact. With the present availability of ultraviolet spectrophotometric equipment the charachteristic absorption properties of many "colorless" metallic complexes in the ultraviolet region of the spectrum should as conveniently be capable of similar utilization. The use of ultraviolet spectropho·tometry for quantitative inorganic analytical purposes has long remained unexploited o An extremely large number of complexes of metals have characteristic: absorption properties in the visible portion of the spectrum and many colorJ.= metric methods of analysis depend upon this facts With the present availability of ultraviolet spectrophotometric equipment the charac= t eristic absorption properties of many "colorless" metallic complexes in the ult.raYiolet region of the spectrum should as conveniently be capable of similar utilizationo With a view to extending the knowledge of "colorless 11 complexes with absorption in the ultraviolet region of the spectrum a study of the zin c~l:lO~·phenanthrollne complexes was undertaken .Experiments are cited which show t.hat the optimum pH to be used in he study is 5 and that maximum absorption of the complex occurs at 292 . 5 mu.. Co~sequently these conditions are used throughout the succeeding portions of the work.A time study of the stability of the complex was carried out . The molar absorbancy indexes and the instability constants of the three complexes are estimated by a method of successive approx= imations . The values obtained for these quantities are as followg 9.1 = 10,000, a2 = 18~500 a 3 = 28 500 and K1 :::: 3.4 x lo-7 x 2 ::: 1 X 10-12 and K.3 : : : : 9.17 X 10"'1.4 for the molar e.bsorbancy indexes and instability constaJJ.ts of the hl~ the ,2gl a:nd the Jgl complexes respectively.An equation was developed involving these six quanti ties ~rnd the analy·tical concentra"Lion of the zinc (II) and 1~10-phenanthroline by means of which~ it should be possible to calctuate the abaorbancy of any mixture of zinc (II) and 1~10-phenanthroline. Results obtained were only fair but were as good as similar calculation made using values given for the three instability constants in the l~terature by Ie M. Kol thoffoThe molar absorbancy index of l,lO=phenanthroline was determined to have a value of 6.?660o This value is also necessary i.n the calcu.~ lations mentioned abovee A method for the determination of zinc(II) is ou lined ar.rl the interference of various ions is shown . A statistical analysis of the data is carried out for the purpose of determining the bes straight line through the data and to prove that the Beer"'·Lambert law is obeyed . Further analysis of the data provides a measure of the error t.o be expected in a determination, and permits estimation of whet...
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