The time history of the reaction processes occurring behind shock waves through argon-diluted mixtures of CO and O2 containing at most 1 ppm hydrogenous compounds has been studied spectroscopically between 1500° and 3000°K. The initial reaction regime was investigated by using spectral portions of the CO-fundamental and CO2−ν3-fundamental infrared bands and spectral portions of the ``CO-flame emission.'' An induction period has been observed which precedes the onset of measurable electronic ground-state CO2 formation and atomic oxygen production. The induction period is inversely proportional to the square roots of the initial mole concentrations of CO and O2. The temperature dependence of the induction time for the initiation of CO2 formation can be represented by an ``apparent activation energy'' which varies from 22 kcal/mole at 1500°K to 40 kcal/mole at 3000°K. Addition of 0.1% H2 results in a decrease of the induction period and a decrease of ``apparent activation energy'' for the induction period. At temperatures above 2400°K, the contamination by hydrogenous species becomes negligible and the induction period is attributed to the mechanism CO+O2→CO2+O,(M+)CO+O→(M+)CO2*,CO2*+O2→CO2+20.Based upon this mechanism the rate coefficients for Reactions (I) and (II) were determined to be: kI=(3.5±1.6)×1012exp[−(51 000±7000)/RT] cm3 mole−1·sec−1and kIII=(1.4±1.1)×1014exp[−(39 000±7000)/RT] cm3 mole−1·sec−1,respectively, for 2400°K≤T≤3000°K.
Vapor pressure measurements have been made on pure iron pentacarbonyl between +31° and −19°C. The experimental results may be expressed in the form
log10 p false(normalmm Hgfalse)=−false(2096.7°K/Tfalse)+8.4959
which corresponds to a heat of vaporization for the liquid carbonyl of
°H=false(9.588±0.12false)normalkcal/normalmole
. This result confirms and extends the earlier measurements made by Trautz and Badstiibner(2) between 0° and 140°C. The need for careful purification of commercially available iron pentacarbonyl is emphasized, particularly for establishing the correct vapor pressure below 45°C.
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