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National Advisory Committee for Aeronautics, Technical Notes - Investigation of Hydrocarbon Ignition

Accurate spontaneous ignition temperatures have been determined
for some 50 pure organic compounds. The effects of a wide variety
of additives and of eight selected metals on the spontaneous—ignitionr
temperature values of representatives of this group also have been
observed. Results are correlated with chemical structure and with
antiknock characteristics where known; more fundamental aspects of
the possible chainrbreaking and chain—branching reactions involved
also are considered.

While considerable data are available on the spontaneous ignition
temperatures of Organic compounds, there is wide discrepancy between
the results of various investigators, and even within the findings of
a single investigator. This difficulty is due to the marked sen—
sitivity of the determinations to a large number of variables, as has
been pointed out previously (reference 1), and, accordingly, to even
minor variations in equipment or procedure. The present study has as
its objective: (1) The determination of a large number of spontaneous—
ignition—temperature values for selected series of organic comp
pounds of high purity in order to correlate structure with ease of
spontaneous flammability, (2) the observation of the effect of metal
surfaces and of a variety of additives on the spontaneous—ignition—
temperature values of certain hydrocarbons, and (3) the development
of sufficient information and theory to permit a more scientific
approach to the formulation of fuels and lubricants of reduced sponr
taneous flammability. This study was made at the Applied Science
Research Laboratory of the University of Cincinnati under the sponsor-
ship and with the financial assistance of the National Advisory
Committee for Aeronautics.

The equipment for this investigation comprised two metal blocks
(one stainless steel and one copper) modeled after the apparatus of
Sortman, Beatty, and Heron (reference 2). The two blocks gave comr
pletely parallel results; however, the copper block was not used at
the higher temperatures because of the rapid formation of a heavy
copper—oxide layer under those conditions.