Abstract
In view of the dangers said to attend the use of acetaldehyde in industrial processes, the sensitiveness to ignition of acetaldehyde vapour in admixture with air or oxygen was investigated. In the first series of experiments, case of ignition was measured by the minimum temperature at which spontaneous ignition occurred on admitting the gas mixture into a glass or metal‐lined tube kept at a specific temperature. This being a common method of determining ignition temperatures, the results could be compared with published data on other inflmmable gases and vapours. The experiment was carried out with mixtures of acetaldehyde and air or oxygen distributed over the range of maximum sensitiveness in each case. The most sensitive mixtures of acetaldehyde with air were those containing 30–60% of acetaldehyde, the lowest ignition temperature recorded being 176deg; c. in an aluminium tube; the most sensitive mixtures with oxygen contained 60–80°, of acetaldehyde, the minimum ignition temperature being 105° c. in glass or aluminium tubes. The results thus show that acetaldehyde is among the most dangerous of industrial solvents in respect of ignition by hot surfaces.
In the second series of experiments, case of ignition was measured by the minimum current in the primary circuit of an induction coil which, on interruption, would produce between standard electrodes sparks which were capable of igniting the gas mixture. This being an arbitrary test, comparative tests with other explosive gases and vapours were also included. The most sensitive mixture of acetaldehyde and air in this test contained approximately 8%, of acetaldehyde. Compared with other inflammable gases and vapours, acetaldehyde did not appear unduly sensitive to ignition by a transient source of heat of this nature.
These experiments indicate that the liability of acetaldehyde mixtures to accidental explosion in industrial operations is more likely to be due to a low ignition temperature than to exceptional sensitiveness to fugitive sources of heat such as electrical or frictional sparks. The formation of peracetic acid during the pre‐ignition oxidation of acetaldehyde could account for a number of the phenomena observed, and the explosive decomposition of peracetic acid round 110° c. may be responsible for the exceptionally low ignition temperatures of certain acetaldehyde—oxygen mixtures.