The engine turned over and backfired, black smoke frothing out of the tail pipe.
Flux.A common event in the exudation of turbid, frothing liquids from wounds in the bark of trees, and the odours of putrefaction and even alcoholic fermentation in these are sufficiently explained by the coexistence of albuminous and saccharine matters with fungi, yeasts and bacteria in such fluxes.
"Frothing" is another objectionable feature with many liquids.
The reaction is accompanied by much frothing, and the whole is filtered when in a state of tranquil fusion.
Moreover, since local cooling, with its consequent viscosity and tendency to froth, are avoided, the frothing is not excessive in spite of the rapidity of the reaction.
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