If the operation be pushed by increasing the heat of the retort to redness, there remains at length only a mass of spungy charcoal, and the substance is totally convened into the following new compounds, namely, the residuary charcoal, the oily matter, and the matter held in solution in the water of the apparatus. This latter proves to consist of a large portion of acetic acid, with which is combined a very little ammonia.
There is no inflammable gas given out in this process unless the heat be carelessly managed. If the vapour of the oily matter as it arises be exposed to the sides of the retort elevated to a high temperature, it is decomposed, and instead of oil there are thus obtained by a violent distillation in a naked fire, scarcely any products but acetic acid and an inflammable gas. This fact is analogous to those occurring in the ordinary process for decomposing such inflammable bodies as can be made to put on the gasseous state─and we ought, in fact, to consider every process of this kind, where a rapid distillation with a hot fire is used, as a succession of decompositions; the matter first produced being afterwards exposed to another process of destruction. It is not therefore perhaps very correct language, to say that vegetables yield a great quantity of inflammable gas on distillation with a naked fire; this is the produce of a second distillation which by the common mode of operating is confounded with the first. As this reasoning applies equally to all other similar processes, it would be desirable to use a more accurate mode of describing this common operation by which we might in some important instances be led to a more correct practice. Thus, for example, in the common mode of distilling coal to produce the inflammable gasses, this double operation is carried on at once by the application of the petroleum and naphtha at first produced to the heated iron of the retort. It is in consequence of this imperfect mode of ex-