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Rh but dark brown. If four or ﬁve hours elapse before the solution is poured into the water, the resin precipitated is found to be com- pletely black. And if the digestion is continued for several days, or until there is no longer any production of sulphureous gas, the tur. pentine is converted into a black porous coal, which does not contain any resin, although a substance hereafter noticed may frequently be separated from it by digestion in alcohol.

When common resin was treated in the same manner, about 43 per cent. of the coal was obtained, which, after exposure to a red heat in a loosely-covered platina crucible, still amounted to more than 30 per cent., and appeared to possess properties very similar to those of some of the mineral coals.

Mr. Hatehett having obtained, in the manner above described, yellow resin, brown resin, black resin, and coal, from a quantity of common turpentine, dissolved a portion of each of these, and also of the turpentine, in nitric acid, and then reduced the solutions to dry- ness. The residua, which varied in colour, from yellow to dark brown, were dissolved in distilled water, and examined by solution of isinglass and other re-agents.

l. The solution of the residuum of turpentine was of a pale straw colour, and did not contain any tan.

2. That of the yellow resin resembled the former in every respect.

3. That of the brown resin was of a deeper yellow, but (lid not afford a vestige of tan.

4. That of the black resin, on the contrary, afforded a. consider- able portion of tan.

5. That of the coal afforded tan in great abundance.

Hence it appears, that these modiﬁcations of turpentine yield tan only in proportion to the quantity of their original carbon, progres- sively converted into coal.

Other substances, particularly various kinds of wood, copal, am- ber, and wax, when reduced into coal in the humid way, were in like manner converted into tan by nitric acid.

But tan may, Mr. Hatehett says, he artiﬁcially produced, without the help of nitric acid; for if any of the resins, or gum resins, after long digestion with sulphuric acid, are digested with alcohol, a dark brown solution is formed, which, by evaporation, yields a mass that is soluble in water or in alcohol, and which copiously precipitates gelatine, acetate of lead, and muriate of tin, but produces only a slight effect on oxymuriate of iron.

In the subsequent section of this paper, Mr. Hatehett mentions some circumstances which induce him to think that a natural process, similar to those above described, sometimes takes place in peat moors, and that tan has been, and continues to be, formed during the gradual carbonization and conversion of the vegetable matter into peat. Supposing this opinion to be correct, it seems, he Bays. at ﬁrst difﬁcult to conceive how the formation of tan is effected during the growth of those vegetablcs from which it has hitherto been obtained; but after adverting to the experiments and observa-