157

ALKALI, POTASH, AND GUNPOWDER.

indebted to the labours of those eminent German chymists,Putt, Model, and Maygraf; and especially after the year1758, when the latter had proved that the basis of commonsalt was not, as had been hitherto believed, an alkalineearth, but a fixed alkali: because it was in many ofits properties different from the fixed vegetable alkali. 5 6Soon afterw'ards the subsLance was discovered in mineralsprings, which has since been proved by Model and others,that it is not essentially different from what is in the eastcalled natrum. It certainly appears that the nitrum of theancients and the natrum of the recent Orientalists , are onlydifferent pronunciations of the same word.

We now advert to the more ancient and general mode ofobtaining alkaline salt. The near affinity of wood-ashes tothe nitrum of the ancients, which is universally acknow-ledged from the evidence they have left us of its propertiesand effects, proves also that it was a lixivious salt. Theo-phrastus says, that nitrum was understood to be the produceof oak-ashes; and Pliny after him remarks, that it was cer-tain the ashes of that wood were nitrous. He also ascribesthe same property to the burnt lees of wine. He also con-siders as a species of nitrum those ashes, which in countriesdestitute of salt, were used for seasoning food, and whichwas prepared by pouring sea or salt water over burning pilesof wood gradually and in small quantities, so that the fireshould not become extinguished, by which process the waterevaporated, leaving the salt behind, but indeed mixed withcharcoal, ashes, and lixivious salts; consequently, it musthave been moist, or perhaps nauseous, if not refined orcleared by some new process. This method of preparingsalt, which is, perhaps, the most ancient which the variouswriters ou the subject have mentioned, from a want mostlikely of actual observation, they have not left us specificinformation, whether it was sea-water or brine that was em-ployed, but speaking in such a manner as if any kind ofwater answered the same purpose.

Varro reports that he saw the last described process em-ployed on the llliine.* Pliny says, 7 that oak-timber hadbeen before burnt for that purpose. Also, in another place,

5 Chymisehes Schrificn, i. 169.

6 “Iu Gallia transalpina. intus ud Rhenum, aliquot regioues acccssi .. . ubi salemnee fossiciurn nec niarUimum haberenl, sed ex quibusduni lignis conibuslis carbo-nibus salsis pro eo uterenlur .”—Dt lie Ru&tica, lib. i. cap. 7. Little, however,depended on the wood; the chief thing was sprinkling it with water.

7 “ Qucrcu cremaui minquaiu multum factitntum rst, et jam pfridem toluraoinissuai.” xxxUlO.