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was called stile. If I am not mistaken, the Italians have no proper appellation for black lead, but call it sometimes matita and sometimes piombino.

SAL AMMONIAC.

Ir is not very probable that Dioscorides, Pliny, and others who lived nearly about the same time, were acquainted with sal ammoniac, or mentioned it in their works; for no part of mineralogy was then so defective as that which is the most important, and which treats of salts. The art of lixiviating earths and causing saline solutions to crystallize was then so little known, that, instead of green vitriol, vitriolic minerals, however impure, were employed in making ink, dye-liquors, and other things. Places for boiling vitriol were not then established; and therefore Pliny beheld with wonder* blue vitriol, which in his time was made only in Spain, as a thing singular in its kind, or which had not its like. On this account those salts only were known which occur in a native state, or which crystallize as it were of themselves, without any artificial preparation, as is the case with bay salt. But that neutral salt, from the muriatic acid and volatile lixivious salt, occurs

* See vol. i. p. 289.

very seldom in a native state, and almost exclusively among the productions of volcanoes. I do not, however, suppose that this volcanic sal ammoniac was the first known, but that it was first considered to be sal ammoniac after that salt had been long obtained by another method, and long used.

But even if it should be believed that our sal ammoniac was known to the ancients, how are we to discover it with certainty in their writings? This salt has little or nothing by which these writers could characterize it. Neither its external form nor taste is so striking that it could be described by them with sufficient precision. The use of it also could not, at that time, be so important and necessary, as to enable us to determine whether they were acquainted with it; whereas, on the other hand, vitriol and alum can easily be distinguished among the materials for dyeing.

Nay, if this salt had been then made, as it is made at present in Egypt, and if any allusion to it were found, one might readily conjecture that sal ammoniac were really meant. But even though it must be admitted that traces of sublimation being employed occur in the writings of Dioscorides. and others, who lived nearly at the same period, we are not authorised to suppose that the knowledge of it was sufficient for the preparation of this salt.

Besides, there are two properties with which the ancients might have accidentally become ac

quainted, and which in that case would have been sufficient to make known or define to us this salt. In the first place, by an accidental mixture of quick-lime, the strong smell or unsupportable vapour diffused by the volatile alkali separated from the acid might have been observed. In the second place, it is very possible that the complete volatilisation of this salt on burning coals may have been remarked; for it had been long known that common salt decrepitates in the fire. This excited wonder; and in examining other salts people were accustomed to observe whether they possessed that property also. Had any one, with this view, thrown a bit of sal ammoniac on a burning coal, he must have seen with astonishment that instead of decrepitating it became entirely volatilised. For this experiment, however, very pure sal ammoniac would have been necessary. Had a little common salt been mixed with it, decrepitation would not have been altogether prevented; and if the sal ammoniac had been rendered impure by earthy particles, as is almost always the case with the volcanic, some earth at least would have remained behind on the coals.

The name sal ammoniacus * is indeed old, but as those who, in consequence of the name, considered the alumen of the ancients to be our alum, and their nitrum to be our saltpetre, were in an error, we should be equally so were we to

'Αλς αμμωνιακός.

consider their sal ammoniac to be the same as ours, Our forefathers believed that the ancient writers were acquainted with all minerals, as well as with all plants; and when they discovered a new one, they searched in old books till they found a name which would suit it, or which at any rate had not been given to another. Our sal ammoniac, in all probability, acquired in the same manner its name, which is not often to be found in the writings of the ancients.*

When every thing they have said of it is collected and impartially examined, no proofs will be found that under that name they understood our sal ammoniae. On the contrary, one will soon be convinced that sal ammoniacus was nothing else than impure marine salt. As the ancients were not acquainted with the art of separating salts, of refining and crystallising them, they gave to each variety or kind in the least different, which was distinguished either by the intermixture of some foreign substance or by an accidental formation, a particular name; and considering the wants of that period, this method was not so bad, For among the impure saline substances, there were always some which were found to be fitter than others

It is indeed a matter of indifference whether the name be derived from apos, arena, or rather from Ammonia, the name of a district in Libya, where the oracle of Jupiter Ammon was situated. The district had its name from sand. An H also may be prefixed to the word. See Vossii Etymol. p. 24. But sal armoniacus, armeniacus, sal armoniac, is improper.

for certain purposes. On this account they distinguished with so much care misy, sory, chalcitis, and melanteria, instead of which we use a substance contained in all these minerals, that is to say, vitriol. Our apothecary shops, however, have at present the lixivious salt under the name of various plants, from which it is extracted, with different degrees of purity.

When this is known, it will excite no wonder that the sal ammoniacus of the ancients was nothing else than our cominon salt. Dioscorides and Pliny speak of it expressly as a kind of this salt; and Columella, in a prescription for an eye-salve, recommends rock salt, either Spanish, Ammoniacal, or Cappadocian. Pliny says, that sal ammoniacus was found in the dry sandy deserts of Africa, as far as the oracle of Ammon. It is stated, both by him and Dioscorides, that this salt

* De re rust. vi. 17.7: Montanus sal Hispanus vel Ainmoniacus vel etiam Cappadocus.

+ Lib. xxxi. cap. 7. sect. 39: Quo exemplo inter Ægyptum et Arabiam etiam squalentibus locis, cœptus est inveniri, detractis arenis; qualiter et per Africæ sitientia usque ad Hammonis oraculum. Is quidem crescens cum luna noctibus. Nam Cyrenaiċi tractus nobilitantur Hammoniaco et ipso, quia sub arenis inveniatur, appellato. Similis est colore alumini, quod schiston vocant, longis glebis, neque perlucidis, ingratus sapore, sed medicinæ utilis. Probatur quam maxime perspicuus, rectis scissuris. Insigne de eo proditur, quod levissimus intra specus suos, in lucem universam prolatus, vix credibili pondere ingravescat. Causa evidens - - -

Lib. v. cap. 126. p. 376: Inter salis genera efficacissimum fossile. Et in hoc ipso genere communiter quidem laudatur calculis vacans, candidum et pellucidum, densum et æquabili compage; pe

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