CHAPTER II

SALTPETRE

The attention of the ancients was naturally attracted by the efflorescences which form on certain stones, on walls, and in caves and cellars; and the Hindus and nomad Arabs must have noticed the deflagration of at least one of them when a fire was lit on it. These efflorescences consist of various salts,—sulphate and carbonate of soda, chloride of sodium, saltpetre, &c.—but they are so similar in appearance and taste, the only two criteria known in primitive times,[19] that early observers succeeded in discriminating only one of them, common salt, from the rest. So close, in fact, is the resemblance between potash and soda, that their radical difference was only finally established by Du Hamel in 1736. Common salt received a distinctive name in remote times; all other salts were grouped together under such vague generic names as _nitrum_, _natron_, _afro-nitron_, &c.

No trace of saltpetre has hitherto been found anywhere before the thirteenth century. The Greek alchemists of preceding centuries are silent. There is no saltpetre in the earliest recipe we possess for Greek fire, No. 26 of the _Liber Ignium_,[20] ascribed to one Marcus Græcus, either as given in the Paris MSS. of 1300, or in the Munich MS. of 1438. It is true that the phrase _sal coctus_ in this recipe has been translated by _saltpetre_ in M. Hœfer’s untrustworthy _Histoire de la Chimie_, but as MM. Reinaud and Favé remark: “Rien n’autorise à traduire ainsi; le sel ordinaire a été souvent employé dans les artifices.”[21] There is no instance in Latin, I believe, of saltpetre being designated otherwise than by _sal petræ_ (or _petrosus_), or by _nitrum_, singly or in combination with some other word, as _spuma nitri_. The substitution of _sal petræ_ for _sal coctus_, in later editions of the recipe, only shows that when the valuable properties of saltpetre became known it was employed instead of common salt. The very fact of the change having been made by most of the later alchemists, proves that to them _sal coctus_ did not mean _sal petræ_, but something else. If _sal coctus_ had meant _sal petræ_, what need was there for the change? This change, however, was not universal. In the version of recipe 26, given in the _Livre de Canonnerie et Artifice de Feu_, published in Paris in 1561, but written long before by a fire-worker well acquainted with saltpetre, we find: “prenez soufre vif, tarte, farcocoly (sarcocolla), peghel (pitch), sarcosti (sal coctum), &c.”[22] The word _coquo_ (to boil or evaporate) was necessarily connected with the preparation of common salt by evaporation,[23] and _coctus_ would correctly distinguish evaporated or artificial salt from natural or rock salt. In his “Natural History,”