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 armonia, a fastening or joining, from the use of sal ammoniac in soldering metals.

That Pliny did sometimes meet with the genuine sal ammoniac is conjectured by his allusion to the "vehement odour" arising when lime was mixed with natrum. Probably this natrum was sal ammoniac. Among the Arabs the term sal ammoniac often means rock salt; but in the writings attributed to Geber, some of which may be as late as the twelfth or thirteenth century, our sal ammoniac is distinctly described. It is also exactly described by Albertus Magnus in the thirteenth century, who mentions an artificial as well as a natural product, but does not indicate how the former was made. From this time sal ammoniac became a common and much-prized substance in alchemical investigations, as from it chlorides were obtained. The "volatile spirit of sal ammoniac" was made by distilling a solution of sal ammoniac with quicklime, and of course the same product was obtained in other ways, especially by distilling harts' horns, and this was always regarded as having peculiarly valuable properties. A "sal ammoniacum fixum" was known to the alchemists of the fifteenth century. It was obtained as a residue after sal ammoniac and quicklime had been sublimed. It was simply chloride of calcium.

The so-called natural sal ammoniac was for centuries brought from Egypt, and was supposed to have been mined in the earth or sand of that country. In 1716 the younger Geoffroy came to the conclusion that it must be a product of sublimation, and he read a paper to the French Academy giving his reasons for this opinion. Homberg and Lemery opposed this view with so much bitterness, however, that the paper was not printed. In 1719 M. Lemaire, French Consul at Cairo,