Note 527 — ALUM.

“This year (1460) is distinguished by the discovery of alum at Tolfa vecchia, no one there having been acquainted with it till that period: and this happened by means of one John di Castro, who had acquired some knowledge of it from a young man of Corneto, and a Genoese, who had learned in Turkey the whole process of making it. The said John having observed that in the mountains of Tolfa there were undoubtedly veins of alum, he caused some of the earth and stones to be dug up, and the first experiments were made on them at Viterbo in the following manner. The stones were first calcined in a furnace; a large quantity of water was then thrown over them; and when they were entirely dissolved, the water was boiled in great leaden caldrons; after which it was poured into wooden vessels, where, evaporating by degrees, the result was alum of the most perfect kind. Pope Pius II., sensible of the great benefit which might arise from this mineral to the Apostolic Chamber, employed more than eight hundred persons at Tolfa in preparing it.”—Historia della Città de Viterbo, di Feliciano Bussi. In Roma 1742, fol. p. 262.