ANALYSIS OF ALUM ORES. ggj 



tation from the Levant, because it annually drew large sums 

 of money to Turkey, This prohibition increased the 

 prosperity of the Roman alum Avorks. 



The following is a brief account of the method employed ^fethod of 

 at Tolfa, near Civita Vecchia. The ore is blown up with 'J-^i^"" '^ ** 

 gunpowder: it is separated from the pieces of the rock, 

 that adhere to it: it is calcined in furnaces, nearly in the 

 same manner as lime is burned : in six or seven hours, being 

 sufficiently calcined and friable, it is taken out, • nd laid on 

 pavements of a long shape, surrounded with walled (renches : 

 on these it is laid in heaps of a moderate height, which are 

 watered for forty days with water from the trenches. The 

 ore being thus decomposed, it is boiled in large caldrons ; 

 and when Ihe water is saturated to a certain point, it is 

 poured into the crystallizing pans; where, after it is cold, it 

 deposits the alum in large crystalline masses. 



Alum is obtained in a very different manner at Solfa- and at Solfater- 

 terra, near Puzzuola. Here nature acts synthetically. ''^' 

 Fumes pregnant with sulphurous and sulphuric acid arc 

 continually issuing from little crevices in the volcanic soil of 

 this place, the former of which deposit a concrete sulphur ; 

 the second gradually penetrate the ancient lavas, which are 

 of an argillaceous nature, combine with their alumine, and 

 thus form an alum ore, which afterward affords by lixivia- 

 tion and crystallization a very pure alum. 



In the sixteenth century the art of fabricating alum Introduced into 

 spread into several parts of Europe; after it had been dis- Europe^^^^ ° 

 covered, probably by accident, that various sorts of argil- 

 laceous schists, impregnated with carbon or bitumen, and 

 subsequently termed aluminous schists, would furnish alum 

 when properly treated ; and the alkali, which did not na- 

 turally exist in them, was added during the process. The 

 'first works of this kind established in Germany appear to Germany, 

 have been those of Commotau in Bohemia, and Schwensal 

 in Saxony. 



Subsequently, that is iu the beginning of the last century, Manufactory at 

 an alum manufactory was commenced at Freienwald, in 

 Brandenburg. At present it belongs to the grand Orphan 

 School at Potsdam, and furnishes annually four hundred 

 tons of alum. 



5 The 



