236 BOOK VII. 



not easily separated, is added sulphur and sand made from stones which 

 easily melt. 



Sal artificiosus^^ suitable for use in assaying ore is made in many ways. 

 By the first method, equal portions of argol, lees of vinegar, and urine, 

 are all boiled down together tiU turned into salt. The second method is from 

 equal portions of the ashes which wool-dyers use, of lime, of argol purified, 

 and of melted salt ; one libra of each of these ingredients is thrown into 

 twenty librae of urine ; then all are boiled down to one-third and strained, 

 and afterward there is added to what remains one libra and four undue 

 of unmelted salt, eight pounds of lye being at the same time poured into 

 the pots, with litharge smeared around on the inside, and the whole is boiled 

 till the salt becomes thoroughly dry. The third method follows. Unmelted 

 salt, and iron which is eaten with rust, are put into a vessel, and after 

 urine has been poured in, it is covered with a lid and put in a warm place 

 for thirty days ; then the iron is washed in the urine and taken out, and 

 the residue is boiled until it is turned into salt. In the fourth method by 

 which sal artificiosus is prepared, the lye made from equal portions of 

 lime and the ashes which wool-dyers use, together with equal portions of 

 salt, soap, white argol, and saltpetre, are boiled until in the end the mix- 

 ture evaporates and becomes salt. This salt is mixed with the concentrates 

 from washing, to melt them. 



Saltpetre is prepared in the following manner, in order that it may be 

 suitable for use in assaying ore. It is placed in a pot which is smeared on 

 the inside with litharge, and lye made of quicklime is repeatedly poured over 

 it, and it is heated until the fire consumes it. Wherefore the saltpetre 

 does not kindle with the fire, since it has absorbed the lime which preserves 

 it, and thus it is prepared^". 



The following compositions^^ are recommended to smelt all ores which 

 the heat of fire breaks up or melts only with difficulty. Of these, one is made 

 from stones of the third order, which easily melt when thrown into hot 

 furnaces. They are crushed into pure white powder, and with half an uncia 



^^Sal artificiosus. These are a sort of stock fluxes. Such mixtures are common in all 

 old assay books, from the Probierbiichlin to later than John Cramer in 1737 (whose Latin 

 lectures on Assaying were published in English under the title of " Elements of the Art of 

 Assaying Metals," London, 1741). Cramer observes (p. 51) that : " Artificers compose a 

 " great many fluxes with the above-mentioned salts and with the reductive ones ; nay, 

 " some use as many different fluxes as there are different ores and metals ; all which, however, 

 " we think needless to describe. It is better to have explained a few of the simpler ones, 

 " which serve for all the others, and are very easily prepared, than to tire the reader with 

 " confused compositions : and this chiefly because unskilled artificers sometimes attempt 

 " to obtain with many ingredients of the same nature heaped up beyond measure, and with 

 " much labour, though not more properly and more securely, what might have been easily 

 " effected, with one only and the same ingredient, thus increasing the number, not at all 

 " the virtue of the things employed. Nevertheless, if anyone loves variety, he may, according 

 " to the proportions and cautions above prescribed, at his will chuse among the simpler kinds 

 " such as will best suit his purpose, and compose a variety of fluxes with them." 



^''This operation apparently results in a coating to prevent the deflagration of the 

 saltpetre — in fact, it might be permitted to translate inflammatur " deflagrate," instead of 

 kindle. 



^^The results which would follow from the use of these " fluxes " would obviously 

 depend upon the ore treated. They can all conceivably be successful. Of these, the first 

 is the lead-glass of the German assayers — a flux much emphasized by all old authorities. 



