BOOK XI. 505 



amount of silver in the copper, he alloys it fourfold ; for instance, if in three- 

 quarters of a centumpondium of copper there is less than the following pro- 

 portions, i.e. : half a libra of silver, or half a libra and a sicilicus, or half a libra 

 and a semi-uncia, or half a libra and semi-uncia and a sicilicus, then rich 

 lead — that is, that from which the silver has not yet been separated — is 

 added, to the amount of half a centumpondium or a whole centumpondium, or 

 a whole and a half, in such a way that there may be in the copper-lead alloy 

 some one of the proportions of silver which I have just mentioned, which is 

 the first alloy. To this " first " alloy is added such a weight of de-silverized 

 lead or litharge as is required to make out of all of these a single liquation cake 

 that will contain approximately two centumpondia of lead ; but as usually 

 from one hundred and thirty librae of litharge only one hundred librae of lead 

 are made, a greater proportion of Utharge than of de-silverized lead is added 

 as a supplement. Since four cakes of this kind are placed at the same time 

 into the furnace in which the silver and lead is liquated from copper, there 

 wiU be in all the cakes three centumpondia of copper and eight centumpondia 

 of lead. When the lead has been liquated from the copper, it weighs six 

 centumpondia, in each centumpondium of which there is a quarter of a libra 

 and almost a sicilicus of silver. Only seven unciae of the silver remain in the 

 exhausted liquation cakes and in that copper-lead alloy which we call 

 " liquation thorns " ; they are not called by this name so much because they 

 have sharp points as because they are base. If in three-quarters of a centum- 

 pondium of copper there are less than seven uncia and a semi-uncia or a bes 

 of silver, then so much rich lead must be added as to make in the copper and 

 lead alloy one of the proportions of silver which I have already mentioned. 

 This is the " second " alloy. To this is again to be added as great a weight 



weighed 225 to 375lbs. This size was wonderfully persistent from Agricola down to modern 

 times ; and was, no doubt, based on sound experience. If the cakes were too small, they 

 required proportionately more fuel and labour ; whilst if too large, the copper began to melt 

 before the maximum lead was liquated. The ratio of the copper and lead was regulated by 

 the necessity of enough copper to leave a substantial sponge mass the shape of the origin^ 

 cake, and not so large a proportion as to imprison the lead. That is, if the copper be in too 

 small proportion the cakes break down ; and if in too large, then insufficient lead liquates 

 out, and the extraction of silver decreases. Ercker (p. 106-9) insists on the equivalent of about 

 3 copper to 9.5 lead ; Lohneys (p. 99), 3 copper to 9 or 10 lead. Schliiter (p. 479, etc.) 

 insists on a ration of 3 copper to about 11 lead. Kerl (Handbuch Der Metallurgischen HiUten 

 kunde, 1855 ; Vol. III., p. 116) gives 3 copper to 6 to 7 parts lead. Agricola gives variable 

 amounts of 3 parts copper to from 8 to 12 parts lead. As to the ratio of silver in the copper, 

 or to the cakes, there does not, except the limit of payability, seem to have been any difficulty 

 on the minimum side. On the other hand, Ercker, Lohneys, Schliiter, and Karsten all 

 contend that if the silver ran above a certain proportion, the copper would retain considerable 

 silver. These authors give the outside ratio of silver permissible for good results in one 

 liquation at what would be equivalent to 45 to 65 ozs. per ton of cakes, or about 190 to 250 ozs. 

 per ton on the original copper. It will be seen, however, that Agricola's cakes greatly exceed 

 these values. A difficulty did arise when the copper ran low in silver, in that the liquated 

 lead was too poor to cupel, and in such case the lead was used over again, until it became rich 

 enough for this purpose. According to Karsten, copper containing less than an equivalent 

 of 80 to 90 ozs. per ton could not be liquated profitably, although the Upper Harz copper, 

 according to Kerl, containing the equivalent of about 50 ozs. per ton, was liquated at a profit. 

 In such a case the cakes would run only 12 to 14 ozs. per ton. It will be noticed that in the 

 eight cases given by Agricola the copper ran from 97 to over 580 ozs. per ton, and in the de- 

 scription of enrichment of copper " bottoms " the original copper runs 85 ozs., and " it cannot 

 be separated easily " ; as a result, it is raised to no ozs. per ton before treatment. In addition 

 to the following tabulation of the proportions here given by Agricola, the reader should refer to 

 footnotes 15 and 17, where four more combinations are tabulated. It will be observed from 



