OF ARTS AND SCIENCES. 61 



The silver of tlie Spanish and Mexican coins was doubtless pre- 

 pared by the American system of amalgamation.* In this process, 

 speaking in general terms, it would appear that silver is reduced by 

 means of metallic mercui'y from a solution of chloride of silver in 

 chloride of sodium, the amalgam which is formed being exposed 

 meanwhile to the action of chloride of copper and perchloride of iron. 



It is to be inferred from the investigations which we have cited, that 

 under these circumstances the amalgam should be almost entirely free 

 from any contamination with the more strongly electropositive metals.t 

 It would seem, indeed, that the American system of amalgamation 

 furnishes purer silver than is obtained by any of the other processes 

 which are employed upon the large scale. 



So far as concerns the occurrence of lead in the silver coin of 

 our own country, it could probably be mainly, if not altogether, avoided, 

 by employing zinc free from lead, such as is manufactured in Pennsyl- 

 vania, as we have already described in our Memoir. 



It is interesting to observe, that the occurrence of lead in some of 

 the silver coins of the ancients | has been thought to indicate "that 

 the process of separating lead and silver was less perfectly executed 

 in the ages of antiquity than is at present the case." § Yet, in none 



* Described by Humboldt in his Essai Politique sur le Eoyaume de la Nouvelle 

 Espagne, (Paris, 1811,) II. 558. See also Karsten, Abhandlungen der phys. Klassc 

 der Akad. der Wissenschaften zu Berlin, 1828, p. 1 ; and Karsten u. Dechen's 

 Archiv fiir Mineralogie, etc., 1829, I. 161 ; and again, ibid. XXV. 178, and in 

 Dingler's Polyt. Journ., 1852, CXXVI. 357. Compare the subsequent statements 

 of Boussingault, Ann. Ch. et Phys., 1832, [2.] LI. 350. 



t In the European system of amalgamation, as practised at Freiberg in Saxony, 

 where the silver is reduced from its chloride by metallic iron instead of quicksilver, 

 a similar degree of purity in the silver is not to be expected. (For analyses of such 

 silver, " Tellersilber," see Kerl, op. cit., I. 234.) 



J Walchner, Schvi^eigger's Journal fiir Ch. u. Phys., 1827, LI. pp. 204, 205. 

 J. W. Draper, Silliman's Am. J. Sci., 1836, [1.] XXIX. 160. Sarzeau, Journal 

 de Pharmacie, 1839, XXV. 503. Briiel and Hausmann, Karsten u. Dechen's 

 Archiv fiir Mineralogie, etc , 1844, XVIII. 505 ; also in J. pr. Chem., XXX. 334. 

 J. W. Mallet, Trans. Royal Irish Acad, 1853, XXII. 319. Briiel and Hausmann 

 refer also to earlier determinations of lead in antique coins by Klaproth (probably 

 in his Beitrage zur chemischen Kenntniss der Mineralkorper, 1795 - 1780, B. VI.), 

 and by Goebel (doubtless in his brochure, Ueber den Einfluss der Chemie auf die 

 Ermittelung der Volker der Vorzeit, etc., Eriangen, 1842) ; but they do not indicate 

 precisely where these analyses are to be found, nor have we any means of ascer- 

 taining this point. 



^ Briiel and Hausmann, loc. cit., Archiv. p 509 ; J. pr. Chem., p. 338. 



