[150] These analyses were made by Schulz in the Laboratory of the Royal Museums.
[151] I quote here the greater part of an article published in Dingler’s “Polytechn. Journal,” 1896, Vol. CCCI. p. 44. The reduction of about 7000 Danish copper coins, undertaken while the above was in the press, gave similarly good results.
[152] The zinc, which in the course of the reduction process may become coated with a thin layer of metallic copper, may be used again. It should be first put through dilute sulphuric acid (in the proportion of 1:2), then washed, rubbed with a steel wire brush and again washed. But it must in such cases be used again while still wet, for if allowed to dry it becomes coated with a layer of oxide and requires to be re-polished.
[153] “Publications de la société pour la recherche et la conservation des monuments historiques dans le grandduché de Luxembourg,” Vol. X. As I have been unable to consult the original, I have here inserted a communication sent to me by Dr Kisa of Cologne. I have tried this method on a few coins.
[154] In another instance—that of a Minotaur group [Ant. Misc. 7382]—the calcium chloride is contained in four shallow glass troughs which are placed round the marble pedestal of the bronze and are loosely covered with a black card.
[155] Grote, “Blätter für Münzkunde,” 1835, I. No. 31, VI.
[156] “Zeitschrift für Numismatik,” Vol. XVII. 1890, p. 100.
[157] “Prometheus,” VIII. 1897, p. 351. A report on the other methods is here given.
[158] “Zeitschrift für Numismatik,” Vol. XX. 1897, p. 325.
[159] “Archaeological Journal,” XLV. 1888, p. 87.