Note note 8, p. 443 — BOOK X.

[Pg 443][8] It is desirable to note the contents of the residues in the retort, for it is our belief that these are the materials to which the author refers as "lees of the water which separates gold from silver," in many places in Book VII. They would be strange mixtures of sodium, potassium, aluminium sulphates, with silica, brickdust, asbestos, and various proportions of undigested vitriol, salt, saltpetre, alum, iron oxides, etc. Their effect must have been uncertain. Many old German metallurgies also refer to the Todenkopf der Scheidwasser, among them the Probierbüchlein before Agricola, and after him Lazarus Ercker (Beschreibung Allerfürnemsten, etc., Prague, 1574). See also note 16, p. 234.