Note note 26, p. 394 — BOOK IX.[1]

[26] Pompholyx. (Interpretatio gives the German as Weisser hütten rauch als ober dem garherde und ober dem kupfer ofen). This was the impure protoxide of zinc deposited in the furnace outlets, and is modern "tutty." The ancient products, no doubt, contained arsenical oxides as well. It was well known to the Ancients, and used extensively for medicinal purposes, they dividing it into two species—pompholyx and spodos. The first adequate description is by Dioscorides (V, 46): "Pompholyx differs from spodos in species, not in genus. For spodos is blacker, and is often heavier, full of straws and hairs, like the refuse that is swept from the floors of copper smelters. But pompholyx is fatty, unctuous, white and light enough to fly in the air. Of this there are two kinds—the one inclines to sky blue and is unctuous; the other is exceedingly white, and is extremely light. White pompholyx is made every time that the artificer, in the preparation and perfecting of copper (brass?) sprinkles powdered cadmia upon it to make it more perfect, for the soot which rises being very fine becomes pompholyx. Other pompholyx is made, not only in working copper (brass?), but is also made from cadmia by continually blowing with bellows. The manner of doing it is as follows:—The furnace is constructed in a two-storied building, and there is a medium-sized aperture opening to the upper chamber; the building wall nearest the furnace is pierced with a small opening to admit the nozzle of the bellows. The building must have a fair-sized door for the artificer to pass in and out. Another small building must adjoin this, in which are the bellows and the man who works them. Then the charcoal in the furnace is lighted, and the artificer continually throws broken bits of cadmia from the place above the furnace, whilst his assistant, who is below, throws in charcoals, until all of the cadmia inside is consumed. By this means the finest and lightest part of the [Pg 396]stuff flies up with the smoke to the upper chamber, and adheres to the walls of the roof. The substance which is thus formed has at first the appearance of bubbles on water, afterward increasing in size, it looks like skeins of wool. The heaviest parts settle in the bottom, while some fall over and around the furnaces, and some lie on the floor of the building. This latter part is considered inferior, as it contains a lot of earth and becomes full of dirt."

Pliny (XXXIV, 33) appears somewhat confused as to the difference between the two species: "That which is called pompholyx and spodos is found in the copper-smelting furnaces, the difference between them being that pompholyx is separated by washing, while spodos is not washed. Some have called that which is white and very light pompholyx, and it is the soot of copper and cadmia; whereas spodos is darker and heavier. It is scraped from the walls of the furnace, and is mixed with particles of metal, and sometimes with charcoal." (XXXIV, 34.) "The Cyprian spodos is the best. It is formed by fusing cadmia with copper ore. This being the lightest part of the metal, it flies up in the fumes from the furnace, and adheres to the roof, being distinguished from the soot by its whiteness. That which is less white is immature from the furnace, and it is this which some call 'pompholyx.'" Agricola (De Natura Fossilium, p. 350) traverses much the same ground as the authors previously quoted, and especially recommends the pompholyx produced when making brass by melting alternate layers of copper and calamine (cadmia fossilis).