Neufeld (“Chem. Centralblatt,” 1904, I. 1621—abstracted from “Zeitschrift für Untersuchung der Nährungs- und Genussmittel,” VII. 478) gives particulars of three varieties: Crenothrix polyspora, which separates iron; Cr. ochracea, which separates aluminium and some iron; and Cr. manganifera, which separates manganese.
Jackson (“Journal of Society of Chemical Industry,” 1902, p. 681) gives micro-photographs of these varieties. Microscopically the masses of Crenothrix are seen enclosed in a gelatinous sheath, in which is imbedded the precipitated metallic hydrate. It is anaërobic and its action is favoured by absence of light. In the absence of dissolved oxygen, the bacillus appears to take its iron from the pipes. Cr. polyspora is found however (“Zeitschrift für analytische Chemie,” XLII. 590) to separate the iron not from the ferrous carbonate (FeCO3) but from iron organically combined. See also Winogradsky, Ueber Eisenbakterien, “Bot. Zeit.,” 1888, and “Chem. Centralbl.” 1904, II. 1332. Transl.]
[17] Wagner in Dingler’s “Polyt. Journal,” CCXVIII. p. 70. Axel Krefting in the above-quoted “Forhandlinger,” p. 4.
[18] Olshausen often noticed on freshly excavated antiquities of various kinds a peculiar smell of resin or gum, especially after treatment with hydrochloric acid (“Verhandl. d. Berl. anthropol. Ges.,” 1884, p. 520). It may be supposed that this odour is due to the traces of hydrocarbons present.
[19] Termed by E. Friedel “Dunstperlen.” “Eintheilungsplan d. Märk. Prov.-Museums,” p. 9.
[20] “Om Konserviring af Jordfundne Jernsager,” in “Aarsberetning fra Foreningen till norske Fortidsmindesmaerkers Bevaring,” 1892, p. 52.
[21] Krause, “Verhandl. d. Berl. anthropol. Ges.,” 1882, p. 533.
[22] Private communication.
[23] “Sitzungsberichte der Alterthumsgesellschaft Prussia,” 1881-2, p. 9.
[24] Merkbuch, Alterthümer aufzugraben und aufzubewahren, 2nd edition, p. 71.