[1] “Lexikon d. gesamten Technik,” Vol. I. p. 257. O. Lueger.

[2] “Merkbuch.” The excavation and preservation of Antiquities, 2nd edition, Berlin, 1894.

[3] “Mittheilungen aus der Sammlung der Papyrus Erzherzog Rainer.” Vol. I. p. 118. See also Flinders Petrie, Archaeological Journal, Vol. XLV. 1888, p. 88.

[4] Aeg. 105. [This and similar notes have reference to the catalogue of the Egyptian (Aeg.) or Antiquarian (Ant.) sections of the Berlin Royal Museums.] The limestone blocks were brought from the Mastaba of Meten, at Abusir near Memphis, explored by Lepsius in 1846. Meten was one of the chief officials under King Snefru, B.C. 2800. The inscriptions relate to his possessions and official career, while the pictorial representations depict hunting scenes and the offering of the gifts for the dead. The statue of Meten was found in the grave and is now in the Egyptian department (No. 1106) of the Royal Museum. Comp. “AusfÜhrliches Verzeichniss der aegyptischen AlterthÜmer,” Berlin, 1899.

[5] Aeg. P. 4730

[6] Aeg. V. A. 2846.

[7] Aeg. P. 4739.

[8] It may be here mentioned that, as is well known to chemists, the efflorescences which often go by the name of “wall-saltpetre,” in most cases do not contain any saltpetre, but consist of sodium sulphate.

[9] Crum Brown, “Chem. Centralblatt,” 1890, I. p. 212; E. Simon, “Ueber Rostbildung u. Eisenanstriche,” p. 4.

[10] J. Spennrath, “Verhandlungen d. Vereins zur BefÖrd. d. Gewerbefleisses,” 1895, p. 245.

[11] “Christiania Videnskabs-Selskabs Forhandlinger” for 1892, No. 16, p. 8.

[12] “Chemische Zeitung. Repetitorium,” 1895, p. 289.

[13] “Chem. Centralblatt,” 1895, I. p. 441.

[14] Id., 1891, I. p. 860.

[15] “Berg- und HÜttenmÄnnische Zeitung,” 1882, p. 469.

[16] [It may not be out of place here to give the main conclusions, drawn from a long series of experiments by Prof. W. R. Dunstan (“Proc. Chem. Soc.,” XIX. 150, 1903).

(a) Pure iron is not oxidised in the presence of gases and water-vapour only, but for the appearance of rust the presence of water in the liquid state is necessary.

(b) The reagents which prevent the rusting of iron are those in the presence of which hydrogen peroxide is decomposed, and which are consequently inimical to its formation: among such reagents the following are given—sodium chloride, sodium sulphate, ferrous sulphate and potassium nitrate.

(c) The action of H₂O₂ on metallic iron leads to the production of red basic ferric hydroxide, which is identical with ordinary rust. The composition of rust may therefore be represented by the formula Fe₂O₂(OH)₂, the reaction being represented by the equations:

Fe + O₂ + H₂O = FeO + H₂O₂.
2FeO + H₂O₂ = Fe₂O₂(OH)₂.

These views are however combated by Moody (“Proc. Chem. Soc.,” XIX. 157 and 239) who concludes that aerial rusting must be regarded as a change involving the interaction of iron and carbonic acid and the subsequent formation of rust by oxidation of the ferrous salt.

He also states that those salts which do not combine with and which are not decomposed by CO₂ have no retarding influence on the formation of rust, e.g. sodium chloride, sodium sulphate, etc.

On the other hand substances which absorb and combine with carbonic oxide (e.g. sodium carbonate or hydroxide, ammonium carbonate, calcium hydroxide), or which are decomposed by carbonic acid (potassium and sodium nitrites), inhibit rusting, which may therefore be regarded as a change involving the interaction of iron and acid and the subsequent formation of rust by the oxidation of the ferrous salt.

O. KrÖhnke (“Wochensch. Brauerei,” XVII. 233) gives the following equations:

Fe + 2CO₂ + H₂O = Fe(HCO₃)₂ + H₂.
2Fe(HCO₃)₂ + O + H₂O = 2Fe(OH)₂ + 4CO₂.

Comp. also Dammer, “Handbuch der anorg. Chem.,” Vols. III. and IV. (supplement).

Considerable attention has also been directed to the influence of bacteria upon iron. Thus the growth of Crenothrix may cause much trouble in waterworks, vide “Centralblatt fÜr Bakterien und Parasitenkunde,” II. 12, 681. A variety, Chlamydothrix (Gallionella) ferruginea (Mig.) appears to play an important part in the formation of rust (comp. Zopf, “Crenothrix polyspora die Ursache der Berliner Wasser-CalamitÄt,” Berlin, 1879. De Vries, “Unter. der Crenothrix Commission,” Rotterdam, 1887 and 1890).

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.

[25] [This fact was noticed by Sir Thomas Browne, 1658, cp. “Hydriotaphia,” cap. iii. Transl.]

[26] In this work the Patina on antiquities only is considered; with that on modern bronzes we are not concerned.

[27] “Mittheilungen d. naturforsch. Gesell. in Bern,” 1865, p. 12.

[28] “Mitth. d. naturforsch. Gesellschaft in Bern,” 1860, p. 69.

[29] “Jahrbuch fÜr Mineralogie,” 1860, p. 813.

[30] Malachite, CuCO₃, Cu(OH)₂.

[31] Azurite, 2CuCO₃, Cu(OH)₂.

[32] “Jahrbuch fÜr Mineralogie,” 1865, p. 400.

[33] The extract which here follows is in part verbatim.

[34] “Annalen der Chemie u. Pharmacie,” 1853, Vol. LXXXV. p. 253.

[35] Von Bibra, “Die Bronzen und Kupferlegirungen,” p. 206 et seq.

[36] See the very full quotation from Wibel’s work given above.

[37] I have not been able to find anything on this point in the literature of the subject.

[38] Atacamite, CuCl₂, 3Cu(OH)₂.

[39] Cf. “Comptes rendus,” 1856, XLIII. p. 735.

[40] “Journal f. praktische Chemie,” XCIV. 1865, p. 314.

[41] “Verhandl. d. Ver. z. BefÖrd. d. Gewerbf.,” 1869, p. 182.

[42] Dingler, “Polyt. Journal,” 1878, Vol. CCIV. p. 483.

[43] “Berg- u. HÜttenmÄnnische Zeitung,” Vol. XXXVII. 1878, p. 329.

[44] Dingler, “Polyt. Journal,” 1879, Vol. CCXXXII. p. 333.

[45] [Several other analyses of bronzes from various sources have been recently published. Thus Natterer (“Monatshefte fÜr Chemie,” XXI. 256, 1900; also “Chem. Centralblatt,” 1900, I. 1262) examined a corroded bronze statuette from Ephesus. The bronze contained:—Tin 6·09%, lead 4·87%, and copper 89·64%, with traces of zinc.

Bassett (“Proc. Chem. Soc.,” 1903, XIX. 95) gives an analysis of the base of an Egyptian statuette, found in the Nile Delta, probably dating from 200-100 B.C. The base was hollow but filled with lead, and was covered with a thick green coating, which in parts entirely replaced the original metal.

Table I.

Table II.

In the second column the chlorine has been calculated as copper chloride, the remaining copper and other metals as oxides.

Traces of calcium were also found, but the amount of sodium was so small that it could only be detected by the flame test. If all the copper had been present as basic chloride (atacamite CuCl₂, 3CuO, 3H₂O), this would require 26·84% CuCl₂, 47·57% CuO, and 10·78% H₂O. It would therefore appear that the substance produced by corrosion is less basic than atacamite, and that ammonium chloride may have played a more important part than sodium chloride in the formation of copper chloride, for in this case the sodium was only found in amount too small for estimation.

An analysis of the earliest piece of bronze known, i.e. that from MÊdÛm, Egypt (3700 B.C.), gives 8·4% of tin (inner core 9·1%) to 89·8 of copper with a small quantity of arsenic.

An analysis of a celt from the Dowris find (King’s County, Ireland, 1825) gave copper, 85·23; tin 13·11; lead 1·14, with traces of sulphur and carbon. The waste material from the same place yielded 89% copper, 11% tin, with traces only of lead, iron and silver.

On the other hand an early bronze celt (Butterwick, E.R., Yorks.) showed a smaller quantity of tin—10·74%, compared with 87·97% of copper. (Guide to Bronze Age Antiquities, British Museum.)

Mr George Coffey has also published (“Brit. Assoc. Reports,” 1899, p. 873) a tabulated series of analyses of Irish celts which proved to be composed of practically pure copper. Transl.]

[46] Schliemann, “Ilios,” pp. 527 and 571.

[47] “Verhandl. d. Berl. anthropol. Ges.,” 1882, p. 537.

[48] Dingler, “Polyt. Journal,” 1884, Vol. CCLIII. p. 514.

[49] It should be observed that the change in the proportions according to Schuler (see page 24) is only true of the analysis, Column III. In Columns I and II the amount of metallic copper of the patina is indeed smaller, but so is also that of lead and especially of tin. But this may be due to a faulty method in the determination of tin noticed by Olshausen (v. “Verhandl. d. Berl. anthropol. Ges.,” 1897, p. 349). The different proportion of the copper compounds in the patina should also be noted, Schuler giving carbonate and hydrate in the proportion 1:1, Arche and Hassack once as 1:2, and again as the result of two analyses as 1:3.

[50] “Atti della Reale Accademia dei Lincei,” 1893, p. 498.

[51] “Étude sur les mÉtaux dÉcouverts dans les fouilles de Dahchour” in “Fouilles À Dahchour.” March-June, 1894, p. 131 et seq. J. de Morgan. See also “Comptes rendus,” 1894, I. 118, p. 768.

[52] “Revue archÉologique,” v. 28, 1896, pp. 67 and 202. In the publication for the second half of the same year Lechat maintains the assertion (comp. Elster, p. 23) that in many cases the antique patina is due to the artist.

[53] Ant. Misc. 7382.

[54] J. J. Rein, “Japan,” Vol. II. p. 528.

[55] Ant. Misc. 8579.

[56] According to Graham-Otto, “Lehrbuch der Chemie,” Vol. III. p. 849, cuprous oxide is decomposed by dilute acids which contain oxygen; the cupric oxide is dissolved and metallic copper remains.

[57] Buto, Aeg. 11867.

[58] Ant. Fr. 29.

[59] [The extraordinary deformation produced by this type of patina may be judged from the fact that the features in this instance were so obscured that the nature of the specimen was not recognised and it had accordingly been mounted upside down. Transl.]

[60] Ant. Fr. 53.

[61] Ant. Fr. 53.

[62] Bischoff, “Das Kupfer und seine Legirung,” p. 43. Layard, “Discoveries in the ruins of Nineveh and Babylon,” p. 191. Fellenberg, “Mittheilungen d. naturforsch. Ges. in Bern,” 1860, p. 68.

[63] “Christiania Videnskabs-Selskabs Forhandlinger” for 1892, 16, p. 5.

[64] [Having been broken off and soldered, the base was not subjected to treatment. Transl.]

[65] E. Friedel, “Eintheilungsplan des mÄrk. Provinzialmuseums,” 1882, p. 20.

[66] Aeg. 2348.

[67] Aeg. 13787.

[68] Olshausen, “Verhandl. d. Berl. anthropol. Ges.,” 1884, p. 532, and 1897, pp. 346-7. KrÖhnke, “Chem. Untersuchungen an vorgeschichtl. Bronzen Schleswig-Holsteins,” p. 41. See also quotation from Schuler, p. 25.

[69] [This celebrated hoard was found Oct. 9, 1868, on the Galgenberg, near Hildesheim (Hanover), 10 feet below the surface. It consisted of more than 60 pieces, including plates, dishes, tripods, etc., the most notable being a crater, 151/ 2 inches in height, ornamented with graceful scroll-work, and a cylix with an Athene in high relief. The workmanship points to a date not later than the first century A.D. Cp. Wieseler, “Der Hildesheimer Silberfund,” Bonn, 1869. Darcel, “TrÉsor de Hildesheim,” 1870. Transl.]

[70] Compare also the analysis by Schertel, p. 51.

[71] “Polytechn. Centralblatt,” 1871, p. 916.

[72] “Polytechn. Centralblatt,” 1871, p. 917.

[73] “Berg- u. HÜttenmÄnn. Zeitung,” 1878, No. 37, p. 327.

[74] Dingler, “Polyt. Journal,” 1871, Vol. CCI. p. 52.

[75] v. E. v. Bibra, “Ueber alte Eisen- u. Silberfunde,” p. 74.

[76] Morgan, “Fouilles À Dahchour,” p. 135.

[77] “Verhandl. d. Berl. anthropol. Ges.,” 1897, p. 348.

[78] Krause, “Verhandl. d. Berl. anthropol. Ges.,” 1883, p. 360.

[79] Muspratt’s “Chemistry,” Vol. III. p. 1389.

[80] “Verhandl. d. Berl. anthropol. Ges.,” 1889, pp. 243 and 244.

[81] Id. 1892, p. 449.

[82] Id. 1897, p. 347.

[83] At that time obtained from the Stralau waterworks.

[84] This was not the well-known Crenothrix only. Cp. “Polytechn. Centralblatt,” 1891-92, p. 195. (See footnote, p. 10.)

[85] It has been found that the formation of this layer of slime may be avoided by the use of tubs which are lined with sheet zinc. The addition of 10-20 cubic centimetres of formalin [40% solution of formaldehyde] to every hundred gallons of water also prevents or restrains the formation of slime. It is not necessary to add formalin each time the water is changed.

[86] Since chlorine compounds (especially common salt) form the predominating substance in the soluble salts contained in limestones their removal may be considered a proof that other salts (e.g. sulphates) have also been removed. Hence it is sufficient to prove the disappearance of chlorine. In the rare cases in which sulphates only are present, a test similar to that mentioned on p. 77, applied to clay objects, should be used. If the water used for soaking salt-containing limestone, earthenware, etc., gives no precipitate, or only turbidity with the silver solution, the determination of chlorine by titration is not applicable.

[87] Though some other kinds of burette may be easier to use, that here recommended (that of Gay-Lussac) is the most convenient for reasons into which we need not enter. The following precautions should be observed: where the burette is not closed by a cork, let a few drops out first to wash away crystals of silver nitrate which may have formed at the mouth. The silver solution should be kept in well stoppered bottles. When filling the burette a glass funnel should be used, so that the cork used for closing the burette is not wetted with the silver solution. Before reading off wait until the level of the fluid is constant, in order that any solution on the sides of the glass tube may have time to run down.

[88] See note, p. 61.

[89] I have found that the amount of chlorine is smaller in winter than in summer. In the summer of 1894, 100 c.c. tap-water from the Stralau Waterworks often required 0·8 c.c. silver solution: but at that time stronger disinfectants were used on account of the cholera, and this may have caused the increase of chlorine; for since then, and even at the present time (winter 1898), 100 c.c. tap-water requires 0·5 to 0·6 c.c. silver solution.

[90] It may be here observed that objects of limestone or of earthenware may be numbered or marked at the back in black iron ink, which does not disappear even after prolonged steeping in water.

[91] Lepsius, “DenkmÄler aus Aegypten und Aethiopien.”

[92] It is scarcely necessary to add that any other form of air-pump may be used.

[93] A powerful pressure of water [in combination with a well-acting pump] may cause the fluid to evaporate with such rapidity as to produce bubbles, but these bubbles are easily distinguished by their size from the minute bubbles of air. To avoid this ebullition, the air should not be pumped out too rapidly.

[94] “Merkbuch,” p. 62.

[95] Flinders Petrie, “Archaeological Journal,” Part 45, 1888, p. 88.

[96] Zapon: for further information and references see Appendix.

[97] “Chemische Zeitschrift,” ii. 1903, p. 203.

[98] For particulars of the composition and action of Kessler’s Fluates (salts of Hydrofluosilicic acid) see H. Hauenstein, “Die kessler’schen Fluate” (2nd ed., Berlin, 1895). The depot is “H. Hauenstein, Berlin N. Reinickendorferstrasse, 2b.”

[99] Ger. Patent, No. 31032. The apparatus was one of those used in the moulding room of the Royal Museums for the impregnation of plaster moulds and casts.

[100] In applying the above test it is advisable to add one or two drops of nitric acid before the addition of the barium salt. In this case, too, should any other than distilled water be used for steeping, a preliminary examination should be made to determine the presence or absence of sulphates.

[101] [Pure hydrochloric acid is usually sold in two strengths. Concentrated acid has a strength of about 32%, whilst the “diluted hydrochloric acid” of the Pharmacopoeia is about 10%. The former should therefore be diluted with about 15, the latter with about 4 volumes of water. Transl.]

[102] “Chemische Zeitschrift,” II. 1903, p. 761.

[103] [Lecythoi: slender narrow-necked painted vessels which were frequently burnt or buried with the dead; cp. Aristophanes, “Ecclesiazusae,” 996:

?? t??? ?e????s? ????afe? t?? ???????? Transl.]

[104] The method of washing objects of unbaked clay suggested by Flinders Petrie in the “Archaeological Journal” (XLV. 1888) is in my experience impracticable.

[105] [Muffle furnaces may be obtained from Messrs Fletcher, Russell and Co., Warrington. If electricity is available, the electric muffle may be used. These may be obtained from Messrs A. Gallenkamp and Co., 19, Sun Street, Finsbury Square, London. The Heat-recorders supplied by H. Watkin, 225, Waterloo Road, Burslem, will be found very convenient in place of Seger’s cones, which may be obtained from Messrs Brady and Martin, Northumberland Road, Newcastle-on-Tyne. Transl.]

[106] “Merkbuch,” p. 78.

[107] [A paraffin prepared from Burmese petroleum. Transl.]

[108] Flinders Petrie, “Archaeological Journal,” XLV. 1888, p. 89.

[109] “Merkbuch,” p. 79.

[110] [It is important to avoid confusion and mistakes arising from the similarity of the terms benzine and benzene.

Benzene (Benzol) is the specific coal-tar product which has the formula C₆H₆.

Benzine (Benzin) is a light-boiling petroleum distillate, lighter than lamp oil, and with a varying boiling-point. It consists of a number of saturated hydrocarbons of the methane series. It is also called benzoline or petroleum naphtha. Transl.]

[111] Appelgren, Finskt Museum, 1895, p. 56.

[112] A communication from Herr Schjerning, Copenhagen.

[113] Speerschneider, “Antiquarisk Tidsskrift,” 1858-60, p. 178.

[114] Blell, “Sitzungsberichte der Prussia,” 1881-82, p. 24.

[115] Krefting, “Aarsb. fra foreningen t. norske fortidsmindesm. bevar.” 1892, p. 54.

[116] Salzer, “Chem. Zeitung,” XI. 1887, p. 574.

[117] Probably first recommended by Salzer, “Chemiker Zeitung,” XI. 1885, p. 574.

[118] “Kongl. Vitterhets Historie och Antiqvitets Akademiens MÅnadsblad,” 1885, p. 134.

[119] The addition of the lime is not advisable, comp. p. 93.

[120] “Chemiker Zeitung,” XI. 1885, p. 605.

[121] “Zeitschrift f. Ethnologie,” XXXIII. 1902, p. 431, and XXXIV. 1903, p. 791.

[122] “Sitzungsberichte,” 1881-82, p. 10 et seq., and 16 et seq.

[123] In this acid treatment bare hands may be used, but care must be taken to avoid splashing clothes or linen, which will cause red or yellow spots. These are best removed by the immediate application of ammonia, but the yellow spots can only be removed by oxalic acid.

[124] [Germ. “Hammerschlag.” The iron scales which chip off from heated iron at a forge or blacksmith’s shop. Transl.]

[125] No. 17, 1897, p. 333 et seq.

[126] A number of modifications in the metals employed and the composition of the bath have been suggested. Setlik (“Chemiker Zeitung,” XXVII. 1903, p. 454) imbeds iron objects which have a very weak core in a zinc-wire basket immersed in a magma of zinc dust and caustic soda. Personally I should prefer not to attempt a reduction process in such cases, but should rely rather upon mechanical removal of the rust, soaking and impregnation. For the treatment of bronzes this observer prefers the Finkener method (q. v.) and suggests caustic soda, sodium chloride, or ammonia chloride, instead of potassium cyanide as the electrolyte. Rhousopulos (“Chemische Zeitschrift,” II. 1903, pp. 202 and 364) uses zinc and hydrochloric acid, and when dry gives to the bronze a coating of wax. I should deprecate the use of either of these substances, the hydrochloric acid because of the difficulty of completely removing it by steeping and the danger of subsequent decomposition of the bronze, the wax because the contained fatty acids may act upon the metal.

[127] [The period required for complete reduction is, in our experience, often considerably longer. We have sometimes found an 8% soda solution more satisfactory. Transl.]

[128] Krefting’s method affords an excellent illustration of the truth of my remarks in the preface that the literature upon these preservation-methods is very scattered and in consequence has been hitherto but little studied. In 1892, when visiting the Museum at Christiania, I had the opportunity of examining some iron objects which had been treated by Krefting’s method. I then obtained his address, and Herr Krefting kindly communicated his method to me by letter, and in the following year forwarded a reprint of his article referred to above. In 1887 he had described his method to Appelgren by letter, but at that time he treated the object after reduction, washing, and drying, by impregnating it with a paraffin-petroleum solution. In 1897 Appelgren published this method, with drying and impregnation, in ignorance of Krefting’s publication in 1893.

[129] The bottle should not be closed by a glass stopper, but by a rubber bung, or by a cork coated with paraffin or wrapped round with parchment. Soda solution attacks glass, and especially ground glass; thus the stopper may become so firmly fixed into the neck of the bottle as to render its removal impossible.

[130] [Excavated by Dr Thurnam, 1848 (vide “Archaeolog. Journal,” Vol. VI. p. 27). Transl.]

[131] “Chemiker Zeitung,” XI. 1887, p. 605.

[132] Ant. Fr. 1154 a.

[133] I should now use paraffin for impregnation. (Author’s note.)

[134] [Great caution must be used to prevent inhalation of the gas, which is extremely poisonous. Transl.]

[135] Instead of potassium cyanide, I have made experimental use of the much more readily fusible potassium sulphocyanide. This converts the iron compounds into iron sulphide, which is easily got rid of. The sulphide which still adheres to the iron and imparts a not unpleasing blackish colour to the object appears to be stable.

The rest of the treatment is similar to that above described. Having so far only experimented with a few specimens I am not yet in a position to offer any judgment as to the practicability of the process. (Author, 1904.) [For practical objections to this method, which we do not consider satisfactory owing to the instability of the products resulting from the reaction, and the difficulty in removing them by the subsequent washing, see Milbauer, “Zeit. f. anorg. Chem.” XLII. 1904, p. 433 (“Journ. Chem. Soc.” Abstracts, i. 121), where it is stated that treatment of Fe₂O₃ at 400°C. leads to the formation of K₂Fe₂S₄. Transl.]

[136] Stolba, “Chemiker Zeitung,” XX. 1896, Repertorium, p. 240. [Sodium sulphide has a very deleterious action upon the skin and fingernails which should be protected when using this substance. Transl.]

[137] Flinders Petrie, “Archaeological Journal,” Vol. XLV. 1888, p. 88.

[138] Cp. Mugdan, “Zeit. Elektrochem.” 1903, ix. p. 442.

[139] [A method used by the explorers of the Palestine Exploration Committee for the preservation of much decayed bronzes, as, for instance, those from wells and cisterns, is to place them immediately they are discovered into a strong solution (1 in 10) of carbolic acid. Transl.]

[140] “Merkbuch,” p. 68.

[141] Instead of calcium chloride strong sulphuric acid may be used for dehydration, but the dry chloride is more simple, and less dangerous. If kept in corked bottles, the corks should be covered with paraffin wax to prevent access of moisture.

[142] First put forward by Chevreul (see pp. 22 and 117).

[143] [The so-called ‘pole paper’ is supplied by most dealers in electrical apparatus. Transl.]

[144] In such a case the hydrated oxide of tin is either present as such in the oxidized bronze, or it is a product of the reduction which has been prevented from falling to the bottom by the high sp. gr. of the potassium cyanide solution. It is also possible that finely divided tin in the reduced bronze may decompose the warm water into oxygen and hydrogen, forming a hydrated oxide of tin. Such a reaction would account for the formation of hydrogen. The hydrogen might at the same time remain occluded until allowed to separate by the cessation of the current and the temperature of the water.

[145] Such, for instance, as is obtained by attaching a suitable nozzle to a fall pipe where there is sufficient water-pressure; v. e.g. “Polytechn. Centralblatt,” 1891-92, p. 199.

[146] I now consider it a better plan not to employ the method of coating with paraffin wax. I thoroughly soak and then dry the reduced bronze with a cloth, and place it in 96% alcohol. This must be renewed after a time, and for large bronzes a third or even a fourth renewal is advisable. The bronze is again wiped and introduced into a drying oven raised to about 212°F. [100°C.]. The unsightly grey colour and rough surface may be much improved by using a brush of the finest wire or very fine emery cloth. The object is finally impregnated with zapon (see Appendix). (Author’s note, 1904.)

[147] [The base was not treated owing to the advanced destruction of the metal. Transl.]

[148] In only about 2% of the bronzes treated in the laboratory of the Royal Museums at Berlin has it been found necessary to interrupt the reduction.

[149] “Polytechn. Centralblatt,” 1891-92, p. 200.

[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.

[160] “Riv. Ital. Numism.” 1903, p. 31; also “Chemiker Zeitung,” XXVII. 1903, p. 825.

[161] [In this connection however it must be remembered that celluloid gives off traces of acid for a long time. This may possibly involve risk of injury to certain specimens. Transl.]

[162] “Mittheilungen des NordbÖhmischen Gewerbe Museum,” 1903, p. 104.

[163] [A few drops of formalin will serve the same purpose. Transl.]

[164] [Lanoline, especially if applied warm, retains the flexibility of the leather very satisfactorily. It may be here mentioned that the leather of old book-bindings may be preserved by the application, by means of a soft brush, of a mixture of white wax with a small quantity of white vaseline and paraffin wax, brought to a pasty consistency with benzine or turpentine.

The ‘Stearine Glaze’ used for the same purpose is made by boiling one part of caustic soda with eight parts of stearic acid and 50 parts of water till dissolved, then mixing another 150 parts of cold water and stirring until the whole sets to a jelly.

Either of these media should be applied very thinly and then polished with a brush or flannel. If the cover is very bad, considerable improvement is effected by repeated applications of the stearine glaze so as to fill up the damaged surface of the leather. In some cases the addition of some dye such as logwood, or one or other of the acid coal-tar dyes, is advantageous.

Lanoline, or wool fat, i.e. lanoline without the water, is useful, but gives a dull surface to the leather.

In some cases a thin coating of diluted white of egg, to which a few drops of clove oil, or some other essential oil, has been added as an antiseptic is beneficial. Transl.]

[165] On preservation in alcohol see p. 159 under the heading ‘Wood.’

[166] “Aarb. for nordisk Oldkynd. og Historie,” 1891, p. 112.

[167] According to an analysis published by L. v. Barth in an account of the collection of papyri belonging to the Archduke Rainer, Part I. p. 120, the salt crystals, after removal of the insoluble constituents, consisted of:

[168] “Merkbuch,” p. 60.

[169] Communicated by Herr Leiner of Constance.

[170] “Antiquarisk Tidsskrift,” 1858-60, p. 176.

[171] Id., p. 174.

[172] Olshausen, “Verh. der Berl. anthropol. Ges.” 1885, p. 242, an oral communication from Herr v. Jenner.

[173] Attention may be drawn to a paper which (Dec. 1904) will shortly be published by the Imperial Commission for Monuments of Art and History in Vienna. At a meeting in Vienna a paper was given by Bolle on the animal enemies of paper, leather, and wood, and their destruction by means of carbon bisulphide. Carbon bisulphide is an infallible poison and has no effect upon colours when used in a perfectly dry state. This may be carried out by a preliminary displacement of the air by carbonic acid which is readily obtained in the liquid form in cylinders. Benzine would probably act equally well, but would require a longer time for its action. References to other methods such as the employment of a vacuum or of heat will be found in the same publication.

[174] Keim, “Technische Mittheilungen fÜr Malerei,” 1888, p. 4.

[175] Communication from Herr Straberger of Linz on the Danube.

[176] Communication by Dr Voss.