Zaffer

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Zaffer , including safflower , safflower or Kobaltsaflor or Kobaltsafflor called, is prepared by heating cobalt ores. From the 16th to the 20th century it was used as a raw material for the production of smalt , a blue, refractory and vitreous pigment that was also used in oil paints . In addition, it is used to produce cobalt glass (cobalt blue colored glass), colored - especially blue - porcelain or corresponding porcelain glazes. Zaffer was manufactured in the blue paint factories .

Manufacture, composition and use

Cobalt blue glasses. Such a coloring can be made with the help of Zaffer.

Zaffer is the product that is made when roasting cobalt ores. It consists mainly of cobalt oxides (especially cobalt (II, III) oxide Co 3 O 4 , in addition also cobalt (II) oxide CoO and cobalt (III) oxide Co 2 O 3 ), which are mixed with arsenates and nickel compounds are. Zaffer is obtained as an intermediate product in the processing of cobalt ores; it can then be further processed into cobalt oxides by purification. In the past, Zaffer was also traded as a pigment, whereby it was used in the form of the unpurified mixture for coloring porcelain, faience and glass. It was mainly used to produce blue, but also black and black-brown glazes. It was also used to make magic inks.

Reaction equations

Idealized exemplary reaction equations for the production of Zaffer are - under conditions under which mainly cobalt (II, III) oxide is formed:

For the representation from skutterudite (food cobalt):

For the representation of safflorite (fibrous, white food cobalt):

The arsenic content oxidizes to arsenic (III) oxide (As 2 O 3 , arsenic). This is volatile in the heat - As 2 O 3 sublimates at 321 ° C. If possible, it is caught in the poison trap and then collected as "poison meal".

Properties and forms of trade

Depending on the ore used, Zaffer is a gray-brown or reddish to bluish powder. It also came on the market ground together with quartz flour or sand.

Zaffer is difficult to melt, which is why it is important to add enough quartz and potash to the production of smalt.

Because of the cobalt and especially the arsenic content, Zaffer is poisonous. "Smalte and Zaffer are pigments that are harmful to health if something gets into the human body."

Historical

Georgius Agricola (1494–1555), who also described cobalt ores, in particular the cobalt arsenates, in his writings, does not mention the term Zaffer. It is assumed, however, that he knew the substance, since he mentions an ore that can be used to color glass and earthenware blue. The first known mention of Zaffer or the Italian "Zaffera" was by Vannoccio Biringuccio (1480-1537) in his work published in Venice in 1540. The cobalt blue produced in Venice was probably based on ores that came from Kashan in present-day Iran or Oman , where cobalt blue had been known for centuries.

In Germany the production of Zaffer was supposedly introduced in 1520 by the German alchemist Peter Weidenhammer ; he is said to have become wealthy through the sale of the pigment. The glassmaker Christoph Schürer began producing cobalt glass in the Bohemian part of the Ore Mountains between 1540 and 1560 . Since 1470 the Saxon Ore Mountains, especially the Schneeberger area, have been the most important suppliers of cobalt ore and Zaffer.

The Priest, glassmakers and Alchamist Antonio Neri (1576-1614) published in 1612 in his book on the glassmaking a description of the preparation of Zaffer by heating in the oven and subsequent washing with vinegar and water.

The chemist Johann Albrecht Gesner published a book in 1744 about the preparation of Zaffer and smalt from cobalt ores. In it he explains that the name Zaffer is undoubtedly derived from sapphire and its color, since safflower is a contraction of sapphiri color , sapphire color .

Color name

The color of the raw material Zaffer varies depending on its composition. In the English-speaking world, however, the word "Zaffre", which corresponds to cobalt safflor, is used to describe a certain dark blue color:

Color “Zaffre” in Anglo-Saxon usage

sRGB : 0 20 168
   zaffre color - hex # 0014a8  

Web links

Individual evidence

  1. ^ A b Colin Mackenzie, Heinrich Ferdinand Eisenbach: Five thousand new English recipes for all incidents in life, or new complete house library . Second part. JB Metzler'sche Buchhandlung, Stuttgart 1825, glass and porcelain painting - preparing Zaffer, p. 287–290 ( p. 288 of the copy of the Bayerische Staatsbibliothek online in the Google book search).
  2. ↑ Colin Mackenzie, Heinrich Ferdinand Eisenbach: Five thousand new English recipes for all incidents in life, or new complete house library . Second part. JB Metzler'sche Buchhandlung, Stuttgart 1825, writing arts - sympathetic ink made of cobalt, p. 7 ( p. 7 of the copy of the Bayerische Staatsbibliothek online in the Google book search).
  3. ^ Jean Hellot : Seconde partie du mémoire sur l'encre sympathique ou teinture . Extraite des Mines de Bismuth, d'Azur and d'Arsenic. In: Académie des sciences (ed.): Histoire de l'Académie royale des sciences avec les mémoires de mathématique & de physique . 1737, p.  228–247 (French, online at Gallica Bibliothèque nationale de France ).
  4. ^ Johann Heinrich Moritz Poppe: Noth- und Hülfs-Lexikon for the protection of human life from all conceivable accidents and for the rescue from the dangers on land and on water . First volume. Johann Leonhard Schrag, Nuremberg 1811 ( limited preview in the Google book search).
  5. ^ A b Georgius Agricola, Herbert Clark Hoover, Lou Henry Hoover: The Project Gutenberg EBook of De Re Metallica, by Georgius Agricola . November 14, 2011 ( gutenberg.org ).
  6. ↑ Ahmad Y. al-Hassan: Lazaward (LAJVARD) And Zaffer Cobalt Oxide In Islamic And Western Luster Glass And Ceramics. In: History of Science and Technology in Islam, http://www.history-science-technology.com/ . Retrieved January 13, 2018 .
  7. ↑ Christian Meltzer : Mountainous description of the Churfürstl. Saxon. freyen and Löbl in the Meißnischen Ober-Ertz-Geburge. Bergk town of Schneebergk. Schneeberg 1684, p.  469 , urn : nbn: de: gbv: 3: 1-65535-p0503-8 : "Peter Weidenhammer / also a Franck / has come poor anhero / but has dealt with the color / if he disregards the knowledge of pearl barley / and in many Centners / each for 25 Rthlr. / negotiated to Venice / thus picked up / that he would come up with large funds / and built a beautiful house on the market. His name is in the big churches / with this year: 1520. "
  8. ^ Antonio Neri : L'arte vetraria distinta in libri sette . Ne quali si scoprono, effetti maravigliosi, & insegnano segreti bellissimi del vetro nel fuoco & altre cose curiose. Ed .: nella stamperia de Giunt. Firenze 1612, Libro Primo. A preparare la Zaffera, che ferue per più colori nell 'Arte vetraria. Approx. XII, p.  15 (Italian, online on Gallica ): “Piglisi la Zaffera in pezzi grossi & mettasi in tegaini di terra tenendola nella camera della fornace per une mezo giorno”
  9. ^ Paul Engle: Conciatore - The Life and Times of 17th Century Glassmaker Antonio Neri - Zaffer . April 15, 2015 (English, conciatore.org [accessed January 10, 2018]): “In his glassmaking book L'Arte Vetraria, Antonio Neri describes his method for purifying and preparing zaffer for use in glass.”
  10. ^ Johann Albrecht Gesner: Historia cadmiae fossilis metallicae sive cobalti et ex illo praeparatorum Zaffariae et Smalti . Pars Prior. Berolini, prostat in Officina Rudigeriana, Berlin (Berolini) 1744, Caput tertium § 2 Zafferae Etymologia, p. 27 (Latin, limited preview in the Google book search): Zaffarae vocabulum procul dubio ab Italico Zaffirus , Sapphirus, gemma illa pulcre caerulea ortum habet, ex quo postea germani metallici Saflor fecerunt, vel forsan ex Sapphiri color, Saph-lor Saflor vocabulum contractum est.