Difference between pages "Cobalt blue" and "Whewellite"

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[[File:1997.182-SC8165.jpg|thumb|]]
 
 
== Description ==
 
== Description ==
  
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A clear blue pigment. (Some early varieties possessed a greenish tinge.)  Cobalt blue is composed of a double oxide of cobalt and aluminum, also called cobaltous aluminate. It is resistant to weathering, sunlight, acids, and alkalis. Though possibly discovered earlier, the process for making cobalt blue by heating [[Cobaltous phosphate|cobalt phosphate]] with [[alumina]] was first published by L.J.Thénard in France in 1803/4 based on experiments he had carried out in 1802. Leithner discovered an alternate process for making cobalt blue from [[cobaltous arsenate|cobalt arsenate]] and alumina. By the early 19th century, cobalt blue was sold as an artists pigment as a replacement for smalt and ultramarine, although it has always been relatively costly. The pigment has been identified in French and British paintings as early as 1806/07.  In recent years, the cobalt blue hue has been imitated using mixtures of [[ultramarine blue, synthetic|ultramarine]] and [[phthalocyanine blue|phthalocyanine]]. The saturated cobalt blue color in glazes and glassware is produced by [[cobaltic oxide|cobalt oxide]].
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A white to colorless mineral composed of [[calcium%20oxalate|calcium oxalate]] monohydrate. Whewellite is formed on the surface of [[marble|marble]] and [[limestone|limestone]] due to the presence of microorganisms, such as [[lichen|lichen]].
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[[File:08.475-CR10038-d1.jpg|thumb|]]
 
  
 
== Synonyms and Related Terms ==
 
== Synonyms and Related Terms ==
  
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cobalt aluminate; Pigment Blue 28; CI 77346; Thénard's blue; Kobaltblau (Deut.); bleu de Thénard (Fr.); bleu de cobalt (Fr.); cobaltblauw (Ned.); blu di cobalto (It.); blu di Therard (It.); mple toy kobaltioy (Gr.); azul de cobalto (Esp.); azul cobalto (Port.); cobalt ultramarine; cobaltous aluminate; king's blue; Olympia blue; Vienna blue; Vienna ultramarine; Leyden blue; Hungary blue; Dresden blue; azure cobalt; Gahn's blue; Leithner blue; new blue;
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calcium oxalate monohydrate; calcium salt of ethanedioic acid; wewelita (Esp.); whewelite (Port.); Whewellit (Deut.)
  
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[[[SliderGallery rightalign|Cobalt blue, Forbes 476, 532 nm.TIF~Raman (MFA)|Cobalt blue (bottle 484).TIF~FTIR (MFA)|Slide29 F475.PNG~XRF(MFA)]]]
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[[[SliderGallery rightalign|whewellite.jpg~Chemical structure]]]
  
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== Other Properties ==
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== Risks ==
  
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Irregular to rounded blue particles with a ‘crusty’ surface, no birefringence, no pleochroism. Appears red through Chelsea filter.
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* Fisher Scientific: [https://fscimage.fishersci.com/msds/80705.htm MSDS]
  
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Unaffected by acids, alkalis, light, and heat.
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==Physical and Chemical Properties==
  
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Strong [[siccative]] properties in oil on account of the cobalt content.
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* Soluble in dilute mineral acids. Insoluble in water, acetic acid.
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* Slightly hygroscopic.
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* Transparent to translucent tabular crystals with good cleavage in all three planes.
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* Luster=vitreous to pearly. 
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* Streak = white. 
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* Fluorescent in UV light.
  
 
{| class="wikitable"
 
{| class="wikitable"
 
|-
 
|-
 
! scope="row"| Composition
 
! scope="row"| Composition
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| CoO.Al2O3
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| Ca(C2O4)-H2O
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|-
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! scope="row"| CAS
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| 5794-28-5
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|-
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! scope="row"| Mohs Hardness
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| 2.5-3.0
 
|-
 
|-
 
! scope="row"| Density
 
! scope="row"| Density
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| 3.83
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| 2.2 g/ml
 
|-
 
|-
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! scope="row"| Refractive Index
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! scope="row"| Molecular Weight
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| 1.66-1.74
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| mol. wt. = 146.11
 
|}
 
|}
  
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== Hazards and Safety ==
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==Resources and Citations==
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Skin contact may cause allergies, especially on elbows, neck and ankles.  Chronic inhalation may cause asthma. 
 
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Ingestion may cause vomiting, diarrhea and the sensation of hotness.
 
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== Additional Information ==
 
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° A. Roy, “Cobalt Blue”, ''Artists’ Pigments: A Handbook of Their History and Characteristics'', Volume 4, B. Berrie (ed.), Archetype Publications, London 2007.
 
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° Pigments Through the Ages: [http://webexhibits.org/pigments/indiv/overview/coblue.html Cobalt blue] Record content reviewed by EU-Artech November 2007.
 
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== Comparisons ==
 
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[[media:download_file_487.pdf|Characteristics of Common Blue Pigments]]
 
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== Additional Images ==
 
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<gallery>
 
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File:50.879-E4999CR-d1.jpg|
 
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File:489 cobalt.jpg|Cobalt
 
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File:Coblue C100x.jpg|Cobalt blue
 
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File:40_Cobalt_blue_200X.jpg|Cobalt blue
 
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</gallery>
 
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== Sources Checked for Data in Record ==
 
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* Nicholas Eastaugh, Valentine Walsh, Tracey Chaplin, Ruth Siddall, ''Pigment Compendium'', Elsevier Butterworth-Heinemann, Oxford, 2004
 
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* External source or communication  Comment: Contributed information: Ashok Roy, November 2007.
 
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* R. J. Gettens, G.L. Stout, ''Painting Materials, A Short Encyclopaedia'', Dover Publications, New York, 1966  Comment: p. 108
 
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* Ralph Mayer, ''A Dictionary of Art Terms and Techniques'', Harper and Row Publishers, New York, 1969 (also 1945 printing)
 
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* External source or communication  Comment: Contributed information: Ashok Roy, November 2007.
 
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* ''The Dictionary of Art'', Grove's Dictionaries Inc., New York, 1996  Comment: "Pigments"
 
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* M. Doerner, ''The Materials of the Artist'', Harcourt, Brace & Co., 1934
 
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* Reed Kay, ''The Painter's Guide To Studio Methods and Materials'', Prentice-Hall, Inc., Englewood Cliffs, NJ, 1983
 
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* R.D. Harley, ''Artists' Pigments c. 1600-1835'', Butterworth Scientific, London, 1982
 
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* Thomas B. Brill, ''Light Its Interaction with Art and Antiquities'', Plenum Press, New York City, 1980
 
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* David Bomford, Jo Kirby, John Leighton, Ashok Roy, ''Art in the Making:Impressionism'', National Gallery, London, 1990
 
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* G.S.Brady, ''Materials Handbook'', McGraw-Hill Book Co., New York, 1971  Comment: p. 611
 
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* ''Dictionary of Building Preservation'', Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
 
  
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* Michael McCann, ''Artist Beware'', Watson-Guptill Publications, New York City, 1979
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* Mineralogy Database: [http://www.webmineral.com/data/Whewellite.shtml Whewellite]
  
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* Website address 1  Comment: Pigments Through the Ages:  http://webexhibits.org/pigments/indiv/overview/coblue.html
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* M. del Monte, C. Sabbioni, G.Zappia. The origin of calcium oxalates on historical buildings, monuments and natural outcrops. The science of the total environment 67, (1987), pp. 17-39
  
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* Wikipedia, the free encyclopedia, at http://www.wikipedia.com  Comment: http://en.wikipedia.org/wiki/Cobalt_blue (Accessed Jan. 15, 2006)
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* B. Ford, I.MacLeod, P.Haydock, "Rock art pigments from Kimberley region of Western Australia: identification of the minerals and conversion mechanisms." ''Studies in conservation'' 39, no. 1 (1994), pp. 57-69
  
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* ''CRC Handbook of Chemistry and Physics'', Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980  Comment: ref. index=1.74 (blue), >1.78 (red)
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* Random House, ''Webster's Encyclopedic Unabridged Dictionary of the English Language'', Grammercy Book, New York, 1997
  
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* Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000
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* Wikipedia,: http://en.wikipedia.org/wiki/Whewellite (Accessed Nov. 29, 2005)
  
  
  
 
[[Category:Materials database]]
 
[[Category:Materials database]]

Revision as of 15:56, 26 June 2022

Description

A white to colorless mineral composed of Calcium oxalate monohydrate. Whewellite is formed on the surface of Marble and Limestone due to the presence of microorganisms, such as Lichen.

Synonyms and Related Terms

calcium oxalate monohydrate; calcium salt of ethanedioic acid; wewelita (Esp.); whewelite (Port.); Whewellit (Deut.)

Chemical structure

Whewellite.jpg


Risks

  • Fisher Scientific: MSDS

Physical and Chemical Properties

  • Soluble in dilute mineral acids. Insoluble in water, acetic acid.
  • Slightly hygroscopic.
  • Transparent to translucent tabular crystals with good cleavage in all three planes.
  • Luster=vitreous to pearly.
  • Streak = white.
  • Fluorescent in UV light.
Composition Ca(C2O4)-H2O
CAS 5794-28-5
Mohs Hardness 2.5-3.0
Density 2.2 g/ml
Molecular Weight mol. wt. = 146.11

Resources and Citations

  • M. del Monte, C. Sabbioni, G.Zappia. The origin of calcium oxalates on historical buildings, monuments and natural outcrops. The science of the total environment 67, (1987), pp. 17-39
  • B. Ford, I.MacLeod, P.Haydock, "Rock art pigments from Kimberley region of Western Australia: identification of the minerals and conversion mechanisms." Studies in conservation 39, no. 1 (1994), pp. 57-69
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997

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