Cobalt blues

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

Paint pigments do not change colors on appHcation. Other common colors are violet from cobalt(II) phosphate [18475-47-3] pink from cobalt and magnesium oxides, aureolin yellow from potassiuim cobalt(III) nitrite [13782-01-9], KCo(N02)4, and cerulean blue from cobalt staimate [6546-12-5]. Large quantities of cobalt are used at levels of a few ppm to decolori2e or whiten glass and ceramics. Iron oxide or titanium dioxide often impart a yellow tint to various domestic ware. The cobalt blue tends to neutrali2e the effect of the yellow. 

Leyd(e)ner Blau. Leyden blue, cobalt blue. Leyd(e)ner Flasche. Leyden jar. 

The compounds of the t/block elements show a wide range of interesting properties. Some are vital to life. Iron is an essential component of mammalian blood. Compounds of cobalt, molybdenum, and zinc are found in vitamins and essential enzymes. Other compounds simply make life more interesting and colorful. The beautiful color of cobalt blue glass, the brilliant greens and blues of kiln-baked pottery, and many pigments used by artists make use of d-block compounds. 

Use sterile fluorescein dye strips and visualize the cornea under a cobalt-blue filtered light abrasions appear green ensure that no foreign body remains in the eye... 

Figure 4.19 shows the p-PIXE X-ray spectra collected simultaneously from a fragment ( 1 mm in diameter) of an archaeological cobalt-blue glass (Uzonyi et al. 2001). This sample contains numerous minor and trace elements from carbon to lead, and the instrument employed both an ultra-thin window (UTW) detector as well as a Be-windowed detector. 

Figure 4.19. PIXE X-ray spectra collected by i-PIXE analysis in a new in-vacuum experimental set-up from a fragment of cobalt-blue glass. Upper spectra from a UTW detector and lower spectra from a Be-window detector. (Reproduced by permission of Uzonyi et al. 2001.)...

Blue - cobalt blue, indanthrone, a-copper phthalocyanine... 

To the eye, cobalt blue and woad have a very similar colour. We say they have the same hue. But woad is considerably paler in intensity, even when the concentration c... 

At heart, this greater intensity may be explained as follows. The ease with which an electron may be photo-excited depends on the probability of successful excitation, which itself depends on the likelihood of photon absorption. If the probability of excitation in the woad was 20 per cent, then 20 from every 100 incident photons are absorbed (assuming each absorption results in a successful electron excitation). By contrast, cobalt blue is more intense because it has a higher probability of photon uptake, so fewer photons remain to be seen, and the absorbance increases. 

Historically, as well as today, different compounds of cobalt have been used for their colors known as cobalt blue, cerulean, new blue, smalt, cobalt yellow, and green. 

Cobalt blue [ColAlO lj], also known as cobalt ultramarine or azure blue, is a compound of aluminum oxide and cobalt. It is used as a pigment that mixes well with both oil and water. It also has cosmetic uses for eye shadow and in grease paint. Cobalt blue is one of the most durable blue pigments in that it resists weathering in paints and holds up to other wear and tear. 

Bernard Palissy, 1510P-1589. French glassmaker, surveyor, potter, agriculturist, and chemist who was familiar with zaifer, or cobalt blue. 

Fig. 4.8 Square-wave voltammograms of graphite-polyester composite electrodes modified by cobalt blue (a,c), and glazed ceramic sample from Valencia, Spain (b,d), immersed into 0.10 M HCl. (a,b) Potential scan initiated at 4-0.65 V in the negative direction (c,d) potential scan initiated at —1.05 V in the positive direction after an electrodeposition step of 60 s at —1.05 V. Potential step increment 4 mV, square-wave amplitude 25 mV, frequency 15Hz[231]...

A small proportion of cobalt blue is added as a stain to whiten the mass. 

The pigment industry started in the 18th century with products such as Berlin blue (1704), cobalt blue (1777), Scheele s green, and chrome yellow (1778). 

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