Glass coloured

Coloured glasses are obtainable by heating microcosmic salt with certain metal oxides which form metal sodium phosphates (Chapter 14.1). Pink phosphate glasses are obtainable with Fe203, blue with WO3, yellow with Ag20 and green with U3O8 (Table 12.27). 

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W. A. Weyl, Coloured Glasses The Society of Glass Technology, Sheffield, UK, 1951, p. 179. 

The elements are obtainable in a state of very high purity but some of their physical properties are nonetheless variable because of their dependence on mechanical history. Their colours (Cu reddish, Ag white and Au yellow) and sheen are so characteristic that the names of the metals are used to describe them. Gold can also be obtained in red, blue and violet colloidal forms by the addition of vtirious reducing agents to very dilute aqueous solutions of gold(III) chloride. A remarkably stable example is the Purple of Cassius , obtained by using SnCla as reductant, which not only provides a sensitive test for Au but is also used to colour glass and ceramics. Colloidal silver and copper are also obtainable but are less stable. 

In many cases the analytical grade material may be replaced by pure recrystallised silver nitrate, but in that case it is advisable to standardise the solution against sodium chloride. Solutions of silver nitrate should be protected from light and are best stored in amber-coloured glass bottles. 

Light filters. Optical filters are used in colorimeters (absorptiometers) for isolating any desired spectral region. They consist of either thin films of gelatin containing different dyes or of coloured glass. 

Mid-1600 Liquid-in-glass graduated thermometers are widely spread Famous are die alcohol thermometers of die Accademia del Cimento in Florence. Their graduation marks are made of coloured glass bits attached to die stem... 

Table 5.3 Some of the chromophores responsible for the colours in ionically coloured glasses. (Compiled from Weyl (1976 60) 8... 

UV, hydrolysis and/or heat stabilized lower cost improved colour and gloss retention cold-temperature ductility and flexibility soft touch food contact fireproofed low compression set and creep reduced oil swelling improved chemical resistance better resistance to microorganisms transparent colourable glass fibre reinforced antistatic grades... 

Weyl, W. A. "Coloured Glasses" Dawson s Pall Mall London, England, 1959 pp. 218-234, 439-514. 

The presence of colloidal tellurium in glass produces a colour tint which varies from blue to brown according to the size of the colloid particles, the blue glass containing larger particles than the brown.3 Polytellurides are present in some coloured glasses and impart a colour which is red or violet-red. 

Colour.—This is measured, when necessary, with the Lovibond tintometer,8 in which the colour of a layer of solution of definite thickness is compared with that of a series of coloured glasses of definite tints and intensities, these being combined so that they give the same tone and the same intensity of colour as the solution. The colour is then expressed in arbitrary degrees of red, yellow and black. 

Specific chemical salts are added to glass before it cools down completely to get different colours. Chemical salts and coloured glass ... 

Cobalt oxide gives purple or blue coloured glass. 

Chromium salts give green or yellow coloured glass. Other coloured glasses are made in this manner. 

Colours of coloured glass depend generally upon the metallic oxide. Some metallic oxide may give different colours or different metallic oxides can give the same colour depending upon the glass mixture. ... 

Weyl, W. A. Coloured Glasses. London, Dawson s of Pall Mall 1959... 

Neodymium 60 Nd Electronics, steel manufacture, glazes and coloured glass (including didymium glass), lasers, magnets, petroleum cracking catalysts, misch metal ... 

A useful reaction which may be carried out at this stage is the microcosmic bead test (Section II.2, test 6). This test is carried out in a loop of platinum wire exactly as for the borax bead test. The presence of a white skeleton (of silica) in the coloured glass indicates silicate. Tin(IV) oxide, Sn02, dissolves slowly in the bead may be mistaken for silica. 

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