Glass and Enamels

In addition to the needs of the laboratory, many other kinds of glass were required, and the work was extended to the investigation of over forty varieties for which formulas have been supplied to approved firms. With shortage of labour and other economic difficulties, firms have undertaken with remarkable energy new branches of work which it is hoped they will be able to retain, in the future, in the face of competition from our quondam enemies. 

Yet another problem has been successfully tackled by Professor Jackson for the Ministry of Munitions, viz., the treatment of day used for maiding vessels employed in glass production. 

In the course of time an enterprising firm, with the aid of chemists and from indigenous sources, produced supplies of potash of high quality in sufficient bulk for the imperative requirements of glass makers, and this factor was of no small consequence, since it is admitted that for certain glasses potash is practically indispensable. 

From the foregoing, it is evident that in spite of the antiquity of the industry, and the fact that good glasses for ordinary and ornamental purposes were produced independently of modem science, many special glasses owe their origin entirely to scientific investigation. It is not too much to say that on the 

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Selenium is used in Xerography for reproducing and copying documents, letters, etc. It is used by the glass industry to decolorize glass and to make ruby-colored glasses and enamels. It is also used as a photographic toner, and as an additive to stainless steel. 

Lithium Borates. Lithium metaborate [13453-69-5], LLBO2 2H20, is prepared from reaction of lithium hydroxide and boric acid. It is used as the fluxing agent for the matrix for x-ray fluorescence analytical techniques and in specialty glasses and enamels. The anhydrous salt melts at 847°C. 

Lithium carbonate is used to prepare Hthium aluminosiHcate glass ceramics which have low thermal coefficients of expansion, allowing use over a wide temperature range. It also finds uses in specialty glasses and enamels. 

Many metal borates find important industrial applications (p. 140) and annual world production exceeds 2.9 million tonnes Turkey 1.2, USA 1.1, Argentina 0.26, the former Soviet Union 0.18, Chile 0.13Mt. Main uses are in glass-fibre and cellular insulation, the manufacture of borosilicate glasses and enamels, and as fire retardants. Sodium perborate (for detergents) is manufactured on a 550 000 tonne pa scale. 

The introduction of divalent calcium and barium oxides into frits in preference to monovalent sodium and potassium generally increases water resistance. Furthermore, oxides of tetravalent and pentavalent metals have a favourable effect on the resistance of glasses and enamels to water. The influence of B2O3 and fluorine in the frit upon chemical resistance is variable and is dependent upon the content of them and the balance of the frit constituents, but they usually cause a diminution in resistance. In general, mill-added clay, silica and opaciher increase water resistance provided the firing or fusing of the enamel is at the optimum. 

The most important use of selenium is as a pigment which gives a red colour to glasses and enamels. However, selenium is a catalyst in many chemical reactions and is widely used in various industrial and laboratory syntheses. 

The photosensitive nature of selenium makes it useful in devices that respond to the intensity of light, such as photocells, light meters for cameras, xerography, and electric eyes. Selenium also has the ability to produce electricity directly from sunlight, making it ideal for use in solar cells. Selenium possesses semiconductor properties that make it useful in the electronics industry, where it is a component in some types of solid-state electronics and rectifiers. It is also used in the production of ruby-red glass and enamels and as an additive to improve the quality of steel and copper. Additionally, it is a catalyst (to speed up chemical reactions) in the manufacture of rubber. 

Fourcroy predicted that this mineral would give chemists the opportunity to make a more thorough study of the properties of chromium and perhaps to discover compounds of it which, because of their rich and varied colors, would be useful in painting and in the manufacture of glass and enamel (90). He also encouraged study of the chromium alloys. The chrome-iron ore is now known as chromite. It is not a chromate, but has the spinel composition, Fe(Cr02)2-... 

England (1) reviewed the literature of the chemistry of medieval glass and enamel, including excerpts from the writings of Theophilus, the medieval scholar. Copper is mentioned as an important colorant. 

Zircon is used in the manufacture of refractories, as opacifier in glazes and enamels, as nucleant in glass-ceramics and also as a raw material for electrotechnical ceramics, chemically resistant glasses and enamels, etc. 

Most of the nitric acid is utilized in the form of 50 to 70% acid for the manufacture of nitrogen-containing fertilizer, particularly ammonium nitrate. Ammonium nitrate is also used as an explosive e.g. in mining, due to its low explosion temperature (safety explosive). Other industrially important nitrates are sodium nitrate, a speciality fertilizer and oxidizing agent in the glass and enamel industries, and calcium and potassium nitrates, which are also used as fertilizers. Nitric acid is also utilized in the digestion of raw phosphate (Odda process, which is not operated in the USA, see Section 2.1.2.4) ... 

Aluminum fluoride is utilized, in addition to cryolite, as a raw material in the electrolytic manufacture of aluminum (temperature of electrolyte 950°C, composition 80-85% Na AlFft, 5-7% AIF, 5-7% CaF2, 2-6% AFO, 0-7% LiF). No fluorine should actually be consumed in this process, modern plants recovering the fluorine in its entirety. Other uses are as a flux (in welding, soldering, manufacture of casts), and as a melting point depressant in glass and enamel. The aluminum fluoride capacities in Europe are given in the table below. 

Cryolite is utilized in the manufacture of aluminum, in the processing of aluminum waste (as a flux in the electrochemical removal of magnesium), as a flux in the aluminization of steel and in welding technology, in the manufacture of glass and enamel, as an additive in the manufacture of abrasives and as an auxiliary product in the remelting of light metals. 

Most of the a-aluminum oxide is utilized for aluminum manufacture (ca. 0.5 t aluminum/t AI2O3). In the USA over 90% of the aluminum oxide production is utilized in the manufacture of aluminum, the rest being utilized in the manufacture of refractory, grinding, ceramic, glass and enamel products and electrocorundum. It is also used as a filler in polymers (polyesters, epoxides). 

Use Production of cerium salts and ceric oxide, opa-cifier in glasses and enamels (imparts yellow color), shielding glass. 

Chile 0.13Mt. Main uses are in glass-fibre and cellular insulation, the manufacture of borosilicate glasses and enamels, and as fire retardants. Sodium perborate (for detergents) is manufactured on a 550 000 tonne pa scale. 

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