Chemical elements
  Calcium
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    Chemical Properties
    Glass
    Cement
    PDB 158d-1ajq
    PDB 1ak9-1ayk
    PDB 1ayo-1bg7
    PDB 1bg9-1byh
    PDB 1byn-1c8q
    PDB 1c8t-1cq1
    PDB 1cq9-1daq
    PDB 1dav-1dva
    PDB 1dvi-1el1
    PDB 1ela-1f4n
    PDB 1f4o-1fkq
    PDB 1fkv-1fzd
    PDB 1fze-1g9i
    PDB 1g9j-1gr3
    PDB 1gsl-1h5h
    PDB 1h5i-1hn4
    PDB 1hny-1i9z
    PDB 1ia6-1iyi
    PDB 1iz7-1jc2
    PDB 1jc9-1jui
    PDB 1jv2-1kck
    PDB 1kcl-1kvx
    PDB 1kvy-1led
    PDB 1lem-1lqd
    PDB 1lqe-1may
    PDB 1mbq-1mxe
    PDB 1mxg-1nfy
    PDB 1ng0-1nwg
    PDB 1nwk-1o3g
    PDB 1o3h-1om7
    PDB 1om8-1p7v
    PDB 1p7w-1pva
    PDB 1pvb-1qdo
    PDB 1qdt-1qq9
    PDB 1qqj-1rin
    PDB 1rio-1s10
    PDB 1s18-1scv
    PDB 1sdd-1su4
    PDB 1sub-1tf4
    PDB 1tf8-1top
    PDB 1tpa-1ujb
    PDB 1ujc-1uyy
    PDB 1uyz-1v73
    PDB 1v7v-1w2k
    PDB 1w2m-1wua
    PDB 1wun-1xkv
    PDB 1xmf-1y3x
    PDB 1y3y-1yqr
    PDB 1yr5-1zde
    PDB 1zdp-2a3x
    PDB 2a3y-2arb
    PDB 2are-2bd2
    PDB 2bd3-2bu4
    PDB 2bue-2c6g
    PDB 2c6p-2cy6
    PDB 2cyf-2dso
    PDB 2dtw-2eab
    PDB 2eac-2fe1
    PDB 2ff1-2fwn
    PDB 2fws-2gjp
    PDB 2gjr-2hd9
    PDB 2hes-2i6o
    PDB 2i7a-2ivz
    PDB 2iwa-2j7g
    PDB 2j7h-2jke
    PDB 2jkh-2kuh
    PDB 2kxv-2o1k
    PDB 2o39-2ovz
    PDB 2ow0-2pf2
    PDB 2pfj-2pyz
    PDB 2pz0-2qu1
    PDB 2qua-2re1
    PDB 2rex-2tmv
    PDB 2tn4-2vcb
    PDB 2vcc-2vqy
    PDB 2vr0-2w3i
    PDB 2w3j-2wlj
    PDB 2wm4-2wzs
    PDB 2x0g-2xmr
    PDB 2xn5-2z2z
    PDB 2z30-2zn9
    PDB 2zni-3a51
    PDB 3a5l-3ahw
    PDB 3ai7-3bcf
    PDB 3bdc-3bx1
    PDB 3bxi-3ch2
    PDB 3chj-3d34
    PDB 3d3i-3djl
    PDB 3dng-3e4q
    PDB 3e5s-3eqf
    PDB 3eqg-3faq
    PDB 3faw-3fou
    PDB 3foz-3gci
    PDB 3gcj-3gwz
    PDB 3gxo-3hjr
    PDB 3hkr-3i4i
    PDB 3i4p-3io6
    PDB 3ior-3k5m
    PDB 3k5s-3kqa
    PDB 3kqf-3lei
    PDB 3lek-3lum
    PDB 3lun-3mip
    PDB 3mis-3n7b
    PDB 3n7x-3nvn
    PDB 3nx7-3owf
    PDB 3ox5-3prq
    PDB 3prr-3sg5
    PDB 3sg6-3u39
    PDB 3u43-3vpp
    PDB 3zqx-4awy
    PDB 4awz-4dtu
    PDB 4dtx-4eoa
    PDB 4epz-5apr
    PDB 5bca-8tln
    PDB 966c-9rnt

Glass






Certain of the metallic silicates, especially alkali silicates, show a remarkable tendency to super-cool, giving a transparent structureless solid, known as a glass, which may be regarded as a liquid in a highly viscous condition. The alkaline earth silicates, aluminium silicate, and others, do not possess this property, or only to a very limited degree, extremely rapid cooling being necessary to obtain them in a vitreous condition. The silicates of iron, manganese, and lead do not readily crystallise unless cooled slowly. By mixing together silicates of the alkaline earths with the more readily crystallisable silicates, glasses are easily obtained which are at the same time capable of resisting the action of water and chemical reagents as the alkali silicates alone cannot do. In this possibility lies the foundation of the glass industry.

Glass of a very imperfect type was produced and employed as early as 1400 b.c., and probably before, in Syria and in Egypt, but it was not until the time of the Roman Empire that glass became an article of general domestic and industrial use. Roman glass was almost invariably of the soda-lime type, rich in silica. After the collapse of the Roman Empire, the Emperor Constantine encouraged the construction of glass furnaces at Byzantium, and these became celebrated throughout the civilised world until, after the taking of Constantinople in 1453, their products were eclipsed in beauty and delicacy by the work of the Venetian glass-blowers. The latter held first place for several centuries, until, in fact, in spite of stringent laws to prevent it, their secrets became known in England, France, and Germany. The Venetians, no doubt, owed part of their superiority in glass manufacture to the natural sodium carbonate which they imported and used. In other countries during mediaeval times the manufacture degenerated, owing to the use of crude wood ashes and the production of a potash-lime glass, very low in silica and with an excess of lime and magnesia. So far as is known, the first English glass factory, if we except those put up during the Roman occupation and one probably conducted by French workmen brought by St. Wilfred to York about 700 a.d., was erected at Chiddingfold in Surrey about the year 1230, and this district remained the only centre of glass manufacture until restrictions on the use of timber for fuel in the time of Elizabeth caused its decline. The fashion for ornamental glass vessels, which prevailed in the sixteenth century, resulted in the establishment, in London and other parts of England, of glass-blowers from France and the Low Countries, as well as a few from Italy. The introduction of coal as a fuel, and the necessity for covering the pots to protect from contamination by the coal, facilitated the use of lead oxide in glass and led ultimately to the manufacture of lead or flint glass in the form now known.

The composition of glass is varied according to the use to which it is to be put. Comparatively small changes in the composition may bring about rather serious changes in properties, and much experimental research has been necessary, and is still required, to discover suitable formulae for glasses for special purposes. Before the War, the manufacture of chemical glass-ware and optical glass was developed on the Continent, but not in Britain. Since then, however, British manufacturers have made remarkable progress.

Ordinary soda-lime glass approximates substantially to the composition Na2O.CaO.6SiO2, but there are very large possibilities of variation by replacing more soda by lime, exchanging soda for potash, or lime for baryta, magnesia, lead oxide, zinc oxide, or alumina, or, finally, by exchanging silica for phosphoric or boric acids. Small quantities of other substances may also be introduced, with the object of aiding in the refining of the glass or of producing coloured or opaque glass.

The earliest pioneers in the systematic study of glass, largely for optical and chemical purposes, were Schott and Abbe, who began their work in 1881, and set up a factory at Jena in 1884.


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