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Topic: काच

श्री. कविंद्र साळुंके यांनी ई-मेलद्वारे खालील शंका विचारली आहे. यावर विज्ञानपिठाच्या सभासदांकडून उत्तर अपेक्षित आहे.

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काच कशापासून तयार करतात?

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Re: काच

वालु,सिलिका आणि रंगासाठी विविध पदार्थ(निश्चित प्रमाण माहित नाहि)

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Re: काच

Dear Shrihari,

Sand itself contains silica. Then why to add silica separately (in addition to sand) to make glass?

I am confused....

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Re: काच

glass is composed of about 75% silica (SiO2) plus sodium oxide Na2O from soda ash, lime CaO, and several minor additives

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Re: काच

चष्माल बसवली जाणारी काच-रंग बदलणारी(day-night/PGK/PBK) कशी तयार केली जाते? ही काच उष्णता की प्रकाश लागल्यावर रंग बदलते? रंग बदलताना रसायनिक क्रिया कशी होते?


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Re: काच

bhausaheb wrote:

glass is composed of about 75% silica (SiO2) plus sodium oxide Na2O from soda ash, lime CaO, and several minor additives

One cannot generalize this…

All the properties of glass - whether optical, chemical, mechanical, thermal, physical, etc. – depend on the composition of the glass. Hence, composition of glass varies with the type of glass.

What has been described above in the earlier post refers to soda-lime glass. This glass is the most common type of glass seen around, e.g. as bottles, windowpanes, etc. Soda-lime glass has a composition different from that of optical glasses. Chemical resistant glasses will have a still different composition. Soda-lime glass contains oxides of calcium and magnesium. On the other hand, chemical resistant glass like borosilicate glass contains oxide of boron. Among the optical glasses, flint and crown glasses have different composition.

In fact, fused silica (quartz) itself is used as a glass where high temperature conditions are encountered. Fused silica finds application in UV spectroscopy also, as it absorbs UV to a minimal extent. Sample hoding cells used in UV spectroscopy are generally made of fused silica, as absorption due to other constituents of the glass cell is totally undesirable.

Thus, silica content of glass may vary from 50-55% to 100% depending on the nature of the glass.

And just an addendum… Glass may not be always silica (SiO2) based. It may be germanium oxide (GeO2) based, it may be lead oxide (PbO) based, it may be phosphorus oxide (P2O5) based...

Last edited by rajeev (21-12-2013 <> 12:01:42 PM)