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Soda-lime glass is made by melting together soda (sodium carbonate), lime (calcium oxide), dolomite (calcium magnesium carbonate), silica (silicon dioxide), alumina (aluminum oxide), and small quantities of other compounds. Wikipedia says this is done in a furnace at "up to" 1675 °C. Many of the carbonates decompose at lower temperatures, 650 °C for dolomite and 851 °C for soda. However, soda-lime glass begins to soften at 700 °C.

Given the high decomposition temperature of carbonates like soda and dolomite, which is close to and sometimes higher than the temperature at which soda-lime glass begins to soften, one might think that there is a potential for some carbonate to remain dissolved in the glass. This is perhaps supported by the fact that silicon and carbon are both Group IV elements and could share spaces in the same lattice structure.

However, I haven't been able to find a quantitative analysis of soda-lime glass which measures oxidized carbon content. Is this because it's difficult to measure, or because no one in the glass industry cares, or because it's actually very close to zero?

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  • $\begingroup$ en.wikipedia.org/wiki/Soda-lime_glass gives contents, so... I don't exactly get why you're asking this. $\endgroup$
    – Mithoron
    Commented Jul 27, 2017 at 22:32
  • $\begingroup$ @Mithoron: "I haven't been able to find a quantitative analysis of soda-lime glass which measures oxidized carbon content" $\endgroup$ Commented Jul 27, 2017 at 22:35
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    $\begingroup$ At the higher temperatures the carbonates are completely decomposed and you are left with the oxides. The carbonate content should be quite negligible in the finished product. $\endgroup$
    – airhuff
    Commented Jul 27, 2017 at 22:35
  • $\begingroup$ Soda lime is made by mixing a few components, which are added to help with reducing the melting point. And at those temperatures any remaining carbon in form of carbonates would decarbonise, therefore as you mentioned, there is virtually close to zero amount of carbon. $\endgroup$ Commented Sep 24, 2022 at 17:26
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    $\begingroup$ Nature abhors a vacuum, the vacuum in this case being absolutely zero carbon atoms in the glass. But the "decomposition temperatures" of the carbonates do not account for CO2 being displaced by another acid such as silica, so probably the carbon is largely gassed out. $\endgroup$ Commented Sep 24, 2022 at 19:09

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