What would be the method of turning Soda Lime Glass into:

A. Lead Glass

B. Fused Silica

Soda Lime Glass is $\ce{SiO2}$ ~70%. Lead Glass is $\ce{SiO2}$ ~ 62.9%. Fused Silica is $\ce{SiO2}$ ~ 99.9%. Can one start with a batch of Soda Glass, chemically separate the $\ce{SiO2}$, and then use that to make Lead Glass/Fused Silica? I'm not expecting it to be cost effective, but I doubt it's physically impossible. Is it?

  • $\begingroup$ Two completely different chemical compositions. So the only way to make a conversion is to sell the soda glass and use the money to buy lead glass. $\endgroup$ – MaxW May 22 '18 at 7:53
  • $\begingroup$ Cannot be done. $\endgroup$ – Waylander May 22 '18 at 7:55
  • $\begingroup$ @Johan88 I added your comment to the question. As your question previously stood it was violating the homework policy and would have been closed. Hope that's fine with you. $\endgroup$ – Avyansh Katiyar May 22 '18 at 8:10
  • $\begingroup$ @AvnishKabaj much appreciated. Thank you. Really don't understand the difference between a hw and a non-hw question but I'm sure you do. Grazie $\endgroup$ – Johan88 May 22 '18 at 8:17
  • $\begingroup$ The policy is very badly titled. It's not limited to questions which are literally homeworkA "homework question" is any question whose value lies in helping you understand the method by which the question can be solved, rather than getting the answer itself. This includes not just questions from actual homework assignments, but also self-study problems, puzzles, etc. $\endgroup$ – Avyansh Katiyar May 22 '18 at 8:25

Everything you suggest, can be done. It is a bit impractical though, the best is to start from the right raw materials.

Soda glass can be purified by high temperature. The sodium oxide will evaporate as the temperature becomes high, but we are talking on the upside of 1600 $^o$C perhaps even up to 2000 $^o$C. All the other alkali and many rare earth oxides will evaporate as well, so if you want any of those back, you'll have to add them. In addition, high temperature silica is a mess to work with when it is pure, viscous and prone to "boiling over" when releasing gases - so YMMV. So there you have pure silica. It'll never be "fused" silica though, the name derives from the process it was taken from - and it is usually in the form of micro-sized globes or spheres. You'll end up with a "lump" or "pile" of silica.

To make lead glass, you have forgotten an important ingredient - lead oxide. So, solidify your silica glass and crush it. Take a batch of molten lead oxide dissolve silica the in it (there is something with "molten lead oxide" that is depressing and discouraging but don't let that keep you from your plan). One should respect lead and its oxide, especially when there is an appreciable vapour pressure of them - you'll be permanently heavy metal poisoned if exposed. So, as the viscosity of this mix will become higher as you add silica in it, you are going to have to apply generous amounts of elbow grease to get this mix. I take no responsibility for your elbows though, take care when sloshing around hot and sticky liquid-ish substances.

Now, with all that being said - use the right raw materials and it is much easier. Still not easy, that's why money can be made making glass - but easier.

| improve this answer | |
  • $\begingroup$ Thanks for the answer. So the sodium oxide and all the other alkali and earth oxides evaporate off, and the sodium dioxide silica alone will remain as a molten heap?? And: that addresses part A. of the question, but can that pile of purr silica then be made into fused silica? No obstacles there right - just need enormous heat? $\endgroup$ – Johan88 May 22 '18 at 11:45
  • $\begingroup$ @Johan88, silica is not "sodium dioxide silica", but SiO2. $\endgroup$ – DrMoishe Pippik May 22 '18 at 12:01
  • $\begingroup$ @Johan88 Well, fused silica is called fused silica because you take an amorphous source of silica, usually in the form of a fume, microscopic and condensed powder. If you use anything else they prefer to call it fused quartz. The properties are similar. Now, can you get to that purity by the above method alone? Possibly not, purity is so paramount for fused silica. Can it be done? yes. with more purification. It will be hideously more expensive. $\endgroup$ – Stian Yttervik May 22 '18 at 13:23

Not the answer you're looking for? Browse other questions tagged or ask your own question.