VENTECH LOW EXPANSION BOROSILICATE GLASS
Laboratory work requires apparatus made in a Borosilicate 3.3 expansion glass which maintains maximum inertness to widest range of chemical substances, withstand thermal shock, high temperature without deforming and resilient enough to withstand the normal laboratory handling, washing and sterilizing processes.
VENTECH is the trade name of such a glass.
CHEMICAL COMPOSITION
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The approximate composition of the borosilicate glass used by us is as follows:
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SiO2 |
- 81% |
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B2O3 |
- 13% |
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Na2O |
- 04% |
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Al2O3 |
- 02% |
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THERMAL PROPERTIES
| The thermal properties of Borosilicate glass are given below: |
| Co-efficient of Linear Expansion |
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| Strain Point |
515 °C |
| Annealing Point |
565 °C |
| Softening Point |
820 °C |
| Specific Heat |
0.2 |
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OPTICAL PROPERTIES
Borosilicate glass shows no appreciable absorption in the visible region of spectrum and therefore appears clear and colorless.
RESISTANCE TO CHEMICALS
Borosilicate glass is inert to almost all materials except hydrofluoric acid [HF] ,phosphoric acid [H3PO4] and hot strong caustic solutions. Of these, Hydrofluoric acid has the most serious effect even when it is present in PPM [parts per million] in solutions. Where as phosphoric acid and caustic solutions causes no problem when cold, but at elevated temperature corrosion occurs . Caustic solutions upto 30% concentration can be handled safely at ambient temperature.
Under actual operating conditions, the effect of turbulance and traces of other chemicals in the solution may increase or decrease the rate of attack. So it is not possible to give exact figures for corrosion by caustic solution.
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