Action of Sodium Hydroxide Solution on Glass at Different Temperatures JSGT_V01_T144-T147
The action of caustic soda on different types of glassware is described. No earlier data are available for a comparison of the effect of 2N-caustic soda with that found by us, but it is worthy of note that with 2N-caustic soda solution the extent of its action on glass, according to our tests, is greater than in other previously published reports. The data for comparison are few and confined to Jena glass. For 2N caustic soda, acting at 100° for three hours, the losses found at the National Physical Laboratory on six different new Jena flasks.varied from 60 to 79 mg per sq. dcm. In our own determinations, the loss (first period) was observed to be 112 mg. It is possible that some of the discrepancy may be accounted for by a slight difference in method. Although in the report cited, no details are given, the practice frequently followed is to heat up the caustic alkali solution to 100° in a silver flask and to transfer it then to the glass vessel under test. In our own experiments, it was essential to avoid this transference, and the flask and alkali were heated as quickly as possible on a hot plate to 100° prior to being placed in the thermostat. This means an additional ten minutes' contact between alkali and glass; but seeing that the period in the thermostat is three hours and the corrosive action of alkali below 80° is slight, the difference of procedure cannot account for much of the margin between the figures quoted and our own.
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