Glass alkali durability tests

The reaction of bases with most silicate glasses produces dissolution rates when tested in 5% NaOH solution at 95°C. The mechanism also involves a complete dissolution process as that described for acid. Weaker alkaline solutions may both leach and dissolve and sometimes show greater dependence on glass composition. And, in the case of strong alkali solutions, the rate of attack doubles for each 10 K increase in temperature or each increase in pH unit. Usually higher alkali durability glasses are used for laboratory wares. 

The choice of materials from which to make the holder is important. Materials must be durable enough to ensure satisfactory completion of the test. It is good practice to select very resistant materials for the test assembly. Insulating materials used are plastics, porcelain, Teflon, and glass. A phenohc plastic answers most purposes its principal hmitations are unsuitability for use at temperatures over I50°C (300°F) and lack of adequate resistance to concentrated alkalies. 

Inwall. US term for the refractory lining of the STACK (q.v.) of a blast furnace, lodoeosin Test or Mylius Test. For determining the durability of optical glass. The amount of free alkali in a... 

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