We don't have any device which is able to measure low air humidity values. Could anyone give a reference to published research concerning relative humidity over silica gel? How much water would contain a small aliquot of bacterial biomass desiccated for 2 weeks at 20°C?
I cann't give you a reference and only a partial answer. The people in our lab mearsured roughly that no humidity is left shortly after closing the chamber. Small amounts of algae biomass desiccate within few hours.
For controled humidity loss, salty solutions are proposed.
If air in the desiccator is removed through vacuum pump, regenerated silica gel (1200C for 2hr) can give about 7-9% RH. This is the result observed in my lab.
If air is not removed, initially RH in closed chamber depends on ambient RH. It takes longer time to reach equilibrium (RH 10%) and silica gel will also get deactivated faster.
Thanks to everybody!
Saranya, could you tell me, please, which device you used to measure RH, and how precise that measurement was
How would you measure water content in samples desiccated over silica gel? Obviously, oven drying and subsequent cooling in chamber with silica gel doesn't make sense because it will give the same values... Maybe, drying over P2O5 (sulfuric acid doesn't seem to work well)?
thermohygrometer from coleparmer. according to manufacturer, accuracy 3%(plus or minus) of reading.
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