Calculation of equilibrium relative humidity (RH)
Up one levelThese equations will allow the calculation of the Relative Humidity that is in equilibrium with precipitant solutions based on Raoult's law and the Flory-Huggins model for the entropy of mixing of polymers. This is useful in finding the starting point for controlled dehydration experiments and assessing the degree of vapour diffusion and matching precipitant concentrations in protein crystallisation experiments
- Equation 1 — last modified 18-01-2012 09:51
- This equation will enable you to calculate the Relative Humidity in equilibrium with a salt solution. You will need to provide the concentration in Mol, the ionisation state of the salt (how many species it dissociates into) and a term describing the the specific volume of the solute (for sodium chloride y = 0.027, for ammonium sulfate y = 0.074, for sodium acetate y = 0.054, for sodium malonate y = 0.095, for magnesium sulphate y = 0.045, for Monopotassium phosphate y = 0.058 and for Dipotassium phosphate y = 0.071)
- Equation 2 — last modified 05-03-2012 16:14
- This equation will allow you to calculate the Relative Humidity (RH) in equilibrium with PEG solutions given in % (w/w). You will need to enter the molecular weight of the PEG in Da.
- Equation 3 — last modified 18-01-2012 09:52
- This equation will allow you to calculate the Relative Humidity (RH) in equilibrium with solutions of substances that neither dissociate into multiple species nor are polymers (e.g glycerol, ethylene glycol, sucrose, TMAO, etc)