Gas solubility in water and alcohol I know that a certain gas is soluble in water but not in alcohol. How can I find the solubility of the gas in mixture of water and alcohol? Do I use a simple linear relation? The gas in question is not a noble gas, but does not react with either liquid.
So long as we assume that this is an ideal situation in which there is really insignificant solubility of the gas in ethanol but significant solubility in water, then yes, you can assume that the concentration in the mixture is linear with the water fraction of the liquid. In other words:  

$${H_m = H_w * x_{w}}$$  

Where:
${H_m}$ = Henry's law solubility of the gas in the water-ethanol mixture
${H_w}$ = Henry's law solubility of the gas in water
${x_{w}}$ = mol fraction of water in the liquid phase