Most solvents we use in the laboratory have some shelf life. Experimental example: Say you have a 4L bottle of anhydrous toluene and you regularly pour out/use small volumes of it over the course of a year. One year from opening date, you have 1L of toluene left. Will this toluene still be "anhydrous" or will it have some small amount of water picked up from humidity in the atmosphere? Isn't toluene immiscible with water? So why would water solvate into a nonpolar solvent like this? is there a way to calculate/estimate the quality of the solvent after some time?