Re: why is 70% ethanol an effective disinfectant?

The reason we use 70% ethanol as opposed to 100% ethanol is that, at 100%, 
ethanol will pull water from the cell so quickly that it can actually act 
to preserve the cell in a dry state. Later, when conditions are right, the 
cell will become viable and divide. At 70%, the destruction of the cell is 
slow enough that too much damage is done and the cell cannot "come back to 
life".