EGTA is an acid so be careful when handling it. The reason we use the acid form of EGTA is for the same reason we use the acid form of PIPES. We want to be able to choose which counter ion we want to add to solution. Whether it be sodium or potassium.
It should be stored in its original container in the desiccator. Also, when using EGTA, always add it to water and not the other way around.