Quick Chemistry question! Will award 10 pts for best!?

I am pretty sure that borax is a solid so it must be mixed with a solution to become aqueous. If the problem is a double replacement problem than you are trying to form a compound by mixing it with HCl. If solid borax got into this it could taint it. You need the test tube to be dry so water doesn't mix with either compound, and you obviously don't want to leave HCl open.