What's the Test of the Water of Bitterness?

The woman is to take an oath saying, if no man has lane with you and if you have not turned aside to uncleanness while you are under your husband's authority. So then she's to drink the water and if she's guilty, then the water of bitterness is to have this effect upon her. If she's not guilty, we read down in verse 28, but if the woman has not defiled herself and is clean, then she shall be free and conceive children.