When a sale is made pursuant to this article, the county treasurer shall execute a deed to the purchaser, upon payment of the price bid, which deed shall have the effect of conveying title to the land sold to the purchaser free of encumbrance, except district assessments, including the unpaid balance of said assessment for the delinquency of which said property was sold, which, upon the date of the sale, had not been called and except as may be otherwise provided by law.