A conditional sale, the condition being that the sale shall be void upon the seller paying to the purchaser a sum of money or doing some other act named. If the condition is performed according to its terms, the mortgage and sale immediately become void and the mortgagee is thereby divested of his title." (Rosales vs. Reyes, G.R. No. L-8162, 10 October 1913, citing Act No. 1508, also known as the "Chattel Mortgage Law," Sec. 3.)