When a person having sold, mortgaged or pledged grain which is in a warehouse and for which a negotiable receipt has been issued, or having sold, mortgaged, or pledged the negotiable receipt representing such grain, continues in possession of the negotiable receipt, the subsequent negotiation thereof by that person under any sale, or other disposition thereof, to any person receiving the same in good faith, for value and without notice of the previous sale, mortgage or pledge, shall have the same effect as if the first purchaser of the grain or receipt had expressly authorized the subsequent negotiations.