Commodity associations as defined in this chapter shall have power to issue notes, payable in such amounts at such rate of interest, and payable at such times as its board of directors may authorize, and to secure the payment of said notes by depositing warehouse certificates, issued against the commodity which such association is organized to handle, then in storage in warehouses, and may sell such notes to the general public and in the sale thereof be exempt from the provisions of chapter 409 relating to domestic and foreign investment companies.