It is a misdemeanor for any person to directly or indirectly purchase for his own account, goods which are received by him upon consignment without prior authority from the consignor, or to fail to promptly notify the consignor of such purchases, if any, on his own account. This section does not, however, prevent any commission merchant from taking to account of sales, in order to close the day’s business, any miscellaneous lot or parcel of any farm product which remains unsold, if such commission merchant forthwith enters such transaction on his account of sales.