In any case hereafter, in which advances of money, repayable on demand, to an amount not less than five thousand dollars, are made upon warehouse receipts, bills of lading, certificates of stock, certificates of deposit, bills of exchange, bonds, or other negotiable instruments, pledged as collateral security for such repayment, it shall be lawful to receive, or to contract to receive, and collect as compensation for making such advances, any sum to be agreed upon in writing by the parties to such transaction.