Any person who shall purchase fuels upon which the tax provided in this chapter shall have been paid and shall sell the fuels outside this state or to the United States government, may be reimbursed the amount of the tax in the manner and subject to the conditions provided in this chapter. All claims for reimbursement shall be made under oath to the tax administrator upon forms to be obtained from the tax administrator, within two hundred forty (240) days from the date of the purchase of the fuels, and shall contain any information and proof that the tax administrator may require, that the claimant has paid the tax and that the fuels have been sold by the claimant outside this state or to the United States government. Claims for reimbursement shall be paid by the general treasurer from the general fund upon certification by the tax administrator and with the approval of the controller. However, any distributor shall be exempt from the payment of any tax on fuels sold by the distributor to the United States government or to a person, firm, or corporation who or which shall use the fuel solely for the operation of railroad transportation equipment on fixed rails or tracks, upon the presentation to the tax administrator by the distributor of proof satisfactory to the tax administrator as to the sale. Provided, that any distributor shall be exempt from the payment of any tax on fuels sold by the distributor to another distributor who is registered with the tax administrator.