All materials, fluids, or substances offered or exposed for sale, purporting to be substitutes for or improvers of fuels or other motor fuels to be used for power, cooking, or heating purposes, shall, before being sold or exposed or offered for sale, be submitted to the Commissioner of Agriculture for examination and inspection and shall receive the approval of the state oil chemist and the Commissioner of Agriculture and shall be sold or offered for sale only when properly labeled with a label, the form and contents of which shall have been approved by the state oil chemist and the Commissioner of Agriculture.