SECTION 1. Section 145, paragraph (b), of the National Internal Revenue Code, as amended, is hereby further amended by adding a new item (4) to read as follows:
"Ad Valorem Tax Rate" (4) Naphtha when used as a raw material in the production of petrochemical products 0% Provided, That naphtha processed by domestic refineries, if available as determined by the Energy Regulatory Board, shall be utilized before any naphtha may be imported for this purpose: Provided, further, That the by-product including fuel oil, diesel fuel, kerosene, pyrolysis gasoline, liquefied petroleum gases and similar oils having more or less the same generating power, which are produced in the processing of naphtha into petrochemical products shall be subject to the applicable ad valorem tax specified in paragraph (b) of this section, except when such by-products are transferred to any of the local oil refineries through sale, barter, or exchange, for the purpose of further processing or blending into finished products which are subject to ad valorem tax under the said paragraph (b) of this section."