Any person engaged in the business of selling, distributing and furnishing natural, or manufactured, or mixed gas in the City shall not be required to pay the occupation tax provided for by §23-1 on the sale of such gas to the United States government, or any of its departments, or any sold to the state, or any of its departments, or any of the political subdivisions thereof, and no part or portion of the tax provided for in such section shall be levied upon or assessed against or taken from the United States government, the government of the state, or any of either of their departments or political subdivisions.