Excise exemption for phosphorus trichloride used in manufacture of trimethyl phosphite, subject to specified procedural compliance. Exemption for the excise duty on phosphorus trichloride used in the manufacture of trimethyl phosphite, relieving the whole of the duty leviable under the tariff schedule for that input. Where such use occurs outside the factory of production, the procedural requirements of the central excise rules (Chapter X) must be followed.