Captive use of sulphur trioxide remained excisable as sulphuric anhydride under the tariff entry.

Sulphur trioxide captively consumed in the manufacture of chlorosulphonic acid was held classifiable under Tariff Item 14-G as an anhydride of sulphuric acid and therefore exigible to central excise duty. The fact that oleum acted as a carrier in the continuous process did not alter the character of sulphur trioxide, which physically participated in the reaction after release. Technical material supported its identification as sulphuric anhydride, and the absence of marketability did not remove it from the tariff entry. The excise levy on the intermediate product was upheld and the appeal failed.

---

---

Issues: Whether sulphur trioxide, obtained in the manufacturing process and captively consumed for producing chlorosulphonic acid, was classifiable under Tariff Item 14-G and liable to central excise duty.

Analysis: The levy was held to relate to sulphur trioxide and not merely to oleum in circulation. On the facts, oleum functioned as a carrier for sulphur trioxide, while sulphur trioxide itself physically participated in the reaction after release from oleum. Technical material showed sulphur trioxide to be sulphuric anhydride, and the tariff entry specifically covered anhydrides. The contention that the gaseous form was not marketable did not displace its classification under the tariff entry, and no material established that sulphur trioxide was outside trade recognition as anhydride.

Conclusion: Sulphur trioxide was rightly treated as anhydride of sulphuric acid and was exigible under Tariff Item 14-G; the levy was upheld.

Final Conclusion: The appeal failed and the excise demand on the captively consumed product was sustained.

Ratio Decidendi: Where a product is specifically covered by a tariff entry as an anhydride, its captively consumed and technically identifiable form remains exigible notwithstanding the assessee's contention that it is used only as an intermediate in a continuous process.

---