Excise duty exemption for potassium metal when produced at designated Heavy Water Plants and used for potassium amide manufacture. An excise duty exemption applies to potassium metal under Chapter 28 when produced at the Heavy Water Plant, Baroda, and either consumed within that factory for manufacture of potassium amide or supplied to Heavy Water Plants at Tuticorin, Talchar, Thal or Hazira for manufacture of potassium amide.