4. When is a sale or purchase of goods said to take place outside a State.
Subject to the provisions contained in section 3, when a sale or purchase of goods is determined in accordance with sub- section (2) to take place inside a State, such sale or purchase shall be deemed to have taken place outside all other States.
A sale or purchase of goods shall be deemed to take place inside a State if the goods are within the State--
in the case of specific or ascertained goods, at the time the contract of sale is made; and
in the case of unascertained or future goods, at the time of their appropriation to the contract of sale by the seller or by the buyer, whether assent of the other party is prior or subsequent to such appropriation. Explanation.-- Where there is a single contract of sale or purchase of goods situated at more places than one, the provisions of this sub- section shall apply as if there were separate contracts in respect of the goods at each of such places.