13. Levy of tax on containers and packing material.

Where any goods is packed in any container or packing materials are sold, such container or packing material shall be deemed to have been sold or purchased along with such goods and the tax under section 11 or section 12 shall be levied on the sale or purchase of such container or packing material at the same rate as applicable to the sale or purchase of the goods contained therein:

Provided that no tax under section 11 or section 12 shall be levied where the container or packing material is sold or purchased along with the goods exempted from tax under section 17.