Claims relating to chemical composition have to always face an objection by the Indian Patent Office (IPO) that claims are statutorily non-patentable under the provision of clause (e) of Section 3 because the subject matter of the claims fall under the provision of section 3(e) of the Patents Act, 1970 (hereinafter the Act) as it relates to a known composition or mere admixture of known components which does not involve any synergistic effects. Therefore claims are not allowed u/s 3(e) of the Act.
Neetu Kumari discusses about Composition claim and section 3 (e) in her Mondaq article http://www.mondaq.com/article.