The Collaborative International Dictionary of English v.0.48:

Sodium sulphate \So"di*um sul"phate\
   A salt well known as a catharic under the name of Glauber's
   salt, which term is properly applied to the hydrate,
   Na2SO4.10H2O.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

sodium sulphate
    n 1: a solid white bitter salt used in manufacturing glass and
         paper and dyes and pharmaceuticals [syn: sodium sulphate,
         sodium sulfate]