The Collaborative International Dictionary of English v.0.48:
Solubleness \Sol"u*ble*ness\, n. Quality or state of being soluble. [1913 Webster] SolusWordNet (r) 3.0 (2006):
solubleness n 1: the property of being dissoluble; "he measure the dissolubility of sugar in water" [syn: dissolubility, solubleness]