Mass of one constituent\(\ce{A}\) divided by the mass of a second constituent\(\ce{B}\) in the same system. \[\zeta_{\ce{A,B}} = m_{\ce{A}}/m_{\ce{B}}\]
Source: PAC, 2008, 80, 233. (Glossary of terms related to solubility (IUPAC Recommendations 2008)) on page 253 [Terms] [Paper]