The three-dimensional predominance volume diagrams (PVDs) for the system Cu-As-S-O were constructed at 900 K using P_As4O6 (g), P_O2 (g), and P_SO2 (g)${\mathrm{P}}_{{\mathrm{A}\mathrm{s}}_4{\mathrm{O}}_6\mathrm{ }\left(\mathrm{g}\right)},\mathrm{ }{\mathrm{P}}_{{\mathrm{O}}_2\mathrm{ }\left(\mathrm{g}\right)},\mathrm{ }\mathrm{a}\mathrm{n}\mathrm{d}\mathrm{ }{\mathrm{P}}_{\mathrm{S}{\mathrm{O}}_2\mathrm{ }\left(\mathrm{g}\right)}$ as independent coordinates. The constant total pressure surface was used to identify the equilibrium phases that are stable at 0.25 atm total pressure. The isobaric surface superimposed on the predominance diagram provides useful insights into the roasting of complex copper sulfosalts such as enargite (Cu₃AsS₄${\mathrm{C}\mathrm{u}}_3\mathrm{A}\mathrm{s}{\mathrm{S}}_4$) and tennantite (Cu₁₂As₄S₁₃${\mathrm{C}\mathrm{u}}_{12}{\mathrm{A}\mathrm{s}}_4{\mathrm{S}}_{13}$). There are nine interior invariant points each with four associated condensed phases at 900 K. The expanded diagrams showing the stability volumes of each individual phase are presented. According to the PVD for the Cu-As-S-O system, the transformation of enargite to copper sulfate follows the Cu₃AsS₄→CuS→CuSO₄${\mathrm{C}\mathrm{u}}_3\mathrm{A}\mathrm{s}{\mathrm{S}}_4\to \mathrm{C}\mathrm{u}\mathrm{S}\to \mathrm{C}\mathrm{u}\mathrm{S}{\mathrm{O}}_4$ or Cu₃AsS₄→Cu₂S→ CuS→CuSO₄${\mathrm{C}\mathrm{u}}_3\mathrm{A}\mathrm{s}{\mathrm{S}}_4\to {\mathrm{C}\mathrm{u}}_2\mathrm{S}\to \mathrm{ }\mathrm{C}\mathrm{u}\mathrm{S}\to \mathrm{C}\mathrm{u}\mathrm{S}{\mathrm{O}}_4$ sequence when the pressure of As₄O₆ (g)${\mathrm{A}\mathrm{s}}_4{\mathrm{O}}_6\mathrm{ }\left(\mathrm{g}\right)$is extremely low. At high As₄O₆ (g)${\mathrm{A}\mathrm{s}}_4{\mathrm{O}}_6\mathrm{ }\left(\mathrm{g}\right)$ pressures however, enargite can directly transform to copper sulfate.

使用P _{As 4 O 6  （g）}，P _{O 2  （g）}和P _{SO 2  （g）}在900 K下构建了系统Cu-As-SO的三维优势体积图（PVD _）${\mathrm{P}}_{{\mathrm{一个}\mathrm{s}}_4{\mathrm{Ø}}_6\mathrm{ }\left(\mathrm{G}\right)}，\mathrm{ }{\mathrm{P}}_{{\mathrm{Ø}}_{\mathrm{2个}}\mathrm{ }\left(\mathrm{G}\right)}，\mathrm{ }\mathrm{一个}\mathrm{ñ}\mathrm{d}\mathrm{ }{\mathrm{P}}_{\mathrm{小号}{\mathrm{Ø}}_{\mathrm{2个}}\mathrm{ }\left(\mathrm{G}\right)}$作为独立的坐标。恒定的总压力表面用于确定在0.25 atm总压力下稳定的平衡相。叠加在优势图上的等压表面可为焙烧复杂的亚硫酸铜盐（例如芒硝（Cu ₃ AsS ₄${\mathrm{C}\mathrm{ü}}_3\mathrm{一个}\mathrm{s}{\mathrm{小号}}_4$）和球铁矿（Cu ₁₂ As ₄ S ₁₃${\mathrm{C}\mathrm{ü}}_{12}{\mathrm{一个}\mathrm{s}}_4{\mathrm{小号}}_{13}$）。有9个内部不变点，每个不变点在900 K时具有四个关联的凝结相。给出了显示每个相的稳定体积的展开图。根据Cu-As-SO系统的PVD，将辉镁石转变为硫酸铜遵循Cu ₃ AsS ₄ →CuS→CuSO _4。${\mathrm{C}\mathrm{ü}}_3\mathrm{一个}\mathrm{s}{\mathrm{小号}}_4\to \mathrm{C}\mathrm{ü}\mathrm{小号}\to \mathrm{C}\mathrm{ü}\mathrm{小号}{\mathrm{Ø}}_4$或Cu ₃ AsS ₄ →Cu ₂ S→CuS→CuSO ₄${\mathrm{C}\mathrm{ü}}_3\mathrm{一个}\mathrm{s}{\mathrm{小号}}_4\to {\mathrm{C}\mathrm{ü}}_{\mathrm{2个}}\mathrm{小号}\to \mathrm{ }\mathrm{C}\mathrm{ü}\mathrm{小号}\to \mathrm{C}\mathrm{ü}\mathrm{小号}{\mathrm{Ø}}_4$As ₄ O ₆  （g）的压力时的顺序${\mathrm{一个}\mathrm{s}}_4{\mathrm{Ø}}_6\mathrm{ }\left(\mathrm{G}\right)$极低。最高As ₄ O ₆  （g）${\mathrm{一个}\mathrm{s}}_4{\mathrm{Ø}}_6\mathrm{ }\left(\mathrm{G}\right)$ 然而，在压力下，硬石膏可以直接转化为硫酸铜。