Ca2H2S2O9 crystallizes in the monoclinic C2 space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(10), two equivalent O(4), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 9-coordinate geometry to one O(10), one O(11), one O(13), one O(3), one O(4), two equivalent O(5), and two equivalent O(8) atoms. In the third Ca site, Ca(3) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(6), one O(7), two equivalent O(12), and two equivalent O(9) atoms. In the fourth Ca site, Ca(4) is bonded in a 9-coordinate geometry to one O(14), two equivalent O(11), two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(14) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(13) atom. In the third H site, H(3) is bonded in a single-bond geometry to one O(13) atom. There are three inequivalent S sites. In the first S site, S(1) is bonded in a tetrahedral geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the second S site, S(2) is bonded in a tetrahedral geometry to one O(5), one O(6), one O(7), and one O(8) atom. In the third S site, S(3) is bonded in a tetrahedral geometry to one O(10), one O(11), one O(12), and one O(9) atom. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(3), and one S(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(3), one Ca(4), and one S(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Ca(2), one Ca(4), and one S(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one S(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Ca(2) and one S(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ca(3), one Ca(4), and one S(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(3), and one S(2) atom. In the eighth O site, O(8) is bonded in a 1-coordinate geometry to two equivalent Ca(2) and one S(2) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to two equivalent Ca(3) and one S(3) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one S(3) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Ca(2), one Ca(4), and one S(3) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Ca(3) and one S(3) atom. In the thirteenth O site, O(13) is bonded in a distorted water-like geometry to one Ca(2), one H(2), and one H(3) atom. In the fourteenth O site, O(14) is bonded in a distorted water-like geometry to one Ca(4) and two equivalent H(1) atoms.
Ca2H2S2O9 crystallizes in the monoclinic C2 space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(10), two equivalent O(4), and two equivalent O(7) atoms. Both Ca(1)-O(1) bond lengths are 2.68 Å. Both Ca(1)-O(10) bond lengths are 2.41 Å. Both Ca(1)-O(4) bond lengths are 2.45 Å. Both Ca(1)-O(7) bond lengths are 2.43 Å. In the second Ca site, Ca(2) is bonded in a 9-coordinate geometry to one O(10), one O(11), one O(13), one O(3), one O(4), two equivalent O(5), and two equivalent O(8) atoms. The Ca(2)-O(10) bond length is 2.71 Å. The Ca(2)-O(11) bond length is 2.50 Å. The Ca(2)-O(13) bond length is 2.37 Å. The Ca(2)-O(3) bond length is 2.54 Å. The Ca(2)-O(4) bond length is 2.47 Å. There is one shorter (2.45 Å) and one longer (2.52 Å) Ca(2)-O(5) bond length. There is one shorter (2.47 Å) and one longer (2.90 Å) Ca(2)-O(8) bond length. In the third Ca site, Ca(3) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(6), one O(7), two equivalent O(12), and two equivalent O(9) atoms. The Ca(3)-O(1) bond length is 2.37 Å. The Ca(3)-O(2) bond length is 2.48 Å. The Ca(3)-O(6) bond length is 2.60 Å. The Ca(3)-O(7) bond length is 2.51 Å. There is one shorter (2.49 Å) and one longer (2.52 Å) Ca(3)-O(12) bond length. There is one shorter (2.48 Å) and one longer (2.63 Å) Ca(3)-O(9) bond length. In the fourth Ca site, Ca(4) is bonded in a 9-coordinate geometry to one O(14), two equivalent O(11), two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms. The Ca(4)-O(14) bond length is 2.37 Å. Both Ca(4)-O(11) bond lengths are 2.49 Å. Both Ca(4)-O(2) bond lengths are 2.57 Å. Both Ca(4)-O(3) bond lengths are 2.68 Å. Both Ca(4)-O(6) bond lengths are 2.56 Å. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(14) atom. The H(1)-O(14) bond length is 0.97 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(13) atom. The H(2)-O(13) bond length is 0.98 Å. In the third H site, H(3) is bonded in a single-bond geometry to one O(13) atom. The H(3)-O(13) bond length is 0.97 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded in a tetrahedral geometry to one O(1), one O(2), one O(3), and one O(4) atom. The S(1)-O(1) bond length is 1.49 Å. The S(1)-O(2) bond length is 1.49 Å. The S(1)-O(3) bond length is 1.49 Å. The S(1)-O(4) bond length is 1.49 Å. In the second S site, S(2) is bonded in a tetrahedral geometry to one O(5), one O(6), one O(7), and one O(8) atom. The S(2)-O(5) bond length is 1.49 Å. The S(2)-O(6) bond length is 1.49 Å. The S(2)-O(7) bond length is 1.50 Å. The S(2)-O(8) bond length is 1.48 Å. In the third S site, S(3) is bonded in a tetrahedral geometry to one O(10), one O(11), one O(12), and one O(9) atom. The S(3)-O(10) bond length is 1.48 Å. The S(3)-O(11) bond length is 1.49 Å. The S(3)-O(12) bond length is 1.51 Å. The S(3)-O(9) bond length is 1.49 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(3), and one S(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(3), one Ca(4), and one S(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Ca(2), one Ca(4), and one S(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one S(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Ca(2) and one S(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ca(3), one Ca(4), and one S(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(3), and one S(2) atom. In the eighth O site, O(8) is bonded in a 1-coordinate geometry to two equivalent Ca(2) and one S(2) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to two equivalent Ca(3) and one S(3) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one S(3) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Ca(2), one Ca(4), and one S(3) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Ca(3) and one S(3) atom. In the thirteenth O site, O(13) is bonded in a distorted water-like geometry to one Ca(2), one H(2), and one H(3) atom. In the fourteenth O site, O(14) is bonded in a distorted water-like geometry to one Ca(4) and two equivalent H(1) atoms.