Evaporative co-crystallization of MCl (M = Na, K, Rb, Cs) with BiOCl in aqueous HCl produces double salts: M x Bi y Cl (x+3y) •zH 2 O. The sodium salt, Na 2 BiCl 5 •5H 2 O (monoclinic P2 1 /c, a = 8.6983(7) Å, b = 21.7779(17) Å, c = 7.1831(6) Å, β= 103.0540(10)°, V = 1325.54(19) Å 3 , Z = 4) is composed of zigzag chains of µ 2-Cl-cis-linked (BiCl 5) n 2nchains. Edge-sharing chains of NaCl n (OH 2) 6−n octahedra (n = 0, 2, 3) are linked through µ 3-Cl to Bi. The potassium salt, K 7 Bi 3 Cl 16 (trigonal R−3c, a = 12.7053(9) Å, b = 12.7053(9) Å, c = 99.794(7) Å, V = 13951(2) Å 3 , Z = 18) contains (Bi 2 Cl 10) 4edge-sharing dimers of octahedra and simple (BiCl 6) 3octahedra. The K + ions are 5-to 8-coordinate and the chlorides are 3-, 4-, or 5-coordinate. The rubidium salt, Rb 3 BiCl 6 •0.5H 2 O (orthorhombic Pnma, a = 12.6778(10) Å, b = 25.326(2) Å, c = 8.1498(7) Å, V = 2616.8(4) Å 3 , Z = 8) contains (BiCl 6) 3octahedra. The Rb + ions are 6-, 8-, and 9-coordinate, and the chlorides are 4-or 5-coordinate. Two cesium salts were formed: Cs 3 BiCl 6 (orthorhombic Pbcm, a = 8.2463(9) Å, b = 12.9980(15) Å, c = 26.481(3) Å, V = 2838.4(6) Å 3 , Z = 8) being comprised of (BiCl 6) 3octahedra, 8-coordinate Cs + , and 3-, 4-, and 5-coordinate Cl −. In Cs 3 Bi 2 Cl 9 (orthorhombic Pnma, a = 18.4615(15) Å, b = 7.5752(6) Å, c = 13.0807(11) Å, V = 1818.87(11) Å 3 , Z = 4) Bi octahedra are linked by µ 2-bridged Cl into edge-sharing Bi 4 squares which form zigzag (Bi 2 Cl 9) n 3nladders. The 12-coordinate Cs + ions bridge the ladders, and the Cl − ions are 5-and 6-coordinate. Four of the double salts are weakly photoluminescent at 78 K, each showing a series of three excitation peaks near 295, 340, and 380 nm and a broad emission near 440 nm.