From Saltwiki

Author: Hans-Jürgen Schwarz
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The chloride salts most frequently found on buildings and monuments are listed. The various salt phases are discussed in detail on separate pages, where their occurrence and deterioration potential is discussed, as well as illustrated by the developed damage patterns.

Salt Formula Solubility at 20°C Deliquescence RH at 20°C Light refraction Birefringence Notes
Bischofite MgCl2•6H2O 5.75 mol/kg nx =1.495
ny = 1.509
nz = 1.528
Δ = 0.003 decomposes at 116-118°C
hygroscopic and deliquescent
Tachyhydrite CaMg2Cl6•12H2O no= 1.520-1.522
ne = 1.512-1.513
Δ = 0.008-0.009 hygroscopic and deliquescent
Fluorite CaF2 0.016 g/l (18°C) n = 1.434
Halite NaCl 6.135 mol/kg nD=1.5443 water soluble
Calcium chloride
Antarcticite CaCl2•6H2O 6.712 mol/kg no =1.417-1.494
ne = 1.393-1.550
Δ= 0.024 hygroscopic and deliquescent
Calcium chloride tetrahydrate CaCl2•4H2O
Sinjarite CaCl2•2H2O
Carnallite KMgCl3•6H2O nx=1.466
Chlorocalcite KCaCl3 nx=
Sylvite KCl 4.595 mol/kg n=1.4903