Carbonate

From Saltwiki
Jump to: navigation, search

Author: Hans-Jürgen Schwarz
back to SaltWiki:Portal

Overview

The carbonate salts that are found most frequently in buildings and monuments are listed. The various salt phases are discussed in detail on separate pages, their occurrence and damage potential is explained and the deterioration patterns are illustrated and referenced.

Salt Formula Solubility at 20°C Light refraction Birefringence Notes
Dolomite CaMg(CO3)2 0.078 g/l (18°C) no = 1.679-1,698
ne = 1.502-1.513
Δ = 0.177-0.185 slowly soluble in 2M HCl
Magnesite MgCO3 0.106 g/l no = 1.700-1.719
ne = 1.509-1.527
Δ = 0.191-0.199 very slowly soluble in 2M HCl
Nesquehonite MgCO3•3H2O 1.79 g/l (16°C) nx = 1.417
ny = 1.503
nz = 1.527
Δ = 0.110 hardly soluble in water
pH about 10
Lansfordite MgCO3•5H2O nx = 1.465
ny = 1.468
nz = 1.507
Δ = 0.042 hardly soluble in water
pH about 10
Hydromagnesite Mg5(OH)2(CO3)4•4H2O nx = 1.515-1.523
ny = 1.530-1.527
nz = 1.544-1.545
Δ = 0.029-0.022 hardly soluble in water
Natrite Na2CO3 210 g/l nx = 1.415
ny = 1.535
nz = 1.546
Δ = 0.131 blooms quickly in dry air and passes into the monohydrate
pH about 12
Thermonatrite Na2CO3•H2O 330 g/l nx = 1.420
ny= 1.509
nz = 1.525
Δ = 0.105 alkaline in aqueous solution
pH about 12
Trona Na3H(CO3)2•2H2O; Na2CO3•NaHCO3•2H2O 130 g/l (0°C) nx = 1.412
ny= 1.492
nz = 1.54
Δ = 0.128 can be produced from an aqueous solution with a high concentration of NaCl and Na2SO4 at 50-85°C
pH about 10
Potash K2CO3 1120 g/l nx = 1.426
ny = 1.531
nz = 1.541
Δ = 0.015
Calcite CaCO3 0.014 g/l (25°C) no = 1.658
ne = 1.486
Δ = 0.172 well soluble in 2M HCl
Potassium carbonate dihydrate K2CO3•2H2O 1470 g/l nx = 1.38
ny = 1.432
nz = 1.573
Δ = 0.193
Kalicinite KHCO3 333 g/l nx = 1.38
ny = 1.482
nz = 1.573
Δ = 0.193 pH about 8
Potassium carbonate hexahydrate K2CO3•6H2O