Saturated Salt Solutions - Controlling Air Humidity
Saturated salt/water solutions can be used to maintain particular values of relative humidities inside sealed containers. A saturated salt solutions is a slushy mixture based on distilled water and a chemically pure salt.
Saturated salt/water solutions can be used to calibrate humidity sensors. Note that the values below may vary with several percents due to temperature variations, impurities in salt or water or slow saturation.
| Saturated Salt Solution | Temperature (ºC) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 50 | 60 | |
| Relative Humidity over the Salt Solution (%) | |||||||||||
| Ammonium nitrate - NH4NO3 | 75 | 70 | 67 | 64 | 60 | 53 | |||||
| Ammonium sulphate - (NH4)2SO4 | 82 | 82 | 82 | 82 | 81 | 81 | 81 | 80 | 80 | 79 | |
| Lithium chloride - LiCl 1) | 11.31 | 11.35 | 11.28 | 11.25 | 11.21 | 11.10 | 10.95 | ||||
| Magnesium chloride - MgCl2 | 34 | 34 | 33 | 33 | 33 | 33 | 32 | 32 | 32 | 31 | 29 |
| Magnesium nitrate - Mg(NO3)2 | 60 | 59 | 57 | 56 | 54 | 53 | 51 | 50 | 48 | 45 | |
| Natrium Cloride - NaCl 1) | 75.51 | 75.65 | 75.67 | 75.61 | 75.47 | 75.29 | 75.09 | 74.87 | |||
| Potassium sulphate - K2SO4 | 99 | 98 | 98 | 98 | 98 | 97 | 97 | 97 | 96 | 96 | |
| Potassium nitrate - KNO3 | 96 | 96 | 96 | 95 | 95 | 94 | 92 | 91 | 89 | 85 | |
| Potassium chloride - KCl | 89 | 88 | 87 | 86 | 85 | 84 | 84 | 83 | 82 | 81 | 80 |
| Potassium acetate - CH3CO2K | 23 | 23 | 23 | 23 | 22 | ||||||
| Potassium hydroxide - KOH | 14 | 12 | 11 | 9 | 8 | 7 | 7 | 6 | 6 | 5 | |
| Sodium chloride - NaCl | 76 | 76 | 76 | 76 | 75 | 75 | 75 | 75 | 75 | 74 | 75 |
| Sodium nitrite - NaNO2 | 65 | 64 | 63 | 62 | 61 | ||||||
| Sodium dichromate - Na2Cr2O7 | 61 | 59 | 57 | 57 | 55 | 54 | 53 | 51 | 50 | 49 | 47 |
1) Saturated aqueous solutions of inorganic salts are convenient for calibration of instruments for measurement of relative humidity
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