I heard that if I saturate some water with NaCl and put it in a closed box, the relative humidity near the water surface should be around 75 % at room temperature.
I am using this to calibrate some electronic sensors measuring relative humidity.
If a saturated solution gives 75 % RH, how can i know which RH more diluted mixtures should result in?
My setup is a small 1l plastic container where in I put a mixture of table salt (iodized) and tap water (about 150 ml). The sensor is hanging a few cm above the water surface and measures for a day or so.
The solutions I use are:
- Fully saturated water (Plenty of undissolved salt crystals)
- 75 % saturated water (3 parts saturated, 1 part pure water)
- 66 % saturated water (2 parts saturated, 1 part pure water)
- 50 % saturated water (1 part saturated, 1 part pure water)
I am also monitoring the temperature in the container, and it is usually swinging a few degrees below 20 °C.