How do I calibrate the humidity chamber for moisture-dependent XRPD analysis?

Dear Valentina Leandri ,

there are some digital humidity indicators that can be used, once previously calibrated.

Nevertheless, some chemicals may indicate the relative amount of humidity, in a relative precise way. Their use are conditioned to a well thermal treatment before use. It is somehow tricky.

Relative humidity cards indicators are widely used, check the link bellow:

Best regards,

WNM

I am using Humidity controller to introduce N₂-H₂O mixed gas characterized by different water vapor pressure into simultaneous TG-DTA and high temperature XRD instruments. In both cases, the gas generated by the humidity controller is transferred to an anterior chamber placed just before the gas inlet of the heating chambers through temperature controlled transfer tube. The anterior and heating chambers are also warmed by circulating hot water at a temperature higher 20degC than the dew point of the N₂-H₂O mixed gas. The temperature and relative humidity of the gas are recorded at the anterior chamber during the measurements of TG-DTA and high temperature XRD using a hygrometer. The water vapor pressure calculated from the temperature and relative humidity data is used as the actual water vapor pressure (kPa) in the reaction (heating) chamber.

I would be glad if this information is useful for You.

Best,

Dear Wagner,

a humidity chamber for XRPD is made is very small and there is no space to fit a hygrometer inside (if it was so easy, I would not have posted this question here). The use of paper which changes color with humidity is also not possible: we need to monitor the relative humidity precisely and the chamber is made of metal, so there would be no way of seeing the paper from the outside while running an analysis. It is not a common chamber we are talking about, it is one for XRPD analysis (see attached picture). In any case, thank you for your suggestions.