You say it starts caking after packaging. Does that mean you are producing the powder yourself? If so, I would not contaminate your fresh powder with other chemicals. I don't know how reactive your powder is, but if possible I would try heating it up to more than 90°C in a nitrogen atmosphere and fill it into an airtight container. While filling it in, you can lead a nitrogen flow into the container by holding a tube to its bottom. Let the nitrogen flow some more seconds than the filling needs and close the container.The humidity should be too low now for hydroscopic caking as long as the container is kept tight.

yes ,we are manufacturing the Dipotassium phosphates by spraying the Phosphoric acid & 2KOH in kiln,then milling,screening and then packing at 70-90°C in PP bags.

 Ok then, it should be easy to try the dry nitrogen supported packaging. You should also try this with plastic Containers instead of pp-bags. According to my experience with Al2O3-powder PP-bags are easyly damaged with small defects while sealing the edges.

If the nitrogen packing does not solve your problem, i guess the caking is not caused by humidity but another mechanism.

thanks Mr.Birger..I will go for  nitrogen packaging  and let you know the results.

hi Mr.Birger,

          finally I bought a nitrogen gas cylinder.Do you have any standard procedure to purge the powder filled pp bags by nitrogen gas?It can help me to follow the correct path.