[editor_uaa]

im working on a research project. researching a new material which can replace Portland cement in future. as opposed to portland cement the new material is based not on silica chemistry but on phosphate chemistry.
i have a jar of binder material. it is very important. this jar contains MgO and KH2PO4 in certain proportion (1.000:0.9333). supposedly, when mixed with water (again certain mass %) an acid-base reaction takes place forming hard ceramic. the last experiment was successfully carried out in febuary this year. now its august and im trying to make another experiment... i mixed my binder (out of the same jar as 7 months ago) with water... and my mix doesnt set (i get a mold but its soft as a cookie). the recent experiment was done with a person who successfully carried it out in feb the same way he did it then.
my question is weather something could have happened to compounds in the jar in the past months. could any of those chemicals degrade??

[oldddog]

KH2PO4 will adsorb moisture. Take some from your container weigh it, place it in a deccicator and weigh it again after 24Hrs. A mass loss would indicate adsorbed moisture. Both components may also have under gone some solid state chemistry and you now have KMgPO4 and H2O.

[editor_uaa]

thanks for ideas... i understand that KH2PO4 would absorb moisture, but wouldnt it harden my powdered mix (since its supposed to be a binder), cause i still have powder?
now about the solid state chemistry... im wondering if it is even possible that my KH2PO4 could turn into KMgPO4 and H2O. and what i mean by possible is the mechanism is described somewhere in books. why would it do that... i would think that MgO is pretty stable?
then there was another possibility, that my KH2PO4 turned into KH2PO3, which is an insoluble salt. see, my half-set mold has some sort of white precipitate on the top? i would love to hear sugestions on how i can figure out what the precipitate is...can i do some kinda lab experiment?
thanks