At this time, it's more of a curiosity question but I still would like to know.

I am (for the first time) going to make my own Dektol (D-72) from raw ingredients. The recipe comes from Ralph's book. I got through converting Sodium Carbonate monohydrate 80g (specified in recipe) to anhydrous (what I have) 66.64g and I started wondering.

For all the ingredients, only Sodium Sulfite and Sodium Carbonate has hydrate specification and nothing else do. Why? Surely, absorbing water will change weight and thus composition. Is there a reason why it matters to these two ingredients and for nothing else?

Also, for Sodium Carbonate, I have anhydrous. I read anhydrous contain NO water and monohydrate contain one molecule of water per molecule of the compound. Question then, how do I know if mine is truly monohydrate? It's in tightly sealed container and it's a granule, not a cake or rock. Further, how do I know (as I know it likes to suck moisture) it didn't become octo-hydrate or dozen-hydrate, or millennium-hydrate? (made up words, but you know what I mean...)