SODIUM CARBONATE & CO

Hallo,
Could somebody help me out, what is the difference, IN USE, between Sodium carbonate anhydricum -monohydrate and -decahydrate.
I know it has to do whit the amount of water but when, let's say, the formula tells to use 100 gr. of anhydricum and there is onely decahydrate available, the ammout to use will be different but how to calculate this?
The same for other products, but is there a general rule than can be used?
Thanks,
Philippe

The following is from Anchell's Darkroom Cookbook, p. 273:

The formula specifies: You have: Multiply by:
--------------------- --------- -----------
monohydrate anhydrous 0.855
monohydrate crystalline 2.31
anhydrous monohydrate 1.17
anhydrous crystalline 2.7
crystalline monohydrate 0.433
crystalline anhydrous 0.37

I'm guessing the forum software will completely corrupt my columns, but you should still be able to extract the information.

Thank you verry mush srs5694!