First of all, waterfree soda is provided as a white powder. If you have small crystals, it will be either the monohydrate or decahydrate. Take an amount of your soda, determine the weight and put it in the oven above 120 °C. If it looses weight after some time, you have a hydrate. I tested my waterfree soda and it only looses about 2 or 3 gramms of 100 gramms, neglectible. If you loose about 20 %, it's the monohydrate. If you loose more than 50 % of weight, it's the decahydrate. Above 34 °C the decahydrate turns to monohydrate, above 107 °C the monohydrate turns to waterfree soda. When you don't loose weight anymore, all the water has evaporated and you now have pure waterfree soda. It might take hours, I have no clue how long.
Once determined which kind of soda you have, you can also use the mono- or decahydrate. Take 1.2x the weight (!) for mono- and 2.7x the weight (!) for decahydrate. Volumetric measuring is not possible, I don't know the specific densities and the scientific determined densities are not usable because they don't regard the huge amounts of air between the crystals/powdergrains.
So you can use the other kinds of soda than the waterfree, anhydrous one, but it makes things complicated. Btw, if you have a pH-meter, the final mix must have a pH of about 9.7. Using the wrong soda or miscalculating will result in a lower pH and reduces the developers activity dramtically.
The image was shot on TMax100 35 mm film @ about 800 ASA without any change of the process. The negs are quite thin and you have to do some adjustments during and after scanning, but it works - not too bad as you can see ;-)
Important note for recipes: when I say "XYZ" I mean "XYZ" and not "ABC".
Cheers - Reinhold