Moisture content of coal

[LRJ]

I understand that the moisture content of coal is normalised by the wet weight of the material as opposed to the dry weight (dry weight is used to normalise for soils). What is the basis for this? I understand it has something to do with volume change.

 

[Compositepro]

I suppose it makes calculating water content from wet weight easier. And wet weight is easier to measured than dry weight.

 

[LRJ]

It's no different - you need to measure wet and dry weight in both cases (to calculate the amount of water that has exited the specimen), it's just the normalising parameter which is different (dry for soil, wet for coal). As I say, I think there is some real reason related to material science for this. I understand coal is not the only material where this is the case - such materials have a particular name, but I can't remember what it is.