As for you, MXE should dissolve fine. I've a fair bit of experience injecting MXE, and it always dissolved either by itself or with a touch of heat. If what you have doesn't do so, then you should accept that whatever you have probably isn't MXE.
Vape it in an electronic cigarette. We know it is you doing the drugs by the way.
Lol me? Drugs? Well you might be on to something... Anyway does vaping work with MXE like that? You wouldn't need freebase? I think it usually comes in hcl and then what about concentration? It might be difficult to analyze 100mg at a time...
As far as water goes I duno. I've tried to dissolve the stuff in it and it doesn't seem to dissolve very well and leaves no results. Maybe i'm not doing things right. Luke warm water doesn't do much. Boiling just seemed to evaporate the water and still cloudy. IN works just fine.
It should dissolve with a little determination. I have had 2 batches that didn't dissolve properly, one was definitely cut, the other one seemed potent enough but I can't be sure.