I apologize if this isn't exactly news.. It probably isn't, but I wasn't able to find any data on DPT HCl's solubility in water besides DPT Primer on Erowid.
Well yesterday I was able to dissolve 60mg DPT HCl in 1.1mL tapwater(for rectal ROA). I started dissolving in hot tapwater, shaked vigorously and ended up heating the solution in the microwave for a couple of seconds. Everything stayed in solution, even after it cooled to roomtemp.
I am very confident that nothing of the compound combusted, but of course I can't say for sure..
Thought it might come handy to someone else maybe