No, it's not water soluble (or very little).
To get decent (quantitatively) trip, you'd need about min. 500mg, something more like 1000mg. Do you have 20 of them?
I'm not sure if titan dioxide is harmful, but don't take my word for it.
I used Tantum Rosa vagina irrigation powder. If you want I can paste you the method I used, but it probably won't be helpful in case of your tablets.
Lastly and most importantly: it's not a trip I want to repeat. It's not fun.
As medicine, it used to be NSAID like eg. tylenol, but benzydamine has been withdrawn in this form from many countries as a drug that possess too much side effects.
I had quite interesting (mostly visually) trip when combined with DXM (500mg Benz. and about 600mg DXM as I remember), but there are many better.
Also I wouldn't repeat that, as I'm concerned about my health. To this day I sometimes see bright dots going before my eyes for take/give 10sec.
I've written more in this thread, you might want to read it.
http://www.bluelight.ru/vb/threads/353442-Benzydamine-NSAID-Stimulant-Psychedelic
pzdr