As dissolving touch, except your weapon is charged with acid until you make a successful attack.
Your touch, claw, or bite is corrosive, and sizzling moisture visibly oozes from your natural weapon or hand. You deal 4d6 points of acid damage to any creature or object you touch with your successful melee touch attack. Acid you secrete denatures 1 round after use, losing all efficacy and ability to deal damage. You are immune to your own acid.
Augment For every 2 additional power points you spend, this power’s damage increases by 1d6 points.
Does the power crit if the weapon crits?
Touch attack powers that do damage crit on a 20 for double damage. But this attack is being made with a weapon, and otherwise emulating a touch power. If the weapon crits on an 18, does the power crit, like with a magus using spell strike? If so, would a x3 crit weapon also lead to x3 damage since there is no wording like spellstrike has to rule that out? Or does the power still only crit on a natural 20 even if the weapon crits on an 18, like nothing in the rules I can think of? Or is this extra damage being applied to the weapon which doesn't crit at all, like a flaming weapon?
I'm leaning toward the spell strike-like version, as that seems like the most reasonable interpretation, but I really have nothing to base that on beyond an unwillingness to to have two separate crit ranges on a single attack.
It is additional damage and not multiplied on s crit. It can only copy across so much of the base spell, some things have to change. It is no longer possible to treat it as a touch spell. And there is no rule allowing you to treat it as spell strike. There are clear rules on how to treat damage added to weapon damage.