Toxic: A number of times per day equal to his Constitution modifier (minimum 1/day), a vishkanya can envenom a weapon that he wields with his toxic saliva or blood (using blood requires the vishkanya to be injured when he uses this ability). Applying venom in this way is a swift action. Vishkanya Venom: Injury; save Fort DC 10 + 1/2 the vishkanya's Hit Dice + the vishkanya's Constitution modifier; frequency 1/round for 6 rounds; effect 1d2 Dex; cure 1 save.
Is it possible to store this venom for later use? As long as it is within the daily limit?
I would say no. Nothing in the ability indicates that it can be used for anything but envenoming a weapon. But then again, it doesn't say how long it lasts on the weapon either which could have the same result as storing some venom for later use.
Uhhh, nothing says it CAN'T, but I don't think that was the intent.
Then again, I see no harm in it either. It's not like you can sell it (it has no listed price as far as I know) and it's not a particularly potent poison either. And it'd actually be weaker (unless you were a 6th level Alchemist) since applying poison isn't usually a Swift action.