You make it to the lab, and sigh in relief. Soon, your troublesome extra baggage will be gone.
It's a problem finding a vessel to hold that much acetone, but you do, and fill it with acetone to the required level minus the volume that your phallus will displace.
You take it to a storage closet for some privacy, drop your sweatpants, and dunk your dick into the vessel of acetone. You watch with satisfaction as the acetone goes to work dissolving the rubber.
What you don't expect is that the rubber dissolves away almost immediately, because there was very little rubber to BE dissolved. The bioactive phallus has been working on your body, busily incorporating itself into your body, and what was once rubber is now living flesh - YOUR flesh, you note to your horror as you pull your new 13 inch dick from the acetone. There was only about an inch left of rubber shell not already converted to flesh by the time you hit the lab, and the acetone did its job and did dissolve that.
You're left with a vessel with cloudy acetone, and 13 inches swinging between your legs. And it's not your old familiar human cock distended to inhuman dimensions; no, you have an equine dick between your legs. You dry your dick with a lab towel, pull up the sweatpants, and leave the storage closet. You dispose of the acetone and disconsolately return to your dorm room.