need help in black plague

[-broasca-]

-im in the building where i killed the woman that helped me ... i need to get 6 chemicals , i only found 5 in the room where the machinery to mix them is ... the entrance to the chemical lab is closed , i opened the door from the computer , but is still closed due to the gass leak ...
-i looked everywere , i cant find the sixth chemical ... neither can i stop the gass leakege ...

need help

ps : the game is awsome