A connecting device for ensuring proper connection of liquid containers is provided. The connecting device comprises a bottle closure having a dip tube passage and a first key code pattern at the top. A rupturable film is disposed in the bottle closure. A connector is provided for coupling with the bottle closure. The connector has an upper member and a lower member. The bottom surface of the upper member has a second key code pattern configured to mate with the first key code pattern. The lower member is pivotally coupled to the upper member. A dip tube penetrates the upper member of the connector. A pre-check member having a puncturing structure for puncturing through the rupturable film is also provided. The pre-check member has a key code pattern substantially identical to the second key code pattern to mate with the first key code pattern.