Caught Red Handed

Mr. Stanley was missing some money that he had kept in this cup board. This is the third time that he was missing money. In earlier occasions he blamed himself for having lost the money. But, this time he knew for sure that something is wrong. Someone is stealing money from him. “Who could it be?”, he asked himself. He made a list of suspects. It read 4 names. Alex, Charles, Robin and Peter.

Mr. Stanley wanted to catch the culprit during the act. He thought of a wonderful plan. He fetched the washing soda from his laundry room. He then took a little of the washing soda and spread it over some of the notes he had. He ensured that the amount was just enough to catch the culprit. He then left the notes in the same place as earlier and left the room.

Mr. Stanley is using a procedure all chemists do during a titration. During a titration, an indicator is used to indicate the end of the reaction that is being performed. The indicator can be added additionally to the reaction mixture to show completion of the reaction. In some reactions one of the products can act as an indicator. Substances commonly used as an indicator exhibit different color in different medium. Phenophthalein, a common indicator, becomes pink in a basic solution and is colorless in acidic solution.

Like other acid base indicators, phenolphthalein has different colors for its acidic (unionized) and basic (ionized) forms. It is colorless in acidic form and pink colored in basic form

When Mr. Stanley returned to his office after 10 minutes, he observed that the notes have gone as he had expected. He immediately summoned his four suspects to his office. He told them about the frequent disappearance of money from his office. All the four were surprised to hear that there has been a series of theft at their workplace. Mr. Stanley said, “I laid a trap this time to catch the culprit.” There was no nervousness or change of expression on anyone’s face. They still seemed surprised.

“Show me your Palms”, he said. All the four extended their hands to show their palms. He then sprayed a solution on phenolphthalein on everyone’s palms. All but Robin’s palms were colorless. The washing soda (Sodium Carbonate) had made phenolphthalein change its colour to pink.

Robin, suspended from work, after being caught Red (pink to be precise) Handed is doing social service to compensate for all the money he had stolen.

Note: Please DO NOT handle chemicals with bare hands. Always be protected from chemicals.