Phenolphthalein 

Don't forget that Phenolphthalein is also used as a laxative. If ingested, even in the concentrations generally found in a high-school or college-level chemistry class, it can actually cause great damage to the gastrointestinal systems of humans and other animals (dogs, etc.) Many think this is funny, but it is actually quite dagnerous.

Class was mysteriously and rapidly cancelled halfway through the lecture after John put a few drops of the phenolphthalein indicator solution in Professor Smith's coffee cup. If WE are not allowed to drink in the chem lab, why should HE?!

Phenolphthalein by James December 3, 2004

phenolphthalein 

An indicator commonly used in acid/base titrations which turns colourless in acidic solutions and is otherwise (in the concentrations commonly used in labs at least) pale pink. And I mean very pale, so it is f*cking useless without a colour chart and very good eyes. It also turns colourless in solutions of pH greater than 12.
The Kastle-Meyer test shows the presence of blood; a dry swab or piece of filter paper is used to collect a sample, then a few drops of phenolphthalein dissolved in alcohol (due to its insolubility in water) is added, followed by a few drops of hydrogen peroxide - this mixture will turn pink in the presence of blood. If you've ever watched 5 seconds of CSI, you have seen someone doing this.
In the past phenolphthalein has been used as a laxative, but is no longer used due to fears that it is carcinogenic.

Person A - "I'm using phenolphthalein but I can't tell if the solution's acidic yet..."
Person B - "Just make up some results - it'll be more accurate."

phenolphthalein by Zadok13 June 14, 2007

phenolphthalein 

1.)A chemical additive that instantly makes anything awesome
2.) Muscle group in the body

1.) Bro that pasta was nasty, until I added some Phenolphthalien
2.) Dude, hit the gym last night, I think my phenolphthalein is getting bigger

phenolphthalein by Nate_trey5 September 15, 2012

phenolphthalein 

The only word in the English language with 5 consecutive vowels

Phenolphthalein turns shit as purple as Stephe's tie, so don't wear flip flops in the lab area.

phenolphthalein by matthewagencollins April 6, 2007