Need Phenolphthalein 1%?
We supply phenolphthalein in 500ml containers, with discounts available on bulk orders. This is our most popular phenolphthalein product, but we also offer a 0.05 w/v solution. We also offer more options with all our products, from customised labelling to specific pack sizes. Simply contact us for further information or free technical advice.
Phenolphthalein is a Popular pH Indicator
With the formula C20H14O4, phenolphthalein is a common pH indicator, turning colourless in acidic solutions or pink in alkaline solutions. As such, it’s very popular to titrate acid-base reactions. This compound is insoluble in water and is typically prepared in alcohol solutions.
It works because the molecule version is colourless, but the ionic version is pink. When a base is added to the solution, the balance between molecule and ions is altered towards the ionic side, resulting in more H ions being removed from the molecule (with the subsequent production of phenolphthalein ion, which is pink). As a result, for pH below 8.2, the solution is colourless, but changes to pink when pH reaches 10.
Other Uses of Phenolphthalein
Despite being a popular pH indicator, this compound can be used in other applications:
- As a laxative, but its popularity is decreasing over fears of being carcinogenic after prolonged use
- In the Kastle-Meyer test to identify the presence of blood. In this case, a sample suspected of containing blood is treated with alcohol and phenolphthalein, followed by a few drops of hydrogen peroxide. If the sample contains haemoglobin, it turns pink. This is commonly used as the first analysis for its easiness, with the added bonus of not destroying the sample, which can later be used for other tests.
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