Number
324-EN
Section
General Section
Use
Sector
Scientific research and development
Function
Dye
Process
Manual activities involving hand contact
Product category
laboratory chemicals
Application
Natural alternative to phenolphtalein
Abstract
Phenolphthalein is used in laboratories as indicators of acidity or alkalinity. Because it is considered a possible carcinogen, alternative substances or methods are recommended. A primary school laboratory decided to produce its own safer pH indicator, using red cabbage juice instead of phenolphthalein.
Substituted substances
Phenolphthalein
CAS No. 77-09-8 EC No. 201-004-7 Index No. 604-076-00-1
Chemical group
Phenols; lactones
Classification: hazard statements
H350 May cause cancer
H341 Suspected of causing genetic defects
H361f Suspected of damaging fertility
Other adverse effects
The substance is: 2B carcinogen (IARC), endocrine disruptor cat. 1 (EU EDC database), as listed in the Substance Database according to SUBSPORT Screening Criteria (SDSC).
Reliability of information
Evidence of implementation: there is evidence that the solution was implemented and in use at time of publication
Reason substitution
CMR
ED
Other type of alternative
Red cabbage juice
Hazard Assessment
Substance to be substituted: Phenolphthalein is suspected of causing genetic defects, may cause cancer and is suspected of damaging fertility. It is also an endocrine disruptor category 1 (EU EDC database), as listed in the Substance Database according to SUBSPORTplus Screening Criteria (SDSC). Alternative substance: Red cabbage juice is a natural material known to be safe.
Description of Substitution
Phenolphthalein turning to strong fuchsia colour when mixed with alkali solutions is one of the best known reactions in chemistry classes. When reading about its potential hazards a primary school professor decided to replace phenolphthalein in laboratory classes. There were several possible options, but the choice was to use red cabbage juice, because it was an indicator pupils could make themselves. The red cabbage, readily available in the area, was chopped and boiled in water to extract colouring staff. Sheets of porous paper were immersed in the juice and then dried. This would make the indicator easier to preserve than in liquid form. The natural red cabbage juice indicator turns red for acid pH and green for alkaline pH values. Preparing their own, safer reagent was an interesting activity for children and it also gave the possibility to discuss chemical hazards and laboratory safety in a friendly, understandable manner.
Case/substitution evaluation
The substitution is a good example since it is easy to implement and eliminates the use of a possible carcinogen and the management of hazardous wastes and packages. It is not meant as a precise testing method, but is very good for school classes.
State of implementation
In use
Date and place of implementation
2012, Romania
Availability ofAlternative
Alternative is available
Type of information supplier
User
Date, reviewed
November 26, 2021