In a recent blog post, the activity Elephant’s Toothpaste was demonstrated. The activity was in keeping with our STAO safety policy regarding chemical use. In that policy, we suggest the use of small quantities of chemicals, at as low a concentration as possible to allow the reaction to proceed. Teachers are also asked to explore safer alternatives to replace reactions that introduce an unacceptable element of risk. In this video, it was suggested that the reaction proceed with 3 or 6% hydrogen peroxide, yeast as a source of catalase, soap and food colouring. As expected, the reaction proceeded well with a coloured soapy foam spilling out of the container. This was a good example of putting our policy (low concentrations, safer alternatives). As peroxide, even in low concentrations (6%), can cause serious damage to eyes, goggles should have been worn by the student in the video.
Hazards of 30% Hydrogen Peroxide
STAO recommends that 30 % hydrogen peroxide be only used by the teacher. Its hazards include:
- It can act as either an oxidyzing agent or reducing agent
- It is caustic
- It can decompose rapidly in the presence of catalysts
- It can rapidly decompose when exposed to metal impurities (especially multivalent)
- It can spontaneously ignite organic materials such as cotton, leather, paper towels
While these properties may seem alarming, they are common among the other oxidizers that are in our chemical inventory and used for lab activities and demonstrations. The “Teacher Use” designation should signify to teachers that the substance has a hazard level above the chemicals used for student activities. Precautions for the use of 30 % hydrogen peroxide include goggles, acid resist gloves, synthetic apron and keeping students at a safe distance from the demonstration. A self-standing chemical shield (aka explosion shield) is also reduces the risk injury without obscuring the view.
Recommended Video Resource
Evonik Industries has produced a 30-minute training video (see link below) covering the industrial use of 50 -70% hydrogen peroxide. The video provides several neat demonstrations showing rapid decomposition, reaction to impurities and spontaneous combustion. It offers several good safety tips appropriate for high school. These include:
- Never pour a decanted sample back into a stock bottle
- Store peroxide at less than 30′ C
- Store the stock bottle within a plastic tray
- Use non-organic PPE’s (not leather)
- Do not wipe spills with paper towels or natural cloths.
- Even very dilute solutions can cause serious eye damage
Dave Gervais
Chair STAO Safety Committee
Resources
1) H2O2 Safety Training Video – Evonik is a leading global manufacturer of hydrogen peroxide
2) Link to Picture of Hydrogen Peroxide burns (35%)