Learning by Accident: Spotty Evidence!


sudan IV, oil and water

sudan IV, oil and water

Curriculum Connection: High-school Biology

I was preparing Sudan IV for a nutrient lab for grade 11 SBI3C biology. In order to use the chemical as an indicator for fats and oils, I needed to mix the Sudan IV powder with ethanol. I followed proper safety precautions (gloves, goggles, fume hood). Somehow, a small amount of the Sudan IV powder got on my hand. I promptly washed my hands with soap and water, and checked the MSDS which advised me to flush the exposed area with water. After flushing, my hand appeared to be clean.

Later in the day, I noticed the red powder was on my hand again. I washed my hands once more and also used an alcohol-based hand sanitizer. Before leaving school, I was talking to a colleague. The colleague suddenly exclaimed, “Are you okay? I think you’re  having an allergic reaction! You have red spots forming on your nose.” I looked in the mirror and, sure enough, I had red spots, not only on my nose, but also on my forehead and neck. I was not immediately alarmed,  however, because I had a pretty good idea about what had happened. The Sudan IV was indicating a positive test for oils…on my face! In the presence of oils, Sudan IV turns bright red. I believe the transfer of the Sudan IV powder went from my hands to my keys and back to my hands.

When I was talking to my colleague at the end of the day, I had been sitting at my desk with my hand on my cheek. This was an important lesson for me: it showed me how easily this Sudan IV powder can be transferred. Next time, I will be using the pre-made Sudan IV that is already in solution.

Submitted by a STAO/APSO member.
Learning by Accident is a STAOBlog feature, in which real-life lab accidents or incidents are recounted and explained. The goal is to highlight the consequence of ignoring safety rules so that science educators will be further encouraged to become knowledgeable, and to take appropriate action, in areas of safety that affect their daily activities in the science classroom. Submissions are encouraged. Anonymity will be guaranteed. Please send written descriptions to: staoblog@stao.org.

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