Letter to the editor

I would like to offer some comments on two articles in the December 2018/January 2019 issue of Chem 13 News

First, Marcoux's Aladdin's Lamp demonstration is well described. An inexpensive source of 30% hydrogen peroxide can be found at beauty shops as 100 volume peroxide. It comes as a cream or liquid (liquid is what you want), and it is significantly cheaper than the catalogue version. In addition, using an old world wine bottle helps dramatize the demo. I used this demo to introduce thermodynamics and must add a word of caution. I had a grade 12 class after lunch and had the wine bottle charged, waiting ready to go in the prep room. During lunch while offering extra help, a fidgety grade 9 student was tired of waiting his turn and walked into the prep room (alas the door was not shut!) and found my prepared demo. He brought the wine bottle into the lab and began to shake it. Luckily, the contents did not spray onto anyone, but the stopper blew off. and I was able to grab the bottle from him before he was burned! You never forget these moments. 

Second, Cash's Using chemistry to clean a teapot is just what I needed to clean my glass coffee carafe and glass mug. The stains are incredibly annoying and often I have had to resort to a paper towel and fork to scrape off the stains. I could not wait to try it; David's method made short and easy work of my coffee pot and mug. I'm stocking up on baking soda! 

Also as a postscript, you can use tea (tannic acid) as a demo for introducing acid/base equilibria. Using the abbreviation HTan, you can show that the Tan-1 ion imparts the colour and that lemon (acid) decreases the colour while base intensifies it. I would ask students to make predictions based on their tea-drinking experience, what would happen when lemon was added? Warning, you need to know your student demographic! I had performed the demo for over 15 years in Hamilton.   There few if any students drank tea, while their parents or grandparents did — usually weak, with sugar and lemon, no milk. Students had no idea of the effect of the lemon on tea. Then I began teaching in Markham — much more multicultural. In my first class, I asked "does anyone drink tea?" Just about every hand went up! My brew was made with 400 mL of boiled water and TWO tea bags — incredibly dark. “Is this the kind of tea you like to drink?" Again every hand went up! Here, most took it with milk and never lemon! Consequently, some adjustments were needed to my line of questioning for this demo!