This is another lab from the homescientist kit manual CK01A, Session XIII-1: Determine Boron Concentration with Curcumin. This is an applied chemistry lab because we took soil and water samples from around the yard to test for the presence of boron. Boron is used in some pesticides and if the concentration in the soil gets too high it can hinder plant growth. This lab didn’t work quite the way it was supposed to. The first part of the lab has you fill four wells in a 24 well reaction plate. One well contains just distilled water, one well has just water plus HCl, one has sodium borate plus water and finally one has sodium borate, HCl and water. Then a drop of tumeric reagent (included in the homescientist kit) was placed in each well. All the wells turned yellow except for the one with the sodium borate with water which turned orange.
I’m not sure what the purpose of the HCl was, except maybe to show that this test doesn’t work with acids? Later in the lab the manual says to add HCl to the test samples, but we just showed that would negate the results so we were a bit confused. So when testing samples we did added the tumeric reagent, noted the color change and then added the HCl to see how it affected the results, and it turned most samples to the negative result (yellow).
Part two of the lab is making a reference matrix around a sample well in the middle, initially containing just distilled water. The procedure for filling the wells is in the lab manual. Now this does not look like it should. You would expect the 1000ppm to be the darkest color with it getting lighter in color as you go clockwise around the sample. All four groups had similar results even when adding more turmeric to make the colors darker. We continued with the lab figuring we could at at least conclude whether or not the samples contained boron even if we couldn’t comment on the concentration.
Part 3 of the lab involves taking small samples of soil from outside (or a house plant), or water samples. I also had some borax, which should definitely test positive for boron so we used it and a pesticide I found in the garage. The students determined there was boron in Borax (it was the darkest color by far), the pesticide and water from our small pond (it was pretty weak but definitely more orange than yellow). So while we couldn’t really comment on the concentration of boron in the samples we were able to conclude whether boron was present or not.
One thing I like to do with the chemicals is put each bottle in a beaker so the students can put the pipette in the beaker so everyone uses the same pipette with each chemical. This keeps us from going through a whole bag of pipettes and keeps the chemical from being knocked over, or dripping on my counter.
So this lab worked to some extent. Still not sure why the instructions said to add HCl to all the samples since that negated all the results. I did find a video of the author of the lab demonstrating this lab but only for part two of the lab.
Students were to watch Crash Course Chemistry #28 Equilibrium before classs since we’re on the chapter about equilibrium in the textbook.
Being Pi Day, one of my students jumped in her car and rushed to the grocery store to provide Pi at the end of class.