Green Chemistry Education Network
I am working on phasing out our current hydrate lab with one that has safer unknowns. The hydrates that have been used in the past are: copper sulfate*5H2O, Barium Chloride*2H2O, Nickel Sulfate*6H2O, Zinc Sulfate*7H2O, Cobalt Chloride*6H2O, Cobalt Sulfate*7H2O, Nickel Chloride* 6H2O. Not all are used by each instructor and some don't work as well as others. I really like the idea of the Klingshirn 2008 Hydrate lab (Copper Sulfate only and reusing it year to year) but multiple unknowns are preferred for this lab.
Since multiple unknowns will be used, I didn't think it was realistic to reuse the materials as not all students follow directions. I had a student test out a number of candidates this summer and have a pilot class testing them out this fall. Results to come.....
Student Waste disposal Directions- One thing that I have found helpful with respect to minimizing the weight of hazardous waste produced from this lab has been to have two separate waste containers. The first one is for dry salts only where it tells the students to scrape their dishes, the second is for liquid wash where is says to a 1 mL of water to the dish, swirl and dump (up to 3 times). While this is really basic, it has helped reduce the amount of liquid waste. With one waste container last year, the waste was about 600-1000 mL per class of 26. This quarter, the liquid waste has been 100-250 mL.
Even if we manage to use salts that can be disposed of as solid waste, the student disposal directions are helpful as students might think a bit more about the waste that they are generating.