I am a teaching assistant at university running a gen chem lab for chemistry majors. Last week we did the usual experiment to test the effectiveness of Tums antacid vs. generic brand by first neutralizing each tablet with an excess of 3M HCl and then back titrating with 0.3M NaOH solution. Before titrating, the students added 5.00 mL of the acid and then 50.00 mL of DI water. They then heated the solution on a hot plate until they saw all the tablet was completely dissolved. Instead of the usual cloudy white watery liquid, one group's solution turned very frothy and bright white and would not settle. After almost 15 minutes on a hot plate at medium heat, the solution took on a light yellow color then proceeded to turn entirely bright yellow, looking almost like drawn butter with a layer of thick white foam on top. Having no clue what this product was, I treated it as unknown waste and discarded it appropriately. Any ideas what this strange product could be? I suspect they may have added 0.3M NaOH instead of the HCl, then heated it, but I am at a loss as to what they may have created!! Thanks for any and all suggestions.