This is what over-heated SPT looks like. Over-concentrated is a more accurate descriptor.
In the luminescence lab, we use heavy liquids like Sodium Polytungstate (SPT) to separate minerals by density and isolate the mineral we want to measure (typically quartz or feldspar). Because SPT is expensive, we reclaim it after a separation by rinsing the sample with lots of deionized water, filtering, and then driving off the extra water by heating and stirring. The process of driving off the water is time consuming. Heating SPT over 200° C has some ill-effects, so the process is slow and we often have the stirring hotplate running all day while doing other things. I forgot to turn the hotplate off before leaving for the night. Fortunately, it isn’t dangerous–it just makes a big and expensive mess. It spattered all over the beaker, hot plate, and bench top and formed a thick crust on the surface of the SPT.
To fix it: clean everything with water, dilute, and stir, stir, stir the SPT to get any crystallized bits back into solution.
Some folks in the lab tell me to set a reminder on my phone, but since I have trouble remembering where my phone is, I need a simple, more physical solution. I’m introducing the SPT bracelet:
Classy, right? The bracelet hangs on the hot plate dial. When I turn the hotplate dial on, I put the bracelet on. When I turn it off, I replace the bracelet on the dial. Simple! I’ll report back on the strategy in a few months, hopefully accident free! –AKZ