Working on the next video which will be the prep of rubidium terbium sulfate. I was going to make plain terbium sulfate because it fluoresces a beautiful green color (europium sulfate fluoresces reddish and thulium sulfate fluoresces blue; might do them in a future video). However, someone already did a video on terbium sulfate nine years ago and I hate to repeat stuff others have already done. As it turns out you can precipitate terbium sulfate from aqueous solution by adding potassium sulfate solution to it. However I did not have any potassium sulfate but I did have rubidium and cesium sulfates (I use them to make Rb and Cs salts by metathesis with Ba salts). Given that rubidium is closer to potassium I decided to go with that. It's evaporating down now and I am getting some nice crystals. Hopefully it is still fluorescent!! The terbium, europium, and thulium halides are not so the anion does make a big difference. Hopefully an extra cation won't make it unhappy.