# Transcript

NARRATOR

First, aqueous sodium hydroxide is added to a solution of potassium sulfate. And then to a solution of thallium(I) sulfate. Now, an aqueous carbonate solution is added to potassium sulfate. And then to thallium sulfate. The hydroxide and carbonate of thallium(I) are soluble, like those of potassium. This is unusual.

Soluble metal hydroxides and carbonates are rare. Potassium also forms an insoluble tetraphenylborate. Will thallium resemble it in this respect? The tetraphenylborate is added first to potassium sulfate. And then to thallium sulfate. The tetraphenylborates are insoluble. These experiments point to a resemblance between potassium and thallium.