Interestingly enough, the most difficult colour for pyrotechnic artists to accomplish is blue.
Strontium, barium, and sodium are all s-block metals, and from where it sits on the periodic table, titanium tends to have few (if any) d-electrons and so it doesn’t tend to show much colour even with its different oxidation states.
Copper, on the other hand, sits on the right hand side of the d-block, so it has a fistful of d-electrons. Those d-electrons jumping about are the reason why transition metals tend to have coloured compounds (and in some cases, coloured flames). Except that most of copper’s oxidation states actually give a greenish teal colour instead of true blue.
Only one oxidation state of copper, Cu(I) aka Cu+, gives blue. And it’s not very stable, preferring to oxidise to the rather greener Cu(II). For this reason, it took a long time before blue fireworks were even available – and even now, a fireworks display which uses a lot of blue is no easy task.
You lot in the US? Think about that later this evening when you’re enjoying your red, white and blue fireworks!
Scientific illustration resource for gastropods (and more, I suppose, but this blog is dedicated to gastropods so that’s what we’re focusing on)
The link goes to a folder for “snails, slugs, and slime” which is a strange categorization, but it has some wondrous images :) Enjoy!
Friends are like gold.
They dissolve in hydrochloric acid mixed with nitric acid (3:1)