# What are those… crystals?

I have been trying to make muratic acid from salt and phosphoric acid (didn't know that it's made at 150 °C). After waiting a few days, a third of the time it was sealed by placing a container over it, I wanted to check if some HCl was created, by adding peroxide and etching a small PCB, after 2 days I noticed small white crystals and the solution turned green.

What are those crystals and why is the fluid green?

Likely the green solution contains copper(II) phosphate, $\ce{Cu3(PO4)2}$. "It is commonly encountered as the hydrated species Cu2(PO4)OH, which is green."
Libethenite, $\ce{Cu3(PO4)2}$, crystals.
You have $\ce{H+}$, $\ce{Na+}$, $\ce{Cu+}$ and/or $\ce{Cu++}$, $\ce{OH-}$, $\ce{Cl-}$ and $\ce{PO4{^-}{^3}}$ in solution. You could identify the white crystals by color (white, so probably no Cu in them) shape, birefringence, and solubility; they might be $\ce{NaCl}$ or $\ce{Na3PO4}$. The less soluble should crystallize first, of course.