# Ultramarine blue colour absorbing agent

Ultramarine blue ($$\ce{Na2Al2SiO8 + Na2S}$$, a sulfide-silicate complex containing sodium and aluminium) is insoluble when mixed in water and gives a blue color appearance to the water solution.

Which chemical (from my understanding, it should be acid) can be used to make the blue color disappear in water (absorb the coloring agent)?

Possibly $$\ce{H2SO4}$$ will absorb the sodium, releasing $$\ce{H2S}$$. I want to understand basically

• What is the coloring agent (is it sodium only)
• Which chemicals can I think about to remove the color (absorption of coloring agents)
• No single component of ultramarine blue gives its blue color. The whole chemical by itself is blue. The sodium itself is not blue. Nor does $\ce{H2SO4}$ "absorb" the blue color. It just reacts with ultramarine blue to form new compounds which are not blue. You make it sound like a physical change where in fact it is a chemical change. – DHMO Jan 13 '17 at 13:13
• Thanks.Rephrasing - Will H2SO4 make the blue disappear. I just want experts opinion before actually trying it in the lab – Narveer Rathore Jan 15 '17 at 6:39
• – DHMO Jan 15 '17 at 6:50