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Pretty in Blue
I've been playing with copper compounds for the last few months. The goal is to work out good methods of plating copper onto stainless steel, so I can make a sturdy electrical connection to it, so I can accomplish a project I've had in mind for a few years.
One experiment went weird. I was trying to dissolve fine copper wire in muriatic acid (AKA hydrochloric acid) using OxiClean as an oxidizer. Instead of the expected blue or green product, I got a sludgy brown. It strongly resembled the goopy "baby-shit" iron precipitates I saw in my first few months working in a chemistry lab, which appeared as a byproduct of mineral analysis. Obviously I couldn't trust this product for my purposes. I have no idea what caused this; nothing in OxiClean should do it. The product is soluble in strong acid and precipitates with baking soda, a fairly weak base. But I decided to see if, after cleaning the sludge by repeated washing, I could get it to react with concentrated household ammonia. That ought to dissolve the copper salts but leave behind any iron compounds. (There are a few other metals whose salts are soluble in concentrated ammonia, such as zinc and silver. But as ammonia is another fairly weak base, there aren't a lot of things that precipitate with baking soda and dissolve in ammonia.) I got the expected dark-blue solution, which I filtered into a glass jar.
The next step was to let the solution slowly dry by evaporation (outdoors!). I covered the jar with a coffee filter and let it dry. At some point, as the ammonia preferentially evaporated away, solids were expected to settle out, perhaps even giving pretty crystals.
What I got was this:
This is a thin surface crust on the solution, and I think that it consists of dark-blue copper/ammonia salts, with veins of light-blue copper hydroxide. The veining appears to be increasing over a period of days. It shows best if the jar is strongly lit from the side, minimizing highlights and reflections from the dark areas. This is a temporary state, since the crust is thin and fragile, and the veins should eventually spread to cover the surface as more ammonia evaporates. All of this is a fortunate accident resulting from my desire to play further with a "failure".
One experiment went weird. I was trying to dissolve fine copper wire in muriatic acid (AKA hydrochloric acid) using OxiClean as an oxidizer. Instead of the expected blue or green product, I got a sludgy brown. It strongly resembled the goopy "baby-shit" iron precipitates I saw in my first few months working in a chemistry lab, which appeared as a byproduct of mineral analysis. Obviously I couldn't trust this product for my purposes. I have no idea what caused this; nothing in OxiClean should do it. The product is soluble in strong acid and precipitates with baking soda, a fairly weak base. But I decided to see if, after cleaning the sludge by repeated washing, I could get it to react with concentrated household ammonia. That ought to dissolve the copper salts but leave behind any iron compounds. (There are a few other metals whose salts are soluble in concentrated ammonia, such as zinc and silver. But as ammonia is another fairly weak base, there aren't a lot of things that precipitate with baking soda and dissolve in ammonia.) I got the expected dark-blue solution, which I filtered into a glass jar.
The next step was to let the solution slowly dry by evaporation (outdoors!). I covered the jar with a coffee filter and let it dry. At some point, as the ammonia preferentially evaporated away, solids were expected to settle out, perhaps even giving pretty crystals.
What I got was this:
This is a thin surface crust on the solution, and I think that it consists of dark-blue copper/ammonia salts, with veins of light-blue copper hydroxide. The veining appears to be increasing over a period of days. It shows best if the jar is strongly lit from the side, minimizing highlights and reflections from the dark areas. This is a temporary state, since the crust is thin and fragile, and the veins should eventually spread to cover the surface as more ammonia evaporates. All of this is a fortunate accident resulting from my desire to play further with a "failure".