I was sorting out some old boxes in one of the rooms in my house, when I found a small container with about 10 grams of this blue crystalline powder. I assume that it contains some form of copper due to the colour, but the label's all ripped and I can't see the name of it.

So what compound is it?

Crystal substance

It appears to glow in the image, but this is just the reflection from the camera flash and it doesn't look like this in real life.

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    $\begingroup$ Seems like a classic case of $\ce{CuSO4.5H2O}$, you may want to do a Google image search and compare your sample to it (since you have the actual thing you're in a better position to judge whether it looks the same) $\endgroup$ Apr 2, 2017 at 15:30
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    $\begingroup$ You could try warming it. If it's what @orthocresol says it is, it should turn white when heated (i.e. when it loses water and becomes anhydrous). I did this for my CHEM 101 lab last semester :) $\endgroup$ Apr 2, 2017 at 21:10
  • $\begingroup$ @Gallifreyan I tried this and it did in fact turn white $\endgroup$ Apr 2, 2017 at 21:41
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    $\begingroup$ I'm voting to close this question as off-topic because not enough information has been included in the question at the moment to deduce a definitive answer; simply a picture with no other information isn't helpful. I reckon there are a lot of blue-colored crystalline compounds around. $\endgroup$
    – M.A.R.
    Apr 2, 2017 at 23:02
  • $\begingroup$ @M.A.R. What other information do you expect me to provide? An answer has already been given, which I managed to test by heating the compound. And whilst there may be other blue crystalline compounds out there, this one is quite clearly the most common. $\endgroup$ Apr 2, 2017 at 23:05

2 Answers 2


As orthocresol also mentioned, it's probably copper sulfate. As you said, the blue color essentially gives it away.

enter image description here

(picture taken from Science Madness Wiki)


It's Copper Sulfate, more commonly known as root killer. It's also used in pools to kill algae. In the home, you flush it very slowly down your toilet drain to kill any tree or bush roots growing in the sewage pipes. It's fairly corrosive, so use it sparingly.


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