[kioplo]

I have an unknown compound that i have to figure out and what i have determined so far is that it is insoluble in water, it forms a precipitate when added to water, it has a melting point over 340 C, and is very soluble in dilute acids.  It would be great if someone could help me narrow down what it could be.  also it is a fine white powder and it smells a lot like naphthalene or moth balls....also when i added it to the nitric acid to test solubility it fizzed for a second while dissolving...

[Mitch]

That is nearly useless information.

We need a mass spec., proton or carbon NMR, an IR, uv-vis(since you think its an aromatic), in order to figure out what it is.

[TCUrob]

I have an unknown compound that i have to figure out and what i have determined so far is that it is insoluble in water, it forms a precipitate when added to water

That's not possible. If your unknown reacts with water, it IS soluble.

[Garneck]

Yeah, an IR with a 1H NMR should be fine here.  

But probably you don't have that.

[xiankai]

all i can deduce atm that it is a metal compound (reacts with acid)

and dont think its insoluble because u still see pieces of it. u may have to add excess water.

[Borek]

it is insoluble in water, it forms a precipitate when added to water

Please explain, how it can precipitate out of the solution if it was never dissolved? Do you mean it behaves like a sand added to water - falls to the bottom and looks like a precipitate?  

[kioplo]

well it made the water cloudy and what my chemistry teacher said was a precipitate, however most of what was added was on the bottom of the container....perhaps it is partly soluble in water, but i do not think that the water was over saturated because there was plenty of water...

[xiankai]

oh yes, u dont add things to acid to test for solubility.

the acid reacts with the compound instead to form different compounds.

and it cant possibly be insoluble, else it will act like an unreactive compound and no reaction takes place at all. what you have mentioned is a result of a reaction.

if u add a white salt and find a white ppt, it could possibly be an insoluble hydroxidem which is the product of the reaction.