Q:

Help interpreting IR spectrum

Whilst attempting to create salicylic acid/2-hydroxybenzioc acid, one of our experiments produced a compound with a melting point of over $300^\circ\mathrm{C}$ ( as high as the machine would go) and the IR absorption spectra attached. Can anyone help us identify the compound we have produced? 
We used:

$4 \,\mathrm{g}$ of oil of wintergreen
$100 \,\mathrm{mL}$ of $2 \,\mathrm{M}$ aqueous sodium hydroxide solution
Sulfuric acid

The experiment was left for two weeks at which point the crystal pictured had formed. 

A:

I do believe something is wrong with this spectrum. I find it highly improbable that a compound would exhibit a single strong absorption peak at low wavenumbers, while showing no other absorbance whatsoever. The fact that there is no overtone of your band also shows me that there was some experimental error when recording this spectrum.

A:

I second @Ezze, there is something fishy here and the spectral data recorded do not match with how a spectrum of your targeted material should look like:

(Notice that this spectrum was recorded in transmission mode with a pellet of KBr and hence differs slightly from the ATR-FTIR setup you likely deploy [the $\ce{CO2}$ bump]).

In addition, the melting point is far to high compared with literature data.
Recommended action Figure out the error with your spectrometer, record a spectrum of a compound you know about its identity and have access to a reference spectrum.  Then record data of your compound (do not stop at 1000 1/cm, record if possible between 4000 to ca. 500 1/cm, as the displayed reference).
Added after your edit: Could it be sodium sulfate?

