Nitride dust is predicted to form in small amounts around carbon stars, but the most likely candidate species such as aluminium nitride (AlN) have not yet been detected. Recently, {alpha}-Si_3_N_4_ was inferred to be the main carrier of the 8.5-12.5um absorption band(s) of an extreme carbon star (AFGL 5625), based on comparison with laboratory KBr dispersion spectra. However, this absorption band has also been attributed to silicon carbide (SiC) and C_3_. To investigate whether or not nitride dust has truly been detected and if it is present in other extreme carbon stars, we (i) gathered new laboratory infrared (IR) absorbance spectra from a suite of nitride compounds, including Si_3_N_4_, using the thin film technique which provides correct relative intensities of weak and strong peaks, and (ii) compared these data to Infrared Space Observatory Short Wavelength Spectrometer (ISO SWS) spectra of seven different extreme carbon stars which also show broad absorption features around ~11m.