The principle of the method specified is reacting a small amount of free acid present in a test portion of acid anhydride hardener or accelerator with rhodamine 6G to colour the test solution pink, measuring the absorbance of the coloured solution at a wavelength of about 510 nm using a spectrometer, determining the free-acid content from a calibration curve. The method is suitable for most anhydrides except for polyester and oligomeric anhydrides which may give too wide a scatter of results.
BS EN ISO 7327:1996 history
0000 BS EN ISO 7327:1997(2000)
1996BS EN ISO 7327:1997 Plastics. Hardeners and accelerators for epoxide resins. Determination of free acid in acid anhydride
1996BS EN ISO 7327:1996 Plastics - Hardeners and accelerators for epoxide resins - Determination of free acid in acid anhydride