Colourometric determination of copper from the effluent of electroplating industry скачать в хорошем качестве

Colourometric determination of copper from the effluent of electroplating industry

Principle: When a monochromatic light of intensity Io is incident on a transparent medium, a part Ia, of it is absorbed; a part, Ir, is reflected; the remaining part It, is transmitted. Io = Ia + Ir + It For a glass air interface Ir, is negligible. Therefore, Io = Ia + It + Ir It/I0 = T is called transmittance, log 1/T = log(Io/It), is called absorbance or optical density. The relation between absorbance and concentration c (expressed in mol/dm3) & path length t, (expressed in cm) is given by Beer-Lambert law. A = log(Io/It) = εct Where ε is the molar extinction coefficient, t is the path length. ε is a constant for a given substance at a given wavelength. If the path length is kept constant, then A α c. Hence a plot of absorbance against concentration gives a straight line. Liquor ammonia is added to a series of standard solutions of copper salt to get dark blue cuproammonium complex. This is diluted to a definite volume. The absorbance of each of these solutions is measured at 620 nm, since the complex shows maximum absorbance at this wavelength. Absorbance values are plotted against concentration to get a calibration curve.