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<br /> <br /> <br />ANALYTICAL -GENERAL <br />VII Calculation <br />Convert the absorbance reading of the aqueous solution or the extract into <br />micrograms of cyanide using the calibration graph. If you are using the colorimeter in <br />direct reading mode your reading is already in micrograms of cyanide and no graph is <br />needed. The graphical method is by far the most accurate of the two and less prone to <br />error. The colorimeter in direct reading mode uses a single point calibation and <br />generates a linear response to absorbance changes whereas the actual response for a range <br />of color standards falls on a typical Beer's Law ettrve. By using the graphical method <br />this linearization error can be avoided as well as the possible error due to the calibradon <br />of the colorimeter with older, contaminated standards. <br />Once the microgram of cyanide is known calculate the cyanide concentration in <br />the original sample solution as follows <br />ppm CNP mgCN" = µg CN' from the Calibration Graph <br />L AGgtat Volume in mIs <br />u.~emweu.rnenx 10 <br />