Threaded ccdc Mode

Good evening, I realize that reagent for the spectrophotometric determination of copper they exist galore, some of which practically specific. Nevertheless I want to add one to the list, not because better than others, rather to the fact that it is almost unknown, although it allows to measure the concentration ccdc of copper in a wide range of concentration ranging from fractions of ppm to more than 1 g / L (more precisely, up to 10 ppm by spectrophotometry and more than 1 g / L to gravimetry). Not to mention ccdc that makes use of reagents readily available and not too expensive, maybe already in the availability of many of you. Principle of the method: weakly acidic solutions ccdc containing copper damage, in the presence of pyridine and solfocianuri, an insoluble complex colored in yellow-green that can be extracted in chloroform and measured photometrically Reagents: 1N sulfuric acid aqueous solution of sulfosalicylic acid to the pyridine 20% aqueous solution of ammonium thiocyanate to 10% chloroform Procedure: 10 ml of the sample are adjusted to pH = 2.5 with 1N sulfuric acid. Adding ccdc 0.1 ml of sulfosalicylic acid solution, 0.3 ml of pyridine ccdc and 0.5 mL of the solution ccdc NH4CNS mixing ccdc well after each addition. Then add 3.0 mL of chloroform and stirred. In the presence of copper, the organic phase assumes a yellow-green color. Pipetting the organic phase in a 10 mm cell with stopper (taking care not to vacuum the water) and it reads the spectrophotometer. How white is used chloroform. Below is the spectrum of the solution in chloroform (Cu ++ = 3.15 ppm) Calibration curve: SI prepared as usual starting with solutions to known content of copper and following the procedure described previously. It performs the reading at a wavelength of 406 nm using cuvettes having a 10 mm optical path and chloroform as white. ccdc Interferences: Only cobalt, if present in concentrations above the copper, disturbing because of the pink color that imparts the extract in CHCl3. The interference of the iron is eliminated thanks to the presence sulfosalicylic acid. Measuring range: With the quantities range extends up to 10 ppm Cu ++. The sensitivity can be increased by using larger volumes of sample, while maintaining the proportional quantities of the various reagents (excluding chloroform). The same reagents can be used for the gravimetric determination. The solution should not contain more than 80 mg of Cu in 200 ml of solution, and must have a pH of about 2.5. Is added 1 mL of pyridine (the solution takes on a blue color) and then again 0.5 g of NH4CNS dissolved in a little water, all cold and under stirring. The precipitate is filtered light green with a Gooch, washed first once with a little water containing 0.3% of NH4CNS + 0.3% of pyridine, then 6-7 times with ethyl alcohol to 75% containing 0.05% NH4CNS of + 0.8% of pyridine and finally with small portions of absolute ethanol (a total of 6 ml of alcohol + 1 drop of pyridine). End with a washing with diethyl ether (20 ml + 1 drop of pyridine). Dry in oven at 45 C for 20 minutes. ccdc Transfer to a great dryer containing dehydrating agent (ideally the P4O10). It weighs as Cu (C5H5N) 2 (CNS) 2. The factor is 0.18817 The analytical method has limited application because in the same conditions also precipitate Zn, Co, Ni, Cd and Pb, but has the advantage of a very favorable factor analytic. It can also be used in the presence of iron, as the precipitate which forms after the addition ccdc of pyridine may be removed by filtration. Do not interfere ccdc the alkali metals and alkaline-earth metals. Regards Mario
Threaded ccdc Mode