Determination Of Nickel By Gravimetric Analysis

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Title : Determination of Nickel by Gravimetric Analysis

Objective :  

  • To determine the amount of nickel in a given salt.
  • To calculate the weight percent of nickel in the salt and to compare with the

              Theoretical value

  • To study the gravimetric analysis method to determine the compound in a

              certain unknown salt

Introduction and background

                 Gravimetric analysis is a technique through which the amount of an analyte (the ion being analyzed) can be determined through the measurement of mass. Gravimetric analysis depend on comparing the masses of two compounds containing the analyte. The basic method of gravimetric analysis is fairly straightforward. A weighed sample is dissolved after which an excess of a precipitating agent is added. The precipitate which forms is filtered, dried or ignited and weighed. From the mass and known composition of the precipitate, the amount of the original ion can be determined.

                  For successful determinations a few criteria must be met. First,  the desired substance must be completely precipitated. In most determinations the precipitate is of such low solubility that losses from dissolution are negligible. An additional factor is the "common ion" effect, this further reduces the solubility of the precipitate. When Ag+ is precipitated out by addition of Cl-

                                  Ag+ + Cl- =<-> AgCl(s)

the (low) solubility of AgCl is reduced still further by the excess of Cl- which is added, pushing the equilibrium to the right. Next, the weighed form of the product should be of known composition.The product should be "pure" and easily filtered. It is usually difficult to obtain a product which is "pure", i.e. one which is free from impurities but careful precipitation and sufficient washing helps reduce the level of impurity.

                  In the experiment, we are going to collect nickel by forming Ni(dmgH)2 from nickel ammonium sulphate salt using Gravimetric analysis. The reagent that is going to be used in this experiment to combine with nickel ion is dimethylglyxomine. The precipitates are then filtered and weighed  after drying up in oven and desiccator.

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        Dimethylglyxomine(DMG) is an chemical compound which normally is used to analysis palladium or nickel by forming complex with the particular ion which will precipitate in the solution. It can be prepared by butanone reacted with hydroxylamine monosulfonate.

        Ni(dmgH)2  is an complex which show bright red in colour. It is slightly soluble in water, so it can be filtered in the experiment.

         

Apparatus and Material

  • Nickel ammonium sulphate (NiSO4(NH4)2SO4·H2O)
  • Concentrated hydrochloric acid (HCl)
  • Dimethylglyoxime reagent(dmg)
  • Filter paper
  • Dilute ammonia solution
  • Beaker (250cm³)
  • Thermometer
  • Glass rod
  • Electrical heater
  • Graduated cylinder

Procedure

  1. Two 0.3 – 0.4 ...

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Mark: 4/5 This is a very good report. A solid introduction is presented and an excellent discussion has been written. The aims of the experiment are clear and calculations are well presented. To gain 5/5, questions 3 and 4 must be answered. Also, better referencing throughout the report is necessary, as well as better formatting.