Gravimetric Determination of Nickel in Steel

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| Gravimetric Determination Nickel in Steel | | 10/15/2013 Fall 2013 | | Objective The purpose of the laboratory is to determine the percentage of nickel (Ni) in the steel alloy. Introduction There are numerous types of steel alloys with different chemical compositions and weights. Some steels are simple in composition, like a steel with 99% iron (Fe) and only 1% carbon (C). However, there are other steels that vary greatly in composition. For the laboratory an unknown steel was used and the nickel content was determined using a gravimetric method and by exploiting the chemical properties of the compounds and solutions. Nickel was precipitated from an alkaline medium with the chelating agent dimethylglyxomine. Chelating agents are essetentially chemicals that combines with a metal to form a chelate Tartaric acid (see Figure 1), for example, is used to form a complex with Iron (III) to prevent its precipitation. The tartrate ion (see Figure 2) forms a complex with iron (III) in slightly alkaline solutions as: Fe2O3·xH2O The product formed by the tartaric acid interference is freed from moisture by drying at 110 degrees Celcius. When working dimethylglyoxamine, carefull attention has to be taken when adding the chemical because both an excess amount and insufficient amount of the organic compound will have an adverse effect. An excess amount of dimethylglyoxamine will ultimately dissolve nickel dimethylglyoxamine which would result in low percent recovery for nickel. An insufficient amount of dimethylglyoxamine, however, will cause some of the reagent to precipitate giving as a result a positive error in the percentage of nickel recovered. Materials and Methods To begin the experiment, three medium-porosity sintered-glass crucibles were brought to a constant mass by heating them for an hour at a constant 110 degrees Celcius. The initial

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