Preparation of Nickel, Cobalt, or Chromium Chloride

Preparation of Nickel, Cobalt, or Chromium Chloride. When working with chlorine for a long period, prepare it by reacting con- 

Spill 0.5 g of powdered metallic nickel (cobalt or chromium) into a boat and place it in the middle part of the quartz tube. Switch on the furnace. Dry the system with a stream of dry carbon dioxide during 30-40 min at 150-200 °C use a thermocouple). Stop the carbon dioxide stream and fill the apparatus with dry chlorine. How can one tell that the apparatus is filled with chlorine Raise the furnace temperature to 700-750 °C. (When synthesizing chromium chloride. 

After cooling the tube, displace the chlorine with a stream of dry carbon dioxide. Transfer the preparation into a preliminarily weighed drawn out test tube (i.e. a tube with one end drawn out to a narrower diameter) and seal it wear eye protection ). Calculate the yield in per cent. What is the colour and composition of the prepared substance  

Preparation of Ammonium Iodide. Put 10 g of the sublimed iodine and pour 50 ml of water into a 250-ml beaker. Simultaneously pour a 20% ammonia solution (40 ml) and a concentrated solution (30 %) of hydrogen peroxide into the mixture from two dropping funnels. Stir the solutions with a mechanical mixer. Add the ammonia and hydrogen peroxide solutions until the colour vanishes completely the latter should not reappear when the mixture is left standing for 10-15 min. 

Evaporate the solution in a porcelain bowl in a water bath up to one-fourth of its initial volume. See that the ammonium iodide crystals formed when the liquid evaporates are not overheated on the bowl walls. If the solution becomes yellow during evaporation, add NHs HjO or H2O2 to it dropwise. Cool the bowl containing the solution with ice and rapidly filter off the crystals on a glass filter No. 2. Dry the ammonium iodide in a desiccator over phosphoric anhydride up to a constant mass (3-5 days). Write the equation of the reaction. 

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