Experimental Procedure
1. Heat about 300 mL of water in a600-mL beaker and maintain at a moderate boil.
2. In an evaporating dish, combine 4.0 g of cobalt(2) chloride hexahydrate(CoCl2∙6H2O)with 10 mL of distilled water. To this,add 15 mL of 10% ethlenediamine(en). Place the evaporating dish on top of the beaker of boiling water. Stir the mixture over this steam bath for 40 minutes;maintain the volume of the solution at about 20 mL by occasionally adding small portions of water. Duringthis process, the cobalt (2) is oxidized to cobalt(3) by the oxygen in the air. Good agitation is necessary to promote dissolution of the oxygen.
3. Transfer the apparatus to the fume hood and add 12 mL of concentrated 12M HCl. (Note:HCl is corrosive – handle with extreme care.) Continue the heating (in the hood) and stirring (without the addition of water) until a thin slurry of crystals has formed. Cool the slurry to room temperature by setting the evaporating dish on the lab bench. Stir occasionally for at least 15 minutes.
4. Filter the mixture using the filering apparatus (250-mL side-arm flask,tubing, Buchner funnel) set up on the lap bench.
When the draining from the Buchner funnel has essentially stopped,add 5 mL of 6 mL HCl to the funnel and gently stir up the mixture with a spatula, taking care not to tear the filter paper. If the product is still brown or blue,repeat the washing process with 6MHCl. If the product is pure green,skip the washing to avoid loss of product.
5. Transfer the moist crystals of trans-[Co(en)₂Cl₂]Cl∙HCl∙2H₂O to a clean watch glass. If there is enough time, dry the material on the steam bath. During the last stages of drying,powder the material on the watch glass by scraping and pressing with a spatula. 21
6. Transfer the dried product, trans--[Co(en)₂Cl₂]Cl, to a previously weighed scintillation vial (provided by your instructor). Reweigh and calculate the yield. At least 1.0 g of peoduct should be obtained. Store your product.