Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: Justin_Is_Here on 09/12/2014 09:18:49
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Calcium nitrate melts at some 40°C and decomposes on further heating. How to separate this salt from water? How to crystallize it out? Don't refer me to use nitric acid.
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The answer depends on a few things: how concentrated is it to start with (do you know how many grams of Ca(NO3)2 per liter of water?); and how dry does it need to be? The tetrahydrate, Ca(NO3)2(H2O)4 is a crystalline solid, but is free of water--extra effort is required to dry the salt to its anhydrous form.
Since there is a limit on how hot the sample can get, you will need to be patient and/or creative. If you put a few mL in small glass dish and leave it out for the water to evaporate (perhaps hastened with a fan) you might be able to get some to crystallize. If it is humid where you are, it might be necessary to go to extra lengths. You can build a small desiccator out of an airtight jar or box by adding a small open vial containing a suitable desiccant (silica gel, anhydrous calcium chloride, calcium sulfate, calcium oxide (quicklime), or magnesium sulfate could all work). Add another small open vial of your solution, and seal the lid tightly. The water will slowly evaporate and be absorbed by the desiccant. Depending how much water needs to be removed, you may need to replace the desiccant few times. See attached diagram.
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Afterthought: calcium oxide is a very aggressive dehydrating agent and is also quite alkaline--be very careful not to get any on your skin or breath in any calcium oxide dust!
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nice idea! ChiralSPO! I'll try it in lab.