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RetortsHousehold ScienceWhere did Mr McDonald go to school? [Retorts, April 1991] Who is teaching our children that the solubility of salt decreases with temperature? It is a matter of common experience that the solubility of most solids increases with temperature, but please don't take my word for it. Take an ordinary glass tumbler and half fill it with cold water. Add teaspoonful of salt and stir. Does it dissolve? Add another teaspoonful or so until, even with stirring, a little is left on the bottom of the glass. Transfer the mixture to a pan and heat gently. It will soon dissolve completely. When you insist on checking things like this yourself, then you are thinking like a scientist. Geoff Wyvill, Dunedin |
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