Question

Some cracker tins include a glass vial of drying material in the lid to keep the crackers crisp. In many cases, the material is a mixture of magnesium sulfate and cobalt chloride indicators. As the magnesium sulfate absorbs moisture (MgSO4 ∙ H2O + 6H2O MgSO4 ∙ 7H2O), the indicator changes color from blue to pink (CoCl2 ∙ 4H2O + 2H2O CoCl2 ∙ 6H2O). When this drying mixture becomes totally pink, it can be restored if it is heated in an oven. What two changes are caused by the heating?

Answer 1

The two indicators given are there to absorb water or moisture. So when the indicator is totally pink it means it has been used to its total potential.

By heating the indicator, this can evaporate the water from the indicator, thus restoring it. This means that the indicator will go back to its blue color and it can be re-used.

So the two changes caused by heating:

1. Indicator changes color back to blue.

2. Water is evaporated from the indicator.