The easiest method to check the purity is by melting it in a pan. Put a pan on medium heat and let it heat for a while, now add a teaspoon of ghee to it. If the ghee melts immediately and turns dark brownish in color, then it is pure ghee.
So by performing these simple tests at home, you can easily find that the ghee you purchased is adulterated or not. These adulterants have dangerous effects on health so please aware of the ghee you are consuming as it is an important part of our diet.