Why is mercuric oxide not used in the lab for the preparation of oxygen?

Question

Why is mercuric oxide not used in the lab for the preparation of oxygen?

Answer 1

its is not widely used due to fact that the mercury residue left back is toxic

Answer 2

It can be and one of the classical experiments does just that.  The big problem is the Mercury residue.

Answer 3

it is the toxicity

when you heat HgO to produce oxygen, the by product is Mercury metal

it is too toxic, @ room temperature, heating it only puts more mercury vapor into the air, increasing the toxicity level

one of my student's has a mercury mine. his dad breathed the mercury fumes from roasting HgS.. He can  tell you what happens to someone that breathes the fumes,... his dad can't