⇒ Take 2 Kg of dry sulphur.
⇒ The specific gravity of Sulphur is 2. So, if you weigh 2 kg of Sulphur under water it would have apparent weight of 1 Kg.
⇒ All things weigh more when they burn (oxygen gets added). Sulphur has atomic mass of 32 u. If it combines with oxygen (atomic mass = 16 u) on a one-to-one basis, it will weigh 1.5 times as much. So, 2 kg will weigh 3 kg.