The sale of something which is non-existent is invalid. Also the sale of that which is not regarded as goods, like flowing blood, corpses and carcasses (except locust and fish), a free person, foetus of camel, offspring of an unborn camel, that animal slaughtered Un-Islamically, untanned skin of a carcass, slaughtered animals mixed with animals which died naturally, human hair, pig hair, human excrement (still in natural state), the sale of that which is not in ones control (except by way of a “Salam-sale” - Insha-Allah to be explained later), fish in water, birds in the air, milk in the udder, pearls in the oyster, wool on the sheep, wine, pig, slaves with which freemen are mixed and grass still in the pastures (Kitaabul Buyoo).
