The farmer, Dharma Patil, had consumed the chemical to protest low returns offered by state government while acquiring his land for a solar power plant.
He hailed from North Maharashtra.
"Patil's postmortem was conducted at the J J Hospital. His body will be handed over to his family later," officials said.
Patil was rushed to a government hospital in south Mumbai after the suicide bid.
The farmer's family had claimed that he took the extreme step after several attempts to get appropriate compensation for his land did not yield any results.
The octogenarian had been visiting the state administrative headquarters for the last three months to complain about the inadequate compensation for his land, his son had said.
The Maharashtra government had offered an assistance of Rs 15 lakh to the farmer, but his son refused to accept it.