Prabhupāda: Mercury. Mercury. Hydrox... What is called? Hydroid?
Devotee: Quicksilver?
Prabhupāda: No. Another name is hydrogeroid. That is the chemical name of mercury. You know it. Hydrogeroid? Yes. Unguentum hydrogeroid. Yes. That is another name of the mercury. Hydrogeroid. So in Sanskrit it is called rasa. Rasāyana. From mercury, rasa, the chemistry is called rasāyana-śāstra. Actually, rasāyana-śāstra, chemical composition, begins from mercury and sulphur. That is the beginning of chemical composition. So rasa-vidhānena, by chemical interaction of sulphur and mercury, if you can add tin and copper, then it becomes gold. You can manufacture gold, provided you know the process, how to mix up copper, tin and mercury. With via media of sulphuric acid. Sulphuric acid is the mother of chemicals. Without sulphur, you cannot make any chemical composition. Therefore all chemical composition are called sulphate, sulphite, like that. So Sanātana Gosvāmī gives this idea of chemical composition. It appears that he knew how to work with chemicals.