The author was feeling rather lonely without Tsetan who had left for Lhasa. There weren't any pilgrims at Darchen as he had reached the place much early in the season. It was then he met Norbu, who was a Tibetan and also an academician. He too was there to visit Kailash and they decided to go there together.
What inference do you draw about the behaviour of Ag+ and Cu2+ from these reactions?