"Harla knows carbon."
"Now we add zinc. Zinc is a light metal easily extracted from the ore. It is fairly abundant, and it is used by early civilizations for making brass or bronze long before the culture has advanced enough to recognize zinc as an element. Does Harla know zinc?"
"He may," said Teresa very haltingly. "What happens if Harla gets the wrong metal?"
"Not very much," said Lou. "Any of the light, fairly plentiful metals that are easily extracted from the ore will suffice. Say tin, magnesium, sodium, cadmium, so on."
"Harla says go on."
"Now we make an electrolyte. Preferably an alkaline salt."
"Be careful," I said. "Or you'll be asking Harla to identify stuff from a litmus paper."
"No," said Lou. He faced Teresa and said, "An alkaline substance burns the flesh badly."
"So do acids," I objected.
"Alkaline substances are found in nature," he reminded me. "Acids aren't often natural. The point is that an acid will work. Even salt water will work. But an alkaline salt works better. At any rate, tell Harla that the stuff, like zinc, was known to civilized peoples many centuries before chemistry became a science. Acids, on the other hand, are fairly recent."