Then Sills grasped his sleeve. “See!” he hissed. “Watch the anode!”

Sure enough, bubbles of gas were slowly forming upon the spongy ammonium amalgam. They shifted their attention to the spoon.

Gradually, they noticed a change. The metallic appearance became dulled, the silver color slowly losing its whiteness. A layer of distinct, if dull, yellow was being built up. For fifteen minutes, the current ran and then Sills broke the circuit with a contented sigh.

“It plates perfectly,” he said.

“Good! Take it out! Let’s see it!”

“What?” Sills was aghast. “Take it out! Why, that’s pure ammonium. If I were to expose it to ordinary air, the water vapor would dissolve it to NH 4 OH in no time. We can’t do that.”