“Sodium-mercury mixture, or sodium amalgam, as it is called,” explained Sills, pointing to it.

He took a bottle labeled “Ammonium Chloride Sol. ” from the shelf and poured a little into the tube. Immediately the sodium amalgam began changing into a loosely-packed, spongy substance.

“That,” observed Sills, “is ammonium amalgam. The ammonium radical ( NH 4 ) acts as a metal here and combines with mercury.” He waited for the action to go to completion and then poured off the supernatant liquid.

“Ammonium amalgam isn’t very stable,” he informed Taylor, “so I’ll have to work fast.” He grasped a flask of straw-colored, pleasant-smelling liquid and filled the test-tube with it. Upon shaking, the loosely-packed ammonium amalgam vanished and in its stead a small drop of metallic liquid rolled about the bottom.