“Then the cyanide of potassium was probably got from there. It’s used by photographers. Better make inquiries.”
“We will,” Carpentaria agreed. “And do you mean to say cyanide of potassium will kill like that? How much prussic acid does it contain?”
“Scarcely any. Not two per cent.—not one per cent.”
“And poor Beppo was dead in a minute.”
“My dear Mr. Carpentaria,” said Rivers excitedly. “The strongest solution of prussic acid known to commerce only contains four per cent, of pure acid. And in the anhydrous state——”
“Anhydrous?”
“That means without water. In the anhydrous state,” Rivers proceeded enthusiastically, “two grains will kill a man in a second of time. Like that! It’s an amazing poison!”
Carpentaria shuddered.
“By the way,” he said, as if casually, “I’ve got a corpse I want you to look at.”
“A corpse?”