What did Captain Crane do?

In episode "The Mechanical Man", near the end, Crane managed to shrug off his paralysis, got something out of his pocket, then threw it across the room. A flash ensued which knocked over the android. Does anybody have an idea of what he threw to cause the explosion? A side question might be, "Why did that relatively small explosion not seem to bother the two humans but knocked down the rather indestructible android?"