Another factor that makes inventory different from other assets is that its usefulness can actually diminish over time. Cash, for instance, maintains its usefulness to you over time.
Lethal injection is done by using three chemicals. The chemicals are usually sodium thiopental (an anesthetic), pancuronium bromide (used to paralyze the person being injected), and potassium chloride (to stop the heart so that the person being injected dies).
Potassium chloride (injected) is also said to be potentially lethal, and more accessible as a method (further information on this method (and cyanide) is available in the book by Stone3). Working out the minimum lethal dose can be tricky though.