In he Evidence Garage, Ziva makes the comment that sulfuric acid is the only acid that will dissolve bone. This is not correct. Almost any acid in sufficient concentration can dissolve bone given enough time.
While being interrogated by Gibbs, Velvet Road claims that she is immune to snake venom because she owns 2 pythons and a cobra and has been bitten many times. However neither of those things would have any affect on a person's reaction to a sand viper bite.
Pythons are constrictors, they don't have venom, and cobra bites are no protection against the venom of an entirely different snake.
(It's like claiming you're immune to the plague because you'd had a cold.)