there's an old wives tale that baking soda will kill a rat because it can't burp. that sounds absurd, and you'd be right to be skeptical. i went looking around through youtube and there's a large amount of anecdotes, and a little bit of skepticism, but no scientific experiments. you'd certainly have to be an asshole to feed baking soda to a pet or captured rat in a controlled environment to see what happens. it's probably against the law and it should be if it isn't.
but i did find one hillbilly with a southern accent that actually caught himself a rat and fed it baking soda, and the thing did die. if it's legal to do that anywhere, it's legal in alabama. it turns out cletus was the only person on youtube that understood science, except he lacked controls in his experiment. the rat might have had a heart attack from getting captured.
then i thought about it.
the myth is that gas will build up and rupture the stomach because the rat can't burp. that might make sense if you're imagining the vinegar & baking soda volcano you made as a kid.
however, when you drop baking soda into hcl you are mixing a much stronger base with a much stronger acid and it should look less like a volcano and more like an explosion. you're not killing the rat by giving it gas, you're getting the rat to eat a bomb that explodes in it's stomach and, if it doesn't kill it, then poisons it by converting it's stomach acid into salt. the difficulty is in getting the rat to eat a sufficient amount of baking soda at one time, and you're not going to do that by rolling it up in flour. you want the rat to drink enough baking soda to cause an immediate reaction. if you can't get it to eat enough baking soda in one sitting, it won't work. it won't work if they keep coming back to nibble at it.
if that's the case, the same thing should happen if humans eat a bunch of baking soda. humans can burp, sure, but that's irrelevant. it's the explosion that kills you first, and the salt poisoning that kills you second.
one source claims there are about 15 reported cases of this in the medical literature. here is one:
i find this alternate mechanism convincing. i agree that you're not going to kill a rat from indigestion, and the issue of whether the rat can pass the gas via belching or burping is a red herring. baking soda's alkalinity far surpasses anything a rat would eat. it's the violence of a sufficient amount of baking soda hitting the hcl that explodes the stomach, causing rupture, and not a build up of gas from indigestion. and, if that doesn't work, the reaction will convert the hcl into salt, and the rat will be poisoned from the salt.
but how do you get the rat in your wall to actually eat that much baking soda at once?