N is peaceful, it was proably the sodium to cause heart attack, that does burn
Yes, I know the lethal injection cocktail for convicts contains 3 different drugs. They mainly use sodium thiopental, a powerful induction anesthetic, as the first drug, followed by pavulon/pancuronium, a muscular relaxant, and potassium chloride as the safety ingredient to ensure death by heart attack.
Now, sodium thiopental suppliers refused to hand over the drug for death penalty executions, so some states have considered alternative substituent drugs. Maybe this is why they tried pentobatbital. But definitely they mixed it with potassium chloride.
The issue with unpeaceful deaths when it comes to prisons, is the procedure. The three drugs are administered one by one, with not enough time between them. So when potassium chloride enters the body, the first drug, the anesthetic, has not reached full effect and the person is still conscious and sensitive.
N in liquid form is designed to be injected. It was used before in hospitals to induce anesthesia. It definitely doesn't hurt. And I think injecting is better than drinking. You don't need to fast, don't need antiemetics, not deal with the bitter taste, and you'll not vomit. And you pass out faster.
SN on the other hand, is not designed for injection. SN burns all the area, the vein, a d the pain spreads in the body.