You will also need:
2 containers containing 2 cups of white vinegar each (a cup is equal to 240 ml), 4 cups of vinegar total
5 tablespoons of baking soda (make sure it is fresh!)
(If your rat weighs more than 1 ½ lbs., you need to use an additional 1 ½ tablespoons of baking soda and an additional cup of vinegar at the end.)
When buying baking soda, it is a good idea to buy at least 2 or 3 boxes as sometimes one box won’t be as fresh as it is supposed to be and you will need to try another box.
Set-up: Place the aquarium where it will be comfortable for you to sit next to it, with your arm inside. The aquarium doesn’t need a lid because CO2 is heavier than air and will stay inside as long as there is no strong air movement. This means you can slowly put your hand in to pet and comfort your rat during the process.
Put the baking soda in the jug. As long as the funnel is dry, the baking soda will go through the funnel. If it gets stuck, poke it down with a chopstick. Put the cap on the jug and run the tube from the jug to the bottom of the aquarium. Place a cloth in the aquarium for your rat to sit on. You can give your rat a treat if you like.
Step 1: While you pet your rat with one hand, slowly pour 2 cups of vinegar into the jug through the funnel with the other hand. It helps to hold the jug between your knees. After doing this, plug the funnel with the cotton ball. The combination of the vinegar with the baking soda will cause fizzing, creating the CO2, but you won’t see any vapor.
Step 2: When the fizzing begins to slow down (about 1-2 minutes), pour about half of the vinegar in the remaining cup into the container. Shake or swirl the jug to thoroughly mix the vinegar and baking soda.
Within 1-2 minutes your rat will become groggy, lie down, and go unconscious. The eyes will probably stay open because it requires muscles to keep them closed and at that point all the muscles are relaxed. Gently touch the inside corner of your rat’s eyelids to test if he is unconscious. A conscious rat will blink, but there will be no blink reflex when a rat is unconscious. An unconscious rat is not aware and cannot feel anything. You may see muscles twitch, but these are just reflexes and your rat is not aware of them. At the very end you may see your rat taking reflexive gasping breaths. Don’t let this upset you, it is just the body’s last ditch effort to breathe on its own because it is no longer getting any messages from the brain. It won’t last for long.
Step 3: Once your rat is unconscious, pour the rest of the vinegar into the jug and mix it up really well with the baking soda. Cover the aquarium with the towel so it won’t be disturbed and leave your rat there for at least 20-30 minutes. You can confirm death by feeling the chest for a heartbeat. The most reliable method to determine death, however, is to wait until the body stiffens.
NOTE:
There have been a few cases where people have followed these instructions, and the rat goes unconscious, but does not die. In most of these cases, it seems that the baking soda was not as fresh as it needs to be. When the people bought a new box of baking soda and tried again, it worked. If this method fails for you, you can contact me so we can try to figure out what went wrong, if you want to try again. Otherwise, you will need to find another method of euthanasia. Even if this method fails, it will not cause your rat any pain, and it is very unlikely that a rat would experience brain damage if this method of euthanasia fails.