Washing soda is a highly alkaline chemical compound which can be used to remove stubborn stains from laundry.
Never ever heard of that. I personally don't like the idea of giving my dog something like that. My vet told me about salt or hydrogen peroxide (3 %)
The safest and most effective way to make your dog vomit is by forcing them to swallow 3% hydrogen peroxide. Never use the stronger hydrogen peroxide that is used for coloring hair as it is far stronger and will cause serious damage.
The dose of 3% hydrogen peroxide is 1 teaspoon or 5 ml per 10 lbs of body weight. Give it, walk the dog around or massage their abdomen to mix it around in the belly and within 20 minutes, they should vomit. If they do not, it is safe to give them one more dose.
Other emetics often suggested are syrup of ipecac, salt water or mustard seeds mixed with water. These are not as effective and can be dangerous. They should only be given if recommended by your veterinarian.
Once the dog has vomited , make sure they do not eat it back down and, if a toxin is suspected, collect a sample for your vet.
Respect and you shall be respected. Animal is always right.