For a 26 lbs puppy, the 1 TBS qty is what emergency vets told me. For a bitch around 75-80 lbs, I was told 1/4 cup of hydrogen peroxide. The puppy laped it up in no time and we acheived the goal. On the other hand, we never did succeed in getting my wise girl to drink the stuff -- in fact, it was all over us, the laundry room walls, the floor, everywhere -- and narry a drop passed over her lips! Fortunately, she did not exhibit any signs of poisoning.
When I was on the road, I was responsible for someone else's dog whom the owner had suspected had consumed chocolate. It took me 3 tries to get him to vomit. Administer Hydrogen Peroxide, wait 10 minutes, administer HP, wait 10 minutes, etc. Fortunately, it came up on the third try -- sure enough, there were a few Hersey's kisses there...probably not enough to hurt, but the owner felt better, if not the dog! Nancy Melone, Ph.D.