I found an interactive chart on the National Geographic website that allows you to pick the dog's weight to get an idea of the effects of certain types of chocolate on your size dog. Of course, it doesn't take into mind the variation that it might have on specific breeds of dogs. But it is still interesting:
http://ngm.nationalgeographic.com/2007/10/pets/chocolate-chart-interactive
We had a basset hound that managed to find and eat a very large baker's sized bag of semi-sweet chocolate chips. It was a Saturday night and we had a house full of guests and I made the discovery about 5 minutes before she started vomiting up the chocolate. I don't know why it didn't kill her…probably her iron constitution and the fact that she weighed almost 70 lbs. Her heart rate was extremely elevated and I was really afraid we'd lose her. Actually, truth be known, as I repeatedly cleaned up vomited chocolate over the course of what seemed like hours ..while still trying to entertain houseguests, I was torn between being afraid she'd die and wanting to kill her myself!! We usually didn't let her sleep in our bedroom because she snored so loudly but that night I made a bed for her on the floor next to our bed so I could monitor her. (She had stopped vomiting by then.)
Pat