[svandamme]

A typical 20 kg dog will normally experience intestinal distress after eating less than 240 g of milk chocolate, but won't necessarily experience bradycardia or tachyarrythmia unless it eats at least a half a kilogram of milk chocolate. If it does not expel the chocolate from its system because of the fat and sugar content, then it would have a 50% chance of surviving after eating 5 kilograms. According to the Merck Veterinary Manual, approximately 1.3 g of baker's chocolate per kilogram of a dog's body weight (0.02 oz/lb) is sufficient to cause symptoms of toxicity. For example, a typical 25 gram baker's chocolate bar would be enough to bring out symptoms in a 20 kg dog.

EDIT , that's copy paste stuff..i'm no vet , i can't even pronounce those fancy words without practicing in front of a mirror for about 2 hours