Calculating that he ate 8 ounces of milk chocolate and 8 ounces of dark chocolate, he should be treated by induction of vomiting (you have already done this) and administration of activated charcoal. This amount and type of chocolate does meet the toxic level of ingestion and should be taken pretty seriously. If you are seeing chocolate in the vomit, it may be possible that he is vomiting enough of it to clear out his system of toxic levels. However, I cannot guarantee that he will vomit enough to eliminate the toxic level he ingested. Do not give him any more peroxide. Never give more than two doses of peroxide. If you are wanting every level of precaution available, take him to an emergency room where they can evaluate him and give activated charcoal and probably keep him for observation and monitoring of his heart rate/rhythm as well as his gastrointestinal signs. If you cannot take him to an emergency room, you've already done the right thing in making him vomit at home. Just be aware that he may not vomit enough to remove all risk of toxicity and that's why a trip to the ER would give you more assurance of safety. Please let me know if you have more questions about this. Best wishes.

It is a liquid suspension of charcoal. When your dog eats the liquid charcoal, it will pass through his stomach and intestines and act like a sponge, soaking up any chemicals from the chocolate and blocking these chemicals from being absorbed into his blood stream. The charcoal does not get absorbed. It will pick up toxic material from his gut and pull it out of his body when he defecates.

Hydrogren peroxide can be caustic (can burn his throat or stomach) if you give more than two doses or give too much in any one dose.

I hope that helps!