Chemistry means that we can share together. Best duty means that we have a duty to be responsible to perform what we have obligation. In this case, I understand that you refer to us.
Chemical compatibility means we can live together. The obligation means we have a duty to act responsibly in practice what we have obligations. In here, I understand that you mean the two of us.
Chemical compatibility means we can live together. The obligation means responsible for actions on treat what we have commitments. In this I see what you mean to us.