A liquidated damages clause sets an amount in a contract in the event of a breach. A liquidated damages clause isn't a penalty, though it may sound like one. A penalty is usually disproportionate to the actual harm, and is meant to punish or deter breaching a contract.
Acidic stools can be caused from absorption problems from the diet and foods you eat. Some people have acidic stools as a result of a lactose intolerance.
Black stools can be due to iron supplements or excess iron in the diet. The most serious cause of black stools is bleeding in the GI tract, due to ulcers or some other cause. If the stool is black due to blood, it usually has a tarry feel. If there is just a black color, most likely it is not blood.