Tetrapod probably had a three-chambered heart, as do modern amphibians and reptiles, in which oxygenated blood from the lungs and de-oxygenated blood from the respiring tissues enters by separate atria, and is directed via a spiral valve to the appropriate vessel — aorta for oxygenated blood and pulmonary vein for deoxygenated blood. The spiral valve is essential to keeping the mixing of the two types of blood to a minimum, enabling the animal to have higher metabolic rates, and be more active than otherwise. The difference in density between air and water causes smells (certain chemical compounds detectable by chemoreceptors) to
Oxygenated treatment corrosion. When OT is used, conductivity after cation exchange (CACE) at the economiser inlet must be maintained below 0.15μS/cm this can be achieved by the use of a condensate polisher. Oxygenated treatment Oxygenated treatment (OT) is a technique used to reduce corrosion in a boiler and its associated feedwater system in flow-through boilers. With oxygenated treatment, oxygen is injected into the feedwater to keep the oxygen level between 30-50 ppb. "Common injection points are just after the condensate polisher and again at the deaerator outlet." This forms a thicker protective layer of hematite (FeO) on top of the magnetite. This