Oxygen dissolves into water and somewhat in blood. This is called "physical dissolution". Only about 6.5 ml of oxygen dissolves into 1L of water at the water temperature of 20 degrees Celsius. The amount of physical dissolutions of oxygen is low, and more oxygen is required for supporting activity of a Human Being. Therefore, erythrocyte (RBC) has much oxygen conveyance protein called hemoglobin. There is an iron atom in hemoglobin. Oxygen molecule combines with this iron atom, and changes into oxy-hemoglobin. It carries oxygen through the flow of red blood cells. Oxygen intake by erythrocyte like this is called "chemical dissolution". It is said that the chemical dissolution of oxygen is about 70 times greater than the physical dissolution and it turns out that oxygen supply is mainly performed by erythrocyte (hemoglobin). In this case, an iron atom is not oxidized in the bond of oxygen molecule and iron atom, so it is called "oxygen addition" and is distinguished from the usual oxidization. It is said that the volume of an erythrocyte is about 1/5 million of 1 (1 mm angle), and about 640 million hemoglobin is contained in an erythrocyte. Iron containing medicine is used for anemia treatment to supply raw material of hemoglobin. It is clear that hemoglobin plays an important role in oxygen conveyance.

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