Soft and very soft waters contain very low or even zero levels of calcium ions [Ca++] and bicarbonate [HCO3-]. This will result in a coffee with high acidity that some might describe as sour.

The PaO2 is one of the components measured in an arterial blood gas (ABG) test, which also reports oxygen (O2) saturation, bicarbonate (HCO3), the partial pressure of carbon dioxide (CO2), and the ...