When the proton concentration equals the base, or alkali, concentration, the pH is neutral. This occurs at a pH of 7 - the derivation of pH is reserved for CHEM 101 should you decide to ever take it. Solutions that are close to neutral include seawater, cerebrospinal fluid, milk, butter and blood. This lowers the pH of the milk. Note, also, though, that at the lowest point of the pH the casein concentration begins to decrease.
Blood is slightly alkaline.
In arterial blood it runs a pH between 7.35 and 7.45. In venous blood, it runs less than 7.35 due to the high amount of carbon dioxide in it. The O 2 saturation changes as we age. The kit comes with everything you will need. Pull back on the plunger with rotation to line the barrel with heparin.