Abstract
On theoretical grounds it must be expected, that the electrical charge of protein molecules fluctuates around a mean value. In this paper the determination of the standard deviation of the charge from this; mean value in isoionic protein solutions is described. The standard deviation was measured in two independent ways, viz. from conductivity measurements and from the slope of the hydrogen ion titration curves. The proteins investigated were bovine carboxy‐hemoglobin, bovine methemoglobin, horse heart metmyoglobin and bovine serum albumin.