Magnesium chloride enhances the coagulation and complement activities of blood serum in parallel degree. These enhancing effects are inhibited by inactivated serum or by disodium phosphate.
Distortion in the results of complement-fixation tests occurs with the addition of ionized magnesium salts to the system. This is due to the antagonistic effect of the inactivated test serum. In the quantitatively standardized test, however, where the titer is expressed as the ratio of the reaction of serum and antigen to that of serum alone, the findings are the same with or without added magnesium salts.