A method for the determination of brilliant vital red in plasma has been described previously by one of us.1 In the present study we have attempted to show that the method is simple and accurate, that it may be used for determination of blood volume and that it dispenses with the use of expensive equipment necessary for methods more recently advocated.2 We have used the method in order to gain some information on "mixing time" and the disappearance of brilliant vital red from the blood stream. Later, we have applied some of this experience in clinical research on children.
METHOD
Standard solutions were made up in heparinized whole blood drawn immediately before injection of the dye. (Heparin does not affect the hematocrit reading.) Sufficient brilliant vital red was added to produce a concentration close to that of the calculated unknown. The dye, usually 10 mg. per kilogram of