A Study of in Vitro Neutralization of Heparin by Thiazine, Oxazine, Phenazine, and Other Dyes††The authors wish to thank the National Aniline Division of Allied Chemical and Dye Corporation and Dyestuffs Division of E. I. du Pont de Nemours & Company for supplying s with the various types of dyes used and for information concerning their structure and physical properties; Dr. M. Kuizenga of the Upjohn Co. for the sodium heparinate used; nd Dorothy Payne for the construction of the graphs.