Abstract
The use of PCl5 in dioxan for the conversion of Naphthol AS-TR to the acid phosphate, even without the addition of catalysts other than pyridine, gave a conversion considerably superior to that obtained using POCl3 in either tetra-hydrofuran or dioxan, with or without the additional catalysts suggested by Burstone. The product proved satisfactory for histochemical localization of alkaline phosphatase in bone, though it is suspected that a certain amount of polymerization had occurred in the process of phosphorylation.