This book contains brief note of Pyrazolone Azo dye which can also be considered as a Environmentally sustainable analytical reagent.The reagent used is water soluble and very economical with compare to other various organic reagent which are very costly.Due to water solubility of the reagent,it is consider as a environmentally sustainable.The reagent was checked for to form complexes with many transition metal ion and also checked for its stability and others parameters using various methods and also used for its important applications,the reagent is also applied for the antibacterial activity,COD/BOD and TGA.so the student and Ph.D student also can used this book for the research purpose and can do their best in this field by knowing different uses of the reagent.