wave length that gives maximum absorbance. The
intensity of the blue color is proportional to the amount
of phosphate present in the sample solution. Various
reducing agents have been reported in the literature such
as sodium sulphide, stannous chloride, and ascorbic
acid and so on. But most of them suffer from some
drawbacks such as stability of color, interferences from
arsenic, the length of the time required for the full color
development, sensitivity and absorption by the blank.
In this investigation, hydrazine hydrate has been used
as the reducing agent for the reduction of molybdo
phosphoric acid to molybdenum blue. The blank gives
no color, which is the major advantage of this method.