On mechanism of reaction of neptunium (4) with arsenazo (3) and arsenazo M in strong acidic media

The reaction of Nsub(p)(4) with arsenazo 3, arsenazo M and the extraction of Nsub(p)(4) 0.1 TOA have been investigated as the function of a number of factors and described with the aid of the first and second order regression equations. Statistical planning of the experiments has been used: plan 25-1, four- and two-factor rotatable plan of the second order. Testing of two-factor rotatable plan of the third order shows that it is less suitable for describing complex formation in concentrated acid-salt solutions than the second order equation. Among the possible second order equations those in which all coefficients for the second order terms are statistically significant have been chosen. Characteristics for all the investigated reactions is the positive linear effect of the concentrations of sodium salts (from 0 to 2.5-3.0 M) within a broad range of reaction conditions: for reaction of Np(4) with arsenazo 3 at concentration ratios from 1:1 to 1:30, with the concentration of HNO3 being from 1 to 7 M. The similarity of the effects of sodium salts indicates a similarity of mechanisms of the corresponding chemical reactions