Five films were obtained containing same concentration of bromo-chloro-phenol blue, BCPB [0.1066 phr] (phr = part per hundred parts by weight of resin) and different concentrations of chloral hydrate [0, 26.66, 53.33, 79.98 and 106.64 phr].
The absorption spectra of BCPB /PVA films without chloral hydrate ([BCPB] = 0.1066phr) were recorded before and after irradiation to different doses and are shown in Fig.
The equilibrium between the two forms of BCPB indicator is represented as follow in equation 1:
The concentration of acid formed due to irradiation of BCPB /PVA films to a dose D is given by the sum of hydrogen reacting with BCPB-, [H BCPB]D, and the free hydrogen percent in the medium, [H+]D  , to maintain the equilibrium given by equation 1, [Total acid formed]D=[HBCPB]D+ [H+]D (2) Where, [HBCPB]D is the concentration of changed BCPB due to the irradiation to a dose D, and [H+]D is the concentration of free acid present in equilibrium after irradiation to a dose D.
Using the reported density of PVA (1.25g.cm-3), the concentration of BCPB before irradiation in the films containing 106.6 phr of sodium salt of -3 BCPB is calculated as 2.294 x 10 mol/L.
The radiation chemical yield of [H+] in BCPB /PVA films containing chloral hydrate is calculated as follows:
Table-1 represents the value of Eg for both direct and indirect transition for PVA dyed BCPB containing different chloral hydrate concentrations.