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TitleMethyl Red
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Page 17

Table 2. Absorbances taken at the selected wavelengths for HMR and MR standards

Relative Concentration HMR MR-

λ520 λ428.5 λ520 λ428.5

0.25 0.139 0.012 0.01 0.073

0.5 0.334 0.028 0.014 0.16

0.75 0.526 0.04 0.023 0.208

1 0.7 0.056 0.026 0.283

Appendix B: Sample Calculations

 Determination of absorptivity/slope of liner plot via least square method
For the linear plot of absorbance recorded at 520nm against relative concentration of HMR:

Sxx=Σ x
2


( Σx )
2

n
=1.875−

6.25
4

=0.3125

S yy=Σ y
2


( Σy )
2

n
=0.897553−

2.8886601
4

=0.17590275

Sxy=Σxy−
( ΣxΣy )



n
=1.29625−

4.2475
4

=0.234375

m=
Sxy
Sxx

=
0.234375
0.3125

=0.6913

 Determination of the concentration of HMR and MR in sample via algebraic method, substitution
For sample 1 only:
(ελ520)HMR = 0.6913
(ελ520)MR = 0.0281
(ελ428.5)HMR = 0.0549
(ελ428.5)MR = 0.2865

−¿
MR

¿
(ελ

520
)

¿
¿

A λ520=[HMR ] (ε λ520 )HMR+¿

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