The dilution factor wil be 65, or 1:65.
The dilution factor is expressed as the ratio between the final and the intial volumes of the solution.
"DF" = V_("final")/V_("initial")DF=VfinalVinitial
The initial volume will be the "0.1 mL"0.1 mL supernatant sample you're using for the protein estimation. Now, the final volume will be equal to the sum of all the volumes you add to the test tube
V_("final") = V_("supernatant") + V_("NaOH") + V_("reagent C") + V_("Folin")Vfinal=Vsupernatant+VNaOH+Vreagent C+VFolin
V_("final") = "0.1 mL" + "0.9 mL" + "5 mL" + "0.5 mL" = "6.5 mL"Vfinal=0.1 mL+0.9 mL+5 mL+0.5 mL=6.5 mL
This means that your dilution factor will be
"DF" = V_("final")/V_("initial") = "6.5 mL"/"0.1 mL" = 65DF=VfinalVinitial=6.5 mL0.1 mL=65, or "1:65"1:65.
You've essentially added "6.4 mL"6.4 mL to your original "1-mL"1-mL sample to make the volume 65 times larger ->→ you've performed a "1:65"1:65 dilution.
More on calculating dilution factors here:
http://socratic.org/questions/how-do-you-calculate-dilution-factor?source=search
http://socratic.org/questions/how-do-you-do-serial-dilution-calculations?source=search
