The serial dilution can be done by half- logarithmic dilution method.
Explanation:
The following step explains the way to obtain [tex]\frac{1}{10^6}[/tex] dilution. The volumes taken are arbitrary.
Take 1 micro-litre (ul) of the concentrated solution in a dilution tube. Add water to it till the total volume becomes 10 ml. Here the solution formed is [tex]\frac{1}{10^4}[/tex] diluted.
Take 100 micro-litre(ul) of [tex]\frac{1}{10^4}[/tex] diluted solution to another tube and add 9900 micro-litre(ul) of water to it. Here the solution formed is [tex]\frac{1}{10^6}[/tex] diluted.