It’s a geometric process which downsamples a concentration.
This procedure conveys useful information in multiple areas:
For measuring population counts using the human eye, you cannot count anything above 10^2, so a 1mL broth which might contain 10^7-10^9 populants can be downsampled to a 1μL broth. There is an innate assumption that the serial dilution process retains a uniform distribution of the original broth.
For virology/immunology, you define strength by the last dilution that still works (neutralizes, infects, agglutinates)
Dose–response curves - these are log-spaced. The serial dilution process is in a sense a geometric process (reduces by a ratio 1:10 each step, which progressively downscales in logarithmic sense).
Serial dilution is how you map an unknown huge concentration into the measurable window of any detector
How do you dilute?
C1 * V1 = C2 * V2
rearrange: V1 = (C2*V2) / C1
V_water = V2 - V1
How do you do serial dilutions?
Scenario: The stock concentration of a mystery substance (MS) is 5 M. Calculate how to dilute to 100 µM (0.1 mM):
SerialDilute(1:499), SerialDilute(1:99) →
Step 1: Dilute 5 M (5,000,000 µM) to 10,000 µM (500x dilution).
Step 2: Dilute 10,000 µM to 100 µM (100x dilution).