Step 1: Write the given concentration. The concentration is $0.0006214 \text{ g/ml}$. Step 2: Express the concentration in standard form (scientific notation). Move the decimal point 4 places to the right to get a number between 1 and 10. $$0.0006214 = 6.214 \times 10^{-4}$$ Step 3: Express the number in the form $10^n$. Let $N = 6.214 \times 10^{-4}$. We want to find $n$ such that $N = 10^n$. Taking the base-10 logarithm of both sides: $$n = \log_{10}(6.214 \times 10^{-4})$$ Using the logarithm property $\log(AB) = \log A + \log B$: $$n = \log_{10}(6.214) + \log_{10}(10^{-4})$$ $$n = \log_{10}(6.214) - 4$$ Step 4: Use logarithm tables to find $\log_{10}(6.214)$. From logarithm tables: The logarithm of $6.21$ is $0.7931$. The mean difference for $4$ in the row for $6.21$ is $3$. So, $\log_{10}(6.214) = 0.7931 + 0.0003 = 0.7934$. Step 5: Calculate the value of $n$. Substitute the value of $\log_{10}(6.214)$ into the equation for $n$: $$n = 0.7934 - 4$$ $$n = -3.2066$$ Step 6: Write the concentration in the form $10^n$. The concentration is $10^{-3.2066} \text{ g/ml}$. The concentration expressed in the form $10^n$ is $\boxed{10^{-3.2066} \text{ g/ml}}$. That's 2 down. 3 left today — send the next one.