The differential method of determining the rate of a reaction makes use of the differential form of a rate law.
Just like the halflife method, the differential method is useful for reactions involving a single reactant, e.g.
where we can write the rate equation as
Taking the natural logarithm on both sides of eq23, we have
To find the rate constant, k, and the order, i:

 Run the experiment in a rigid vessel and record the concentrations of N_{2}O_{5 }via spectroscopic methods at various times.
 Plot a graph of [N_{2}O_{5}] versus time.
 Find the gradients to the curve at selected concentrations, i.e. find at various [N_{2}O_{5}].
 With reference to eq24, plot a graph of versus ln[N_{2}O_{5}] using the values determined in step 3.
The gradient and the vertical intercept of the line in the second graph give the values of i and lnk respectively. The differential method is commonly used together with the initial rate method and the isolation method in determining the unknowns of a rate equation with multiple reactants.