8. Given that the molecular formula of a series of compounds is $C_{m} \mathrm{H}_{n}$ (where $m, n$ are positive integers), the calculation formula for the ratio of carbon atoms is $\frac{m}{m+n}$. A series of molecular formulas for these compounds are given: $\mathrm{CH}_{4}, \mathrm{C}_{2} \mathrm{H}_{6}, \cdots, \mathrm{C}_{n} \mathrm{H}_{2 n+2}, \cdots$. Then, in this series of molecular formulas, the range of the ratio $x$ of carbon atoms is
8. $\frac{1}{5} \leqslant x<\frac{1}{3}$