$1 \mathrm{~kg}$ of pure carbon is burned to carbon dioxide $\left(\mathrm{CO}_{2}\right)$, using exactly the amount of oxygen required for the reaction. The gas is collected in a container with a volume of $v=30$ liters and a constant temperature of $t=25^{\circ} \mathrm{C}$. The pressure $p$ exerted by the gas on the walls of the container needs to be calculated. According to the chemical formula of carbon dioxide, 6 grams of pure carbon burns to 22 grams of carbon dioxide. The weight of 1 liter of air at $0^{\circ}$ and $760 \mathrm{~mm}$ pressure is $q=1.293 \mathrm{gr}$, and the density of carbon dioxide relative to air at $0^{\circ}$ and $760 \mathrm{~mm}$ pressure is $\sigma=1.526$. The expansion coefficient of carbon dioxide is $\alpha=\frac{1}{273}$.
The amount of carbon dioxide formed will be $m=\frac{1000}{6} \cdot 22=3667 \mathrm{gr}$.

Its volume is reduced to $0^{\circ} \mathrm{C}$ and $760 \mathrm{~mm}$ pressure. The volume is:

At $t^{\circ}$ C and unknown pressure $p$: $v$.

At $0^{\circ}$ C and unknown pressure $p$: $\frac{v}{1+a t}$.

At $0^{\circ}$ and normal $760 \mathrm{~mm}$ pressure: $\frac{v}{1+a t} \cdot \frac{p}{760}$.

The mass of this carbon dioxide can be obtained by first calculating the mass of an equal volume of air and then multiplying it by the density of the carbon dioxide (relative to air), thus

$$
m=\frac{v}{1+a t} \cdot \frac{p}{760} \cdot q \cdot \sigma
$$

or substituting

$$
3667=\frac{30}{1+\frac{25}{273}} \cdot \frac{p}{760} \cdot 1.293 \cdot 1.526
$$

from which

$$
p=\frac{3667 \cdot 298 \cdot 760}{273 \cdot 30 \cdot 1.293 \cdot 1.526}=51,390 \mathrm{~mm}=67.6 \mathrm{~atm}.
$$

(Nándor Ehrenfeld, Nyitra.)