Dalton's partial pressure formula is - "The total pressure of a gas mixture that does not react with each other at a certain temperature is equal to the sum of the partial pressures of each component gases present in that mixture". Suppose , in a closed vessel of V volume at constant temperature , a number of elements in a gas mixture are chemically mixed in a non-chemical state. The total pressure of the gas mixture , P and the partial pressure of the component gases are P1, P1, P1 ... Pn respectively . So , according to Dalton's partial pressure formula , P = P1 + P2 + P3 + ... + Pn