What is the difference between Blood:Gas Partition Coefficient? 1) It is the ratio of the concentration of a gas in blood to its concentration in the gas phase at equiLiBrium. 2) It is the ratio of the concentration of a gas in the gas phase to its concentration in blood at equiLiBrium. 3) It is the ratio of the partial pressure of a gas in blood to its partial pressure in the gas phase at equiLiBrium. 4) It is the ratio of the partial pressure of a gas in the gas phase to its partial pressure in blood at equiLiBrium.