the combustion products of the vapor may already be so high as to bring about alterations in the properties of the flame and, consequently, in the magnitude of the net response. This may also constitute a factor contributing to the decrease of the net response. If the decrease were due to some variations in the working parameters (detector temperature, flow rate of the gases), it should be the same with both types of stationary phase.The above account indicates that the enhancement of the decrease in the net response due to the background one is likely a case applying especially to the flame ionization detector. Since this effect cannot be suppressed by any method of compensating for the background response, it is advisable that the use of stationary phases producing a high background signal be avoided in accurate quantitative analysis by gas chromatography.