Abstract: A method and apparatus are described for determining the heating value of natural gas. The apparatus utilizes a chromatographic column, and a first sensor connected by a length of tubing in series with a second sensor, all of which are placed in a thermally isolated chamber, in order to keep the temperature constant. The method operates on a principle of comparison of the mass of natural gas, which contains hydrocarbons, higher hydrocarbons, and noncombustibles, with the mass of pure methane. In determining the heating value of the natural gas, the amount of noncombustibles present in the natural gas is determined, and this amount is subtracted from the mass of the natural gas to yield the mass of the hydrocarbon content. From the mass of the hydrocarbon content, the amount of higher hydrocarbons in the natural gas is determined.