A study was made of a method for the flame photometric determination of iron. In Part I of this report, the flame emission spectrum of iron, measured by means of a Beckman Model DU spectrophotometer with a flame attachment, is compated to that measured with an ORNL high-sensitivity, recording, single-beam instrument, in order to determine which instrument is best suited for this application. Although it was found that the Beckman product has the higher resolving power over the wavelength region of 360 to 400mu, it does no posses the sensitivity or ease of operation of the ORNL instrument. On this basis, the ORNL flame spectrophotometer is used in subsequent tests. After selecting the best-suited instrument for the flame photometric determination of iron, it was necessary to establish the optimum operating conditions for this particular method. These conditions are described in Part II.