The flame photometer in determination of sodium and potassium.

angle capillary tube whence it is atomized into an electrically heated glass cham­ ber. The fine spray is carried into a flame of oxygen and propane gas by a steady current of ] 5 to 25 pounds of compressed air. The light emitted by the combusted material is admitted into the spectrophotometer where it is resolved into its spectrum by means of a quartz prism. Adjustment of the prism permits selec­ tion of the wave length characteristic of the element under analysis. The band of light, whose width is determined by a slit opening, then impinges on a photo­ cell and the resultant current is measured. The current is proportional to the quantity of the element activated by the flame, and is quantitatively expressed as per cent emission. The rate of flow of the sample through the capillary must be constant. It was found that the tips of all capillaries received from the manufacturer were far too constricted and consistently caused bubbles, with decreased delivery. The tips were carefully broken off and filed until a rate of flow of approximately 0.4 ml. per minute was obtained. It is a recommended practice when placing the sample under the capillary tube to note if the stream contains any bubbles, which can usually be discharged from the capillary by the quick removal and replacement of the sample a number of times. If bubbles persist, the tube is disconnected, attached to a suction apparatus and cleaned by aspirating dichromate solution through it. To obviate any contamination of the sample by dirt or moisture in the com­ pressed air line, a porous stone filter is placed between the air valve and the air port on the machine.