A review of the literature revealed many designs of electrode chambers which confined various gas atmospheres. The gases He, A, Oa, CQa, steam, or certain mixtures thereof were preferred in certain chamber designs, samples analyzed, elements determined, and excitation requirements. However, COa was found satisfactory when applied to one method of semiquantitative spectrographic analysis and used in conjunction with the final gas jet design described. Experiments with the gas jet and COa gas demonstrated that a relatively simple and reproducible method is available for the analysis of sample spectra in the intense CH band region from approximately 3500 to 4200 A. This part t of the spectrum contains many sensitive atomic and ionic excitation lines that can supplement other sensitive lines which may be obscured through interference.

Time-intensity plots of Si, Fe, Ti II, Cu, and Li lines using 0.25-inch cupped electrodes containing different proportions of sample and admixtures.____._-_____-____-___-___-34. Time-intensity plots of Si, Fe, Ti II, Cu, and Li lines using deep-bore electrode No. 2 (bore depth 0.75 inch) containing different proportions of sample and admixtures._________ 35. Gas jet for 0.25-inch-diameter cupped electrode. A, Photograph showing electrode; B, diagram showing jet parts in exploded view._______._._._.____.____.__.__..._____-_ 241 36. Photograph of gas jet for 0.125-inch-diameter deep-bore constant-feed electrode shown in position on arc stand. ______ 37. Diagram of gas jet shown in figure 36 mounted directly on optical bench_______________________________________ 243 38. Spectra obtained from a G-1:LUB4Of. graphite mixture arced in atmospheres of COg, Ar-Og, and He-Og gases using deepbore electrodes-______________________________________ 244 39. Water-cooled gas jet used with deep-bore constant-feed electrode No. 3. A, Photograph showing ceramic cup of figure 36 replaced by brass collar; B, diagrams of top and side views. 246 40. Time-intensity plots of several elements using a gas-cooled and water-cooled jet with deep-bore constant-feed electrode No. 3._____________.