Atomic emission characteristics of a premixed acetylene-nitrous oxide, total consumption flame.
It is well known that most of the burners presently used to produce high temperature, premixed flames have the tendency to be discouragingly wasteful of the sample solution, often bringing only a small fraction of the amount used into the flame. This paper reports on the construction and performance of a highly efficient total consumption burner that produces a nonturbulent acetylene-nitrous oxide flame from premixed gases. The eighteen flame emission detection limits tabulated for a select group of elements compare favorably with the best values heretofore reported in the literature, and the apparent freedom of alkaline earth emission from phosphate interference indicates the total consumption flame here described to be less subject to chemical interference than is the conventional diffusion flame. The relatively low cost burner that has been developed is convenient to operate and can be quickly assembled from commercially available components.
Relative free-atom populations in nitrous oxide-acetylene flames used in analytical spectroscopy
Abstract The spatial variations are presented of free-atom absorbances of Ag, Fe, Cu, Or, Ba, Al, Re, V and Ti when solutions of these elements are nebulized into nitrous oxide-acetylene names of various stoichiometries. The data reported show that: (a) the free atoms of stable monoxide-forming elements are highly localized in this flame; (b) the overall variation in the spatial absorbance profiles and the absorbances observed at the site of maximum absorbance as the flame stoichiometry is varied can be directly related to the stability of the monoxides of these elements, indicating that the formation of these compounds plays a major role in populating and depopulating these flames of free atoms; (c) values of β (the ratio of free-atom concentration of analyte in the flame gases to the total analyte concentration in all forms) for many elements are meaningful quantities only if they refer to a particular point in a specified flame at a given stoichiometry; and (d) atomization behavior in the nitrous oxide-acetylene flame is largely determined by equilibrium processes. To correlate experimental results with theory, a thermodynamic model was utilized.
Study of the Electron Density Distribution in the Simpler Hydrocarbons
The electronic charge distribution is calculated in the molecules of acetylene and ethylene, by making use of a function which characterizes the effect of bond formation on the electronic density. In agreement with earlier results on methane, the effect is found to consist in a charge removal from the vicinity of the nuclei and a build up of electron density in the regions of the bonds.In acetylene, the calculation of the charge drifts subsequent to the bonding indicates that these are fairly small, as had been found earlier in simpler molecules. It is also observed that the electrons associated with the CC bond tend to accumulate, in ethylene, above and below the molecular plane, and in acetylene, at some distance from the CC axis. This point is in favor of the Pauling picture of bent multiple bonds.