Aciorojnce-w/UkrArV-Flgure 1. Lead interference at the Sb 217.58-nm line using Sb lamp, 20-µ depositions of 1, 10, 25 pg/tvL Pb and a 0.5-nm (top trace) and a 2-nm bandwidth(2) Spectral Interference by Sb on the Determination of Pb at 217.00 nm. The absorbance of 10 Mg/mL Sb is equivalent to that of 0.005 /¿g/mL Pb, a ratio of about 2000:1. Even this small effect can be avoided by using the very good Pb line at 283.33 nm, where there are no known spectral interferences.(3) Spectral Interference by Ni on the Determination of Sb at 231.15 nm. The absorbance of 1000 µg/mL Ni is equivalent to that from 0.02 µg/mL Sb, a ratio of 50000:1. Moreover, the Sb line at 231.15 nm is rarely used, because the 217.58-nm line is generally preferable. LITERATURE CITED(1) Koizumi, H.

does increase the sensitivity of the collection step, it does so at the expense of selectivity.Equation 9 predicts a 14-mV anodic stripping peak potential shift as the scan rate is increased from 1 to 3 V/min. A 13-mV anodic shift was observed experimentally. The stripping electrode potential at which the collection peak is observed shifts 29 mV anodically over the same scan rate range, resulting in the increase in with scan rate indicated in

The infrared spectra of polycrystalline LiBH, and LiBD, have been recorded in the region 4000-50 cm-' at 80 OK. Raman spectra of polycrystalline samples were also recorded at this temperature. The spectra of the BH4-and BD,-lattice vibrations are consistent with symmetrically equivalent borohydride ions which lie on either general positions, two-fold axes or mirror-planes. Six lattice vibrations of translatory origin appear in the infrared spectrum of LiBH, and a mode of libratory origin is inferred from an absorption tentatively assigned as a second overtone of a librational mode.

0b°Values as high as 4800 have been reported by others (15, 16). 6 Values as high as 700 have been reported by others (15, 16).regarding the validity of the reported results; they can only be considered as qualitatively suggestive of accuracy. SUMMARYThe present results have shown that fluoride compounds are fairly rapidly converted to CaF2 in the arc in the presence of excess calcium, that complete vaporization of the CaF2

Using both infrared and laser Raman techniques the low temperature vibrational spectra of KBH,, KBD,, NaBH,, and NaBD, have been recorded. The spectra of the external lattice vibrations are consistent with the following borohydride ion site symmetries: Td for potassium borohydride and D,, for sodium borohydride. Translational frequencies are assigned and librational frequencies are inferred from absorptions tentatively assigned as second overtones. Comparison of the low and high temperature vibrational spectra suggests the following disorder-order phase changes: Oh5 + TdZ for potassium borohydride and Oh5 3 DZd9 for sodium borohydride.En utilisant les techniques de I'infrarouge et du laser Raman, les spectres de vibration a basse temperature de KBH,, KBD,, NaBH, et NaBD, ont ete enregistres. Les spectres de vibration du reseau externe sont consistants avec les sites de symetrie suivants pour les ions borohydrures: Td pour le borohydrure de potassium et D2, pour le borohydrure de sodium. Les frequences de translation sont assignees et les frequences de vibration deduites a partir des absorptions qu'il est possible d'assigner aux deuxiemes harmoniques. La colllparaison des spectres de vibration a basse et haute temperature suggere les changements de phase desordre-ordre suivants: Oh5 + TdZ pour le borohydrure de potassium et Oh5 + D2,' pour le borohydrure de sodium.