A spot test for nitrates

Isopiestic determination of the activity coefficients of some aqueous rare-earth electrolyte solutions at 25.degree.C. 6. Europium trinitrate, yttrium nitrate, yttrium chloride

“…Published differential thermal analysis results (16) indicate that it should be possible to thermally decompose rare-earth nitrates to form the pure oxides. However, a sample of Y(N03)3 that was heated overnight at 770 °C gave a distinct positive test for nitrate ions (15). In addition, semiquantitative tests with Eu(ND3)3 and Y(ND3)3 indicated that weighing samples as the oxides could give concentration errors of as much as 1 % at 1 mol/kg, and 3% at very high concentrations.…”

“…This was necessary to avoid coprecipitation of nitrate ions, which would give high results for the apparent concentrations (5). Rare-earth sulfate samples, prepared in this manner, were "nitrate free" as determined by the sensitive chromotropic acid test (15).…”

Interference of nitrate in the determination of formaldehyde by the chromotropic acid method

“…In our case we were able to remove NaN03 altogether from our culture medium and replace it with NH4C1 as the nitrogen source. Nitrite can be removed from the samples as nitrogen gas by the addition of urea (4) or destroyed by the use of sulfamic acid (8). When the chromotropic acid procedure of P. W. West and B. Sen is and NaN03 In concentrations of (A) 1.0 mg/mL, (D) 0.5 mg/mL, ( ) 0.05 mg/mL, (O) 0.005 mg/mL, or (•) none.…”

“…In liquid-solid chromatography, however, n and h are unequivocally defined only for isocratic, isothermal chromatographic systems in which the mobile phase velocity at any instant is identical throughout the system. The use of theoretical plate number and plate height, without further qualification, to describe gradient chromatographic systems (specifically, in the present context, radial (7), evaporative (8), or multiple development (9) TLC, all of which produce or mimic solvent velocity gradients) can be confusing and misleading.…”

“…Very different numbers (all nominally representing equivalent plates) can result from the measurement of different characteristics on the same chromatogram. This is because a common effect of HPTLC techniques is a reduction in both average spot top-to-bottom width and separation (8). The result is almost always an increase in sensitivity (sample zones are more concentrated for a given migration distance).…”