Cooling absorbance ratio

Erk [20] described a spectrophotometric method for the simultaneous determination of metronidazole and miconazole nitrate in ovules. Five capsules were melted together in a steam bath, the product was cooled and weighed, and the equivalent of one capsule was dissolved to 100 mL in methanol this solution was then diluted 500-fold with methanol. In the first method, the two drugs were determined from their measure d%/dk values at 328.6 and 230.8 nm, respectively, in the first derivative spectrum. The calibration graphs were linear for 6.2—17.5 pg/mL of metronidazole and 0.7—13.5 pg/mL of miconazole nitrate. In the second (absorbance ratio) method, the absorbance was measured at 310.4 nm for metronidazole, at 272 nm for miconazole nitrate and at 280.6 nm (isoabsorptive point). The calibration graphs were linear over the same ranges as in the first method. 

Fig. 7.4. Ratio between the mechanical work pdV (p = 34 bar and 7 = 5 mK) and the cooling power for a mole of 3He during the solidification process. Note that at 1 mK, pdV is ten times the energy absorbed in the solidification of a mole of 3He. The cooling in practice ends at 0.8-0.7mK. Data from [3-4].

There is an optimum fuel and oxidant flow rate to the flame, or, more precisely, an optimum fuel-oxidant flow rate ratio. If the flame is oxidant-rich, it is too cool. If it is fuel-rich, it is too hot. Again, monitoring the absorbance of an analyte standard while varying the flow rates helps to find the optimum ratio. Instrument manufacturers literature will also provide assistance. Safety issues relating to the proper flow rate of these gases will be addressed in Section 9.3.7. 

An autoclave (7) is supplied with an aqueous solution that contains 600 g of ammonium nitrate and 40 g of ammonia per litre. Calcium cyanamide in the ratio of 500 g CaCN2 to every litre of solution is then added from container (2) after being weighed at (3). The autoclave is closed, carbon dioxide is introduced, while the contents are cooled with water so that the temperature does not exceed 100°C. When no more carbon dioxide is absorbed, the supply is stopped, and so is the inflow of cooling water. The reaction mixture is now steam heated to 160°C. Afterwards a communicating valve joining the autoclave (7) with a second autoclave (75) is opened. The other vessel (75) is filled with ammonium nitrate solution prepared for the next charge. In this way the major part of the ammonia passes from autoclave (7) over to autoclave (75). After the reaction is finished the mixture is raised from the auto-... 

The effect of increasing the compression ratio, defined as the ratio of the volumes at the beginning and end of the compression stroke, is to increase the efficiency of the engine, i.e., to increase the work produced per unit quantity of fuel. We demonstrate this for an idealized cycle, called the air-standard cycle, shown in Fig. 8.9. It consists of two adiabatic and two constant-volume steps, which comprise a heat-engine cycle for which air is the working fluid. In step DA, sufficient heat is absorbed by the air at constant volume to raise its temperature and pressure to the values resulting from combustion in an actual Otto engine. Then the air is expanded adiabatically and reversibly (step AB), cooled... 

Cases have been observed where the isotopic line absorption profiles completely overlap, e.g. boron-10 and -11 in a krypton-filled lamp at 249.7 nm [244]. Hannaford and Lowe [245] later showed that this was caused by an unusually large Doppler half-width induced by the fill-gas, and, if neon is used, the 208.9 and 209.0 nm lines can allow the determination of boron-10 and boron-11 isotope ratios. The 208.89/208.96 nm doublet was found to be more useful than the 249.68/249.77 nm doublet. Enriched isotope hollow-cathode lamps were used as sources. A sputtering cell was preferred to a nitrous oxide/acetylene flame as the atom reservoir, as it could be water-cooled to reduce broadening and solid samples could be used, thus avoiding the slow dissolution in nitric acid of samples of boron-10 used as a neutron absorber in reactor technology. 

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