Reduced dissolution time

Reduce the particle size of the NBS by milling to reduce dissolution time. 

Reduction in particle size can reduce dissolution time, but its overall effect in reducing reaction in the films around the dissolving particles may not be sufficient. Also, milling of a noxious material such as NBS is not feasible. 

Tile whole success of the preparation depends upon reducing the time interval between the addition of the phthalic anhydride and the acidification of the reaction mixtme to a minimum vigorous stirring will assist the initial dissolution, but prolon d stirring leads to excessive evolution of oxygen. The more rapidly the anhydride dissolves, the smaller the oxygen evolution, and the better the yield of monoperphthahc acid. 

Applications The majority of SFE applications involves the extraction of dry solid matrices. Supercritical fluid extraction has demonstrated great utility for the extraction of organic analytes from a wide variety of solid matrices. The combination of fast extractions and easy solvent evaporation has resulted in numerous applications for SFE. Important areas of analytical SFE are environmental analysis (41 %), food analysis (38 %) and polymer characterisation (11%) [292], Determination of additives in polymers is considered attractive by SFE because (i) the SCF can more quickly permeate throughout the polymer matrix compared to conventional solvents, resulting in a rapid extraction (ii) the polymer matrix is (generally) not soluble in SCFs, so that polymer dissolution and subsequent precipitation are not necessary and (iii) organic solvents are not required, or are used only in very small quantities, reducing preparation time and disposal costs [359]. 

At such elevated temperatures these and other acids become more corrosive. Materials that digest slowly or will not digest at the atmospheric boiling points of the acids become more soluble so dissolution times are greatly reduced. The aggressive digestion action... 

Low temperature etching. Our data suggests that, under hydrothermal conditions the rate of pit formation is dramatically reduced, although perhaps not completely stopped, at C = Ccrjt. Etch pits on a natural, hydrothermally-etched quartz surface therefore indicate extended dissolution times, but not necessarily etching at C < Ccrit This is because the rate of etch pit formation even above Ccr t can be significant at elevated temperatures (as shown by crystal R9). However, at low temperatures, formation of etch pits when C > C would be less likely, and natural surfaces etched at low temperature should record the saturation state of the etching fluid. 

Alternate Sample Introduction — Obviously, elimination of the sample dissolution stage would greatly reduce analytical time, as it is the slowest step in the analytical scheme. Pulsed-laser vaporization using a CO2—TEA laser seems promising(63, 64). Another possibility is the introduction of a suitable prepared slurry of the sample into the nebullzer(65). Thermal vaporization studies using heated substrates such as tanta-lum(66), carbon filaments(67), or carbon rods(39) have been reported. Silvester(39) de fined the problems of vapor transport, carrier gas expansion, and solid phase chemistry associated with electrothermal sample introduction to an ICP. 

Provided that the temperature remains below Tc, where the micellar solution Li separates into and L" phases (see Fig. 1), the rate of dissolution of pure nonionic surfactants increases with increasing temperature. For example, dissolution time fo for a drop of Ci2(FO)6 with Ro = 73 pm was 11 s at 35 °C. As indicated above, to is proportional to Rq, so that to would be about 13 s at this temperature if Ro were 78 pm. As indicated in the preceding paragraph, a drop with Ro = 78 pm dissolved more slowly, taking 16 s, when the temperature was reduced to 30 °C. 

The dissolution time for the unreprocessed fuel would be at least 1 million years due to the limited water supply, even if a rapid oxidation of uranium to the hexavalent state and a subse-guent formation of water soluble carbonate complexes are assumed (15). Since the conditions are reducing in the groundwater (see beTow) the dissolution time would probably be several orders of magnitude larger. The unsignificant dissolution of uranium and fission products observed in the Oklo-deposit (16) is an example of a similar extremely slow leaching process in the natural environment. 

It should be emphasised that the simplest way of avoiding the formation of deep etch patterns, namely, by reducing the time of the solid-with-liquid interaction, does not seem to be the best one because it only masks the phenomenon, not eliminating its cause. Therefore, it appears to be much more reasonable to increase the disc diameter and to reduce the volume of the liquid phase (within acceptable limits and taking account of other re-strictions 5 5 ), so that during dissolution of a solid from zero up to... 

Magnesium stearate 0.25-5 Water insoluble, excellent lubricant, reduces tablet strength, prolongs disintegration and dissolution times... 

Glass dissolution leads to a dull appearance of the glass with small dots or short cracks that are detectable only under the microscope. The thickness of the glass plate or the grains reduces with time, up to complete dissolution in extreme cases. 

Microwave ovens are now widely used for rapid and efficient drying and acid decomposition of samples. Laboratory ovens are specially designed to overcome limitations of household ovens, and these are discussed below. Advantages of micro-wave digestions include reduction of dissolution times from hours to minutes and low blank levels due to reduced amounts of reagents required. 

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