Working with liquids

Measuring and dispensing liquids The equipment you should choose to measure out liquids depends upon the volume to be dispensed, the accuracy required and the number of times the job must be repeated (Table 3.1). Table 3.1 Criteria for choosing a method for measuring out a liquid  

Method Best volume rnnge Accuracy Usefulness for repeftitivo me j. iiti iiiiMil 

Weighing Any (depends on accuracy of balance Very high Inconvenient 

Conical flasks, beakers, measuring cylinders and volumetric flasks measure the volume of liquid contained in them, while burettes, pipettes, pipettors, syringes and microsyringes mostly measure the volume delivered from them think about the requirements of the experiment. 

Hold correctly during use (Fig. 3.1) - keep the pipette vertical, with the middle finger gripping the barrel to support the pipette while the thumb and index finger provide controlled pressure on the bulb, and squeeze gently to provide individual drops. 

Method Best volume range Accuracy Usefulness for repetitive measurement 

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Lean burn/dry low-NOx combustors can generate NOx emissions levels as low as 9 ppm (at 15% 02), while those with liquid fuel combustors have NOx emissions limited to approximately 25 ppm (at 15% 02). There is no substantial difference in general performance with either fuel. However, the different heats of combustion result in slightly higher mass flows through the expansion turbine when liquid fuels are used, and thus a very small increase in power and efficiency performance is obtained. Also, the fuel pump work with liquid fuel is less than with the fuel gas booster compressor, thereby further increasing net performance with liquid fuels. 

Petersen P, Bredahl E, Lauritsen O, Laursen T Examination of the liver in personnel working with liquid rocket propellant. Br J /wdMrd 27 141-146, 1970... 

The volume of a cylindrical tank may be measured in cubic feet or cubic yards, or you may get to work with liquid measures such as gallons or quarts. tBE Equivalences are used to change from one unit to another. 

When working with liquid nitrogen, do not tightly close the lid of the blender or mill container, so that the gas can escape. 

Note The high pressures referred to are of the order of 2000-6000 psi. Since we are working with liquids instead of gases, high pressures do not pose an explosion hazard. Leaks occur on overpressurizing the worse problems to be expected are drips, streams, and puddles. 

In applications, increased capability in PEPT will enable more work with liquids and with multi-phase systems, and product-oriented studies aimed at probing the formation of microstructure. At the other extreme lies large-scale pilot- or process-level study which must be carried out in situ, using the new mobile PEPT camera. In large-scale applications, it will not in general be possible to provide trajectory information for the entire process volume. The challenge here is to develop "minimal" PEPT, in which location information is provided at as coarse a level as possible, consistent with the objectives of the study. 

As noted already, one of the greatest difficulties in working with liquid-liquid dispersions is the efficient separation of the phases after contact. An inefficient phase separation can lead to unacceptable losses of solvent and extractant. One way around this problem is to support the solvent phase on particles of an appropriate polymeric resin, which is then contacted with the feed phase. The phase separation (after contact) is facilitated and the losses of solvent and extractant are reduced. Initial studies were... 

Although it may seem reasonable that an increase in viscosity of the spray fluid should increase the drop size, there is little fundamental information on the relationship between the drop size of the sprays and the viscosity of the spray liquid. Moreover, the information that is available is conflicting. Besides the work of Yeo and Dorman, where a viscosity term was found unnecessary when working with liquids having relatively low viscosities, other workers have found that a function of viscosity was necessary to describe drop size (16,17, 20), but the value of this function has varied from v01 to v106 (where v is the kinematic viscosity of the liquid). More recently, Dombrowsld and Johns (9) have examined the breakup of sheets of viscous liquids formed from fan-jet nozzles and have derived a theoretical expression for the size of drops produced. The expression is very complex and includes viscosity terms, but it is difficult to use in a practical fashion to predict drop size and its variation with a particular physical parameter of the spray fluid. 

The primary advantage of solid epoxy adhesives is that they avoid the disadvantages of working with liquids. Waste and cleanup are minimized, and health problems are reduced because the end user handles only a solid substance. Since they are essentially one-component adhesives, they also eliminate the need to meter and mix individual components. 

Sodium Pbenylethynetellurolate5 An apparatus suitable for work with liquid ammonia under a nitrogen atmosphere is set up. A 500-m/flask is charged with 250 ml of liquid ammonia freshly distilled from sodium. In the liquid ammonia are dissolved 1.15 g (0.05 mol) of sodium, a catalytic amount of iron(III) nitrate is added, and 5.1 g (0,05 mol) of phenylacetylenc are added dropwise over 0.5 h to the sodium amide solution. The mixture is allowed to stand for 40 min and then 6.4 g (0.05 mol) of finely powdered tellurium arc added to the sodium acetylide solution. The ammonia is evaporated and the residue of sodium phenylethyne-tellurolate can be dissolved in an appropriate solvent for further reactions. 

Sodium Benzenetellurolate1 This reaction must be carried out under nitrogen or argon in an apparatus suitable for work with liquid ammonia2. A filtered suspension of 0.35 g (15 mmol) of sodium in 25 ml of liquid ammonia is added to a suspension of 3.1 g (7.5 mmol) of diphenyl ditellurium in 15 ml of liquid ammonia. The blue color of the sodium/ammonia solution changes rapidly to yellow. The reaction is complete when the solid ditellurium compound has disappeared. The reaction mixture is then filtered, the ammonia is evaporated, and the grey residue is washed with petroleum ether yield 3.1 g (95%). 

Diethyl Tellurium17 (Liquid Ammonia Method) An apparatus suitable for work with liquid ammonia is set up. 12.7 g (0.1 mol) of fine tellurium powder are suspended in liquid ammonia and then 4.6 g (0.2 mol) of sodium are added to the suspension. The mixture is stirred for 4 h. 10.9 g (0.1 mol) of ethyl bromide are added dropwise to the liquid ammonia, and the mixture is stirred for 30 min. The ammonia is evaporated. Water is added to the residue, the aqueous solution is extracted with diethyl ether, and the extract is dried with magnesium sulfate. The ether is evaporated and the residual liquid is distilled yield 7 g (38%) b.p. 138°. 

Methyl Phenylethynyl Tellurium1 An apparatus suitable for work with liquid ammonia is set up. Sodium amide is prepared in a 1 -l flask by adding 6.0 g (0.26 mol) of sodium to 250 ml of liquid ammonia, than 25 g (0.25 mol) of phenylacetylene are added dropwise. 30 g (0.24 mol) of tellurium powder are added over 20 min in small portions to the well-stirred sodium amide solution. 36 g (0.25 mol) of methyl iodide are added dropwise over 10 min to the tellurolate solution. The ammonia is then evaporated, the residue is extracted with diethyl ether, the extract is washed with water and the organic phase dried with anhydrous magnesium sulfate. The ether is distilled off and the residue fractionally distilleed under vacuum yield 28 g (48%) b.p. 122-12472 torr (0,267 kPa). 

Triphenyl Tellnronium Acetonitrosolate1 3.9 g (10 mmol) of triphenyl telluronium chloride are suspended in 50 ml of liquid ammonia in an apparatus sui table for work with liquid ammonia. To this suspension is added a solution of 1.9 g (10 mmol) of silver acetoni trosolate in 50 ml of liquid ammonia. The mixture is refluxed at the boiling point of liquid ammonia for 1 h, the ammonia is evaporated, and the residue is dried at 20° under high vacuum. 200 ml of methanol are added to the dry residue, the mixture is stirred for 30 min, silver chloride is filtered off, and the bfue filtrate is evaporated to dryness. The residue is recrystallizcd from water and then from liquid ammonia yield 2.9 g (65%) m.p. 139° (dec.). 

A capacitance cell suitable for work with liquids or solutions is shown in Fig. 1 it is made with a small variable-air capacitor of the type formerly in common use in radios and electronic circuits. It should have a maximum capacitance of 50 to 200 pF. This device is more convenient than a fixed-plate capacitor, since with the latter device it is necessary to measure separately the stray capacitance due to electrical leads, etc. In the cell shown, the variable capacitor is used in two positions fully closed (maximum capacitance) and fully open (minimum capacitance) these positions are defined by mechanical stops for the pointer on the knob that rotates the capacitor shaft.f The difference ACbetween the closed (b) and open (a) positions is independent of the stray capacitance. Thus the dielectric constant of the liquid or solution is given by... 

Rather less common are condensations between a-hydroxyketones, ammonia and an imidate. Equivalent amounts of the hydrochloride salt of the imidate and the or-substituted carbonyl compound (cr-halogeno-and a-acetoxyketones also take part) are heated (40-70°C) in liquid ammonia (3-48 h) at elevated pressures. Yields of imidazoles vary between 10 and 90%, but the requirements of working with liquid anomonia in an autoclave may make this approach unappealing if alternatives are available [42,43]. Examples include 4-hydroxymethyl- (35%), 4-hydroxymethyl-2-phenyl- (73%), 4-hydroxymethyl-2-(p-tolyl)- (68%) and 2-benzyl-4-hydroxymethylimidazoles (85%) [44]. 

Dimethyl Ditellurium [Liquid Ammonia Method] An apparatus suitable for work with liquid ammonia is assembled. A 500 ml, three-necked flask is fitted with a reflux condenser, a dropping funnel, and a stirrer. In the flask, 3.2 g (0.14 mol) of clean sodium are added to 100 ml of anhydrous ammonia at — 78°, the mixture is stirred for 1 h, and 18.2 g (0.14 mol) of high purity, powdered tellurium are added in 0.5 g portions. After all the tellurium has been added, 24 g (0.17 mol) of methyl iodide are added dropwise to the stirred, dark-green ammonia solution over 20 min. The cooling bath is then removed, the ammonia is allowed to evaporate, and water is added to the residue. The aqueous mixture is extracted with four 50 ml portions of diethyl ether, the combined deep-red extracts are dried overnight with anhydrous calcium chloride, the diethyl ether is evaporated under vacuum, and the residue is distilled yield 7.6 g (38%) b.p. 97°/9 torr. The freshly prepared dimethyl ditellurium is a heavy, dark-red liquid that solidified on standing for a few days at 20°. The liquid is regenerated when the solid is distilled under vacuum. Similarly prepared were ... 

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