Metering burette

Cobalt naphthenate is generally supplied in solution in styrene, the solution commonly having a cobalt concentration of 0.5-1.0%. The cobalt solution is normally used in quantities of 0.5-4.0% based on the polyester. The accelerator solution is rather unstable as the styrene will tend to polymerise and thus although the accelerator may be metered from burettes, the latter will block up unless frequently cleaned. Cobalt naphthenate solutions in white spirit and dimethyl phthalate have proved unsatisfactory. In the first case dispersion is difficult and laminates remain highly coloured whilst with the latter inferior end-products are obtained and the solution is unstable. Stable solutions of cobalt octoate in dimethyl phthalate are possible and these are often preferred because they impart less colour to the laminate. 

Pipette 25 mL of an aluminium ion solution (approximately 0.01 M) into a conical flask and from a burette add a slight excess of 0.01 M EDTA solution adjust the pH to between 7 and 8 by the addition of ammonia solution (test drops on phenol red paper or use a pH meter). Boil the solution for a few minutes to ensure complete complexation of the aluminium cool to room temperature and adjust the pH to 7-8. Add 50 mg of solochrome black/potassium nitrate mixture [see Section 10.50(C)] and titrate rapidly with standard 0.01 M zinc sulphate solution until the colour changes from blue to wine red. 

Materials The methods used for the purification of aluminium bromide and chloride and for preparing phials of these catalysts, and the purification of methyl bromide, methylene chloride, and ethyl chloride, have been described [9]. The solvents were stored in a vessel coated with a sodium mirror and attached to the vacuum line, and they were metered into the observation cell by distillation from a hanging burette. 

Most of the instruments, commonly used in an analytical laboratory, such as UV-Spectrophoto-meter, IR-Spectrophotometer, single—pan electric balance, pH-meter, turbidimeter and nephelometer, polarimeter, refractometer and the like must be calibrated duly, before use so as to eliminate any possible errors. In the same manner all apparatus, namely pipettes, burettes, volumetric flasks, thermometers, weights etc., must be calibrated duly, and the necessary corrections incorporated to the original measurements. 

Soap-film flow meter A modified form of the soap film flow meter used by Krishnamurthi, Kumar, Datta, and Kuloor (K10) for collecting bubbles at atmospheric pressures is shown in Fig. 2. This device, which makes use of the movement of a soap film in a burette, can also be employed to calibrate low rate gas flow meters. Gas enters the apparatus from the top. A soap film is formed at the tip of the calibrated burette by raising a metallic loop dipped in soap solution. A water-seal is used to prevent the gas from escaping through... 

A special arrangement of taps and ducts below a standing burette is shown in Fig. 3.2 and has proved useful for metering freshly distilled styrene into a reactor (KPG). The device allows any excess in the burette to be returned to the reservoir at the end of the metering and is useful when fresh distillation immediately before the reaction is desirable, as is the case for thermally polymerisable monomers. It also prevents residual monomer from polymerising in the ducts. 

Both hanging and standing burettes have some disadvantages for metering smaller quantities (up to a few grams) of material into a reaction vessel ... 

An automatic or manual titration apparatus may be used. In the latter case, the burette is graduated in U.U05-mL increments and the pH meter is provided with a wide reaching scale and glass-calomel electrodes. After each test the reaction vessel is evacuated by suction and washed several times with water, the washings being removed each time by suction,... 

Automatic titration device with a 25 0.02 mL burette and a pH meter giving a reading to 0.01 are suitable (or manual titration burette (25 0.02 mL... 

A related form of an automatic potentiometric titrator is instrumentation that permits the maintenance of the acidity or basicity of a solution over a period of time. Such devices are known as pH-stats, and find application in kinetic studies of hydrolysis reactions. The general approach is (by either manual or automatic means) to add either acid or base such that the pH in the solution is maintained constant over a period of time. Normally the amount of acid or base added as a function of time is sought in order that kinetic measurements may be made for the system. In its simplest form the acidity of the solution is monitored with a pH meter and controlled at a preselected value by the addition of acid or base from a burette the quantity delivered as a function of time is recorded in a notebook. Obviously for the fast reactions this becomes difficult and dependent on the dexterity of the individual. 

The reagent of known concentration is usually used as the titrant. The titrant is poured into a buret (also spelled burette) until it is nearly full, and an initial buret reading is taken. Buret numbering is close to zero when nearly full. A known volume of the solution of unknown concentration is added to a flask and placed under the buret. The indicator is added or the pH meter probe is inserted. 

NOTE Instruction in the operation and principles of operation of pH meters may be necessary. Provide burette brushes and solvent (CHCI3) for cleaning burettes and removing stopcock grease, unless burettes with Teflon stopcocks are used. 

A steady gas flow calibrating a flow meter of this kind can be obtained from a needle valve attached to a regulator set to 5- 10 psi gauge pressure or more (to avoid perturbations due to small variations in outlet pressure). At small flow rates the volume of gas flow over an interval of time measured with a timer can be determined with a gas burette a three-way stopcock can be used to switch the gas burette in and out of the system. For larger flow rates a water-filled inverted graduated cylinder or volumetric flask, its mouth held under the surface of a water bath, can be used to collect gas from a rubber tube held underneath it for a time interval measured with a timer. For precise work, a correction should be made for the partial pressure of water vapor in the gas collected. 

The modified Wicke - Kallenbach cell developed in our laboratory [26,27], was used for measurement of isobaric counter-current ternary diffusion. Figure 1 shows schematically the diffusion set-up including the modified Wicke-Kallenbach cell.. Gl-4 are gas sources FMC are flow-meter controllers D is the diffusion cell 01-2 are gas outlets VI-3 are valves B is a calibrated glass burette with soap film. The diffusion cell contains a metallic disc with cylindrical holes into which the porous pellets are mounted. Volumes of cell compartments are approximately 150 cm. ... 

Material Becherglas (50 mL), Messpipette (10 mL), Burette (25 mL), Magnetriihrer und Riilirfisch, pH-Meter Aluminiumchlorid (AlCb-OHaO), 2-molare Salzsaure, 2-molare Natronlauge... 

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