Block-heating

A skilled worker can use a micro-Bunsen burner for most types of heating. Nevertheless, as there is a tendency for a liquid to shoot out of a small test tube when heated, it is preferable to place the tube in a hot water-bath or in a metal heating block. A small glycerol bath is suitable for distillations and heating under reflux, the glycerol being subsequently easily removed from flasks, etc., by washing with water. 

Sublimation. This is a most useful process for small-scale work as the losses are comparatively small. This can be performed (a) In a long narrow tube sealed at one end. The material is shaken to the closed end of the tube, which is then inserted horizontally in a metal-heating block (Fig. 50) (b) In the cold-finger device (Fig. 35, p. 62)-... 

Dijferential Thermal Analysis (DTA) A sample and inert reference material are heated at a controlled rate in a single heating block. If an exothermic reaction occurs, the sample temperature will... 

The autoclave is cooled to room temperature, and the carbon dioxide is bled off. The solid reaction product is taken from the autoclave, pulverized, and dissolved in 1 1. of water at 50-60°. Ten grams of decolorizing carbon is added, and the mixture is stirred well and filtered to remove cadmium salts and carbon. The filtrate is heated to 80-90° and acidified with concentrated hydrochloric acid to pH 1 (Note 5). 2,6-Naphthalenedicar-boxylic acid precipitates. It is separated from the hot mixture by filtration. It is then suspended in 500 ml. of water at 90-95° (Note 5), separated by filtration, and washed successively with 300 ml. of water, 300 ml. of 50% ethanol, and 300 ml. of 90% ethanol. After being dried at 100-150°/150 mm. in a vacuum oven, the 2,6-naphthalenedicarboxylic acid weighs 42-45 g. (57-61%). It decomposes on a heated block at 310-313°. 

One of the interesting properties of PBPCP [187] was its fast heat dissipation characteristics and so it was tested by the well-known oxy-acetylene panel test (ASTM 285-70) for ablative materials. Figure 13 shows the survival of a flower for 100 s. kept on the 6.35-mm asbestos fiber-reinforced hexamine-cured panel. The ablation rate value of this material was 3.2 x 10 in/s in comparison with 3.6 x 10 in/s for asbestos-phenolic. As the char content of PBPCP was only 27% compared with 60% for conventional phenolics, mechanisms involving transpiration processes rather than heat blocking by char formation might be playing a greater role in this case [188]. 

Figure 3.18 Laboratory melt polymerization setup (a) 250 mL (b) 50-mL reactor in either oil bath or heating block.

Fifteen grams of this prepolymer powder in a wide-bore reaction tube (Fig. 3.18b) which is flushed with nitrogen is placed in a heating block. The heating block is warmed over a period of 1 h to 270°C and maintained at this temperature for 4 h, after which the reaction vessel is removed. The yellow polymer obtained has an r]i h of 1.9. The polymer has a melting temperature of 391°C, a heat of fusion of 148 J/g, a Tg dry at 120°C, and a Tg wet at —15°C. 

To a 50-mL straight-wall three-necked flask (Fig. 3.18b) equipped with a magnetic stirrer, nitrogen inlet/outlet, and condenser unit in a heating block are added 11.29 g of nylon salt and 0.093 g of hexamethylene diamine (2 mol % excess). This mixture is reacted for 2 h at 210° C and 3 h at 270°C. The resultant polymer is colorless and transparent and has a r/rei of 2.54 (1% solution in m-cresol, 25°C). 

Example 12. PA-6,1 from diphenyl isophthalate.65 To a well-dried 50-mL straight-wall three-necked flask with nitrogen inlet/outlet, condenser unit, and magnetic stirrer in a heating block (Fig. 3.18b), 15.1 g of diphenyl isophthalate and 6.15 g of 1,6-hexamethylene diamine are added. The mixture is heated to 190° C over a 1-h period and to 253° C over a further 40 min, a vacuum is then... 

Figure 4.9 Schematics of electrospray LC-MS interfaces with (a) a heated capillary and (b) a heated block to allow high mobile-phase flow rates. From applications literature published by (a) Thermofinnigan, Kernel Hempstead, UK, and (b) Micromass UK Ltd, Manchester, UK, and reproduced with permission.

Energy transfer is directional, and for this reason it is essential to keep track of the signs associated with heat flows. For example, if we drop a heated block of metal into a beaker of cool water, we know that heat will flow from the metal to the water q is negative for metal and positive for the water. The amount of heat flow is the same, however, for both objects. In other words, ijwater = metal more general terms ... 

In-sltu Raman experiments were performed on a Spex 1401 double monochrometer Raman spectrometer, using a Spectra-Physlcs Model 165 argon Ion laser with an exciting wavelength of 5145 A. The In-sltu Raman cell consists of a quartz tube situated In a temperature controlled heating block. The Raman spectra were collected In the 180° backscatterlng mode. 

Fabrication was done by photolithography and deep reactive ion etching (DRIB). The catalyst was inserted by sputtering. Such a prepared microstructure was sealed with a Pyrex cover. The bonded micro device was placed on a heating block containing four cartridge heaters. Five thermocouples monitored temperature on the back side. A stainless-steel clamp compressed the device with graphite sheets. 

Transfer an aliquot of the sample extract equivalent to 0.5-g of crop (5 mL) into a disposable test-tube (10-mL) and evaporate the sample in a heating block at 50 °C under a stream of dry air to < 1 mL. Add 5 mL of acetonitrile-water (3 7, v/v) to the sample and ultrasonicate the solution to ensure that the sample is fully dissolved. 

Precondition a Cig (EC) SPE column (l-g/6-mL) with methanol (5mL) followed by another 5 mL of acetonitrile-water (3 7, v/v). Transfer the sample on to the column and allow it to percolate through the column under vacuum, discarding the column eluate. Wash the column with 5 mL of acetonitrile-water (3 7, v/v). Dry the column under high vacuum for 15 min and wash it with hexane (5 mL). Elute the azoxystrobin from the column with 5 mL of ethyl acetate-dichloromethane (11 9, v/v), and evaporate the eluate to dryness under a stream of air in a heating block at 50 °C. Dissolve the sample in 1 mL of acetonitrile-water (1 1, v/v) and filter the solution through a 0.45-p.m syringe filter, transferring the filtrate to an autosampler vial ready for LC/MS/MS analysis. 

Heating block, Reacti-Therm III with Reacti-Vap Evaporator or equivalent Culture tubes with screw-caps, 50-mL Volumetric flasks, 10-mL... 

Concentrate the acetonitrile extracts obtained above to dryness below 40 °C with the rotary evaporator. Dissolve the residues in 2 mL of acetone. Quantitatively transfer the acetone extracts to a culture tube with a Teflon screw-cap containing 250 xL of acetone-olive oil keeper (1 1, v/v). Evaporate the acetone on a heating block not exceeding 40 °C under a stream of air. Wrap the threads on the Teflon culture mbe with Teflon tape and add 2.0 mL of 50% (w/w) sodium hydroxide. Cap tightly and heat the Teflon culture tube at approximately 200 °C for 3 h. 

Basic laboratory equipment centrifuge with cooling condition control at 4°C, heat block, pH meter, eppendorf BioPhotometer, microtube, and so on. 

Atmospheric Pressure Chemical Ionization. As its name reveals, APCI[16] is a Cl carried out at atmospheric pressure instead of under vacuum, as occurs for classical Cl. As for ESI, the sample must be in a solution that is continuously flowing into the APCI source (flow rate between 0.2 and 2 ml min ). The solution passes through a pneumatic nebulizer and is desolvated in a heated quartz tube or heating block, thus producing vaporization of solvent and analyte molecules (Figure 2.4). 

Fig. 12. Column heating block and Vapourtec R-4 Flow Reactor Heater...

Differential Thermal Analysis (DTA) A sample and inert reference material are heated at a controlled rate in a single heating block. This test is basically qualitative and can be used for identifying exothermic reactions. Like the DSC, it is also a screening test. Reported temperatures are not reliable enough to be able to make quantitative conclusions. If an exothermic reaction is observed, it is advisable to conduct tests in the ARC. 

Never use a wet rag or sponge to quickly cool off the heating block. This might permanently warp the block. You can use a cold metal block to cool it if you re in a hurry. Careful. If you slip, you may burn yourself. 

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