Constant temperature bath

If there is no external temperature control (using a simulated constant temperature bath), molecular dynamics simulations are constant energy. 

If the constant temperature algorithm is used in a trajectory analysis, then the initial conditions are constantly being modified according to the simulation of the constant temperature bath and the relaxation of the molecular system to that bath temperature. The effect of such a bath on a trajectory analysis is less studied than for the simulation of equilibrium behavior. 

This test was prepared and is limited to type 1 (low-density) polyethylenes. Specimens are annealed in water or steam at 212°F (100°C) for 1 h and then equilibrated at room temperature for 5-24 h. After conditioning the specimens are nicked according to directions given. The specimens are bent into a U shape in a brass channel and inserted into a test tube that is then filled with fresh reagent (Igepal). The tube is stoppered with an aluminum-covered cork and placed in a constant temperature bath at 122°F (50°C). 

The mixing can be performed isothermally and reversibly by sinking the apparatus in a constant temperature bath, and opposing the expansive forces of the gases by forces differing only infinitesimally from them, and applied to the piston rods. 

If a constant-temperature bath is not available, a bucket of water, initially at 25°, serves to dissipate the heat of reaction. At higher temperatures the potassium permanganate is rapidly consumed, presumably by reaction with the acetone. 

In a 300-mL round-bottom flask, a 5% sodium hydroxide solution (250 mL) was heated to 80° C in a constant-temperature bath. The catalysts were added in the following amounts in separate experiments trioctylmethy-lammonium chloride (TOMAC) (0.04 g, 0.0001 mol) trioctylmethylammo-nium bromide (TOMAB) (0.045 g, 0.0001 mol) hexadecyltrimethylammo-nium bromide (HTMAB) (0.045 g, 0.0001 mol) tetraethylammonium hydroxide (TEAOH) (0.015 g, 0.0001 mol) and phenyltrimethylammonium chloride (PTMAC) (0.02 g, 0.0001 mol). PET fibers (1.98 g, 0.01 mol) were added to the mixture and allowed to react for 30, 60, 90, 150, and 240 min. Upon filtration, any remaining fibers were washed several times with water, dried in an oven at 130-150°C, and weighed. The results are shown in Table 10.1. 

The entire apparatus was immersed in a constant temperature bath at 25 °C. The upstream hydrogen pressure was maintained constant at 77.00 cm Hg. The time variation of the pressure in the constant volume container is given in the next column. 

The considerations above show that temperature is definable only for macroscopic (in the strict sense, infinitely large) systems, whose definition implies neglect of the disturbance during first thermal contact. The canonical ensemble is now seen to be characterized by its temperature and typically describes a system in equilibrium with a constant temperature bath. 

The substituted styrene monomer and azo-Wr-isobutyronitrile initiator were placed in a glass reactor which then was attached to a vacuum manifold. The reactor was evacuated and cooled in a dry-ice-acetone bath. The appropriate quantity of SO2 monomer was distilled into the reactor, the reactor was then sealed under vacuum and placed in a constant temperature bath for three to eight hours. After the... 

Viscosity depends on temperature. The higher the temperature, the lower the viscosity Pancake syrup, for example, flows more freely when heated. For reasonable accuracy when measuring viscosity, the temperature must be very carefully controlled. This means that the viscometer and sample must be immersed in a constant temperature bath and the temperature given time to equilibrate before the measurement is recorded. A calibrated thermometer must be used to measure the temperature. 

Set up a constant temperature bath for capillary viscometry at a temperature of 25°C. 

Pour the first liquid to be measured into the viscometer tube and place the tube in the constant temperature bath. After allowing plenty of time for the temperature to equilibrate, measure the time of flow in the manner discussed in Section 15.2.4. Using the known calibration constant, calculate the kinematic viscosity at 25°C. Repeat with each of the other alcohols. 

Prepare 500 mL of a 2% solution of carboxymethylcellulose, sodium salt, in water in the manner described in the U.S. Pharmacopeia reference above. Since the solution preparation is time-consuming, your instructor may prepare it ahead of time. Using a rotational viscometer with an appropriate spindle and a constant temperature bath, measure the viscosity of this solution at various temperatures. Plot viscosity vs. temperature. 

Prepare a carboxymethylcellulose solution as in Part A. Prepare dilutions to bracket the suspected concentration in the unknown. Measure the viscosities of the solutions and the sample with a rotational viscometer and in a constant temperature bath set at 25°C. Plot viscosity vs. concentration and determine the concentration in the unknown. 

Step (a) To a 500 mL round bottom flask containing a stir bar was added shell reagent (Y) G = 3.5 methyl ester PAMAM dendrimer, EDA core, (32 g, 2.6 x 10-3 mol, 164 mmol ester, 25 equivalents per core dendrimer (X) and 32 g of methanol. This mixture was stirred until homogeneous. To this mixture was added lithium chloride (7 g, 166 mmol, 1 equivalent per ester) and stirred until homogenous. To this mixture was added (drop-wise) PAMAM dendrimer, EDA core, G = 6 (6 g, 1.0 x 10-4 mol) in 20g of methanol in 10 min. This mixture was warmed to 25 °C and placed in a constant temperature bath at 40 °C for 25 days. 

Figure 1. Sketch of the hydrostatic balance densitometer— A) magnetic stirrer (B) glass float (C) stirring motor (D) constant temperature bath (E) nickel thermometer (F) lucite plug (G) sample container (H) nylon wire (1) suspension hook (]) Mettler H20 balance (33)...

C, is a cylindrical glass vessel with a volume of 450 cm. The piezometer contains the solution and 330 gms of Hg. The top of the piezometer is fitted with a Taper joint for filling. A precision bore capillary, E, (2mm in diameter) is fitted to the bottom of the piezometer. The piezometer is suspended (6) in a brass or stainless steel pressure vessel, H. A glass boiler tube, J, encloses the upper portion of the capillary. The pressure vessel is filled with ethylene glycol which serves as a thermal and pressure medium. The entire apparatus is submerged in a constant temperature bath controlled to 0.001 C. The temperature inside the pressure vessel is monitored with a Hewlett-Packard quartz crystal thermometer (to determine when thermal equilibrium is reached after compression and decompression). 

Figure 5. Sound vilocimeter for use at atmospheric pressure—(A) constant temperature bath (B) magnetic stirrer (C) solution cell (D) transmitting transducer (E) reflector (F) receiving transducer (85)...

Figure 12, Sketch of the high pressure sound velocimeter (A) constant temperature bath (B )bomb stand (C) pressure bomb (D) plug (E) transmitting transducer (F) reflector (G) O-ring (112)...

Surface tension measurements. Solutions of the betaines were prepared with quartz-condensed, distilled water, specific conductance, 1.1 X 10" mho cm" at 25°C. All surface tension measurements were made by Wilhelmy vertical plate technique. Solutions to be tested were immersed in a constant-temperature bath at the desired temperature 0.02°C and aged for at least 0.5 h before measurements were made. The pH of all solutions was > 5.0 (usually, in the range 5.5-5.9), where surface properties show no change with pH. 

Prior to conducting the sorption experiment, the coal extract (200 mg) was first placed in a Wig-L-Bug capsule and ground for 1 minute under nitrogen. This grinding effectively reduces the extract to a fine powder, which is then used for the sorption experiment. Approximately 50-70 mg of the extract was then placed on the sample pan and the hangdown tube was replaced. The sample was maintained at 30.00 0.02 C by means of a constant temperature bath which surrounded the hangdown tube. 

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