Heating water baths

Ethyl bromoacetate (1). Fit a large modified Dean and Stark apparatus provided with a stopcock at the lower end (a convenient size is shown in Fig. Ill, 126, 1) to the 1-htre flask containing the crude bromoacetic acid of the previous preparation and attach a double surface condenser to the upper end. Mix the acid with 155 ml. of absolute ethyl alcohol, 240 ml. of sodium-dried benzene and 1 ml. of concentrated sulphuric acid. Heat the flask on a water bath water, benzene and alcohol will collect in the special apparatus and separate into two layers, the lower layer consisting of approximately 50 per cent, alcohol. Run ofi the lower layer (ca. 75 ml.), which includes all the water formed in the... 

Equip a 500 ml. three necked flask with a reflux condenser, a mercury-sealed mechanical stirrer and separator funnel, and support it on a water bath. Attach an absorption device (Fig. II, 8, 1, c) to the top of the condenser (1). Place 134 g. (152 ml.) of A.R, benzene and 127 g. of iodine in the flask, and heat the water bath to about 50° add 92 ml. of fuming nitric acid, sp. gr. 1-50, slowly from the separatory funnel during 30 minutes. Oxides of nitrogen are evolved in quantity. The temperature rises slowly without the application of heat until the mixture boils gently. When all the nitric acid has been introduced, reflux the mixture gently for 15 minutes. If iodine is still present, add more nitric acid to the warm solution until the purple colour (due to iodine) changes to brownish-red. 

The purification of Hquid nitro alcohols by distillation should be avoided because violent decompositions and detonation have occurred when distillation was attempted. However, if the distillation of a nitro alcohol cannot be avoided, the utmost caution should be exercised. Reduced pressure should be utilised, ie, ca 0.1 kPa (<1 mm Hg). The temperature of the Hquid should not exceed 100°C hot water should be used as the heating bath. A suitable explosion-proof shield should be placed in front of the apparatus. At any rise in pressure, the distillation should be stopped immediately. The only commercially produced Hquid nitro alcohol, 2-nitro-1-butanol, is not distilled because of the danger of decomposition. Instead, it is isolated as a residue after the low boiling impurities have been removed by vacuum treatment at a relatively low temperature. 

Fibers. Poly(vinyl alcohol) fibers possess excellent strength characteristics and provide a pleasant feel in fabrics. The fiber is usually spun by a wet process employing a concentrated aqueous solution of sodium sulfate as the coagulating bath. Water insolubiUty, even in boiling water, can be obtained by combining stretching, heat treatment, and acetalization with formaldehyde. Super hydrolyzed PVA is the preferred material for fiber production. 

In an indirect bath heat exchanger, the heating medium provides Iil u to an intermediary fluid, which then transfers the heat to the fluid h)cuig heated. An example of this is the common line heater used on many gas well streams to keep the temperature above the hydrate formal ion lem perature. A fire tube heats a water bath, which provides heat to tlie v.all siieam flowing through a coil immersed in the bath. Details pertaining to dcsi jit of indirect bath heaters are presented in Chapter 5. 

In fire tube type heaters, the coils are immersed in a bath of water. The water is heated by a fire tube that is in the bath below the coils. That is, the fire tube provides a heat flux that heats the water bath. The water bath... 

A mixture of 17 g of the methiodide and 32 ml of a 40 % aqueous potassium hydroxide solution is heated with stirring in a flask fitted with a condenser. The heating bath should be kept at 125-130°, and the heating should be continued for 5 hours. The cooled reaction mixture is then diluted with 30 ml of water and washed twice with 25-ml portions of ether. The aqueous layer is cautiously acidified in the cold with concentrated hydrochloric acid to a pH of about 2 and then extracted five times with 25-ml portions of ether. The combined extracts are washed twice with 10% sodium thiosulfate solution and are dried (magnesium sulfate). Removal of the solvent followed by distillation affords about 3 g of 4-cyclooctene-l-carboxylic acid, bp 125-12671-1 mm. The product may solidify and may be recrystallized by dissolution in a minimum amount of pentane followed by cooling in a Dry-Ice bath. After rapid filtration, the collected solid has mp 34-35°. 

B. ds-1,2-Cyclohexanediol. A 500-ml., round-bottomed flask equipped with a reflux condenser and a magnetic stirring bar is charged with 17.56 g. (0.0667 mole) of thallium(I) acetate (Note 1), 160 ml. of glacial acetic acid, 3.0 g. (3.7 ml., 0.0365 mole) of cyclohexene (Note 3), and 8.46 g. (0.0333 mole) of iodine (Note 4) in the order given. The suspension is stirred and warmed in a heating bath at 80° for 30 minutes. An 80-ml. portion of water is added, stirring is continued, and the mixture is heated at reflux for... 

The checkers recommend that excessive heating and evacuation be avoided dming rotary evaporation to minimize the loss of product during this operation. They kept the heating bath temperature below 80° and used a water aspirator. 

Future Directions. The GEMM package is still under development. There are several areas where new capabilities are forthcoming. One feature just completed is the incorporation of periodic boundary conditions so that systems in a water box may be studied. Another feature that has just been completed and is now being tested is the ability to perform Langevin dynamics, so that systems can be coupled to a heat bath (16). 

These four main types of apparatus being defined, (scientiste and manufacturers have let their imagination go in order to create apparatus). There are now about ten models, which differ by the volume of liquid used (from 2 cm to about 70 cm, the metal used for the cup (brass, aluminium), the heating mode (water bath, Bunsen burner, electrical), the type of gas used by the pilot light (natural gas, butane), the level of complexity of automatic controls some apparatus equipped with several cups can actually be programmed in order to make measurements automatically without the help of the operator. The liquid can be shaken manually or, thanks to an electrical motor, the ignition can be manual or automatic. 

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