Boiling chips

Generation Spontaneous generation of gas bubbles within a homogeneous liquid is theoreticaUy impossible (Bikerman, Foams Theoiy and Industrial Applications, Reinhold, New York, 1953, p. 10). The appearance of a bubble requires a gas nucleus as avoid in the liquid. The nucleus may be in the form of a small bubble or of a solid carrying adsorbed gas, examples of the latter being dust particles, boiling chips, and a solid wall. A void can result from cavitation, mechan-ic ly or acoustically induced. Blander and Katz [AlChE J., 21, 833 (1975)] have thoroughly reviewed bubble nucleation in liquids. 

Ethyl 3-amlnopropsnoate (5). To a tu solution of 4 in THF (frem the bromo ester with NaN3 In OMSO) was added a molar equivalent of Ph3P, t 5 equiv of water and a boiling chip (N2 evolution) Alter 8 h at 20°C and evaporation, the residue was treated with El20-hexane and PhaPO was filtered This process was repeated and 5 was distilled at 40-45° and 10.5 torr (83%). 

If it is inconvenient to add sulfur tetrafluoride directly from a cylinder, it may first be condensed in a calibrated trap containing a boiling chip and cooled in a acetone-dry ice bath. When cooled to — 78°, 119 g. of sulfur tetrafluoride is about 62 ml. The sulfur tetrafluoride can be added to the cooled flask by allowing it to distil slowly from the trap. 

An applicator stick (available from drug stores) can be used very conveniently to ensure smooth boiling. If a boiling chip is used, it should be colored (Carborundum, for example) to make its separation from the product convenient. 

To 1 g of 2j5-azido-3a-iodo-5a-cholestane ° in 10 ml benzene is added 0.4 g trimethyl phosphite. A boiling chip is added and the mixture allowed to stand at room temperature for 4 days. The solvent is removed in vacuo, with most of the trimethyl phosphite being removed at 0.1 mm. This crude product (100) is dissolved in 10 ml of dry ether and added dropwise to a stirred mixture of 0.5 g of lithium aluminum hydride in 10 ml of ether. After stirring at 25° for 3 hr, the excess of hydride is destroyed by the addition of 2 ml 20 % sodium hydroxide and the aluminum salts are filtered. The solution is washed with ether, and the ether removed in vacuo giving 0.71 g [76 %] of product (95) mp 101-103°. 

Twenty-five grams (0.212 mole) of 3-sulfolene, and 15.0 g (0.153 mole) of pulverized maleic anhydride are added to a dry 250-ml flask fitted with a condenser. Boiling chips and 10 ml of dry xylene are added. The mixture is swirled gently for a few minutes to effect partial solution, then gently heated until an even boil is established. During the first 5-10 minutes, the reaction is appreciably exothermic, and care must be exercised to avoid overheating. 

A 500-ml, three-necked, round-bottom flask is equipped with a condenser, a dropping funnel, and a thermometer in the reaction mixture. In the flask is placed a mixture of 85% hydrazine (115 ml, 118 g) and 225 ml of 95% ethanol with a few boiling chips. The solution is brought to reflux (mantle) and cinnamaldehyde (100 g, 0.76 mole) is added dropwise over about 30 minutes followed by an additional 30 minutes of refluxing. A still head is attached to the flask and volatiles (ethanol, water, hydrazine hydrate) are slowly distilled at atmospheric pressure until the pot temperature reaches 200° (about 3 hours). Hereafter, phenylcyclopropane is collected over the range 170-180°. When the pot temperature exceeds 250°, the recovery is complete. The crude product (55-65 g) is washed twice with 50-ml portions of water and dried (anhydrous potassium carbonate). Distillation under vacuum through a short column affords the product, bp 60°/13 mm, 79-80°/37 mm, n f 1.5309, about 40 g (45%). 

A solution of potassium hydroxide (5 g) in 8 ml of water is placed in the distilling flask and 25 ml of 95% ethanol is added no boiling chips). The flask is heated in a water bath to 65° and a solution of 21.5 g(0.1 mole) of V-methyl-iV-nitroso-/ -toluene-sulfonamide in 130 ml of ether is added through the dropping funnel over a period of about 25 minutes. The rate of addition should about equal the rate of distillation. When the dropping funnel is empty, another 20 ml of ether is added slowly and the distillation is continued until the distilling ether is colorless. The combined ethereal distillate contains about 3 g (approx. 0.07 mole) of diazomethane and is approximately 0.5 M. 

It may also be refluxed with boiling chips without stirring. A heating mantle may be used in place of a steam bath... 

The checkers employed a sealed ampoule of bromomethane of b.p 5° (obtained from Eastman Organic Chemicals) which was cooled to 0° and opened. After a boiling chip had been added to the ampoule, it was connected to the gas-inlet tube of the reaction apparatus with rubber tubing, and the ampoule was warmed in a water bath to distil the bromomethane into the reaction vessel. 

A. fi(-)-a-(l-Naphthyl)ethylamine. A mixture of 58.44 g. (0.20 mole) of (-)-2,3 4,6-di-0-isopropylidene-2-keto-L-gulonic acid hydrate [(-)-DAG] (Note 1) and 1.7 1. of acetone (Note 2) is placed in a 3-1. Erlenmeyer flask. A boiling chip is added, and the mixture is heated to a gentle boil. To the resulting hot solution is added cautiously but rapidly, over a 1 minute period, 34.24 g. (0.20 mole) of racemic y.- 1 -naphthyl)et hylamine (Note 3) in 100 ml. of acetone. The mixture is allowed to stand at room temperature for approximately 4 hours. The (-)-amine (-)-DAG salt is filtered with suction, washed with 100 ml. of acetone, and dried in a vacuum oven at 60° to constant weight. The yield of the crude (-)-amine (-)DAG salt is 73-76 g., m.p. 205-207° (decomp.) (Note 4), [a]p —14.2° (c 1.01%, methanol). For crystallization, the crude salt and 4.2 1. of ethanol (Note 5) are placed in a 5-1. round-bottomed flask fitted with a reflux condenser and a mechanical stirrer. The mixture is stirred and heated at reflux... 

Tests at the boiling point should be conducted with minimum possible heat input, ana boiling chips should be used to avoid excessive turbulence and bubble impingement. In tests conducted below the boiling point, thermal convection generally is the only source of liquid velocity. In test solutions of high viscosities, supplemental controlled stirring with a maraetic stirrer is recommended. 

Transfer the aqueous fraction from the hexane-aqueous partition (25-30 mL) into a 50-mL round-bottom flask. Add 3-3.5 mL of concentrated HCl (such that the final acid concentration is > 1N and several boiling chips to the round-bottom flask and reflux the sample for 1 h under a water-cooled condenser. This acid reflux step will cleave any conjugated acid metabolites in the crop matrices. 

Acetone, pesticide grade or equivalent Acetonitrile, pesticide grade or equivalent n-Hexane, pesticide grade or equivalent Toluene, pesticide grade or equivalent Boiling chips Olive oil, reagent grade Sodium hydroxide (50%, w/w)... 

Weigh a finely ground representative crop sample (20 g for grain or 10 g for straw) into a cellulose extraction thimble. Assemble a Soxhlet extractor using a 500-mL round-bottom flask containing 200 mL of acetone and boiling chips. Place the extraction... 

Obtain a test tube containing an unknown liquid from your teacher and add one or two boiling chips to it. 

M sodium hydroxide (NaOH) (5 mL) red litmus paper boiling chips hot plate 250-mL beaker 10-mL graduated cylinder test tubes (8) test-tube rack stirring rod dropper beaker tongs... 

Set up a boiling-water bath by adding 150 mL of water to a 250-mL beaker. Add a few boiling chips to the water and place the beaker on the hot plate. Heat the water until it starts boiling. 

An ebullator tube through which dry nitrogen was drawn has been used for the subsequent distillation under reduced pressure, but it is far more advantageous to use about six boiling-chips. Because of its rapid reaction with water, ketene acetal must be protected from moisture of the air. 

A good barostat is necessary. Control of the reduced pressure by adjusting a leak in the system is entirely unsatisfactory, for as a result of a small increase in pressure, the liquid ceases to boil, the column drains, and the boiling-chips are rendered ineffective. The barostat used by the submitters is essentially that described by Ellis 2 in which the relay is replaced by the thermionic relay described by Waddle and Saeman.3... 

In a 1-1. round-bottomed flask are placed 36.0 g. (0.132 mole) of 2-(/>-tolylsulfonyl)dihydroisoindole,1 2 36.0 g. (0.38 mole) of phenol, 270 ml. of 48% hydrobromic acid (Note 1), and 45 ml. of propionic acid. A few boiling chips are added, and the flask is fitted with a reflux condenser in the top of which is placed a T-tube connected to a source of low-pressure nitrogen and to a mercury bubbler. The mixture is heated under reflux for 2 hours in an atmosphere of nitrogen. The deeply colored reaction mixture is cooled to room temperature, transferred to a 1-1. separatory funnel, and washed with two 200-ml. portions of ether (Note 2). The aqueous phase is then added dropwise over a 1-hour period to a vigorously stirred (Note 3) solution of 200 g. of sodium hydroxide in 600 ml. of water in a 2-1. Erlenmeyer flask immersed in an ice bath. The solution is transferred to a 3-1. separatory funnel and extracted with five 300-ml. portions of ether. The ethereal extracts are combined, dried over anhydrous potassium carbonate (Note 4), and filtered. The solvent is distilled, and the dark residual oil is transferred to a distillation... 

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