Conical vial heating

The Conical Vial As Vial Packaging Oops Tare to the Analytical Balance Electronic Analytical Balance Heating These Vials... 

Heat the reaction mixture with an aluminum block or sand bath at about 120°C (see inset in Technique 6, Figure 6.2A) and stir gently. If you are using a sand bath, the conical vial should be partially buried in the sand so that the vial is nearly at the bottom of the sand bath. After the solid has dissolved (it may dissolve, precipitate, and redissolve), heat the mixture for an additional 20 minutes to complete the reaction. 

Remove the vial from the heat and allow it to cool. When the vial has cooled to the touch, detach the air condenser and remove the spin vane with clean forceps or a magnet. Rinse the spin vane with two or three drops of warm water, allowing the water to drop into the conical vial. Place the conical vial in a small beaker and let it cool to room temperature. If crystallization has not occurred, scratch the inside of the vial with a glass stirring rod to initiate crystallization. Cool the mixture thoroughly in an ice bath for 15-20 minutes and collect the crystals by vacuum filtration on a Hirsch funnel (see Technique 8, Section 8.3, and Figure 8.5). Rinse the vial with about 0.5 mL of ice-cold water and transfer this mixture to the Hirsch funnel. 

Caffeine can be purified by sublimation (Technique 17, Section 17.5). Assemble a sublimation apparatus as shown in Figure 17.2A. Add approximately 0.5 mL of methylene chloride to the Erlenmeyer flask and transfer the solution to a clean, 5-mL, thin-walled, conical vial, using a clean and dry Pasteur pipette. Add a few more drops of methylene chloride to the flask in order to rinse the caffeine out completely. Transfer this liquid to the conical vial. Evaporate the methylene chloride from the conical vial by gentle heating in a warm water bath imder a stream of dry air or nitrogen. 

Assemble a reflux apparatus on top of your hot plate using a 20- or 25-mL round-bottom flask and a water-cooled condenser (refer to Technique 7, Figure 7.6A but use a round-bottom flask instead of the conical vial). To control vapors, place a drying tube packed with calcium chloride on top of the condenser. Use a hot plate and the aluminum block with the larger set of holes for heating. 

Assemble a distillation apparatus using your smallest round-bottom flask to distill from (Technique 14, Figure 14.10, but insert a water condenser as shown in Experiment 7A). Use a hot plate with an aluminum block to heat. Preweigh (tare) and use a 5-mL conical vial to collect the product. Immerse the collection vial in a beaker of ice to ensure condensation and to reduce odors. Distill your ester and record its boiling-point range in your notebook. 

As distillate condenses in the Hickman head, transfer the liquid from the reservoir to a preweighed 3-mL conical vial. If your Hickman head does not have a side port, it will be necessary to use a 9-inch Pasteur pipette. In the latter case, it is helpful to bend the tip of the pipette slightly by heating it in a flame. The distillate can then be removed without removing the thermometer. Be sure to cap the conical vial used for storage each time after you transfer the distillate. Continue to distill the mixture, and transfer the distillate to the vial until the temperature in the Hickman head increases above 78°C or until the temperature in the Hickman head drops several degrees below 78°C and remains at this lower temperature for 10 minutes or more. You should collect about 0.4 mL of distillate. The distillation should then be interrupted by removing the apparatus from the heat source. 

Place 0.120 g of p-aminobenzoic acid and 1.20 mL of absolute ethanol into a 3-mL conical vial. Add a magnetic spin vane and stir the mixture until the solid dissolves completely. While stirring, add 0.10 mL of concentrated sulfuric acid dropwise. A large amount of precipitate forms when you add the sulfuric acid, but this solid slowly dissolves during the reflux that follows. Attach a water-cooled condenser and heat the mixture at a gentle boil for 60-75 minufes with an aluminum block at about 105°C. Stir the mixture during this heating period. 

Place 0.18 g of acetanilide in the dry 5-mL conical vial and connect the air condenser but not the drying tube. Melt the acetanilide (mp 113°C) by heating the vial in a community sand bath or aluminum block set to about 160°C. Remove the vial from the heating source and swirl the heavy oil while holding the vial at an angle so that it is deposited uniformly on the cone-shaped bottom of the vial. Allow the conical vial to cool to room temperature and then cool it further in an ice-water bath. (Don t place the hot vial directly into the ice-water bath without prior cooling, or the vial will crack.)... 

Remove the air condenser. In a hood, transfer 0.50 mL of chlorosulfonic acid CISOjOH (MW = 116.5, d = 1.77 g/mL) to the acetanilide in the conical vial using the graduated pipette provided. Reattach the air condenser and drying tube. Allow the mixture to stand for 5 minutes and then heat the reaction vial in the... 

Prepare a hot water bath at 70°C. Place the crude p-acetamidobenzenesulfonyl chloride into the original 5-mL conical vial and add 1.1 mL of dilute ammonium hydroxide solution. Stir the mixture well with a spatula and reattach the air condenser and drying tube (gas trap) using fresh, moistened glass wool. Heat the mixture in the hot water bath for 10 minutes. Allow the conical vial to cool to the touch and place it in an ice-water bath for several minutes. Collect the p-acetamidoben-zenesulfonamide on a Hirsch funnel and rinse the vial and product with a small amount of ice water. You may stop here. 

Transfer the solid into the conical vial and add 0.53 mL of dilute hydrochloric acid solution. Attach the air condenser and heat the mixture in an aluminum block at about 130°C until all the solid has dissolved. Then heat the solution for an additional 5 minutes. Allow the mixture to cool to room temperature. If a solid (unreacted starting material) appears, heat the mixture for several minutes at 130°C. When the vial has cooled to room temperature, no further solids should appear. 

The stream of air or nitrogen must be very gentle or you will blast your solution out of the conical vial. In addition, do not overheat the sample. Do not continue the evaporation beyond the point where all the methylene chloride has evaporated. Your product is a volatile oil (i.e., liquid). If you continue to heat and evaporate, you will lose it. It is better to leave some methylene chloride than to lose your sample. 

Figure 6.2 shows a reaction mixture being heated with an aluminum block on a hot plate/stirrer unit. Also shown in Figure 6.2 is a split aluminum collar that may be used when very high temperatures are required. The collar is split to facilitate easy placement around a 5-mL conical vial. The collar helps distribute heat farther up the wall of the vial. 

Microscale Methods. A simple means of evaporating a solvent is to place a conical vial in a warm water bath or a warm sand bath. The heat from the water bath or sand bath will warm the solvent to a temperature where it can evaporate within a short time. The heat from the water bath or sand bath can be adjusted to provide the best rate of evaporation, but the liquid should not be allowed to boil vigorously. The evaporation rate can be increased by allowing a stream of dry air or nitrogen to be directed into the vial (Figure 7.17A). The moving gas stream will sweep the vapors from the vial and accelerate the evaporation. As an alternative, a vacuum can be applied above the vial to draw away solvent vapors (Figure 7.17B and 7.17C). 

A convenient water bath suitable for microscale methods can be constructed by placing the aluminum collars, which are generally used with aluminum heating blocks into a 150-mL beaker (Figure 7.17A). In some cases, it may be necessary to round off the sharp edges of the collars with a file in order to allow them to fit properly into the beaker. Held by the aluminum collars, the conical vial will stand securely in the beaker. This assembly can be filled with water and placed on a hot plate for use in the evaporation of small amounts of solvent. 

A flame is the preferred heating device for a sublimation. The burner can be held by its cool base (not the hot barrel ) and moved up and down the sides of the thin-walled outer vial or tube to "chase" any solid that has formed on the sides toward the cold tube in the center. With an aluminum block, a ring of solid often forms on the inside walls of the apparatus just where it leaves the heating block. If this happens, using the aluminum collars will improve the situation considerably. When using a conical vial, use a thin-walled conical vial instead of a regular conical vial, because the thicker glass can shatter when heated by a flame. 

Setting Up Transfer 2 mL of impure cyclohexane confaining a nonvolatile dye to a 5-mL conical vial. Equip the vial with a spinvane, the Hickman stillhead, and a condenser as shown in Figure 2.38. Place the apparatus in the heating source and have your instructor check your apparatus before you start heating the vial. 

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