Vacuum rack

Toluene, the major solvent, was stirred for three days with several portions of sulphuric acid, washed, dried, and stored over calcium hydride on a vacuum rack. The toluene was distilled out immediately prior to the reaction. The dichlorides were vacuum distilled at the time of the reaction into three fractions, and the middle fraction, about 60% of the total, used. The dichlorides were obtained from Petrach, stored in a nitrogen glove bag and handled by syringe. 

The mechanical fore pump is a heavy item which sets up considerable vibration. This vibration disrupts the menisci of mercury manometers and is otherwise undesirable. To minimize the transfer of vibrations to the vacuum line, the fore pump generally is mounted on the floor (rather than on the bench of the vacuum rack) and the connection between the fore pump and the vacuum system is made with heavy-walled vacuum tubing or flexible corrugated metal tubing. 

Since fluorine and most volatile fluorides are corrosive and highly toxic, the vacuum rack for a fluorine handling system generally is placed in a hooded enclosure (Fig. 10.20) and the fluorine tank is often enclosed in a separate enclosure which can be manipulated remotely (Fig. 10.21). 

Fig. 10.20. Hooded vacuum rack. (Reproduced from D. R. Ward, Laboratory Planning for Chem-istry and Chemical Engineering, H. F. Lewis, (ed.) (1962) by permission of the copyright holder, Van Nostrand Reinhold Co., Inc., New York.)...

As mentioned in Section 5.1.B, the transmission of vibration from the mechanical pump to a vacuum rack decreases the accuracy of manometer readings. To minimize this problem, it is generally best to mount the pump on the floor below a vacuum rack and to connect the pump to the system with a short length of heavy-walled rubber tubing, Tygon tubing, or flexible metal tubing. 

Placing items on a vacuum rack so that they fall into the rack (see Sec. 7.7.1, point 3)... 

Physical Chemistry/Instrumental Analysis The Physical Chemistry laboratory, containing 20 student stations, is used also for Instrumental Analysis and for certain courses in the Community and Technical College which administers two-year associate degree programs. The laboratory is equipped with three four-foot induced-air hoods and a five- and a six-foot walk-in hood, each with a built-in vacuum rack. Against one wall are located four peninsular work benches ventilated by a single canopy hood. 

Liquid oxygen also may cause bad fires or explosions. Care should be taken to avoid handling combustible materials in traps cooled by liquid oxygen, and combustible solvents should be kept at least several feet away. Liquid oxygen and Dry-Ice-acetone should not be used at the same time as coolants on a single vacuum rack. 

This is a list of the component parts to build the vacuum rack shown in Figure 6-20, p. 68. The vacuum tubing is either wired on or attached with hose clamps your choice. All joints are 24/40 standard taper with the exception of the thermometer, which is 10/30. 

A Nicolet NIC-7199 F.T. infrared spectrometer was used to determine the nature of the adsorbed species. For CO adsorption, the sample disc was mounted in an IR cell connected to a vacuum rack. It was evacuated at 200°C and 10 4mm Hg for 4.5 hours before 100 Torr of CO was introduced at 120°C. It was allowed to stand for 20 minutes and without outgassing further, the IR spectra were recorded. For S02 adsorption, disc made by pressing the sample powder with KBr, was mounted in the spectrometer directly. 

Low-pressure operations are common in many laboratories. Laboratories are often equipped with a house vacuum system, vacuum pumps, rotary evaporators, water aspirators, vacuum concentrators, vacuum ovens, and other apparatus that operate under reduced pressure. Some labs build elaborate vacuum racks... 

Low-pressure operations are common in many laboratories. Laboratories are often equipped with a house vacuum system, vacuum pumps, rotary evaporators, water aspirators, vacuum concentrators, vacuum ovens, and/or other apparatus that operate under reduced pressure. Some labs build elaborate vacuum racks for special purposes (see Figure 5.3.4.1). All glass vessels under vacuum should be considered potential risks for implosions with the result being flying glass shards, chemical splashes, and fires. The violence of implosions is limited due to the fact that the pressure differential between inside and outside the vessel cannot be more than 1 atmosphere (unlike pressure vessels, where the pressure differential can be much greater). 

Use of ultrafiltration (UF) membranes is becoming increasingly popular for clarification of apple juice. AH particulate matter and cloud is removed, but enzymes pass through the membrane as part of the clarified juice. Thus pasteurization before UF treatment to inactivate enzymes prevents haze formation from enzymatic activity. Retention of flavor volatiles is lower than that using a rack-and-frame press, but higher than that using rotary vacuum precoat-filtration (21). 

Example of an HACCP System. The HACCP system can be used to ensure production of a safe cooked, sHced turkey breast with gravy, which has been vacuum packaged in a flexible plastic pouch and subjected to a final heat treatment prior to distribution (37). Raw turkey breasts are trimmed, then injected with a solution containing sodium chloride and sodium phosphate. Next, the meat is placed into a tumbler. After tumbling, the meat is stuffed into a casing, placed onto racks, and moved into a cook tank, where it is cooked to an internal temperature of at least 71.1°C (160°F). After... 

Figure 7. Configuration of the materials durability test system 1, Zymark robot arm 2, Mettler balance 3, blotting station 4, capping station 5, specimen rack 6, water bath 7, block oven 8, vacuum oven 9, freezing chamber 10, NDT station 11, automated micrometer, and 12, washing station. O, specimen holder.

Connect a vacuum manifold to a vacuum source not to exceed 20 in Hg, and place a 1-L waste liquid trap between the manifold and the vacuum source. To use the manifold, remove the cover, and place a Luer hub solvent guide needle on the male Luer fitting of each flow control valve. Remove the collecting vessel rack, and replace the cover. Close all control valves on the manifold cover. 

Add the NIPA-containing isooctane sample to the reservoir, and elute the solution dropwise. Add 10 mL of isooctane to rinse the glass tube, and apply this rinse to the column before the column runs completely dry. Next, allow the column to go to dryness for at least 1 min under vacuum. Release the vacuum, and insert the collecting rack with 5-mL tubes. Elute NIPA dropwise with 5mL of isooctane-ethyl acetate (9 1, v/v) under a vacuum of about 10 inHg. After the elution is complete, apply full vacuum (approximately 20 inHg), and allow the columns to drain completely dry. Release the vacuum slowly. 

Inspect the culture tubes in the manifold to determine if there is water in the organic eluent for any sample. If a water layer is present, quantitatively transfer the organic phase into a clean culture tube using a small amount of additional solvent as necessary. Return the culture tube containing the organic extract to its proper location in the manifold rack. Remove the Cig and sodium sulfate mbes, and reinstall the silica tubes on the manifold. With the sample remaining in the culture tube, continue to apply vacuum to the manifold to remove excess solvent. When the solvent volume is < 1 mL, discontinue vacuum, and allow the sample to return to room temperature. Adjust the sample volume in the culture mbe to 1 mL with isooctane-ethyl acetate (9 1, v/v). Transfer the entire sample into an autosampler vial for GC/MS analysis. Sample extracts may be stored for up to 1 month in a refrigerator (< 10 °C) before analysis. 

In the last several years, on-line extraction systems have become a popular way to deal with the analysis of large numbers of water samples. Vacuum manifolds and computerized SPE stations were all considered to be off-line systems, i.e., the tubes had to be placed in the system rack and the sample eluate collected in a test-tube or other appropriate vessel. Then, the eluted sample had to be collected and the extract concentrated and eventually transferred to an autosampler vial for instrumental analyses. Robotics systems were designed to aid in these steps of sample preparation, but some manual sample manipulation was still required. Operation and programming of the robotic system could be cumbersome and time consuming when changing methods. 

Many silane coupling agents can be applied to substrates by volatilization in an enclosed chamber under heat or vacuum. In this approach, the substrate is placed within the chamber in a fashion to allow for vapor phase molecules to access all areas that are to be derivatized. This method is commonly used for silanizing glass slides or substrates that are difficult to suspend in a silane solution. Slides are often placed in racks within the chamber and all surfaces get modified... 

Place slides in rack into vacuum oven. 

To start the experiment all the tubes are placed in a rack at the same time and allowed to warm to room temperature finally they are placed in a thermostat at 50 °C.The tubes are removed at intervals of 1 h and immediately cooled in an acetone/dry ice bath.The samples that are still fluid are diluted with approximately 50 ml of chloroform and dropped into about 500 ml of stirred heptane or petroleum ether. For the very viscous or solid samples 1-2 g are dissolved in 50-100 ml of chloroform and the solution is added dropwise to 500-1000 ml of heptane or petroleum ether with stirring.The polymers are filtered off and dried to constant weight in vacuum at 50 C.The yield, the limiting viscosity number (measured in chloroform at 20 °C) and the degree of polymerization are plotted against reaction time. 

The coals were acetylated in the apparatus shown in Figure 2. The reaction chamber was 40 mm. in diameter and about 15 cm. long. This apparatus was connected to the same vacuum line as the sorption system. A steel rack, shaped to fit within the reaction chamber and provided with a taut nichrome wire to hold the sample buckets, is shown in Figure 3. 

Rack for vacuum line, 103 Radon, vapor pressure of, 305 Raman spectroscopy, 187 Reaction vessels ... 

The degree of automations has literally revolutionized nucleic acid purification. The core of these systems are the automated liquid-handling workstations that involve the movement of multiple probes in Cartesian axes (x, y, z) over a deck configured with lab ware, such as microplates, tube racks, solvent reservoirs, washbowls, and disposable tips. They have the ability of aspirating and dispensing solvents from a source to a destination. Devices such as vacuum manifolds, heating blocks, and shakers have also been modified to handle 96-well (or more) plates. The multiprobe liquid handlers have a variable tip spacing that allows them to expand their tip-to-... 

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