Plastic stoppers

Procedure. Treat 10 mg of sucrose with 1 mL of anhydrous pyridine, 0.2 mL of HMDS, and 0.1 mL of TMCS in the plastic-stoppered vial (or similar container). Shake the mixture vigorously for about 30 seconds and allow it to stand for 10 min at room temperature if the carbohydrate appears to remain insoluble... 

The construction of two typical infrared cells is shown in Fig. 19.6. Such cells have to be carefully filled by using a syringe or Pasteur pipette to ensure that no air is trapped inside. To prevent evaporation the ports should be plugged with small plastic stoppers once the cell has been filled with the solution. 

FIGURE 4.6 A tapered ground glass stopper may be used with a flask with a ground glass opening. A tapered plastic stopper may also be used. 

Tubes are sealed with plastic stoppers and incubated at 39°C for 8 h in a heating block. The reaction is stopped by placing the tubes on ice. The samples can be immediately analysed by HPLC or kept at -20°C until analysis. 

Two brands of sparkling wine are marketed, and the types include white, pink, burgundy, and Cold Duck. Bottle sizes are 187 mL, 375 mL, 750 mL, and 1.5 L and are made at an adjoining glass factory. The 750-mL bottles weigh 0.26 oz. Plastic stoppers are used as closures for the 375-mL and 750-mL size bottles. See Figure 13. 

The most common upper-neck shape (finish) for sparkling wine bottles is one that accommodates a crown cap, a natural cork, and/or a plastic stopper. The internal diameter (i.d.) of the neck is extremely important, as the tightness of the fit between the bottle wall and the cork or plastic stopper is critical. Glass manufacturers, therefore, have tight specifications for the internal diameter of the neck. The designed headspace is approximately 4 percent of the total volume of the bottle below the bottom of the cork. This allows for liquid expansion without excessive increase in pressure. 

For the purpose of automatic filling and emptying the cuvette, several modifications can be made in the plastic stopper. For example, in Figure... 

The simplest type of extraction vessel is a separatory funnel several types are shown in Figure 9-4. They are usually either cylindrical (A), globe shaped (B), or pear shaped (C, D). They may have either glass or plastic stoppers and stopcocks and may have a standard taper joint at the bottom. They usually are made of borosilicate glass, but the wine red colored "low actinic" also can be obtained for use with light-sensitive compounds. 

Glass jar or bottle with glass or plastic stopper for carrying acid, c. Freparatim. 

Chem. Descrip. LDPE CAS 9002-88-4 EINECS/ELINCS 200-815-3 Uses PE for film extrusion (food pkg., commodity pkg., industrial pkg. and film), extmsion coating (hard pkg. for liqs., soft pouches, photographic paper, paper pkg. and sacks), inj. and blow molding (plastic stoppers, medical components), compounding for cables, tube extni-sion, pipe coating... 

Picric acid. This acid and related nitro compounds, e.g. styphnic acid, are explosive and shorrld not be kept dry. The acid is generally stored wet by covering the crystMs with water. Solutions in ethanol arrd benzene are used occasionally. They shorrld be stored in the cold (to minimise evaporation), and a rabber or plastic stopper (not a ground glass stopper) should be used. Note that picric acid and picrates stain skin protein with a yellow colour that is not readily washed off. This can be avoided by wearing rabber gloves. 

Filling Separatory Funnels. The stopcock should be closed and a clean beaker placed under the funnel before any liquids are added to the funnel in case the stopcock leaks or is not completely closed. A separatory funnel should never be more than three-quarters full. The upper opening of the funnel is then stoppered with a ground-glass, plastic, or rubber stopper most separatory funnels are now fitted with a ground-glass or plastic stopper. 

Centrifuge the content of the tubes for 5-10 min (Note h) having replaced the glass stoppers on the centrifuge tubes with plastic stoppers to prevent breakage during centrifugation. 

Cavity cells fit the sealed-cell definition, but are made according to a different principle. These cells consist of a single block of window material into which a rectangular cavity has been bored. They can be filled, cleaned, and flushed with a hypodermic needle and syringe. A conical hole in the block above the cavity will accept a plastic stopper The stopper prevents evaporation of the sample. If these cells are damaged or broken, they cannot be repaired. 

---