Glass sleeve

A common operation in practical organic chemistry is for stirring, refluxing, and addition of a liquid from a dropping funnel to be carri on simultaneously. The most convenient apparatus for this purpose is a three-necked flask, fitted as in Fig. 11, 7, 11, a. If a three-necked flask is not available, the three-way adapter inserted into a bolt-head flask (Fig. 77, 7, 11, 6) may be used. A further simplification, suitable for elementary students, is to employ a two-way adapter as in Fig. 77, 7, 11, c the stirrer passes through a closely-fitting glass sleeve which is extended... 

Although a glass sleeve for the stirrer is fairly satisfactory, it is better to use a seal of the conventional type (Org. Syn. Coll. Vol. 1,31, Fig. 2a) filled with water rather than mercury. 

The prepared flattened section is inserted into a glass sleeve shaped to fit, and the glass is fused on to the metal, pinched with tweezers and strongly heated. The seal must be carefully annealed. With soft glasses the copper glass interface is coloured red, while with harder glasses the colour is more of a yellowish red. 

Catalytic hydrogenations were performed generally under 500 psig of H2 at 25 or 80 °C in H20 or 1 1 H20/EtOH media, typically with a total volume of 5 mL the substrates were essentially insoluble in water, but dissolved readily in the mixed medium. H20/NaOH and H20/buffer imply, respectively, use of a 1 1 mixture of the Ru catalyst solution with either 5.0 mM aq. NaOH or a pH 10 buffer solution (made from 44 mM NaHC03 and 17.6 mM NaOH (19)). Catalyst concentrations were either 4.1 or 2.05 mM, while the substrate (S) concentration was always 100 mM. The reaction mixture was placed into a glass sleeve equipped with a magnetic stir bar in air. The sleeve was placed in a steel... 

A 5-1. three-necked flask is fitted with a stirrer (which may be of the glass-sleeve type lubricated with paraffin oil, or a mercury-sealed Hirshberg stirrer), an efficient condenser fitted with a calcium chloride drying tube, and a gas inlet tube. The gas inlet tube is connected with polyethylene tubing through a small bubble counter containing a nonvolatile hydrocarbon to the cylinder of boron trichloride. 

The electrode consists of two concentric glass tubes, the inner one of which contains mercury in contact with a paste of mercury, mercury(I) chloride (calomel), and potassium chloride. This is in contact with a solution of potassium chloride in the outer tube which itself makes contact with the sample solution via a porous frit, fibre or ground-glass sleeve (Figure 6.1). 

Split Simple Starting point for method development Use with isothermal and temperature programmed GC Fast very sharp peaks Choice of glass sleeve not trivial Limits detection concentration to ppm Most sample wasted through split vent Loss of low-volatility, labile analytes... 

Figure 3.1 Schematic representation of a non-sophisticated cell for equilibrium electrochemical measurements. The example shown is a Daniell cell comprising Cu +,Cu and Zn, Zn half cells. The need for the glass sleeves is discussed in Chapter 9.

To appreciate that it is advisable to immerse the whole electrode in solution, rather than just its tip, because of surface tension effects, and to learn that encasing the metal of the electrode within a glass sleeve is the best way to avoid ambiguity in this respect. 

It was also shown that silver-silver chloride electrodes are easily made by anodizing a silver wire (all but the tip encased in a glass sleeve) immersed in a chloride-containing solution. A few elementary tests of the quality of such a Ag 1 AgCl electrode were also described. 

We obtained the best results with the Carbopack B-DA/4% Carbowax 20M, 80-120 mesh Supelco column, 2000 x 2 mm. It was initially conditioned for 21 h at 245°C, but the normal running temperature is 175°C. The injector/detector temperature is 200°C and a flame ionization detector is used. A glass sleeve is fitted to the injector and the glass wool plug removed from the column inlet. The carrier gas is nitrogen with a flowrate of 40 ml min at 310 kN m. The sample solution (9 ml) is mixed with 1 ml of pivalic acid solution (1.5% m/v) as internal standard. Then 1 ml of this solution is mixed with 1 ml 0.3 M oxalic acid solution and 3 ml deionized water before injecting 1 pi into the septum. 

Fig. 3.22. Arrangement of the leads inside the conductivity cell shown in Fig. 3.23. Cu copper wire, Sd soldered joint, W tungsten wire, SW spot-weld, Pt platinum wire, S soda glass sleeve, SS silver-soldered joint, P borosilicate glass arm fused to the cell, PtP platinum plate electrodes held together with lead glass beads L.

Direct vaporisation injection. For packed columns and megabore columns of 530 pm, which typically use a flow rate of 10 ml/min, direct vaporisation is a simple way to introduce the sample. All models of this type of injector are a variation of a simple assembly which uses a metal tube with a glass sleeve or insert. The glass insert is swept by the carrier gas and heated to the vaporisation temperature for the analytes undergoing chromatography. One end of the injector contains a septum made of silicone rubber that allows the syringe needle to pass through it into the system. The other end of the injector is connected to the head of the column (Fig. 2.4). The entire sample is injected into the column in a few seconds. 

In quantitative analyses, the use of the split/splitless injector can cause concentration errors because of the discrimination of compounds that are of different volatility. The composition of the fraction that enters the column can be very different from that which is eliminated. This mode of operation should be excluded when an external standard is used (cf. 4.9). However, this problem can be corrected, up to a point, by use of a proper glass sleeve inserted into the injector. 

The glass sleeve A can be raised or lowered in the cone. a,so4 and the pressure in the combustion tube altered thereby. With a head of 5—7 cms. of HgSO and proper adjustment of the packing plug in the combustion tube, air ought to pass through the apparatus at the rate of 3—4 c.cs. per... 

The lubricant for the ground-glass sleeve of the stirrer may be silicone oil or mineral oil however, Teflon oil is preferred. Glycerin should not be used. 

The reactions are carried out in a 1-1. round-bottomed flask (Fig. 18) sealed to a dropping funnel and a gas inlet tube A.% The neck of the flask is closed with a rubber stopper bearing a gas inlet C and an outlet tube B (i.d. at least 5 mm.). The latter is connected to a filter assembly which consists of a 25-mm.-i.d. filter tube with a fritted-glass filter plate D (porosity B). The distance from the filter plate to the top of the tube should be at least 35 cm. As shown in Fig. 18, tubes B and C extend into the flask through glass sleeves and are attached to these sleeves by means of rubber tubing so that B and C may be raised or lowered. 

The silver-silver chloride electrode consists of a mounted platinum screen that has been heavily plated with silver from a cyanide bath, rinsed, aged in an acidified silver nitrate solution, rinsed, coated with a thin layer of silver chloride by anodizing in a dilute HCl solution (preferably no more than a few days before use), and kept in dilute HCl pending use. This is mounted in a glass sleeve with a small hole in the bottom to admit the cell... 

To anhyd benzene (300 mL) was added 6-chloro-2-iodo-9-) -(2,3,5-tri-0-acetyl-)S-D-ribofuranosyl)purine (0.284 g, 0.527 mmol). The solution was transferred to a Hanovia photochemical reactor, purged with Nj, and photolyzed for 16.5 h by employing a 450-W Hg UV source with a Vycor glass sleeve filter. The solvent was then removed (40 °C, reduced pressure) and the residue chromatographed (silica gel plates, EtOAc/hex-ane, 7 3), the band at = 0.63 afforded a light yellow low-melting solid yield 0.207 g (80%). 

Cylindrical pellets arc made from the USDA samples expressly to remove consideration of native biomass morphology. We have shown biomass morphology alters pyrolysis slate (Chan et al 1988). If necessary, the sample is ground further in a Wile mill and reformed in a cylindrical die to the native density, approximately 1.0 g/cm, Three holes are made radially in the pellet with a small drill and thermocouples are inserted at distances of 2, 4 and 6 mm from the heated lace of the pellet. The pellet is then fitted tightly in a glass sleeve joined to the reactor via an O-ring seal. Real time intraparticle temperatures are displayed on the computer monitor and digitized at a rate of 1 Hz. The moisture content of the pellet is constant al a 5.0 wt %, equilibrium moisture except for some data in Chan et al (1988). 

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