Side-arm method

Side arm method. Steady state static system... 

Fig. 15. Schematic representation of the side arm method of Smith [54] for determining recombination coefficients.

The heat released to a catalytic surface on which atom recombination occurs has been used for many years as the basis of thermocouple and calorimeter probes for the detection and measurement of atom concentrations. The method is nonspecific in that all atoms or radicals in the system can contribute to heat release. Its use has thus been confined to relatively simple systems in which few active species are present. In particular, the rate of heterogeneous recombination of H and O atoms has been studied using a thermocouple gauge and Smith s side-arm method. 

The pure quinaldine can now be isolated by either of the following methods, (a) Transfer the acetylated mixture to a Claisen flask (preferably having a short fractionating column below the side-arm) and distil the mixture slowly at water-pump pressure by heating the flask in an oil or silicone bath. The first fraction, of b.p. ca. 50715 mm., contains acetic acid and... 

If a small Beckmann thermometer, similar to that used in the Sucharda-Bobranski method (p. 442) is available, the above method can be readily modified by replacing the tube T (Fig. 79) by an ordinary small boiling-tube without the side-arm A. The thermometer B and the stirrer S are fitted as in Fig. 79. The volume of solvent (usually ca 5 ml.) must of course cover the bulb of the thermometer. 

Method 1. Use the apparatus depicted iu Fig. Ill, 56, 1, but omit the thermometer also attach a cotton wool (or calcium chloride) tube to the side arm of the filter fiask receiver in order to prevent the entrance of moisture into the apparatus. Mount the reaction fiask in a water bath e.g., a large beaker or other convenient vessel). It is important that all the apparatus be perfectly dry, since both phosphorus trichloride and acetyl chloride are decomposed by water. The set-up should be assembled in the fume eupboard. 

The crude liquid acid (about 300 g.) is cooled with running water and 15 cc. of concentrated sulfuric acid is added the clear yellow oil becomes cloudy. The acid is esterified by the method described in Org. Syn. 3, 54, with the following changes all three flasks, the alcohol flask, the trap, and the esterification flask are i-l. round-bottom wide-neck flasks. The alcohol flask and the trap are set on adjacent steam baths. The esterification flask is placed in an oil bath which is heated by a free flame. A safety tube leads from the alcohol flask and dips under 7.5 cm. of mercury contained in a side-arm tube. 

Fig. 6. Side-arm tube of the apparatus for the determination of the coefficients of the heterogeneous recombination, y, of atomic gases previously dissociated in the rf discharge zone. The heterogeneous recombination proceeds on the inner glass walls of the horizontal side-arm tube and on a catalytically active cylindric sample of the metal investigated (Smith-Linnett method).

The jet is sealed into the jacket with an ordinary internal seal (Method 1, p. 73), and the side arm is attached at the shoulder the jet must be perfectly central (Figure 53, IIT). 

A second method of construction is to form the first ring seal and side arm from the prepared parts shown in Figure 56,1. The inner tube is slightly flared at the far end from the ring seal. In the second stage of the construction the outer tube is drawn off so that the shoulder is very close to this flared end (Figure 56, II). The shoulder... 

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