Soda lime traps

To prepare the standard pH buffer solutions recommended by the National Bureau of Standards (U.S.), the indicated weights of the pure materials in Table 8.15 should be dissolved in water of specific conductivity not greater than 5 micromhos. The tartrate, phthalate, and phosphates can be dried for 2 h at 100°C before use. Potassium tetroxalate and calcium hydroxide need not be dried. Fresh-looking crystals of borax should be used. Before use, excess solid potassium hydrogen tartrate and calcium hydroxide must be removed. Buffer solutions pH 6 or above should be stored in plastic containers and should be protected from carbon doxide with soda-lime traps. The solutions should be replaced within 2 to 3 weeks, or sooner if formation of mold is noticed. A crystal of thymol may be added as a preservative. 

After leaving the reactant zone, the product stream entered a 0.5 in diameter PTFE tube cooled either by salt-ice bath or acetone-carbon dioxide slush bath [15,16]. The gas mixture was scrubbed in a soda-lime tower. Hydrogen fluoride was trapped by adding sodium fluoride to the reaction mixture or simply adding water. Then, the product solution was extracted with dichloromethane, washed with aqueous NaHCOj solution and dried over MgS04. Thereafter, the solvent was evaporated, leaving the crude product. 

The methylamine generator consists of a i-l. flask fitted with a dropping funnel and outlet tube, which in turn is connected to a 25-cm. drying tower containing soda-lime, followed by a i-l. safety trap (Note 1). In the flask is placed 200 g. of technical sodium hydroxide flakes, and 263 g. of a 33-35 per cent solution of methylamine in water (Note 2) is dropped in slowly at such a rate that an even current of gas is evolved. When the addition has been completed and the gas bubbles very slowly into the... 

The scission reaction was carried out with a fixed addition of 1.50g of the dry resin, 10 mg of ferrous sulfate heptahydrate and 50 ml of 3% w/v hydrogen peroxide in a round Pyrex flask. The evolved carbon dioxide was vented to the atmosphere through serial traps containing sulfuric acid followed by a soda lime sorption tube. The magnetically stirred reaction flask was submerged in an oil bath heated with an immersed electrical coil and a magnetic stirrer positioned below the bath. The temperature was maintained at 50 +/- 1 C. After varied times 1.0 ml samples of liquid were withdrawn. There were fewer than six withdrawals in a given reaction sequence. 

The pentafluoride products are easily recovered by vacuum evaporation of the HF, SiF4, and excess MF6. These volatile substances are passed through soda-lime and charcoal traps to scrub the HF and MF6. For each hexafluoride a... 

In spite of the Dry Ice cooled trap and soda-lime tower, some low-boiling material (as evidenced by the odor) often reaches the pump. It is therefore recommended that an old pump be used and the oil changed immediately after the experiment. 

A 1-1. three-necked flask is equipped with a mercury-sealed stirrer, an inlet tube, and a reflux condenser which is connected through a soda-lime tube to a gas-absorption trap.1 The apparatus is dried in an oven and assembled rapidly to exclude moisture it is advisable to set up the apparatus in a hood to vent ammonia which may escape by accident. The flask is cooled in a Dry Ice-trichloroethylene bath, and 200 ml. of anhydrous (refrigeration grade) ammonia is introduced through the inlet tube from an ammonia cylinder which is either inverted or equipped with a siphon tube. Just before the apparatus is assembled, 8.1 g. (0.35 gram atom) of sodium is cut, weighed, and kept under kerosene in a small beaker. The Dry Ice bath is removed, the inlet tube is replaced by a rubber stopper, and a crystal of hydrated ferric nitrate (about 0.2 g.) is added. A small (about 5-mm.) cube of the sodium is cut, blotted rapidly with filter paper, and added quickly to the liquid ammonia. The solution is stirred until the blue color disappears, after which the remainder of the sodium is added in narrow, thin strips about as rapidly as... 

The equipment consisted of an electrically heated vertical nickel tube of 2-cm diameter and 45-cm length. This reaction lube had an intermediate partition permeable to gases. A1F3 (30 g, 0.36 mol) was put in the upper half of the tube. The lower half remained empty, and was used to preheat the gas. Gases emerging from the upper end of the tube were cooled to 30 C to cause condensation of the CC14. and then passed through a soda lime tower and finally condensed in a trap cooled with dry ice/acetone. 

A vacuum pump should be scrupulously protected from corrosive vapors and materials which will be absorbed in the pump oil or condense in the pump. For most laboratory operations a low-temperature trap is employed for this purpose, and in the case of fluorine handling systems a soda-lime trap is used to neutralize the corrosive gases. Despite these precautions, the pump oil does eventually break down and become contaminated. Regular oil changes should be scheduled for a pump at about yearly intervals for a well-protected pump and more often for pumps which are not well protected. 

Fig. 10.15, Metal vacuum systems for handling fluorine and reactive fluorides, (a) A design used extensively at Argonne National Laboratory constructed of nickel tubing and Monel valves (A) with cone joints (illustrated in Fig. 10.13) (D) nickel U-trap (E) Monel Bourden gauge (0-1000 ion) (F) 130-mL nickel reactor can (Fig. 10.17) (G) 1,500-mL nickel storage or measuring can, (H) 85-mL nickel can, (i) brass valve (K) soda-lime trap to protect vacuum pumps (L) Monel valve. (Reproduced by permission of the copyright holder, The University of Chicago Press, from Nobel Gas Compounds, H. H. Hyman (Ed.), Chicago, 1963.)...

Small quantities of ammonia may if necessary be prepared with the aid of the apparatus depicted in Fig. 4.2. Concentrated ammonia solution (d 0.88) is gently heated in the flask surmounted by an efficient reflux condenser. The gas is further dried by passage through a column which is loosely packed with soda lime or calcium oxide lumps, and is then passed through a Drechsel bottle to act as a safety trap. 

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