Filters, charcoal-based

These substances contain the -C=NH group and, because they are strong, unstable bases, they are kept as their more stable salts, such as the hydrochlorides. (The free base usually hydrolyses to the corresponding oxo compound and ammonia.) Like amine hydrochlorides, the salts are purified by solution in alcohol containing a few drops of hydrochloric acid. After treatment with charcoal, and filtering, dry diethyl ether (or petroleum ether if ethanol is used) is added until crystallisation sets in. The salts are dried and kept in a vacuum desiccator. 

One gram of 6,7-dihydro-5H-dibenz[c,e] azepine hydrochloride was dissolved in water, made alkaline with concentrated ammonia, and the resultant base extracted twice with benzene. The benzene layers were combined, dried with anhydrous potassium carbonate, and mixed with 0.261 g of allyl bromide at 25°-30°C. The reaction solution became turbid within a few minutes and showed a considerable crystalline deposit after standing 3 A days. The mixture was warmed VA hours on the steam bath in a loosely-stoppered flask, then cooled and filtered. The filtrate was washed twice with water and the benzene layer evaporated at diminished pressure. The liquid residue was dissolved in alcohol, shaken with charcoal and filtered. Addition to the filtrate of 0.3 gram of 85% phosphoric acid in alcohol gave a clear solution which, when seeded and rubbed, yielded 6-allyl-6,7-dihydro-5H-dlbenz[c,e] azepine phosphate, MP about 211°-215°C with decomposition. 

As, Se, Sb, Br, I and Hg) were observed on the base-treated filters using the combined techniques of PGAA, INAA and IC. The base-treated filters proved to be very efficient collectors of the acidic gas-phase species, but apparently allow some elemental and organic species to pass through as shown by studies with activated charcoal-impregnated filters. 

It is from the morphine that diamorphine is prepared. This is achieved by mixing the morphine with acetic anhydride and heating to approximately 85°C for about 5 h, or until all of the morphine has dissolved. Water is added to the mixture, followed by activated charcoal which absorbs any impurities. The mixture is repeatedly extracted with charcoal and filtered until the solution is clear. Sodium carbonate, dissolved in hot water, is slowly added to the mixture and the heroin base precipitates as a solid, which is then filtered and dried. The decolourizing and filtering process can be repeated a number of times until the desired colour/purity is achieved. From each kilogram of morphine, up to 700 g of diamorphine can be produced. 

Thirteen and fifteen-hundredths grams (0.069 mol) of copper (I) iodide is dissolved with stirring in a solution of 130 g. of potassium iodide in 100 ml. of water. If the resulting solution is not colorless, it is shaken for several minutes with 1 g. of decolorizing charcoal and filtered, t The colorless solution is next shaken vigorously for five minutes with 12.5 ml. (10.15 g. = 0.050 mol)t of freshly distilled tri-n-butylphosphine (density = 0.812 g./ml.) in a 250-ml. g ass-stoppered Erlenmeyer flask until the initially formed greasy mass becomes crystalline. The white crystals are collected on a 6-cm. Buchner funnel and washed free of any occluded copper(I) iodide with several 10-ml. portions of saturated potassium iodide solution. They are then similarly washed with distilled water and 95% ethanol, and air-dried. The yield of crude product is 19.0 g. (96.7% based on tri-n-butylphosphine). 

To overcome the problems of gas-sensor failure due to poisoning of the elements, several manufacturers have used specific filter devices in front of the elements. For example, filters to remove alkyl lead compounds from petrol vapour have included paradichlorobenzene and fibrous silica (3). However, the most commonly used material is based on active charcoal. Such filters (4) effectively absorb many common poisons and inhibitors including silicones, alkyl lead compounds and halogen-containing species. However, along with the absorption of potentially harmful vapours, carbon filters will also absorb hydrocarbons. This effect in practice limits the use of such filters to detectors for C3 and lower hydrocarbons. They cannot be employed in general flammable gas detectors. 

Upon completion, the reaction solution was treated with charcoal and filtered through a plug of celite. The celite plug was rinsed with ethyl acetate and the combined organic layers were concentrated under reduced pressure, followed by purification of the crude product thus obtained. Pure sUyl ethers 3 were characterized based on analytical and spectral studies. 

Amino-4 -methylthiazole slowly decomposes on storage to a red viscous mass. It can be stored as the nitrate, which is readily deposited as pink crystals when dilute nitric acid is added to a cold ethanolic solution of the thiazole. The nitrate can be recrystallised from ethanol, although a faint pink colour persists. Alternatively, water can be added dropwise to a boiling suspension of the nitrate in acetone until the solution is just clear charcoal is now added and the solution, when boiled for a short time, filtered and cooled, deposits the colourless crystalline nitrate, m.p. 192-194° (immersed at 185°). The thiazole can be regenerated by decomposing the nitrate with aqueous sodium hydroxide, and extracting the free base with ether as before. 

Purified by recrystn from isopropanol-di-idopropyl ether (charcoal) and recrystallised twice more. The free base, b 55-56°/l 1 mm, 60-63°/23mm and 90°/56mm, is relatively unstable and should be converted to the hydrochloride immediately, by dissolving in iso-propanol and bubbling dry HCI through the soln at 0°, and filtering off the hydrochloride and recrystallising it. The picrate has m 107.3-107.8° (from EtOH), [Cason JOC 24 247 1959 JACS 70 3098 7945]. 

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