Infrared drying

Attempted Reaction of (Me4N) [Cr(HO-A)2] with Acetic Anhydride in Acetonitrile. Seven-tenths gram (0.00147 mole) of (Me4N) [Cr(HO-A)..] was mixed with 250 ml. of acetonitrile and 1 ml. (0.009 mole) of acetic anhydride. After refluxing for 1 hour a small quantitv of starting material was recovered by filtration and the solution was concentrated to 15 ml. The solid which crystallized was isolated by filtration, washed with acetonitrile and ether, and air-dried. Infrared examination proved this compound to be starting material. 

Thus, oil and grease measured by both the methods are susceptible to show variation. While gravimetric method measures all substances that are solvent extractables and nonvolatile under the conditions of distillation and drying, infrared method measures the absorbance of carbon-hydrogen bond of substances extracted. Also, compounds boiling below the distillation temperature of the extraction solvent may occur in the extract and contribute to oil and grease measured by the infrared method. 

One gram samples of the copolymers were suspended in a mixture containing methanol (50 ml), sodium methoxide (10 ml of a 20% solution in methanol), benzene (5 ml) and water (1-5 ml). The mixtures were refluxed with stirring for 6-24 hrs, until the copolymers dissolved. The reaction mixtures were then poured slowly Into a large excess of acidified watei with rapid stirring, to precipitate the products. These were washed with water and dried. Infrared spectra of the copolymers were examined to ensure the complete decomposition of the anhydride groups. 

Moisture content. Oven drying. Infrared drying, Karl Fischer method. Near Infrared. 

Having removed the larger droplets, it may remain only to encourage natural evaporation of solvent from the remaining small droplets by use of a desolvation chamber. In this chamber, the droplets are heated to temperatures up to about 150 C, often through use of infrared heaters. The extra heat causes rapid desolvation of the droplets, which frequently dry out completely to leave the analyte as small particles that are swept by the argon flow into the flame. 

In the far-infrared region strong absorption by the water vapour normally present in air necessitates either continuously flushing the whole optical line with dry nitrogen or, preferably, evacuation. 

Infrared and Microwave Inks. These ate inks which have been formulated to absorb these radiant energies. The energy causes the inks to heat and dry through the partial evaporation of solvent. Absorption of the ink into a porous substrate can also be part of the overall drying mechanism with these inks. They have not found wide commercial success due to the variabiHty of the it absorption with ink color and the energy inefficiency of microwave systems in drying nonwater-based inks. 

Special drying methods, such as superheated steam, solvent, vacuum, infrared radiation, and high frequency dielectric and microwave heating, are occasionally employed when accelerated drying is desired and the species being dried can withstand severe conditions without damage. None of these methods is of significant commercial importance. 

Water Transport. Two methods of measuring water-vapor transmission rates (WVTR) ate commonly used. The newer method uses a Permatran-W (Modem Controls, Inc.). In this method a film sample is clamped over a saturated salt solution, which generates the desired humidity. Dry air sweeps past the other side of the film and past an infrared detector, which measures the water concentration in the gas. For a caUbrated flow rate of air, the rate of water addition can be calculated from the observed concentration in the sweep gas. From the steady-state rate, the WVTR can be calculated. In principle, the diffusion coefficient could be deterrnined by the method outlined in the previous section. However, only the steady-state region of the response is serviceable. Many different salt solutions can be used to make measurements at selected humidity differences however, in practice,... 

The individuality of received complexes was proved by X-ray phase analysis (DRON-3.0). Preparative investigation of complexes was made. Infrared spectrums of complexes were made (Uh-20, KBr). It was proved that in the III complex hydroxylamine is coordinated with Fe (II) by oxygen in the form of n-oxyde-o-NH -and in IV - by nitrogen in the form of NH OH. The composition of IV hasn t been proved in dry ruminant because of surplus age of reagent. Tire composition of III responds to formula of [Fe(NH,OH) Cl,]. 

Monitor temperature of material being dried by infrared, resistance temperature device, (RTD) etc. 

No attempt should be made to purify perchlorates, except for ammonium, alkali metal and alkaline earth salts which, in water or aqueous alcoholic solutions are insensitive to heat or shock. Note that perchlorates react relatively slowly in aqueous organic solvents, but as the water is removed there is an increased possibility of an explosion. Perchlorates, often used in non-aqueous solvents, are explosive in the presence of even small amounts of organic compounds when heated. Hence stringent care should be taken when purifying perchlorates, and direct flame and infrared lamps should be avoided. Tetra-alkylammonium perchlorates should be dried below 50° under vacuum (and protection). Only very small amounts of such materials should be prepared, and stored, at any one time. 

Beyond the complexities of the dispersive element, the equipment requirements of infrared instrumentation are quite simple. The optical path is normally under a purge of dry nitrogen at atmospheric pressure thus, no complicated vacuum pumps, chambers, or seals are needed. The infrared light source can be cooled by water. No high-voltage connections are required. A variety of detectors are avail-... 

Fig. 4.17. Dried VPD-droplet (left) worst case, the VPD solution exploded under fast drying using an infrared lamp, droplet size of a few mm (right) best case (WSPS),VPD solution dried under controlled conditions using vacuum and carrier gas (L. Fabry, S. Pahike, L. Kotz, Fresenius J. Anal.

An existing eontrol arrangement uses a PID eontroller to eontrol the temperature of the proeess air (measured by thermoeouples) and the dry elay moisture eontent measured by samples taken by the works laboratory. If this is out of speeifieation, then the proeess air temperature is raised or lowered. The dry elay moisture eontent ean be measured by an infrared absorption analyser, but on its own, this is eonsid-ered to be too noisy and unreliable. 

Estrone methyl ether (100 g, 0.35 mole) is mixed with 100 ml of absolute ethanol, 100 ml of benzene and 200 ml of triethyl orthoformate. Concentrated sulfuric acid (1.55 ml) is added and the mixture is stirred at room temperature for 2 hr. The mixture is then made alkaline by the addition of excess tetra-methylguanidine (ca. 4 ml) and the organic solvents are removed. The residue is dissolved in heptane and the solution is filtered through Celite to prevent emulsions in the following extraction. The solution is then washed threetimes with 500 ml of 10 % sodium hydroxide solution in methanol to remove excess triethyl orthoformate, which would interfere with the Birch reduction solvent system. The heptane solution is dried over sodium sulfate and the solvent is removed. The residue is satisfactory for the Birch reduction step. Infrared analysis shows that the material contains 1.3-1.5% of estrone methyl ether. The pure ketal may be obtained by crystallization from anhydrous ethanol, mp 99-100°. Acidification of the methanolic sodium hydroxide washes affords 10-12 g of recovered estrone methyl ether. 

In a 250 ml Erlenmeyer flask covered with aluminum foil, 14.3 g (0.0381 mole) of 17a-acetoxy-3j5-hydroxypregn-5-en-20-one is mixed with 50 ml of tetra-hydrofuran, 7 ml ca. 0.076 mole) of dihydropyran, and 0.15 g of p-toluene-sulfonic acid monohydrate. The mixture is warmed to 40 + 5° where upon the steroid dissolves rapidly. The mixture is kept for 45 min and 1 ml of tetra-methylguanidine is added to neutralize the catalyst. Water (100 ml) is added and the organic solvent is removed using a rotary vacuum evaporator. The solid is taken up in ether, the solution is washed with water and saturated salt solution, dried over sodium sulfate, and then treated with Darco and filtered. Removal of the solvent followed by drying at 0.2 mm for 1 hr affords 18.4 g (theory is 17.5 g) of solid having an odor of dihydropyran. The infrared spectrum contains no hydroxyl bands and the crude material is not further purified. This compound has not been described in the literature. 

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