Time after desiccation

To determine under controlled conditions how effects of shoot cover crop residues taken from the field change with time after desiccation and how such effects are modified by temperature, moisture, and nitrogen levels. 

Cover Crop Residues Taken from the Field Change with Time After Desiccation and How Such Effects Are Modified by Temperature, Moisture, and Nitrogen Levels (Section 3.4.5)... 

Add 10 g. of the crude hydrazobenzene to 80 ml. of ethanol contained in a flask fitted with a reflux water-condenser. Heat the mixture on a water-bath until the ethanol bolls, and then add 10 g. of zinc dust and 30 ml. of 30% aqueous sodium hydroxide solution. Remove the flask from the water-bath and shake the contents vigorously from time to time. After about 10 minutes, replace the flask on the water-bath and boil the contents for 3-5 minutes. Filter the mixture at the pump, transfer the filtrate to a beaker and cool in ice-water with stirring. The hydrazobenzene separates as colourless crystals, which are filtered off at the pump and drained. A portion when dried in a desiccator has m.p. 124°. 

Figure 25-33. The water vapor concentration in a stream of hydrogen (7.5 L/h) with an initial HjO Hj ratio of 0.029 after desiccation with the equal mass (4 g) of different substances versus time The water vapor ratio in the dried gas was calculated from the potential differences measured at 550 °C between the inner electrodes of two parallel galvanic solid-electrolyte tube cells, one of which contained a stream of hydrogen saturated with water vapor at 15 °C [90].

Commercial, crystallized SnClg 2 HgO (226 g.) is added with stirring to 204 g. of acetic anhydride (99-100%) in a 600-ml. beaker. The dehydration starts instantaneously with Intense heat evolution and the (CH3CO)gO occasionally reaches boiling (use a hood) the anhydrous salt separates out in fine, white crystals at the same time. After 1.5 hours of this treatment it is filtered to dryness under suction, washed with two 15-ml. portions of dry ether, and dried in a vacuum desiccator. The yield is quantitative (189 g.). The product can be further purified by high vacuum distillation in a Vycor container or, preferably, in one of quartz. 

Con 2 Phenolic acids were rapidly lost from surface wheat cover crop residues after desiccation and thus release of phenolic acids to soils was limited in time, roughly 3 or 4 weeks, for the cover crop residues tested. The rate of and time for depletion of phenolic acids from surface residues was determined largely by the extent and frequency of rainfall/irrigation events. For most of the growing season phenolic acids in soil extracts were, in fact, largely derived from older decomposed... 

Place an intimate mixture of 125 g. of powdered, anhydrous zinc chloride and 26-5 g. of acetophenonephenylhydrazone in a tall 500 ml. beaker in an oil bath at 170°. Stir the mixture vigorously by hand. After 3-4 minutes the mass becomes hquid and evolution of white fumes commences. Remove the beaker from the bath and stir the mixture for 5 minutes. Then stir in 100 g. of clean, white sand in order to prevent solidification to a hard mass. Digest the mixture for 12-16 hours on a water bath with 400 ml. of water and 12 ml. of concentrated hydrochloric acid in order to dissolve the zinc chloride. Filter off the sand and the crude 2-phenylindole, and boil the solids with 300 ml. of rectified spirit. Treat the hot mixture with a little decolourising carbon and filter through a pre-heated Buchner funnel wash the residue with 40 ml. of hot rectified spirit. Cool the combined filtrates to room temperature, filter off the 2-phenylindole and wash it three times with 10 ml. portions of cold alcohol. Dry in a vacuum desiccator over anhydrous calcium chloride. The yield of pure 2-phenylindole, m.p. 188-189°, is 16 g. 

The required desiccant weight is a function of several factors the water removal requirements (mass/time), the cycle time, the equiUbrium loading of water on the desiccant at the feed conditions, the residual water loading on the desiccant after regeneration, and the size of the mass-transfer zone of the desiccant bed. These factors, in turn, depend on the flow rate, temperature, pressure, and water content of both the fluid being dried and the regeneration fluid (see Adsorption, gas separation). 

B. Palladium on carhon catalyst (5% Pd). A suspension of 93 g. of nitric acid-washed Darco G-60 (Note 10) in 1.21. of water contained in a 4-1. beaker (Notes 3 and 4) is heated to 80°. To this is added a solution of 8.2 g. (0.046 mole) of palladium chloride in 20 ml. (0.24 mole) of concentrated hydrochloric acid and 50 ml. of water (Note 2). Eight milliliters (0.1 mole) of 37% formaldehyde solution is added. The suspension is made slightly alkaline to litmus with 30% sodium hydroxide solution, constant stirring being maintained. The suspension is stirred 5 minutes longer. The catalyst is collected on a filter and washed ten times with 250-ml. portions of water. After removal of as much water as possible by filtration, the filter cake is dried (Note 11), first in air at room temperature, and then over potassium hydroxide in a desiccator. The dry catalyst (93-98 g.) is stored in a tightly closed bottle. 

Di-(2-ethylhexyl)phthalate ( di-iso-octyl phthalate) [117-81-7] M 390.6, b 384°, 256-257°/lmni, d 0.9803, n 1.4863. Washed with Na2C03 soln, then shaken with water. After the resulting emulsion had been broken by adding ether, the ethereal soln was washed twice with water, dried (CaCl2), and evaporated. The residual liquid was distd several times under reduced pressure, then stored in a vacuum desiccator over P2O5 [French and Singer J Chem Soc 1424 1956]... 

Dinonyi phthaiate (mainly 3,5,5-trimethyihexyi phthaiate isomer) [28553-12-0 14103-61-8] M 418.6, m 26-29 , b 170 /2mm, d 0.9640, n 1.4825. Washed with aqueous Na2C03, then shaken with water. Ether was added to break the emulsion, and the soln was washed twice with water, and dried (CaCl2). After evaporating the ether, the residual liquid was distd three times under reduced pressure. It was stored in a vacuum desiccator over P2O5... 

Boric acid (boracic acid) [10043-35-3] M 61.8, m 171 , pK 9.23. Crystd three times from H2O (3mL/g) between 100° and 0°, after filtering through sintered glass. Dried to constant weight over metaboric acid in a desiccator. It is steam volatile. After 2 recrystns of ACS grade it had Ag at 0.2 ppm. 

Calcium hexacyanoferrate (II) (IIH2O) [ 13821 -08-4] M 490.3. Recrystd three times from conductivity H2O and air dried to constant weight over partially dehydrated salt. [Trans Faraday Soc 45 855 1949.] Alternatively the Ca salt can be purified by pptn with absolute EtOH in the cold (to avoid oxidation) from an air-free saturated aqueous soln. The pure lemon yellow crystals are centrifuged, dried in a vacuum desiccator first over dry charcoal for 24h, then over partly dehydrated salt and stored in a dark glass stoppered bottle. No deterioration occurred after 18 months. No trace of Na, K or NH4 ions could be detected in the salt from the residue after decomposition of the salt with cone H2SO4. Analyses indicate 1 Imols of H2O per mol of salt. The solubility in H2O is 36.45g (24.9 ) and 64.7g (44.7 ) per lOOg of solution. [J Chem Soc 50 1926.]... 

Lithium nitrate [7790-69-4] M 68.9, m 253", d 2.38. Crystd from water or EtOH. Dried at 180° for several days by repeated melting under vacuum. If it is crystallised from water keeping the temperature above 70°, formation of trihydrate is avoided. The anhydrous salt is dried at 120° and stored in a vac desiccator over CaS04. After 99% salt was recrystd 3 times it contained metal (ppm) Ca (1.6), K (1.1), Mo (0.4), Na (2.2). 

The problem of the cooling of hot vessels within a desiccator is also important. A crucible which has been strongly ignited and immediately transferred to a desiccator may not have attained room temperature even after one hour. The situation can be improved by allowing the crucible to cool for a few minutes before transferring to the desiccator, and then a cooling time of 20-25 minutes is usually adequate. The inclusion in the desiccator of a metal block (e.g. aluminium), upon which the crucible may be stood, is also helpful in ensuring the attainment of temperature equilibrium. 

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