Lead, vacuum filter productivity

After the completion of the reaction, the nitrator contents are discharged into a lead vacuum filter of 1000 1. capacity for separating the product from the spent acid. The spent acid has the composition ... 

Benzoyl isothiocyanate 814 A mixture of dry lead thiocyanate (65 g prepared from lead acetate and potassium thiocyanate), benzoyl chloride (55 g), and benzene (100 ml) is boiled for 1 h, then filtered and distilled in a vacuum. The product (30 g) boils at 119°/10mm. 

It is useful now to identify the concentration of the antibiotic product (i.e. the titer) during the different steps identified earlier (Belter et al., 1988). The product concentration level in the fermentation broth may vary between 0.1 and 5 g/liter. Removal of insolubles via microfiltration, rotary vacuum filter and centrifuging increases the product concentration marginally, in the range of 1-5 g/liter. Product isolation via solvent extraction enhances the product concentration to 5-50 g/liter. Purification by chromatography or crystallization leads to a product concentration level between 50 and 200 g/liter. The polishing step may not enhance the concentration in general much, but it certainly improves the purity. If a membrane process such as reverse osmosis is used to concentrate a very dilute solution of the antibiotic, 10-30 times the initial concentration may be achieved. 

Phenylpftenanttirldlne (3).3 Amine hydrochloride 1 (2.72 g, 9 28 mmol) in EtOH (75 mL) was treated with 0 926 N cold solution of KCXI. Colorless crystals appear The mixture was shaken lor 30 mtn in ice, water was added and the product was filtered and dryed (PaOs) to afford 2.7 g of 2 (100%), rnp 102°C (hexane) 2 (2 0 g, 6 6 mmol) in anh pyndine (20 mL) was treated with an excess of NaOCHa (exothermc) Alter 20 h the solvent was removed In vacuum, the residua triturated with EtaO and the extract treated with dry HCI to obtain the hydrochlonda of 3, mp 107-108°C (from petroleum ether), mp 95-100° (Irom water) Olphenylmethyieneanlllna (5). To a suspension of lead tetraacetate (4.9 g, fO mmol) in PhH (100 mL) under Na was added a solution of tnphenyhnethylamine 4 (2 6 g, 10 mmol) in PhH (100 mL) dropwise under stirring The mixture was refluxed for 1 h, cooled, filtered, washed and the solvent evaporated The residue was crystallized from EtOH to give 2 2 g of 5 (85%), mp 111-112°C. 

Isolation of Sesquiterpene Lactones. The ether extract was evaporated and dissolved in 952 ethanol. Then an equal volume of 42 aqueous lead acetate was added. After 1 hour the mixture was filtered to remove precipitated chlorophyll and phenolic products and the ethanol removed under vacuum. The aqueous layer was extracted with chloroform giving a dark colored oil from which the sesquiterpenes were isolated by a combination of chromatographic procedures, i.e., LH-20 gel permeation, silica gel using both packed columns and thin layer plates. A variety of solvents were also used to purify the individual sesquiterpene lactones, e.g., benzene-acetone (1 1), ethyl acetate, chloroform-methanol (9 1). On thin layer chromatographic plates, spots were visualized by spraying with 22 aqueous KMn04 solution. 

Lead tetraacetate is added in small quantities, with stirring, to an ice-cold suspension of 11 g. of ethyl 3-(D-arabino-tetrahydroxybutyl)-5-methyl 4-furoate in 100 ml. of benzene plus 40 ml. of glacial acetic acid. Addition is stopped when there is a positive reaction with potassium iodide-starch paper. The mixture is stirred for a further ten minutes, filtered, and the benzene solution washed twice with water. The benzene layer is then dried with anhydrous sodium sulfate, filtered, and the filtrate evaporated to dryness. The residue (6 g.) is mixed with a solution of 7.5 g. of sodium hydroxide plus 20 g. of silver nitrate in 40 ml. of water, and heated for 40 minutes on a steam bath. The aqueous solution is filtered, acidified to Congo Red while being cooled with ice, and the crystals formed are removed by filtration, washed with ice-cold water, and dried over phosphorus pentoxide in the vacuum desiccator yield, 2.2 g. After recrystallization from water, the product has m. p. 234r-235°. 

The specimens are prepared from a colloidal dispersion of egg-yolk lecithin in excess water. In order to obtain reasonable contrast, the water is doped with lead acetate (approximately 0.25 wt % ). However, we have no idea of the proportion of lead in the final product, which is prepared as follows. A microscope grid is soaked in the solution and then allowed to dry either in air or on its edge on filter paper. The specimen is then introduced into the high vacuum 10"6 torr) of the electron microscope (Philips EM300) and observed at 100 kV with the help of a tilting stage. 

Procedure Prepare two solutions, a sodium azide solution, and a lead-II-acetate solution by dissolving 8.3 grams of sodium azide into 71 milliliters of water, and dissolve 21 grams of lead-II-acetate into 179 milliliters of water. Then quickly place each solution into a freezer and chill to about 5 Celsius. Thereafter, place the sodium azide into an ice bath, and then rapidly add the lead-II-acetate solution. Upon mixing, the LZ will instantaneously precipitate. After mixing both solutions, carefully filter-off the precipitated product, carefully wash with 100-milliliters of ice-cold water, and then dry in a desiccator filled with anhydrous magnesium sulfate. Do not vacuum dry or air-dry. The dry product should never be kept dry. For storage, keep the dry LZ suspended in a water free solvent such as kerosene. The product can be stored wet with water for short periods of time. 

Place 3000 milliliters of 40% nitric acid into a beaker, and then gently heat this mixture to about 30 Celsius. Thereafter, carefully mix the moist filter cake, prepared at the end of step 1 to the nitric acid solution over a period of about 30 minutes, while stirring the nitric acid and keeping its temperature around 30 Celsius. Immediately after the first addition of the filter cake, nitrogen oxide gases will be evolved, followed by the formation of a foam (the foam will dissipate after about 10 minutes). After the addition, raise the temperature of the mixture to 95 Celsius, and then hold this temperature for 1 hour. After heating for 1 hour, remove the heat source and allow the reaction mixture to cool to room temperature. Note A precipitate will form. When the reaction mixture reaches room temperature, filter-off the precipitated product, wash with 300 milliliters of 2% nitric acid, and then with 600 milliliters of cold water. Then vacuum dry or air-dry the product. The result will be pale yellow crystals, well suitable for use in preparing lead styphnate, or styphnic acid compositions. 

Place 132 milliliters of the magnesium styphnate solution (prepared in step 1) into a flask and heat to 80 Celsius while stirring. Then slowly add 114 milliliters of the lead nitrate solution (prepared in step 2) over a period of 40 minutes while maintaining the temperature of the magnesium styphnate solution at 80 Celsius and stirring. After addition of the lead nitrate solution, continue heating the mixture at 80 Celsius for 10 minutes and then remove the heat source, and allow the mixture to cool to room temperature. Afterwards, filter-off the lead styphnate precipitate, and then wash with 1000 milliliters of water. Then vacuum dry or air-dry the product (no heat). 

Procedure Place 80 milliliters of a 4% sodi urn hydroxide solution into a flask, and then quickly add 9.2 grams of picric add. Shortly thereafter, add 320 mi IN liters of water. Then dissolve 15 grams of lead nitrate into 600 mi IN liters of water, and then heat this mixture to 80 Celsius. Thereafter, Add drop-wise, the picric add mixture to the lead nitrate solution over a period of 1 hour. During the addition, rapidly stir the lead nitrate solution aid keep its temperature st 80 Celsius. After the addition, removethe heat source, and allow the reaction mixture to cool to room temperature. During the cool down period, rapidly stir the reaction mixture. Afterwards, filter-off the pred pitated lead picrate, wash with several hundred milliliters of cold water, and then vacuum dry or a r-dry the product. 

Stirring, and 700 g. (1.03 mole) of red lead oxide (Pt)304) is added in portions of 15-20 g. A fresh addition is made only after the color due to the preceding portion has largely disappeared, and the temperature is kept between 55 and 80°. At the end of the reaction the thick and somewhat dark solution is cooled, and the crystalline lead tetraacetate which separates is collected and washed with acetic acid. The crude product without being dried is dissolved in hot acetic acid, and the solution is clarified with Norit, filtered, and cooled. The colorless crystalline product is dried in a vacuum desiccator over potassium hydroxide in the dark and stored in the desiccator yield 320-350 g. (70-77%). 

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