Filtration wash time

Since adequate washing cannot realistically be obtained in less than about 50 msec, the complex half-life must be at least 250 msec (k i < 2.8 s ) for reasonable binding measurements to be obtained. Uirfortunately, the dissociation rates of many important receptor-ligand complexes are faster than this and these are not amenable to measurement by these techniques. To study the equilibrium binding of [ Hjmuscimol, we routinely use a filtration (wash) time of 0.5 sec and a wash volume of 2 ml. 

Phthalylacetic acid. Heat a mixture of 30 g. of phthalic anhydride, 40 ml. of acetic anhydride and 5 g. of potassium acetate under reflux in an oil bath at 155-165° for 15 minutes. Pour the reaction mixture into ice-cold water, collect the yellow precipitate by suction filtration, wash it three times with 25 ml. of water and once with 10 ml. of 50 per cent, ethanol. Dry the. product at 100° the yield of crude plithalylaeetie acid is 20 g. Recrystallise from hot methanol yellow needles, m.p. 245-246°, are obtained. 

The soiution is aliowed to cool and the crystals of the P2P-bisulfite addition compound are then separated by vacuum filtration, washed with a little clean dH20 then washed with a couple hundred mLs of ether, DCM or benzene. The filter cake of MD-P2P-bisulfate is processed by scraping the crystals into a flask and then 300mL of either 20% sodium carbonate solution or 10% HCi soiution are added (HCI works best). The soiution is stirred for another 30 minutes during which time the MD-P2P-bisulfite complex will be busted up and the P2P will return to its happy oil form. The P2P is then taken up with ether, dried and removed of the solvent to give pure MD-P2P. Whaddya think of that ... 

Wash Time Cake-washing time is the most difficult of the filtration variables to correlate. It is obviously desirable to use one which provides a single cni ve for all of the data. Filtration theory suggests three possible correlations [Eqs. (18-59) to (18-61)]. These are listed below, beginning with the easiest to use ... 

Since the washing stage is essentially the case of filtration at constant cake thickness, q may be replaced by and assuming the viscosity of the washing liquid to be the same as that of the filtrate, the following relationship between washing time and filtrate amount is developed ... 

The resistance of the filter plate is negligible. The problem is to determine the filtration, washing and drying times, the cake thickness, the volumes of filtrate, washing liquid and drying air. The solution to this design case is outlined below in steps. 

The filtration time of 20 m of a suspension in a filter press is 2.5 hours. Determine the approximate washing time of the cake for 2 m of water, assuming that the washing rate is 4 times less than that of filtration at the end... 

For question 14, how much will the washing time change if the filtrate viscosity is double and the viscosity of the wash water is 1 cP ... 

Determine the required washing time under the following set of conditions Washing Intensity — 6 Liters/m -min., Cake Thickness = 40 mm, Initial SoUds Concentration in the Filtrate of the Wash Water = 120 g/Liter Final Concentration = 2 g/Liter. Assume a wash rate constant, K = 375 cmVLiter. 

For the conditions described in the above question, determine the washing time if the amount of wash water is 2.4 Liter/m and the washing is cocurrent with the filtrate. 

The reaction mixture is allowed to stand at room temperature for 30 minutes, during which time crystals of the product form. The product is collected by filtration, washed with a little cold ethanol, and recrystallized from ethanol or methylcyclohexane. The faintly yellow product has mp 150-151°. 

Zinc-Copper Couple A 500-ml Erlenmeyer flask equipped for magnetic stirring is charged with a mixture of zinc powder (49.2 g, 0.75 g-atom) and hydrochloric acid (40 ml of 3 % aqueous solution). The contents of the flask are rapidly stirred for 1 minute, and the liquid is decanted. Similarly, the zinc is washed with the following three times with 40 ml of 3% hydrochloric acid solution, five times with 100 ml of distilled water, five times with 75 ml of 2 % aqueous copper sulfate solution, five times with 100 ml of distilled water, four times with 100 ml of absolute ethanol, and five times with 100 ml of absolute ether. These last ethanol and ether washes are decanted onto a Buchner funnel to prevent loss. The residue is collected by suction filtration, washed again with anhydrous ether, and dried in air. Finally, the zinc-copper couple is stored (20-24 hours) in a vacuum desiccator over phosphorous pentoxide. 

A solution of 100 g of sodium bisulfite in 200 ml of water is added, and the stirring is continued for 10 hours with exclusion of air. A thick precipitate separates after a few minutes. The bisulfite compound is collected by suction filtration, washed with ether until colorless, and then decomposed in a flask with a lukewarm solution of 125 g of sodium carbonate in 150 ml of water. The ketone layer is separated, and the aqueous layer is extracted four times with 30-ml portions of ether. The combined organic layers are dried over anhydrous magnesium sulfate, the ether is removed at atmospheric pressure, and the residual oil is fractionated under reduced pressure through a short column. The cycloheptanone, bp 64-65°/ 2 mm, is obtained in about 40% yield. 

To a suspension of 3.0 g of 7-[D-(-)-a-amino-p-hydroxyphenylacetamido] -3-[5-(1-methyl-1,2,3,4-tetrazolyl)thiomethyl] -A3arboxylic acid in 29 ml of water was added 0.95 g of anhydrous potassium carbonate. After the solution was formed, 15 ml of ethyl acetate was added to the solution, and 1.35 g of 4-ethyl-2,3-dioxo-1 -piperazinocarbonyl chloride was added to the resulting solution at 0°C to 5°C over a period of 15 minutes, and then the mixture was reacted at 0°C to 5°C for 30 minutes. After the reaction, an aqueous layer was separated off, 40 ml of ethyl acetate and 10 ml of acetone were added to the aqueous layer, and then the resulting solution was adjusted to a pH of 2.0 by addition of dilute hydrochloric acid. Thereafter, an organic layer was separated off, the organic layer was washed two times with 10 ml of water, dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The residue was dissolved in 10 mi of acetone, and 60 ml of 2-propanol was added to the solution to deposit crystals. The deposited crystals were collected by filtration, washed with 2-propanol, and then dried to obtain 3.27 g of 7-[D-(-)-a-(4-ethyl-2,3-dioxo)-1 -piperazinocarbonylamino)-p-hydroxyphenylacetamido] -3-[5-(1 -methyl-1,2,3,4-tetrazolyl)thiomethyl]-A product forms crystals, MP 1BB°C to 190°C (with decomposition). 

To a solution of 2.5 grams (18.1 mmol) of potassium carbonate in 25 ml of water was added 225 ml of methanol followed by 5.0 grams (9.6 mmol) of estradiol 3,17 -dicyclo-pentanepropionate. The mixture was stirred for 2 /2 hours at 20 2°C during which time some precipitation occurred. The mixture was poured into 700 ml of water with efficient stirring and the precipitated solid was removed by filtration, washed with water and dried. 

The filtrate was adjusted to a pH of 9 by adding concentrated ammonia, and than a 1 N aqueous iodine-potassium iodide solution was added dropwise, whereby the tetrahydro-pyrimido-[5,4-d] pyrimidine obtained by hydrogenation with zinc in formic acid was converted by oxidation into 2,6-bis-(diethanolamino)-8-piperidino-pyrimido-[5/4-d]-pyrimidine. The completion of the oxidation was checked by means of a starch solution. The major amount of the oxidation product already separated out as a deep yellow crystalline precipitate during the addition of the iodine solution. After the oxidation reaction was complete, the reaction mixture was allowed to stand for a short period of time, and than the precipitate was separated by vacuum filtration, washed with water and dried. It had a malting point of 157°C to 158°C. The yield was 8.0 g, which corresponds to 95% theory. 

To a solution of 106 g (0.74 mol) of 2-amino-4water containing 69 ml of concentrated hydrochloric acid (29.2 g, 0.8 mol) are added 60.8 g (0.8 mol) of ammonium thiocyanate. The solution is placed in an evaporating dish and heated on a steam bath for 5 hours. The solid which results is then removed from the concentrated solution by filtration, washed with a small amount of water and dried. The filtrate is placed in an evaporating dish and heated on a water bath for 2 hours. At the end of this time, the mixture is cooled, and the solid which precipitates out is removed by filtration. Both solid products are 5[Pg.1605]

Synthesis in m-cresol. The dianhydride (1.35 mmol) is added to a stirred solution of 1.35 mmol of die diamine in die appropriate amount of m-cresol containing 6 drops of isoquinoline under N2 at room temperature. After 3 h, it is heated to reflux (ca. 200° C) and maintained at that temperature for 3 h. During this time, the water of imidization is distilled from die reaction mixture along with 1 to 3 mL of m-cresol. The m-cresol is continually replaced to keep the total volume of the solution constant. After die solution is allowed to cool to room temperature, it is diluted witii 20 mL of m-cresol and then slowly added to 1 L of vigorously stirred 95% ethanol. The precipitated polymer is collected by filtration, washed witii ethanol and ether and dried under reduced pressure at 125°C for 24 h. 

In conclusion, the following experiments on filtration-washing-deliquoring should be performed to produce data (viscosity of liquids, effective solid concentration, specific cake resistance, cake compressibility, etc.) that are necessary to evaluate times of individual steps of filtration at an industrial scale, i.e. to obtain the proper basis for scale-up of filtration processes measure the filtrate volume versus time make marks on your vacuum flask and take down the time when the filtrate level reaches the mark => no more experiments are needed for preliminary evaluations of filtration properties of slurries initially fines pass the filter medium => recirculate them to the slurry,... 

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