Precipitate stainless steel filters

After digestion, the americium oxalate is filtered onto a Kynar (Pennwalt Company) frit in a stainless steel filter boat (Figure 9). The precipitate is washed with 0.1 M oxalic acid and dried by pulling air through the frit. 

Dry SO, (ca. 100 mL) was condensed into a reactor, If the reaction was run at - 10 C (reflux), the reactor consisted of a flask equipped with a dry icc condenser. For runs at rt. a stainless steel autoclave with a stainless steel filter was employed. SO, (60-90 mmol) was added through a serum cap, followed by addition of the appropriate iodide (50 mmol). Immediate formation of iodine crystals was observed. The reaction was allowed to stir at the chosen temperature for a period of 0.5 to 4h. If the reaction was run in the autoclave, the precipitated iodine was filtered off. SO, was evaporated and ihc residue was treated with H,0 (150 mL) and the resulting mixture was heated to 90 C and kept at that temperature for 0.5 h. The organic layer was extracted with Lt20, dried and the solvent evaporated. 

These are the type of precipitate collectors reported most often [3-9,12-14]. Such filters were originally used as cleaning devices in high performance liquid chromatography. The constructions of two different designs of stainless-steel filters are shown in Rg. 

Adeeyinwo and Tyson [10] used a stainless-steel disc filter with 2 m pore size, 6 mm diameter, and 2 mm thickness to separate calcium from an interfering aluminium matrix by oxalate precipitation. The results were inferior to those obtained using membrane filters, giving poor reproducibility. These results are consistent with the experiences of Valcarcel et al.[7] using disc type stainless-steel filters mentioned above. ... 

This is the simplest type of FI manifold used for on-line precipitation, used principally with stainless-steel filters [13,16], the variations of which are shown in Fig 7.2 a-c. In the normal FIA or hFIA mode, the sample may be either injected directly into the precipitant J (Fig. 7.2 a) or injected into a water carrier and later meiged with the precipitant (Fig. 

Moniero et al.[24] developed an indirect AAS method for the determination of local anaesthetics (lidocaine. tetracaine and procaine hydrochlorides) in pharmaceutical preparations using FI on-line precipitation-dissolution. A cobalt solution is injected into a carrier stream containing the sample, and the precipitate formed is retained on an online stainless steel filter. The determinations were made by measuring the residual cobalt concentration in a similar way as for the indirect determination of sulphonamides (cf. Sec. 9.4.2). A sampling frequency of 100 h was achieved with a precision of 0.6% r.s.d.. 

A FIA indirect method was described for saccharin determination by Yebra et al. [88]. This method was based on the precipitation of silver saccharinate in an acetic acid medium. The precipitate was dissolved in ammonia, and the dissolved silver was continuously measured by FA AS. The FIA precipitation-dissolution manifold used is similar to that used for cyclamate determination [83] however, in this work, a Scientific System 05-105 column fitted with a removable screen-type stainless-steel filter (pore size 0.5 pm, chamber inner volume 580 pL, filtration area 3 cm ), originally designed as a cleaning device for liquid chromatography, was employed for filtration purposes. 

Pentaerythritol may be nitrated by a batch process at 15.25°C using concentrated nitric acid in a stainless steel vessel equipped with an agitator and cooling coils to keep the reaction temperature at 15—25°C. The PETN is precipitated in a jacketed diluter by adding sufficient water to the solution to reduce the acid concentration to about 30%. The crystals are vacuum filtered and washed with water followed by washes with water containing a small amount of sodium carbonate and then cold water. The water-wet PETN is dissolved in acetone containing a small amount of sodium carbonate at 50°C and reprecipitated with water the yield is about 95%. Impurities include pentaerythritol trinitrate, dipentaerythritol hexanitrate, and tripentaerythritol acetonitrate. Pentaerythritol tetranitrate is shipped wet in water—alcohol in packing similar to that used for primary explosives. 

Lime-Sulfuric. Recovery of citric acid by calcium salt precipitation is shown in Figure 3. Although the chemistry is straightforward, the engineering principles, separation techniques, and unit operations employed result in a complex commercial process. The fermentation broth, which has been separated from the insoluble biomass, is treated with a calcium hydroxide (lime) slurry to precipitate calcium citrate. After sufficient reaction time, the calcium citrate slurry is filtered and the filter cake washed free of soluble impurities. The clean calcium citrate cake is reslurried and acidified with sulfuric acid, converting the calcium citrate to soluble citric acid and insoluble calcium sulfate. Both the calcium citrate and calcium sulfate reactions are generally performed in agitated reaction vessels made of 316 stainless steel and filtered on commercially available filtration equipment. 

Normal lead styphnate (LS) [Structure (2.10)] was first reported by Von Herze in 1914, although its basic salt, that is, basic LS was prepared by Griess [7] way back in 1874, by the reaction of acidified magnesium styphnate with lead nitrate/acetate in hot aqueous solution. It is precipitated as mono hydrate and consists of reddish-brown rhombic crystals. It is filtered off, washed with water, sieved through a stainless steel sieve and dried. Like other initiatory explosives, it is kept in wet conditions until used. 

Manufacture at Bobingen [38,61] was on the following lines. A reactor of aluminium or stainless steel (capacity 1.2 m3) is filled with acetic anhydride and then 0.4% of BF3 is added. Acetic anhydride is warmed to 60-65°C and at this temperature ammonium nitrate and paraformaldehyde are added gradually. Due to the high temperature and the presence of boron fluoride the reaction starts at once and heat is evolved. The heating is then turned off and the temperature maintained by cooling, within the range 60-65°C. The addition of the reactants requires approximately 6 hr, after which the contents of the reactor are cooled to 20°C. The precipitated cyclonite is separated from the solution on a vacuum filter. The by-products remain in the spent liquor. 

The lead picrate for this purpose was produced in the following way [42]. Into a stainless-steel reactor equipped with a stirrer of the type used for the manufacture of lead azide and other initiators (cf. Fig. 49) 8 1. of a solution containing 1.44 kg of lead nitrate and 151. of ice water were poured. Fifteen litres of a solution containing 1.5 kg of picric acid were then added. During the reaction the temperature should be maintained between 6 and 10°C. Since the temperature rises with the precipitation of lead picrate, 7-8 more litres of ice water must be poured into the reactor, usually a few minutes after the picrate has begun to precipitate. After 4 hr the liquid was decanted from above the precipitate the latter was transferred to a cloth filter and washed with alcohol (101.) to which an aqueous solution of lead, nitrate (500 ml of a 30% solution) has been added to avoid the dissolution of lead picrate during washing. 2.2 kg of product was obtainable from one batch. 

A 0.5-L stainless steel autoclave was charged with 4-fluorotoluene (45 g, 0.41 mol) and 20 % H N03 (264 mL. 0.85 mol). The mixture was heated for 2 h to 190-195 C and maintained at this temperature for 4 h while the pressure rose to 70 atm. On opening the autoclave, brown nitric oxides escaped while the product remained as a precipitate at the bottom of the autoclave. The crude product was dissolved in cold 5% aq NaOH and the solution was filtered and acidified. The white product was filtered off with suction, washed with cold H20, and dried at 100 C yield 55 g (96%) mp 181 182 C. 

Bipolar membrane synthesis also holds promise for regenerating spent pickling liquors in stainless steel manufacture. As shown in Fig. 43(b), waste acid laden with metal ions can be continuously neutralized, filtered to remove the precipitated metal oxide, and the clarified salt solution split into its acid and base components in a bipolar membrane unit [Type (IV) shown in Table IX], As much as 95% of the hydrofluoric and nitric acid used are returned to the pickling bath, thereby solving a waste... 

The reaction mixture is cooled to 25-30°C as quickly as possible, which takes about 2-3 hr. Picric acid precipitates in fine crystals. The nitrator contents are then drawn off into stainless steel centrifuges or onto iron vacuum filters. The charge of a centrifuge amounts to 250 kg. As a result, 750-780 kg of picric acid can be obtained, which constitutes about 85% of the theoretical yield. 

The quantity of water used in the reaction must be sufficient to ensure that calcium chloride remains in the solution, whilst calcium hypochlorite is precipitated as a solid substance. Filtration is very difficult and is carried out by means of a special hydraulic press which operates under a pressure of 150 atm. sq. cm. Stainless steel gauze is used as a filter cloth. 

Removal of the precipitate from the filter If the precipitate is bulky, sufficient amounts for examination can be removed with the aid of a small nickel or stainless steel spatula. If the amount of precipitate is small, one or two methods may be employed. In the first, a small hole is pierced in the base of the filter paper with a pointed glass rod and the precipitate washed into a test-tube or a small beaker with a stream of water from the wash bottle. In the second, the filter paper is removed from the funnel, opened out on a clock glass, and scraped with a spatula. 

Chloro-9-(5-methyltetrahydro-2-furyl)purinc (2.0 g, 8.4 mmol) was dissolved in ethanolic NH, (sat. at 0"C, ESOml.) and the solution heated to 85 C for 5 h in a stainless steel bomb. The resulting brown solution was diluted with EtOAc (150 mL) and filtered to remove the NH CI. KOH pellets (0.5 g) were added and the solution evaporated to dryness in vacuo. The remaining brown oil was extracted with boiling petroleum ether (bp 60-110 C, 70 mL) and then with boiling benzene (100 mL). The benzene extract was treated with Norit and evaporated to a total volume of 25 mL. Petroleum ether (bp 30 - 60°C) was added to the benzene solution until a precipitate formed. This solid was filtered and recrystallized (benzene/ petroleum ether, bp 30-60°C) yield 1.6 g (89%) colorless crystals rap 127-128°C. 

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