Filtration filter cones

Centrifugation alone is not sufficient to separate Np solid material from the solution (j) ). Thus, the Np solution concentrations and oxidation state analyses were determined from aliquots filtered through approximately 1.8 nm pore-size Centriflo membrane cones (Amicon Corp., Lexington, MA). Each filter cone was pretreated with an initial aliquot of the suspension to be filtered. Tests using successive filtration confirmed that no significant amounts of Np were being sorbed by the filter cones. The solutions were alpha counted by liquid scintillation techniques. Major cations in the solutions were determined by inductively coupled plasma spectrometry (ICP) analyses. 

To filter the mixture, swirl the suspension of the solid in the liquid so that there is a fairly even distribution of solid in the liquid, and then pour the mixture into the filter cone, making sure that you do not pour any of the mixture outside the filter paper otherwise you will need to repeat the filtration, and do not overfill the filter cone. Transfer all the mixture in this way and finally wash the last bit of solid and liquid into the filter cone with a small amount of filtered solution and then a little pure solvent. 

If filtration is rapid, keep the filter cone topped up with the hot solution being filtered, since this keeps the filter cone and filter funnel hot. If you allow the filter cone to empty of liquid, cooling and crystallization may occur. 

Quantitative tests for RDX are described in this Volume under Cyclotrimethylenetrinitramine (RDX), Analytical Procedures Xy Alkali Solubility Test. Shake ca 0,5g of the sample for 2mins in a test tube with 5ml of 10% NaOH soln, filter and acidify the filtrate with coned HCl, Cool the tube under tap w, and rub the inside of the tube with a glass rod, A white ppt, appearing after about 5mins, is a positive test for EDNA and its presence can be confirmed by treating the sample with Thymol Reagent - a brown color is a positive test for EDNA (See also Chart B)... 

Filtering solids - if you allow the solid to settle you will have difficulty pouring the thick slurry of solid and liquid from the bottom of the beaker or conical flask into the filter cone and you will need to use more filtrate to complete the filtration effectively. 

Method-I. Dissolve 5 g of the crude product in a minimum quantity of cold aqueous sodium carbonate solution (10% w/v) a second relatively small crop of the gummy impurity thus obtained may be discarded. Add 0.5-1.0 g of powdered animal charcoal, stir for a few minutes and filter at the pump. Acidify the filtrate with cone. HCl carefully to Congo Red Paper. The acid is precipitated on chilling, filter at the pump, wash with a small amount of cold water, drain well and finally dry it in a vacuum desiccator. The yield of the recrystallized product is 4.25 g having mp 152.5-154.5°C. 

This filtration technique is most useful when the solid material being filtered from a mixture is to be collected and used later. The filter cone, because of its smooth sides, can easily be scraped free of collected solids. Because of the many folds, fluted filter paper, described in the next section, cannot be scraped easily. The filter cone is likely to be used in microscale experiments only when a relatively large volume (greater than 10 mL) is being filtered and when a Hirsch funnel (Section 8.3) is not appropriate. 

The filter cone is prepared as indicated in Figure 8.1. It is then placed into a funnel of an appropriate size. With filtrations using a simple filter cone, solvent may form seals between the filter and the funnel and between the funnel and the lip of the receiving flask. When a seal forms, the filtration stops because the displaced air has no possibility of escaping. To avoid the solvent seal, you can insert a small piece of paper, a paper clip, or some other bent wire between the funnel and the lip of the flask to let the displaced air escape. As an alternative, you can support the funnel by a clamp fixed above the flask rather than placed on the neck of the flask. A gravity filtration using a filter cone is shown in Figure 8.2. 

The above intermediate (8 g, 0.03 mol) in THF (80 ml) was stirred with Raney nickel (40g) for 2h and then carefully filtered. [CAUTION Raney nickel can ignite during filtrationf Cone. HCl (2 drops) was added to the filtrate and it was evaporated in vacuo. Recrystallization of the residue from 2-propanol gave the product (6,0 g) in 89% yield. 

Methoxy 6( 2 Chlorobenzoyl)-ben2o(c acid (2).2 3-Metboxy-2(3-cblorobenzoyl)-benzolc acid 1 (1.0 g, 3.4 mmoQ was heated In cone. H2S04 (6 mL) for 1 h at 6S°C. The cooled reaction mixture was poured into ice and neutralized. The cyclized product was filtered off (0 2 g) and the filtrate was acidHIed to give 2, rrp 205°C. 

Tanks with conical bottoms discharge cakes by gravity and those with dished bottoms have a spade that rakes and conveys the cake towards the outlet. Hence, the conical types require more headroom as compared to the dished type having the same filtration area. Conical tanks also have often an additional scavenging plate at the lower part of the cone to filter the residual slurry heel that remains below the main plates. The slurry heel that remains at the very bottom of the tank is removed through a special dip pipe to avoid discharging a wet cake. To facilitate better cake... 

Boil the tartaric acid and caustic soda solution for three hours in a round flask (I litre), or preferably in a tin bottle furnished with reflu. condenser. The use of a tin vessel obviates certain clitli-cultiesof filtration which the solution of the silica by the action of the alkali on the glass entails. The liquid, after boilinjg, is carefully neutralised with cone, hydrochloric acid (it is acl is-able to remove a little of the solution beforehand in case overshooting the mark) and an excess of calcium chloride solution is added to the hot liquid. The mixture is left overni hl. and the calcium salts filtered off at the pump, washed with water, and well pressed. 

The ether is allowed to evaporate on the water-bath and th e nitrile is then hydrolysed by continuing to heat it on the water-bath with the addition of 4—5 times its volume of cone, hydrochloiic acid until crystals appear on the surface. Water is added and the hot liquid decanted and filteied from any oil. On cooling, the crystals are filtered, washed vvith a little cold ivaterand dried. A fuither quantity can be extiacted from the filtrate with ether. It may be recrystallised from benzene. Yield, 10—15 grms. 

A solution of a 11-chlorodibenzoxazepine 11 (20 mmol) and an amine (40 mmol) in xylene (50 mL) was heated under reflux for 5 h, cooled and filtered. The filtrate was extracted with dil HC1 and the aqueous extract was basified with coned aq NH3, whereupon the product separated. It was extracted with Et20, the extract was dried and evaporated and the residue was recrystallized (Et20 or Et,0/petroleum ether). 

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