Filter stick

Because of the sensitivity of chromium(II) to air oxidation, synthetic work on these systems requires the use either of vacuum-line techniques12 or of a nitrogen-filled box,6 or both. This synthesis describes the preparation of chromium(II) complexes using a combination of a closed ground-glass filter stick 18 and a nitrogen-filled box.6 The filter stick enables preparations, filtrations, and recrystallizations to be carried out... 

The product and the filter stick (Fig. 4a), together with a number of 24/40 S.T. test tubes and deoxygenated solvents, are transferred into the nitrogen-filled glove box.8 The filter stick... 

Selas filter stick, 50mm. high diam of disc 11mm... 

Weigh accurately the precipitation receptacle alone (6) and also together with filtering stick (11). Remove the stick and transfer into (6) ca 50mg of residue (obtd on extraction of proplnt by the method indicated in Quantitative Test 2). Reweigh (6) and the difference in wt is the wt of the sample. Add 5m 1 of anhydrous ether, stopper with cork (5) and connect by means of rubber hose (4) to the apparatus shown as B. 

Procedure a)0.4g sample of rocket chge was treated in a fared 100 ml beaker with 50 ml of hot benzene and the mixt allowed to stand on a hot bath for 10 mins with frequent stir ring b)The beaker was removed, cooled to 10-12° and, by means of a filtering stick, the supernatant soln of a material, later identified as TNAns, was removed c)The residual material, later found to be HNDPhA, was washed 3 times with 5 ml of cold benzene (10°) and dried to const wt. The increase in wt of the beaker was considered as the amt of HNPhA d)After evaporating the benzene from soln (b) the residue was identified as TNAns by its mp (65-67°) and its equivalent wt of 13.5 was detnd by reduction with titanous sulfate e)The residue in beaker of proced (c) was identified as HNDPhA by its mp (242°) and its equiv wt of 12.6 f)The TNAns was confirmed, as such, by the mp of a mixt of the unknown material and pure TNAns (mixed mp), and the similarity of spectrophotometric curves and... 

Here a three-necked, pear-shaped flask A is fitted with a condenser and calcium chloride tube B, a filter stick C (this being a glass tube having a sintered... 

Filter sticks of a range of dimensions and porosities are available from J. Bibby Science Products Ltd. The choice of size of flasks and filter sticks will be governed by the scale of the recrystallisation. Broadly speaking pear-shaped flasks are more suitable for the range 100 mg to 5 g, but may be replaced by round-bottomed flasks for operations on a larger scale. 

The filter stick should be attached to a suction pump via a filter trap so that the mother-liquor may be collected, and, if need be, concentrated for further crystal crops furthermore it is essential that the suction be carefully controlled (by the use of additional stopcocks which are not shown) so that the filter stick may be lowered at the same rate as the level of mother-liquor falls. Undue immersion of the filter stick leads to some troublesome difficulties in removing contaminating mother-liquor from the outside of the filter stick. 

During all manipulations, it is important that nitrogen pressure be continuously applied to the filter stick except for the brief moments when it is necessary to reverse the direction of nitrogen flow. 

Filter Stick Use either a 10-mm diameter sintered-glass filter stick of 10- to 15-pm maximum pore diameter, or a filter stick made of stainless steel and having a 0.5-in. disk of 10- to 15-pm maximum pore diameter. Determine conformance with the pore diameter specified as follows Clean sintered-glass filter sticks by soaking in hydrochloric acid, or stainless steel sticks by soaking in nitric acid, wash with water, rinse with acetone, and dry in air followed by drying in an oven at 105° for 30 min. 

FIGURE 9 Assembly for Checking Pore Diameter of Filter Sticks. 

Thoroughly wet the clean filter stick by soaking in water, and then connect it with an apparatus (see Fig. 9) consisting of a mercury-filled manometer, readable to 0.5 mm a clean and filtered air supply a drying bulb filled with silica gel and a needle-valve type air pressure regulator. Apply pressure slowly from the air source, and immerse the filter just below the surface of water contained in a beaker. 

Filtration Assembly Connect the Filter Stick with an air pressure inlet tube and delivery nozzle and ground-glass joint to fit a 25- x 170-mm test tube as shown in Fig. 10. If a stainless steel Filter Stick is used, make the connection to the test tube by means of a cork. 

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