Crucible porcelain filter

This operation is the separation of the precipitate from the mother liquor, the object being to get the precipitate and the filtering medium quantitatively free from the solution. The media employed for filtration are (1) filter paper (2) porous fritted plates of resistance glass, e.g. Pyrex (sintered-glass filtering crucibles), of silica (Vitreosil filtering crucibles), or of porcelain (porcelain filtering crucibles) see Section 3.24. 

The precipitate, collected in a sintered-glass (porosity No. 4) or porcelain filtering crucible, may be weighed more rapidly as follows. Wash the copper(I) thiocyanate five or six times with ethanol, followed by a similar treatment with small volumes of anhydrous diethyl ether, then suck the precipitate dry at the pump for 10 minutes, wipe the outside of the crucible with a clean linen cloth and leave it in a vacuum desiccator for 10 minutes. Weigh as CuSCN. 

I. 0-1.3 g of 48 per cent hydrofluoric acid (CARE ). Allow the solution to stand for 10-20 hours, and cool in an ice bath for 2 hours. Collect the precipitate in a porcelain filtering crucible, and wash it with five 10 mL portions of saturated nitron tetrafluoroborate solution (Note 2) drain the precipitate after each washing. Dry at 105-110 °C for 2 hours, and weigh as C20H16N4 HBF4. 

The reduction is avoided by first charring the paper without inflaming, and then burning off the carbon slowly at a low temperature with free access of air. If a reduced precipitate is obtained, it may be re-oxidised by treatment with sulphuric acid, followed by volatilisation of the acid and re-heating. The final ignition of the barium sulphate need not be made at a higher temperature than 600 800 °C (dull red heat). A Vitreosil or porcelain filtering crucible may be used, and the difficulty of reduction by carbon is entirely avoided. 

Perchlorate as potassium perchlorate (ca 400 mg as the sodium salt in 25 mL solution). Warm the solution to 80-90 °C and treat with a slight excess of a cold saturated solution of potassium acetate. Allow to cool and after 1 hour collect the precipitate on a weighed porcelain filtering crucible. Wash twice with 0.05M potassium chloride and then with four 5 mL portions of equal volumes of anhydrous ethyl acetate and anhydrous butan-l-ol. Dry the precipitate at 110°C for 30-60 minutes and then heat at 350 °C in an electric furnace for 15 minutes. Weigh as KC104 (Section 11.68). 

Acid-Soluble Substances Suspend 5.0 g of sample in 100 mL of 0.5 N hydrochloric acid, and heat on a steam bath for 30 min, stirring occasionally. Filter the suspension through a suitable tared, porous-bottom, porcelain filter crucible. Wash the residue with three 10-mL portions of 0.5 N hydrochloric acid, evaporate the combined filtrate and washings to dryness, and ignite at 450° 25° to constant weight. 

Boil the ash obtained as directed under Ash (Total), below, with 25 mL of 2.7 N hydrochloric acid for 5 min, collect the insoluble matter on a tared, porous-bottom porcelain filter crucible or ashless filter, wash it with hot water, ignite to constant weight at 675° 25°, and weigh. Calculate the percent acid-insoluble ash from the weight of the sample taken. 

A porcelain filtering crucible. B weighing bottle containing about 7.5 g ofKCl. 

Gooch crucible A porcelain filtering crucible filtration is accomplished by means of a glass fiber mat or a layer of asbestos fiber. 

If a precipitate is to be ignited in a porcelain filter crucible, the moisture should be driven off first at a low heat. The ignition may be done in a muffle furnace or by heating with a burner. If a burner is to be used, the filter crucible should be placed in a porcelain or platinum cradble to prevent reducing gases of the flame diffusing through the pores of the filter. 

To identify acrylonitrile polymers, take a sample of the material and add a small amount of zinc dust and a few drops of 25% sulfuric acid (1 ml concentrated sulfuric acid added to 3 ml water, slowly). Heat this mixture in a porcelain crucible. Cover the crucible with filter paper moistened with the following reagent solution Dissolve 2.86 g copper acetate in 1.0 liter water. Then dissolve 14 g benzidine in 100 ml acetic acid, and to 67.5 ml of this... 

Carbon dioxide gas Porcelain crucible Paper filters Determination... 

Porcelain filtering crucible A 1 or round filter, diameter 5 cm Hydrochloric acid (1.125 g/ml)... 

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