Filtering in the absence of air

Poor sample preservation will often lead to results considerably in error. If pH, alkalinity, HiS and NH3 are not determined in the field, their values must be considered suspect (27-28). Sample preservation may require filtering in the absence of air by pressurizing the vessels with an inert gas... 

I. The apparatus of Fig. 198 Is used. A solution of 8 g. of P3O3CI4 In 20 ml. of CHCI3 Is added In drops, with stirring and cooling, to a solution of NH3 In 750 g. of dry CHCI3. The procedure described above (p. 584) Is then followed and the reaction product Is suction-filtered In the absence of air. The product Is washed with dry CHCI3 and Is dried In vacuum. The apparatus shown In Fig. 71, p. 88, may be used for extraction with liquid NH 3. The yield Is 75%. 

After several minutes, a violet color is observed in the solution, and the chromium acetate powder is transformed (with an increase in bulk) into chromium (II) chloride which still contains some acetic acid. The flask is swirled during this operation to prevent clogging of the inlet tube. The white crystals are filtered in the absence of air, washed with absolute, air-free ether, and dried at 110 to 120 °C. The acetic acid is thus eliminated, and pure white, analytically pure CrClg is obtained as a residue. Yield 4-5 g. 

A solution of KReO 4, containing 30 ml. of hydrochloric acid per 100 ml. of solution, is saturated for four hours with H3S. The precipitated sulfide is washed with KgS-saturated, 3% HCl water. The product is filtered in the absence of air, washed and then dried, first in a high vacuum for two hours at 140°C and then in high vacuum over freshly prepared PsOs (60 hours at 165-170°C). 

Ruthenium (III) chloride (2H2O) (P-form) [14898-67-0] M 207.4 + HjO, m >500 (dec), d 3.11, pK 3.40 (for aquo Rh hydrolysis). Dissolve in H2O, filter and concentrate to crystallise in the absence of air to avoid oxidation. Evaporate the solution in a stream of HCl gas while being heated just below it boiling point until a syrup is formed and finally to dryness at 80-100 and dried in a vacuum over H2SO4. When heated at 700° in the presence of CI2 the insoluble a-form is obtained [Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Vol II 1598 1965 J Org Chem 46 3936 1981]. 

The precipitate is filtered and dried at 100°C. If an alkali metal carbonate is used instead of ammonium carbonate, a hydrated basic carbonate is obtained which upon heating with ammonium chloride at 150°C in the absence of air produces anhydrous carbonate. 

Benzyl alcohol [100-51-6] M 107.2, f.p. -15.3°, b 205.5 , 93°/10mm, d 0.981, n 1.54033. Usually purified by careful fractional distn at reduced pressure in the absence of air. Benzaldehyde, if present, can be detected by UV absorption at 283nm. Also purified by shaking with aq KOH and extracting with peroxide-free ethyl ether. After washing with water, the extract was treated with satd NaHS sol, filtered, washed and dried with CaO and distd under reduced pressure [Mathews JACS 48 562 7926]. Peroxy compounds can be removed by shaking with a soln of Fe(II) followed by washing the alcohol layer with distd water and fractionally distd. 

All operations should be performed in the absence of air. o-Phenylene-hw(dimethylarsin) (DAS) (1.4g) was dissolved in 50 mL of free-from-air ethanol in a three-funnel flask. A solution of 0.62g of K2[MoC15(OH)2] in 5mL of 6N HC1 was added. After that the flask was vacuumed more than once and filled by the free-from-air nitrogen. After the pressures were levelled the flask was carefully heated at 50°C for 24 hr. The bright-yellow precipitate was filtered, washed with a small amount of diluted HC1, free-from-air ethanol, and dried in vacuum. Yield 0.5 g. 

A powder containing at least 90 per cent, of the octahydrated ferrous phosphate is obtained by mixing solutions of sodium acetate (2 parts), sodium phosphate (10 parts), and ferrous sulphate (8 parts), and allowing to stand in the absence of air for several days. The precipitate is collected on a calico filter and dried at 40° C.16 If the liquid... 

Fig. 50a. stem for precipitation, purification and isolation in the absence of air-, ff) condensation trap of the vacuum system J) reaction flask K) condenser M) flask with PaOsJ 0) filter tube with extension 0 and glass frit 0" 1-7) ground joints e-7 stopcocks metal... 

Two grams of chromium (II) acetate hydrate is mixed (in the absence of air) with 2.49 g. of 2,2 -dipyridyI (equivalent to 1.5 moles of dipyridyl per g.-atom of Cr). Now, 40 ml. of deaerated water is added and the resulting suspension is machine-shaken for three hours. The black precipitate is filtered off from the deep-red mother liquor (through a very fine fritted-glass filter), washed with water and alcohol, and dried over air-free PgOs. Yield about 1 g. 

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