Precipitates, apparatus for removing

Praseodymium, separation of mixtures with lanthanum from monazite, as magnesium nitrate double salt, 2 56, 67 Praseodymium (III) nitrate, analysis of anhydrous, 5 41 Praseodymium (III) oxide, for synthesis of nitrate, 5 39w. Precipitates, apparatus for removing liquid from, 8 16 Purpureochromic chloride, 2 196 6 138... 

D. 2,3-Diamino pyridine (Note 12). In an apparatus for catalytic hydrogenation (Note 13) 56.4 g. (0.3 mole) of 2,3-diamino-5-bromopyridine suspended in 300 ml. of 4% sodium hydroxide solution is shaken with hydrogen in the presence of 1.0 g. of 5% palladized strontium carbonate (Note 14). When absorption of hydrogen is completed, the catalyst is removed by filtration, and, after saturation with potassium carbonate (about 330 g. is required), the resulting slushy mixture is extracted continuously with ether until all the precipitate completely disappears (usually about 18 hours, but this depends on the efficiency of the extraction apparatus). The ether is removed by distillation, and the residue of crude 2,3-diaminopyridine is recrystallized from benzene (about 600 ml. is required) using 3 g. of activated charcoal and filtering rapidly through a preheated Buchner funnel. The yield of 2,3-diaminopyridine, obtained as colorless needles, m.p. 115-116°, pKa 6.84, is 25.5-28.0 g. (78-86%) (Note 15). 

Dimethyl-2,3-dihydro-1,2-benzoisothiazolel,l-dioxide(60 g,0.304 mol)and NaF(16.8 g)in dry CHCI3 (500 mL) were cooled to — 40°C before the diluted mixture 10% F2/ N2 (w/ w) was introduced at a rate such that the flow in the second trap was about 15-25 mL min 1 (0.275 mol F2). After approximately 2 h, the contents of the second trap started to darken noticeably and the fluorination was discontinued. N2 was bubbled through the apparatus for about 1 h to purge the system of residual F2. The solvent was removed by rotary evaporation from the solution containing precipitate. After evaporation of the solvent, the crude mixture was purified by recrystallization from pentane (500 mL) at 0CC yield 42 g (64% from substrate, 71% from F2) mp 115-116.5 C. 

Bromine (117 g., 0.73 mole) is added slowly to 51.5 g. (0.29 mole) of 2,4-dichlorotoluene (p. 113), during which operation the reaction mixture is held at a temperature of 180-200°. (Hood.) The reaction mixture is stirred for 1 hour at 100° with 80 ml. of concentrated sulfuric acid followed by a short period at 140° imtil no more bromine or hydrogen bromide is evolved. The resulting mixture is cooled and poured into crushed ice. The precipitated solid is removed by filtration and placed in a steam-distillation apparatus with some sodium carbonate. Steam distillation gives the aldehyde in the distillate, from which it is collected by filtration. There is obtained 51.6 g. (92%) of 2,4-dichlorobenzaldehyde, m.p. 74.5°. 

Fio. 6, Apparatus for effecting the removal of liquid from a precipitate. 

Another method for removing interfering anions (including acetate and formate) is to precipitate the carbonate by adding calcium chloride. The precipitation, washing and isolation of the calcium carbonate can be accomplished in the bulb of the gas evolution apparatus, if the latter is placed in a centrifuge tube. 

The purification of KL was conducted by extracting KL in the soxhlet apparatus for 6 h with n-pentane to remove lipophilic, nonlignin matters such as wax and lipids (Sun and Tomkinson, 2001). The precipitate was filtered and washed twice with pH 2 water to remove the excess n-pentane and non-lignin phenolic compounds, which may still remain after the pulping process. The purified KL was then dried further in the vacuum oven at 45°C for another 48 h. 

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