Crystal drying

Diaminonaphthalene [2243-62-1 ] M 158.2, m 190°, pK 4.12. Rerystd from boiling H2O, but is wasteful due to poor solubility. Boil in chlorobenzene (charcoal), filter hot and cool the filtrate. This gives colourless crystals. Dry in a vac till free from chlorobenzene (odour), and store away from light. 

Manganese (II) acetylacetone [14024-58-9] M 253.2, m -250°. Purify by stirring 16g of reagent for a few min with lOOmL absolute EtOH and filter by suction as rapidly as possible through coarse filter paper. Sufficient EtOH is added to the filtrate to make up for the loss of EtOH and to redissolve any solid that separates. Water (15mL) is added to the filtrate and the solution is evapiorated with a stream of N2 until reduced to half its vol. Cool for a few min and filter off the yellow crystals, dry under a stream of N2, then in a... 

The solvent was evaporated to yield a colorless solid residue, which was taken up In ethyl acetate-ice water. The two layers were separated and the aqueous layer was extracted with ethyl acetate. The combined organic layers were washed with water, saturated sodium chloride solution and filtered through anhydrous sodium sulfate. The solvent was evaporated to yield 1.20 grams of light tan crystals, MP 151° to 155°C, ultraviolet maximum at 224 mp (E = 4,095). Two recrystallizations from ethanol afforded 1st crop, 0.619 grams (62%) of colorless crystals (dried at 120°C in vacuo for 17 hours), (VIP 232.8° to 238.0°C, ultraviolet maximum at 224 mp (E = 4,840) 2nd crop, 0.142 gram (14%) of colorless crystals, MP 234° to 242°C. 

Postcondensation Heating/2nd crystallization/drying Nitrogen/hot loop... 

In the hood, behind the shield, the reaction mixture is then poured into 500 ml of vigorously stirred ice water. The nitroso compound begins to separate as a fine, yellow precipitate. The product is removed by filtration and washed thoroughly with about 1 liter of cold water. After pressing the crystals dry, they are air-dried for 3 hr. Finally they are dried over calcium chloride in a desiccator yield 2.4 gm (88%), m.p. 121°C (decomposes explosively). 

The reaction is 8NH3+3Br,=6NH4Br+Na. The liquid should remain strongly ammoniacal during the addition of the bromine, and it should be continually shaken. If the bromine is run in too rapidly, or if the liquid becomes acid, the explosive nitrogen bromide may be formed. Heat the liquid nntil all the free ammonia is driven off, and evaporate the soln. to enable the ammonium bromate to crystallize. Dry the aihmonium salt by warming the dish over a flame. The yield is 220 grms. of ammonium bromate. 

Prepare hot saturated solutions of aluminium and potassium sulphates. To do this, dissolve 6.66 g of aluminium sulphate crystallohydrate in 5 ml of hot (/ 70 °C) water. Calculate what amount of potassium sulphate is equimolecular to 6.66 g of the aluminium sulphate crystallohydrate. Weigh this amount of potassium sulphate and dissolve it in 10 ml of hot water. Pour the potassium sulphate solution into that of aluminium sulphate. Cool the solution, filter off the precipitated crystals, dry them between sheets of filter paper, weigh them, and determine the yield of the substance in per cent. Examine the shape of the crystals under a microscope and draw them. 

Quinidine [56-54-2] M 324.4, m 171 , [alg g +301.1 (CHCI3 contg 2.5% (v/v) EtOH). Crystd from benzene or dry CHCiypet ether (b 40-60°), discarding the initial, oily crop of crystals. Dried under vacuum at 1(X)° over P2O5. 

Crystd from benzene or dry CHCiypet ether (b 40-60°), discarding the initial, oily crop of crystals. Dried under... 

SPREAD OUT FILTER TO LET BORIC ACID CRYSTALS DRY. USE FOR EXPERIMENTS ONLY. 

Ammonium paratungstate is recovered from the strip solution by evaporative crystallization, dried and calcined to produce blue oxide 208... 

The solid state polymerization of hexamethylcyclotrisiloxane has been investigated over the temperature range —196° to 60°C. The rates of polymerization have been related to the presence of ion scavengers, H20, NH3, in the monomer and to the size of the crystals. Using large crystals dried over sodium, G values of polymerization of 11 X 103 were obtained at 50°C. This is five times larger than previously reported values. The reaction is concluded to be surface initiated and to be terminated at a crystal face or at a defect. 

Ammonia removal is the next step in the gas cleanup process. A typical approach is to contact the coke-oven gas with a solution of sulfuric acid to form ammonium sulfate, which is then recovered by crystallization, dried, and sold as fertilizer. More modem processes for ammonia removal include the water wash process, in which the coke-oven gas is scrubbed with water that dissolves the ammonia along... 

If much hydrochloric acid is allowed to remain with the crystals, drying is extremely difficult. 

---