Crystallization with agitation

Agitated tank crystallizer for continuous and discontinuous operation, crystallizer with forced suspension circulation, horizontal crystallizer and multistage, crystallizer with agitator and controlled flow (DTB), vortex crystallizer according to Standard-MESSO. 

The mother Hquor from the cmde ferrous sulfate crystallisation contains neady all the chromium. It is clarified and aged with agitation at 30°C for a considerable period to reverse the reactions of the conditioning step. Hydrolysis reactions are being reversed therefore, the pH increases. Also, sulfate ions are released from complexes and the chromium is converted largely to the hexaaquo ion. Ammonium chrome alum then precipitates as a fine crystal slurry. It is filtered and washed and the filtrate sent to the leach circuit the chrome alum is dissolved in hot water, and the solution is used as cell feed. 

The total yield of the crude precipitation obtained in the above manner comprising about 1 kg is then dissolved In chloroform so as to form a 15% solution of a crude penicillin salt. To the filtered chloroform solution is added ethyl acetate slowly and with agitation until the solution becomes turbid as crystallization begins. Thereafter crystallization is allowed to proceed undisturbed for about 30-60 minutes in a cold room having a temperature of about 5°C. Sufficient ethyl acetate is slowly added to provide a final concentration of about 50% ethyl... 

The rate of primary nucleation and width of the associated metastable zone are difficult to measure with precision in the laboratory, because of their dependence on environmental factors. Dust particles contaminating a solution, and imperfections on the surface of the crystallizer and agitator are often... 

Data measured in the presence of crystals with slow cooling and moderate agitation. The working value for a normal crystalliser may be 50 per cent of these values or less. 

CA 59, 13763(1963) (Powdered AN expls prepd by mixing ingredients, such as AN 60, NaN03 12, KC1 4.5, NaCl 3.5, DNN 7, flour 1 urea 3%, followed by heating to 120° with agitation. The resulting melt is then sprayed thru a nozzle into a dry, cool flue to crystallize as a powder of desirable particle size)... 

To 100 grams of a-aminobenzylpenicillin slurried in 2,500 ml of acetone is added 200 ml of a 22% solution of potassium ethylhexanoate in dry n-butanol and the mixture is warmed to 45°C whereupon the acid dissolves. After the mixture is agitated for 1 hour at 40° to 45°C, the product begins to crystallize out. Agitation is continued for 4 hours at 45°C after which the product, the potassium salt of hetacillin, is collected by filtration, washed with 500 ml of dry acetone, dried for 17 hours at 40°C and found to weigh 70.0 grams. 

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