Boiling period

Acetylsalicylic acid decomposes when heated and does not possess a true, clearly-defined m.p. Decomposition points ranging from 128° to 135° have been recorded a value of 129-133° is obtained on an electric hot plate (Fig. II, 11, 1). Some decomposition may occur if the compound is recrystaUised from a solvent of high boiling point or if the boiling period during recrystallisation is unduly prolonged. 

This example is based on the model description of Sec. 3.3.4, and involves a multicomponent, semi-batch system, with both heating and boiling periods. The compositions and boiling point temperatures will change with time. The water phase will accumulate in the boiler. The system simulated is based on a mixture of n-octane and n-decane, which for simplicity will be assumed to be ideal but which has been simulated using detailed activity coefficient relations by Prenosil (1976). 

The heat transferred during one boiling period is given by equation 14.13 ... 

Assay Accurately weigh a portion of sample equivalent to about 475 mg of Calcium Phosphate, Monobasic, Anhydrous [Ca(H2P04)2], dissolve it in 10 mL of 2.7 N hydrochloric acid, add a few drops of methyl orange TS, and boil for 5 min, keeping the volume and pH of the solution constant during the boiling period by adding hydrochloric acid or water... 

The reflux boiling is continued for 10 hours. During this time the mixture will turn black. At the end of the boiling period, the mixture is allowed to cool down. When it is cool, 200 ml of benzene or toluene is added to the flask. The mixture is shaken well for a couple of minutes, then allowed to sit. The benzene floats up to the top, and has dissolved in it most of the unreacted amide, and other unwanted garbage. 

If a liquid is pure and its container is clean, considerable superheating is possible as discussed earlier. Under these conditions boiling could occur in a cyclic manner first a quiet, non-boiling period as the liquid superheats then an explosion when the nucleation rate becomes large and finally a sudden drop in the liquid temperature after the superheat has disappeared as heat of vaporization. The process would then repeat. 

Crystals. The technical grade may have a pleasant odor Soly in water at 25" 59 g/100 ml. Sparingly sol in alcohol. Insol in ether. Aq solns are stable to short boiling periods. 

Strauss) CUSO4 boiling periods with fresh solution for each bending at carbides... 

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