Exercises distillation

Recovery of the wopropyl alcohol. It is not usually economical to recover the isopropyl alcohol because of its lo v cost. However, if the alcohol is to be recovered, great care must be exercised particularly if it has been allowed to stand for several days peroxides are readily formed in the impure acetone - isopropyl alcohol mixtures. Test first for peroxides by adding 0-6 ml. of the isopropyl alcohol to 1 ml. of 10 per cent, potassium iodide solution acidified with 0-6 ml. of dilute (1 5) hydrochloric acid and mixed with a few drops of starch solution if a blue (or blue-black) coloration appears in one minute, the test is positive. One convenient method of removing the peroxides is to reflux each one litre of recovered isopropyl alcohol with 10-15 g. of solid stannous chloride for half an hour. Test for peroxides with a portion of the cooled solution if iodine is liberated, add further 5 g. portions of stannous chloride followed by refluxing for half-hour periods until the test is negative. Then add about 200 g. of quicklime, reflux for 4 hours, and distil (Fig. II, 47, 2) discard the first portion of the distillate until the test for acetone is negative (Crotyl Alcohol, Note 1). Peroxides generally redevelop in tliis purified isopropyl alcohol in several days. 

The purification of Hquid nitro alcohols by distillation should be avoided because violent decompositions and detonation have occurred when distillation was attempted. However, if the distillation of a nitro alcohol cannot be avoided, the utmost caution should be exercised. Reduced pressure should be utilised, ie, ca 0.1 kPa (<1 mm Hg). The temperature of the Hquid should not exceed 100°C hot water should be used as the heating bath. A suitable explosion-proof shield should be placed in front of the apparatus. At any rise in pressure, the distillation should be stopped immediately. The only commercially produced Hquid nitro alcohol, 2-nitro-1-butanol, is not distilled because of the danger of decomposition. Instead, it is isolated as a residue after the low boiling impurities have been removed by vacuum treatment at a relatively low temperature. 

Procedure. For practice in this determination, employ either a very dilute ammonium chloride solution or ordinary distilled water which usually contains sufficient ammonia for the exercise. 

Other A/7V-dialkylformamides including commercially available TV-methylformanilide, N-formylmorpholine, /V-formylpipcridinc, A/iV-diethylformamidc and A, jV-dimethylformamide (DMF) can be employed with essentially the same procedure. With /V,/V-dimethylformamide, care has to be exercised because of the volatility of the product, which can be purified by distillation or chromatography of its hydrochloride salt. 

A detailed study of the phase relationships in the magnesium oxysulphate cement was carried out by Urwongse Sorrell (1980b). They used X-ray analysis to examine the phases present in the cement, and established the composition of the invariant liquids after equilibration by measuring specific gravity with the aid of a pycnometer. Specific gravities were related to concentration by means of a calibration exercise in which 30 stock solutions of sulphuric acid at concentrations between 0 and 79-5 wt % were prepared with distilled water. 

This provides an excellent exercise in distillation under diminished-pressure. 

Exercise caution during the addition of the water in the distillation phase to prevent aspiration of the distillate back into the 500-mL round-bottom flask. 

A feed mixture of methanol and water containing a mole fraction of methanol of 0.4 is to be separated by distillation at a pressure of 1 atm. The overhead product should achieve a purity of 95 mole % methanol and the bottoms product a purity of 95 mole% water. Assume the feed to be saturated liquid. Using the x—y diagram constructed in Exercise 1 and the McCabe-Thiele construction ... 

A direct sequence of two distillation columns produces three products A, B and C. The feed condition and operating pressures are to be chosen to maximize heat recovery opportunities. To simplify the calculations, assume that condenser duties do not change when changing from saturated liquid to saturated vapor feed. This will not be true in practice, but simplifies the exercise. Assume also that the reboiler duty for saturated liquid feed is the sum of the reboiler duty for saturated vapor feed plus the heat duty to vaporize the feed. Data for the two columns are given in Tables 21.7 and 21.8. 

In a synthesis experiment, the point of the exercise is to prepare a clean sample of the product you want. All the operations in the lab (e.g., distillation,... 

To better understand these high-volume materials, we divided all those substances reported as produced in quantities of one million pounds per year or more into several categories such as organics, inorganics, polymers, etc. This exercise was most revealing. We found that those materials which can be classified as petroleum derivatives (gasoline, kerosine, distillation cuts,... 

The results of interlaboratory study II are presented in Fig. 4.5.1. Five sets of results were obtained for the LAS exercise, and four sets for the NPEO exercise. For LAS, the within-laboratory variability ranged between 2 and 8% (RSD) for sample III (distilled water spiked with lmgL-1 LAS), 1 and 13% for sample 112 (wastewater influent), and 3 and 8% for sample 113 (sample 112 spiked with lmgL-1 LAS). Between-laboratory variations (calculated from the mean of laboratory means, MOLM) amounted to RSDs of 15, 30 and 30% for samples III, 112 and 113, respectively. The LAS values reported were in the range of 700—1100 p,g L-1 in sample III, 1100-1800 p,g L-1 in sample 112 and 1900-3000 p,g L-1 in sample 113, indicating that even in the matrix wastewater influent, the spiked concentration of lmgL-1 LAS could be almost quantitatively determined by all laboratories. 

After the reaction is completed the products can be poured into water and ice and the aqueous hydrofluoric acid disposed of down the drain. Care must again be exercised as the mixing of hydrogen fluoride and water generates considerable heat. No hazards or disposal difficulties are incurred with hydrofluoric acid in the usual drain lines as these are made of iron pipe and the hydrogen fluoride is soon absorbed as firm complexes with the iron. It is not detectable at any great distance from the source. For some reactions this simple form of disposal is not satisfactory, for example, in the preparation of an acyl halide or other product which reacts with water. Here distillation of the hydrogen fluoride... 

In order to rationally prove this to yon, who are investigating the separation of Natnre. and purpose to understand the division of the elements, lest yon shonld think my words inventions, and not tme, I tell yon that if you distil earth, you will find that, first of all, there is an escape of air, which, in its turn, always contains fire, as they are both of a spiritual essence, and exercise an irresistible mntnal attraction. In the next place, there issnes water from the earth, and the earth, in which is the precions salt, remains by itself at the bottom of the vessel. 

Caution. Diethyl ether used as a solvent should be free of peroxides before further drying and distillation from lithium tetrahydroaluminate(l-) is attempted. During distillation, caution must be exercised never to permit the still pot to run dry. 

Caution. Carbon monoxide is an odorless, extremely toxic gas and must be handled in an efficient hood. Solid Cu(CO)Cl exhibits a very high CO dissociation pressure and should be handled with the same care as carbon monoxide. Ethyl vinyl ketone (EVK) is a strong lachrymator and must be handled in a well-ventilated hood. EVK may contain peroxides and caution must be exercised when distilling. 

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