Glycerine distillation

Wiped Film Evaporator (WFE) An alternate method of distilling glycerine is by using a wiped film evaporator system (Figure 8). Pfaudler Corp. describes... 

Typical activated carbon usage is in the range of 0.5-1.0%. This can vary depending on the amount of odor and color impurities in the distilled glycerine. 

It has been found that glycerine left inside processing vessels, especially carbon columns, can degrade and develop hard-to-remove odors. Therefore, process equipment should be cleaned completely after shutdown, and carbon columns blown down with air and washed with water. Also, fresh carbon can sometimes contain odor-causing impurities. The carbon can be washed with distilled glycerine that can be subsequently redistilled or sold as a lower grade. 

A combination with distillation is illustrated by the purification of glycerine. Ordinarily, it is difficult to decolorize crude glycerine to water-whiteness, but the task is easier after one distillation, and even more so after redistillation. In industrial practice, virgin carbon is applied to the twice-distilled glycerine, and the spent carbon from this stage is added to the crude glycerine to remove foam-formers that hinder distillation. 

Distillation improves the quality of glycerin, but even a double-distilled product often contains color and odor that can be removed only by activated carbon. The ease with which glycerin can be decolorized increases with distillation. A crude glycerin is relatively difficult to decolorize to a water-white product, but the task becomes easier after the glycerin has been distilled and is much easier on a twice-distilled glycerin. A low-soluble ash is required in carbons to be used for pharmaceutical glycerin. 

Why is it absolutely necessary to make use of freshly prepared double-distilled glycerine in the cyclization of ort/io-benzoyloxyacetophenone ... 

Every care is taken that the still does not become overheated this precaution not only prevents loss of glycerine through carbonisation, but also obviates the production of tarry and other bodies which might affect the colour, taste, and odour of the distilled glycerine. The vacuum to be used will, of course, depend upon the heat of the fire and still, but as a general rule good results are obtained with an 18 inch vacuum. 

Distilled Glycerine.—This class of commercial glycerine, although of limited use in various other branches of industry, finds its chief outlet in the manufacture of explosives. 

Chemically pure ylyoerim or double distilled glycerine is produced by redistilling once distilled glycerine. Every care is taken to avoid all fractions which do not withstand the nitrate of silver test. The distillation is very carefully performed under strict supervision. 

In addition to distilled glycerines, refined glycerines which liave only been bleached by bone-charcoal are also irscd in commerce.. For this purpose they are diluted to -TO per cent with water and passed througlr a filter battery. 

Comparatively, the purest is the saponification glycerine. It contains only 0-5 per cent ash, but much lime and magnesia. It is also concentrated to 28" and differs from distillation glycerine in that when treated with lead acetate there is only a slight and slow deposit , and hydrochloric acid does not cause any turbidity. 

The purest is the double distilled glycerine with a percentage of water of only 2-3 per cent. It must be colourless and should not possess any unpleasant smell. Once-distilled glycerine must also answer these requirements, but it generally contains slight quantities of salts. 

This test, by means of which it is easy to distinguish concentrated from distilled glycerine, is carried out in such a way that the glycerine is diluted with twice or three times its volume of water and ammonium oxalate added the pro.scnco of lime salts will cause a deposit of calcium oxalate. 

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