Народ выполнить это задание.Ex.1. Give a summary of the text.
Text 2. Extraction of Drugs (continued)
Sugar-beet is widely grown in Europe. The sugar-content of beet varies from 10 per cent and is dependent on the variety of beet, the climate, soil and other conditions. Beet also contains a variety of undesirable substances such as amino-acids, other organic acids of low molecular weight and ash-forming salts, these substances being readily soluble are extracted along with the sugar.
The first stage of extraction is a diffusion process. The beet is cut into shreds and extracted by water at 78 to 80°C in a battery of diffusers. The diffusers are arranged so that the shredded beet passes from a liquid containing less sugar and finally to pure water. An advantage of the diffusion process is that the walls of the beet cells are used as a filter so that proteins and other colloidal substances are not extracted. The juice is heated up to 80–90°C. It coagulates and absorbs any colloidal impurities and neutralizes free acids. The acids bring about inversion of the sucrose. The liquid is then treated with carbon dioxide and passed through filter presses to remove calcium carbonate and the precipitated impurities. After passing carbon dioxide and filtering the juice is further processed by passing sulphur dioxide and filtration. The filtrate which contains some 12 to 15 per cent of sucrose is evaporated under reduced pressure to a thick juice. This juice reaches the super-saturation or graining point. At this stage the semi-crystalline mass of sucrose crystals and molasses passes to a centrifuge where the mother liquor is separated and the crystal washed with a little water. The sugar is then cooled, dried and screened.