To make white sugar, sulfur dioxide is added to cane juice before it gets evaporated. This gas does the bleaching of the juice so that it does not turn brown and produces white sugar. At later stages, phosphoric acid, calcium hydroxide or carbon dioxide is added to absorb impurities.
The first REM sleep period usually occurs about 70 to 90 minutes after we fall asleep. A complete sleep cycle takes 90 to 110 minutes on average. The first sleep cycles each night contain relatively short REM periods and long periods of deep sleep.
The amount of sleep each person needs depends on many factors, including age, health, recent physical exertion, and mental activity. There is genetic influence, too. Some people just need more sleep than others and this runs in families. Infants sleep about 16 hours a day, while teenagers need 9 hours on average. For most adults, 7 to 8 hours a night appears to be the best amount of sleep, although some people may need as few as 5 hours or as many as 10 hours of sleep each day.