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.
These are called rapid eye movement (REM) sleep, and non-rapid eye movement (Non-REM) sleep. In adults, non-REM sleep occupies around 80 percent of the night, and REM sleep 20 percent. However, REM sleep does not occur in one large block. Actually, we go into REM sleep in cycles of around 90 minutes. That is, REM sleep occurs around once every 90 minutes.