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,
calcium hydroxide or carbon dioxide is added to absorb impurities.
This juice is then filtered through a bed of carbon and then crystallized in a vacuum many times. Finally the crystals are left to dry on their own to get paper white crystals of sugar.
To make sugar, machines are used: sugar cane (or sugar beet) is initially pressed and the juice is then mixed with lime to achieve the desired ph balance and to help settle out impurities. Reduction of this solution through evaporation produces a solid mass that is passed through centrifuge to get sugar crystals. It is then dried further to produce granules. This sugar is light brown in color and is termed raw sugar. The brown color of raw sugar is due to presence of molasses. Raw sugar is the most natural sugar you can hope to lay your hands on.
THE ABOVE comes from a sugar company.
In BALTIMORE, there was or still is a company that makes sugar and used cow bones to make the sugar white.
In Hawaii they say 1# of raw cane sugar ends up as 2# of white sugar.
I think the only way a person would know for sure is to go through a sugar company and watch it being made.