Generally speaking, caustic soda is exist as a kind of liquid. So people can measure how many consumption we have used very conveniently. At the same time, sodium hydroxide could adjust the pH value of water, neutralization the waste water and even elimination of heavy metal ions in water by precipitation.
Maybe little people know the sodium hydroxide is used for making paper. The original material for making paper is straw or wood. These materials have a lot of lignin, gum and other non cellulose except many cellulose. Before making paper, we should separate unnecessary impurity with mechanical method. And then using the fiber to make paper. However this fiber of paper pulp is very short and paper will be in bad quality and easy to broken. At this time, you may try to use the sodium hydroxide to help. Cooking the original with sodium hydroxide solution. Then people would be very curious. Since the sodium hydroxide without any damage capability for cellulose component and could decomposition of non cellulose gum.
Article From: http://www.hiseachem.com/news/Water-Treatment-By-Sodium-Hydroxide.htm