Chemical Engineering in Daily Life - Question 11 - Standard Answers Available
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This post was last edited by yjqin1 on 2015-8-22 at 18:25. The chemical reagents that could be found in rural areas during the 1960s and 1970s included slaked lime, soda ash, baking soda, alcohol, and vinegar. I always want to create stronger acids or bases, such as sulfuric acid, salt acids, sodium hydroxide, and things like that. It’s hard! Besides, there were no indicators available at that time. It wasn’t until 1981, when I was admitted to TJDX and could take inorganic chemistry experiments, that it happened for the first time in my life; I was so happy. But I don’t have many strong memories of those chemistry lab experiments from my first year in college ； And those \"chemical experiments\" done out of mischief in childhood can be remembered for a lifetime. At that time, I didn’t have phenolphthalein or litmus available as indicators, but I noticed that the new \"flesh\" extracted from sorghum stalks changed color in the presence of alkaline substances, shifting from a near-white color to yellow; the higher the alkalinity, the darker the color became. I found that a solution of baking soda hardly causes any discoloration of the \"flesh,\" while soda ash leads to more noticeable discoloration. The worst case is the supernatant formed when slaked lime is added to water. On a whim, I mixed slaked lime suspension with a concentrated sodium carbonate aqueous solution, and found that the liquid that splashed on my hand was smoother. When the \"pulp\" is added to the supernatant, the color becomes the darkest. Please explain why?
When slaked lime suspension and concentrated sodium carbonate aqueous solution were mixed, it was found that the liquid that splashed onto the hand was smoother. When the \"pulp\" is added to the supernatant, the color becomes the darkest. Isn’t this exactly the method used for producing alkali through digestion? You must be an expert in this field; I’m here to learn from you
This post was last edited by *lihuagong on 2015-8-17 16:19. The teacher explained it in great detail: the stronger the alkalinity, the darker the color change. Specific heat; NaOH is more basic than Ca(OH)2, and the reaction takes advantage of the formation of calcium carbonate precipitate. The teacher has been this smart since childhood; it’s a natural talent of theirs, haha:lol
But I noticed that the new \"flesh\" extracted from sorghum stalks changes color in the presence of alkaline substances. What is this phenomenon?
The fresh flesh contains sugar, and sugar turns yellow when it comes into contact with alkali; the higher the concentration of alkali, the darker the color
This post was last edited by yjqin1 on 2015-8-22 at 18:24. The standard answer is: The main components of the \"flesh\" part in sorghum straws are hemicellulose, cellulose, and lignin. Lignin undergoes a color change when exposed to alkaline solutions; the higher the alkalinity of the solution, the darker the color change in this flesh portion. The alkalinity of the various solutions tried, in descending order, is: the supernatant obtained from the reaction of sodium carbonate with slaked lime (sodium hydroxide solution) > slaked lime (calcium hydroxide solution, pH≈12.5) > aqueous sodium carbonate solution (pH≈11.5) > sodium bicarbonate solution (pH≈7.8). One of my doctoral students is currently working on a thesis about using straw to produce fuel ethanol and butanol. The experiment involved acidolysis and basic catalytic hydrolysis, which reminded me of the simple experiments I did when I was young. I recall another thing: in 1988, there was already a general trend of people engaging in business activities; TJDX recruited 23 doctoral students in total that year (quite valuable, right?) Currently, TJDX recruits over 500 doctoral students per year). The doctoral students of the class of 88 also established a company named Boshi Company, the name being a pun on \"boss\", while the school motto of TJDX is \"seeking truth from facts\". I serve as the deputy manager. One day, a group of people came from Inner Mongolia, led by a vice president and a chief engineer (a master’s graduate). They requested a technology using soda ash produced from salt lakes in Inner Mongolia to produce sodium hydroxide. Back then, sodium hydroxide was very expensive. It’s about using sodium carbonate and lime milk to react, thereby producing sodium hydroxide and calcium carbonate precipitate. To others, this might seem like a wild idea, but I know it’s possible; I conducted such experiments when I was young. They finally succeeded and made a small fortune for a while. In 2011, people were eating roasted whole sheep in Ordos while talking about this matter. This company (Boyuan Group) has been in existence for nearly three decades; it is now the world’s largest producer of natural soda ash, with its annual turnover from diversified operations reaching as high as 18 billion yuan per year. This branch factory needs to use a four-effect evaporator to evaporate and crystallize 42,000 tons of liquid material per day (containing 12% sodium carbonate) in order to produce sodium carbonate, which is then exported abroad; the business is very successful. A few years ago, I also had a contract with them for membrane concentration services; it was worth several million.