Adding copper ion solution to milk will denature protein and form a precipitate. This phenomenon is called.

Copper ion solution is usually blue. When copper ions are mixed with alkaline solution, a reduction reaction will occur, resulting in precipitation. In fact, the precipitation formed by putting copper ion solution into milk is that copper ions are reduced by alkaline substances in milk, and the precipitation formed is not protein, but precipitated copper salt. This phenomenon is called biuret test in chemistry.

There is a chemical joke that the precipitation phenomenon formed by pouring copper ion solution into milk is called copper salt emulsion polymerization. Actually, it's just a joke. Of course, this is not emulsion polymerization of copper salt, but copper ion solution is reduced to precipitated copper salt by alkaline substances in milk. This chemical phenomenon is a reduction reaction. Most notably, the smoke bomb thrown in this question is to denature protein and form a precipitate. In fact, this is a smoke bomb deliberately thrown by the questioner. This deposit has nothing to do with protein's dime, so this is the difficulty of this problem. Many students were misled into thinking that the precipitated substance was formed in protein, but it was actually just a copper salt. Even if copper ion solution is mixed with other alkaline solutions, precipitated copper salt will be produced. It's just that protein in milk is emphasized here, so many people are misled.

It is very important that copper ion solution is a toxic solution. In daily life, copper ion solution is blue, and its biggest use is as disinfectant. Especially, copper ion solution is often added to the swimming pool water for disinfection, which is why the swimming pool water is always blue. In addition, the disinfection products of some toilets used daily at home is also blue, because these products all contain copper ion solution, and the most important thing is that the copper ion solution must not be mixed with food.

? The principle and origin of problem analysis

First, the origin of the problem

In a chemical experiment, protein was denatured and precipitated by adding copper ion solution into milk. In fact, this method is called biuret protein content test, which is also commonly known as biuret test. The precipitate formed in this chemical experiment is copper salt.

Second, principles.

Biuret (NH _ 2 ConHCONH _ 2) reacts with copper sulfate in alkaline solution to produce purplish red compound. In this experiment, because many peptide bonds in milk protein can also react with CU2 copper ions in alkaline solution, a purplish red compound is precipitated. The darker the color, the higher the protein concentration. If the color is lighter, the protein concentration is low. This means that the purple-red composite copper salt produced by the reaction has the same color depth as that of protein.

Third, practical application.

It is precisely because the copper ion solution will react with the basic peptide bond in milk to generate a purplish red compound to precipitate copper salt, and the color of this purplish red compound precipitation is directly proportional to the protein concentration in milk, so this chemical experiment is applied to detect the protein concentration in milk.

Putting copper ion solution into milk will denature protein and form a precipitate, which is called biuret experiment. Biuret (NH _ 2 ConHCONH _ 2) reacts with copper sulfate in alkaline solution to produce purple-red compound, which is called biuret test. Simply put, the protein peptide bond in milk reacts with copper ions to form copper ion precipitation. Also known as biuret phenomenon.