Why use 75% alcohol instead of 95% alcohol for disinfection?

Alcohol molecules have great permeability. It can penetrate through the membrane on the surface of bacteria and penetrate into the interior of bacteria, solidifying the proteins that form the basis of bacterial life and killing bacteria, A hard layer is formed, which prevents alcohol molecules from penetrating into the bacteria. On the contrary, it protects the bacteria from death. After a certain amount of water is mixed into pure alcohol, alcohol will not make the proteins on the surface of bacteria solidify all at once, so a large number of alcohol molecules get into the bacteria and make the proteins solidify, After repeated experiments, people know that 75% alcohol has the strongest bactericidal power, so medical disinfection alcohol generally contains 75% pure alcohol and 25% water. I remember reading an article "what is the best concentration for disinfection with alcohol?" someone must say: "of course, the higher the concentration, the better!" the answer is No, It will make the outer wall of bacteria solidify in a short time, forming a shield, and the subsequent alcohol can no longer be killed. The bacteria are still alive behind the barrier. The most effective concentration is to adjust the concentration of alcohol to be "soft" and let the moisturizer penetrate into it silently. The effect is good

Why 70% alcohol has better germicidal efficacy than 95% alcohol

We know that medical alcohol contains 75% alcohol, not pure alcohol,
So why can alcohol disinfect? The scientific name of alcohol is ethanol, which has great penetration ability and can penetrate into bacteria,
This is why some animal specimens in the laboratory are often soaked in alcohol
Why is 75% alcohol in medical alcohol not pure distiller's grains
When the concentration is very high, the protein on the surface of bacteria will be coagulated quickly, resulting in the formation of a hard layer, which has a protective effect on bacteria,
To prevent further infiltration of alcohol, therefore, concentrated alcohol is not as good as dilute alcohol. If you mix some water in alcohol, the concentration of alcohol will become thinner
However, thin alcohol does not rush to coagulate the protein on the surface of the bacteria, but infiltrates into the bacteria, and then dissolves the whole bacteria
In order to achieve the purpose of sterilization

Can 95% alcohol disinfect?
According to the principle of alcohol disinfection, 75% alcohol has the best disinfection effect
But recently we bought 95% alcohol. It's written on the package for disinfection. What's the matter?

No, 95% alcohol can quickly solidify the protein membrane on the surface of bacteria, thus preventing alcohol from entering the bacteria. Generally, 95% alcohol is used as fuel, but it can also be used for high-temperature disinfection with its flame. The "disinfection" on the alcohol you buy should refer to flame disinfection!

What's the difference between "cylinder" and "cylinder"?

It should be "cylinder", the place where mixed gas is burned, but it is called "cylinder" in Hong Kong and Taiwan

What are the differences between high speed cylinder and ordinary cylinder?
Please note: I said the cylinder is pneumatic components, that kind of cylinder is nothing else. Please make no mistake

The speed of high-speed cylinder can reach 3 M / s, and that of ordinary cylinder can only reach 0.6 m / s

What is the difference between single acting cylinder and double acting cylinder?

The switch action of double acting cylinder is driven by air source;
Single action switch action only open action is driven by air source, and close action is spring return; single action is divided into normally open type and normally closed type
Normally open type: (ventilation off, air off on);
Normally closed type: (ventilation on, air off)

In a four stroke internal combustion engine, the flywheel speed is 3000r / min, the piston area s is 120cm2, and the distance L of the piston moving in the cylinder in one stroke is 0.03m. If the average pressure of the gas in the power stroke is 5 × 105Pa, we try to find: (1) what is the pressure of the gas in the power stroke of the internal combustion engine? (2) what is the power of the internal combustion engine? If the internal combustion engine burns 0.03kg of fuel every 1min, Try to find: (3) what is the efficiency of internal combustion engine? (qfuel = 4.2 × 107j / kg)
Ask for a good answer~

（1）F=PS=5×10^5×120×10^(-4)=6000N
(2) One time work: w = FS = 6000 × 0.03 = 180J
One time: 1 min for 3000 turns, 1 s for 50 turns, 25 times of work, so 180 × 25 for 1 s = 4500j
So the power is 4500W
(3) 1 min work w = 4500 × 60 = 270000j = 2.7 × 10 ^ 5J
Energy released from consumed fuel: q = 0.03 × 4.2 × 10 ^ 7 = 1.26 × 10 ^ 6J
Efficiency: 2.7 × 10 ^ 5J / (1.26 × 10 ^ 6J) = 21%

As shown in the figure, this is the internal combustion engine working time Stroke. The internal energy of the gas in the cylinder as the piston descends (select "decrease" or "increase"), the temperature of the gas__ (select "decrease" or "increase")

It can be seen from the figure that the intake valve and exhaust valve are closed, and the piston moves downward, so it is the power stroke; at this time, the high temperature gas inside the internal combustion engine expands rapidly, and when doing external work, the internal energy is converted into mechanical energy, so the internal energy of the gas decreases, and the temperature of the gas decreases

The ()
A. Internal energy increases and temperature increases B. internal energy decreases and temperature decreases C. internal energy increases and temperature decreases D. internal energy decreases and temperature increases

Compression stroke is the stroke that mechanical energy is transformed into internal energy. Internal energy increases and temperature increases. A. internal energy increases and temperature increases, which is in line with the meaning of the topic. B. internal energy decreases and temperature decreases, which is not in line with the meaning of the topic. C. internal energy increases and temperature decreases, which is not in line with the meaning of the topic. D. internal energy decreases and temperature increases, which is not in line with the meaning of the topic

The lowest temperature in the cylinder of four stroke internal combustion engine is at the end of () stroke, and the highest temperature is at the beginning of () stroke
The lowest temperature in the cylinder of four stroke internal combustion engine is at the end of () stroke, and the highest temperature is at the beginning of () stroke

The lowest temperature in the cylinder of four stroke internal combustion engine is at the end of the (suction) stroke, and the highest temperature is at the beginning of the (expansion) stroke

Why use 75% alcohol instead of 95% alcohol for disinfection?