Let’s talk about the safety issues in chemical experiments

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Safety protection in chemical experiments is extremely important. Those of us in this field are inevitably exposed to various dangers. How can we take safety measures to protect ourselves? Please share your own methods, experiences, and insights :) Safety precautions in chemical experiments • In chemical experiments, various chemicals and equipment are used, as well as water, electricity, and gas. Additionally, experiments are often conducted under conditions of high or low temperatures, high pressure, vacuum, high voltage, high frequency, or in the presence of radiation sources. Without the necessary knowledge of safety precautions, this can lead to severe losses of life and property. • Education on safety precautions for chemical experiments is very important. Proper use of chemical substances and safety precautions • Poison prevention • Most chemical substances possess varying degrees of toxicity. Toxic chemicals can enter the body through the respiratory tract, digestive tract, and skin, causing poisoning. • If HF enters the human body, it can damage teeth, bones, the hematopoietic system, and the nervous system ； • Organic compounds such as hydrocarbons, alcohols, and ethers have varying degrees of **effect on the human body** ； • Arsenic trioxide, cyanides, and mercuric chloride are highly toxic substances; even a small amount inhaled can be fatal. • Toxicity prevention precautions • Before conducting the experiment, it is necessary to understand the toxicity, properties of the chemicals being used, as well as the appropriate protective measures ； • The use of toxic gases (such as H2S, Cl2, Br2, NO2, HCl, HF) should be carried out in a fume hood ； • Prolonged exposure to vapors such as benzene, carbon tetrachloride, ether, and *** can weaken a person’s sense of smell, so it is necessary to be highly vigilant ； • Organic solvents can penetrate the skin and enter the body, so direct contact with the skin should be avoided ； • Highly toxic substances such as mercury salts, cadmium salts, lead salts, etc., should be stored properly ； • Experimental procedures must be followed properly, and hands should be washed before leaving the laboratory. • Fire prevention • Prevent leaks from gas pipes and gas lamps; be sure to close the valves properly after using gas ； • Organic solvents such as ether, alcohol, acetone, carbon disulfide, and benzene are flammable; large quantities of them should not be kept in the laboratory. They must not be poured down the drain, as this could lead to fires due to accumulation ； • Metal sodium, potassium, aluminum powder, calcium carbide, yellow phosphorus, and metal hydrides require careful handling and storage, especially as they should not come into direct contact with water ； • In the event of a fire, one should remain calm, assess the situation, and take appropriate measures to extinguish it ； Depending on the situation, water, sand, foam, CO2, or CCl4 fire extinguishers can be used to put out the fire. • Explosion prevention • The explosions of chemical substances can be divided into chain reactions and thermal explosions • Flammable gases such as hydrogen, ethylene, acetylene, benzene, ethanol, ether, propane, ethyl acetate, carbon monoxide, water gas, and ammonia, when mixed with air to reach their explosive limits, are highly prone to chain reactions once triggered by a heat source ； • Explosive substances such as peroxides, perchlorates, lead azide, copper acetylide, and trinitrotoluene can undergo thermal explosions when subjected to shock or heat. • Explosion prevention measures • To prevent branch explosions, it is essential to stop flammable gases or vapors from spreading into the indoor air, by ensuring good ventilation inside. When large amounts of flammable gases are used, the use of open flames and electrical devices that may generate sparks is strictly prohibited ； • To prevent thermal explosions, strong oxidizers and strong reducers must be stored separately; when using them, handle them with care and keep them away from heat sources. • Burn prevention • In addition to high temperatures, substances such as liquid nitrogen, strong acids, strong bases, strong oxidizing agents, bromine, phosphorus, sodium, potassium, phenol, and acetic acid can also cause skin burns ； Care should be taken to avoid skin contact, and especially to prevent it from getting into the eyes. Safe use of mercury • Mercury is a commonly used substance in chemical laboratories; it is highly toxic and does not easily leave the body, leading to cumulative poisoning ； • 0.1-0.3 g of high-mercury salts (such as HgCl2) can be fatal ； • The vapor pressure of mercury at room temperature is 0.0012 mmHg, which is 100 times higher than the safety concentration standard. • Operating procedures for the safe use of mercury: (1) Mercury must not be exposed to air directly; it should be covered with water or other liquids ； (2) Any remaining amount of mercury must not be poured down the sink ； (3) The mercury storage container must be a sturdy, thick-walled vessel, and the vessel should be placed on a porcelain plate ； (4) The container holding mercury should be kept away from heat sources ； (5) If mercury falls on the floor, countertop, or sink, try to collect the mercury droplets using a straw. Then, use a metal sheet that can form a mercury amalgam (such as Zn, Cu, Sn, etc.) to sweep over the area where the mercury is spilled several times, and finally cover it with sulfur powder ； (6) The laboratory should be well-ventilated ； If you have wounds on your hands, do not come into contact with mercury. Safe use of electricity • Personal safety protection • The electricity commonly used in laboratories is alternating current with a frequency of 50 Hz and 200 V. A current of 1 mA can cause tingling or a stinging sensation in the human body; currents above 10 mA lead to strong muscle contractions, while currents above 25 mA result in breathing difficulties and pose a life threat ； Direct current also poses similar dangers to the human body. • To prevent electric shock, the following should be done: (1) When repairing or installing electrical appliances, the power supply must be turned off first ； (2) Keep your hands dry when using electrical appliances ； (3) The exposed parts of the power supply should be equipped with insulation devices, and the electrical enclosure should be grounded ； (4) Do not use a voltage tester to check high-voltage electricity ； (5) Do not touch electrical appliances with both hands at the same time to prevent electric current from passing through the heart ； (6) Once someone gets an electric shock, the power supply should be cut off first, followed by providing first aid. Safe use of electricity for instruments and equipment • All instruments should be connected to an appropriate power supply in accordance with the instructions; those that require grounding must be grounded ； • For DC electrical equipment, pay attention to the positive and negative poles of the power supply to avoid incorrect connection ； • If the power supply is three-phase, the neutral point of the three-phase supply must be grounded, so as to reduce the contact voltage in the event of an electric shock ； When connecting a three-phase motor, make sure that the rotation direction is correct; otherwise, disconnect the power supply and swap the phase wires ； • When making connections, ensure that the joints are secure, and select appropriate wiring according to the rated current of the electrical appliance ； • After connecting the circuit, it must be carefully checked to ensure there are no errors before powering it on for use ； • The power supply should be turned off promptly when the instrument malfunctions. Safety precautions when using high-pressure containers • Chemical experiments often involve high-pressure gas cylinders as well as ordinary pressurized glass instruments; improper use can lead to explosions, so it is necessary to know the relevant basic knowledge and operating procedures • Identifying gas cylinders (for cylinders of the same color, check the gas name): Oxygen cylindersky blue ； Hydrogen cylinderDark green ； Nitrogen cylinderBlack ； Pure argon cylinder  gray ； Helium cylinder  brown ； Compressed air → Black ； Ammonia cylinderYellow ； Carbon dioxide cylinderBlack. Safe use of high-pressure gas cylinders • Gas cylinders should be used for their intended purpose only, and must not be modified arbitrarily ； • Gas cylinders should be stored in a cool, dry place away from heat sources; the distance between gas cylinders containing flammable gases and open flames should be at least 5 meters ； Hydrogen cylinders should be isolated as much as possible ； • Handle gas cylinders gently and carefully, and place them securely ； • Various types of barometers should generally not be used together ； • Oxygen cylinders must not be contaminated with oil; be careful of oil on hands, wrenches, or clothing ； • The gas in the cylinder must not be used up to prevent backflow ； • When opening the valve, one should stand on the side of the pressure gauge; it is not allowed to point the head or body at the main valve of the gas cylinder, to prevent the valve or pressure gauge from flying out and causing injury. Safety precautions when using radiation source instruments • Radiation in chemical laboratories mainly refers to X-rays; prolonged and repeated exposure to X-rays can cause fatigue, reduced memory, headaches, and a decrease in white blood cell counts. • The method of protection is to avoid direct exposure of various parts of the body, especially the head, to X-rays; shielding and time reduction are necessary during operations, with materials such as lead and lead glass being commonly used for shielding.