At normal temperature and pressure, hydrogen is a gas that is extremely flammable, colorless, transparent, odorless, odorless, and difficult to dissolve in water. Hydrogen is the smallest gas known in the world. The density of hydrogen is only 1/14 of that of air. That is, at 0 ° C, the density of hydrogen is 0.089g / L at a standard atmospheric pressure. Therefore, hydrogen can be used as a filling gas for airships and hydrogen balloons (because hydrogen is flammable and not very safe, airships are now filled with helium). Hydrogen is the substance with the smallest relative molecular mass and is mainly used as a reducing agent.
Hydrogen (H2) was first produced artificially in the early 16th century, when the method used was to place metals in strong acids. From 1766 to 1781, Henry Cavendish discovered the element of hydrogen. The combustion of hydrogen produces water (2H₂ + O₂ ignition = 2H₂O). Lavoisier named the element “hydrogenium” (“the substance that produces water”) Meaning, “hydro” is “water”, “gen” is “generating”, and “ium” is the universal element suffix). When British doctor B. Hobson wrote The New Museum (1855) in the 1850s, he translated “hydrogen” into “light gas”, meaning the lightest gas.
The industry generally produces hydrogen from natural gas or water gas, instead of using a high energy consumption method of electrolyzing water. The produced hydrogen is widely used in the cracking reaction of the petrochemical industry and the production of ammonia. Hydrogen molecules can enter the lattice of many metals, causing “hydrogen embrittlement”, which makes hydrogen storage tanks and pipes require special materials (such as Monel alloy), and the design is more complicated.
Attentions for operating
Hydrogen is a colorless, odorless, non-toxic, flammable and explosive gas. There is a danger of explosion when mixed with fluorine, chlorine, oxygen, carbon monoxide and air. The mixture of hydrogen and fluorine at low temperature and darkness The environment can spontaneously explode. When the volume ratio with chlorine is 1: 1, it can also explode under light. Because hydrogen is colorless and odorless, the flame is transparent when burning, so its presence is not easy to be detected by the senses. In many cases, odorous ethyl mercaptan is added to hydrogen in order to detect the smell and to give the flame color at the same time.
Although hydrogen is non-toxic and physiologically inert to the human body, if the hydrogen content in the air increases, it will cause hypoxic asphyxia. As with all cryogenic liquids, direct contact with liquid hydrogen will cause frostbite. Liquid hydrogen overflow and sudden large-area evaporation will also cause environmental anoxia, and may form an explosive mixture with air, causing a combustion explosion accident. Mixing with air can form explosive mixtures, which will explode when exposed to heat or open flames. The gas is lighter than air. When it is used and stored indoors, the leaked gas rises and stays on the roof. It is not easy to discharge, and it will cause an explosion when it encounters Mars. Hydrogen reacts violently with halogens such as fluorine, chlorine, and bromine.
Because hydrogen is a flammable and compressed gas, it should be stored in a cool, ventilated warehouse. The temperature in the warehouse should not exceed 30 ° C. Keep away from fire and heat sources. Protect from direct sunlight. It should be stored separately from oxygen, compressed air, halogen (fluorine, chlorine, bromine), oxidants, etc. Never mix storage and transportation. The lighting, ventilation and other facilities in the storage room should be explosion-proof. The switch is located outside the warehouse and equipped with the corresponding variety and quantity of fire equipment. Prohibit the use of spark-prone machinery and equipment tools. Pay attention to the product name during inspection, pay attention to the date of inspection, and use the advanced warehouse first. Lightly load and unload during transportation to prevent damage to cylinders and accessories.