Put two tablets of dichlorosulfanilamide benzoic acid into 1 liter of water, and how long can it be disinfected after standing?

1. When drinking water and disinfection are in trouble, especially in hot areas and desert areas, water supply becomes very important. (1) Water sources Natural water sources include the following: surface water, such as rivers, lakes and streams. Groundwater, such as well water, spring water, underground reservoir, etc. Biological water, such as some plants with sufficient water, such as bananas, bamboos and cacti. Water in the sky, such as rain, snow, dew and melted ice. (2) The purified rainwater, spring water, well water and mountain stream can be directly drunk. Still or slow-flowing water contains a lot of organic matter and bacteria, which can only be drunk after purification. Purification is to eliminate organic matter in water, disinfect and remove odor. In the case of survival in danger, you can purify drinking water in the following simple ways. Find a container, such as canvas bag, polyethylene plastic bag, big tin can, sleeves tied at one end or even socks, which can be used as a container. Spread a layer of fine gravel on the bottom of the container, then spread a layer of sand and a layer of carbon powder, and so on for many times. The more layers, the better, each layer is about 2.5 cm thick. If there is no sand, use fine gravel instead. In addition, there is a way to purify water. Dig a shallow pit half a meter away from the water source. After a period of time, clear and clean water will seep out of the pit. (3) disinfection, boiling disinfection. At sea level, boil for at least 1 min; In higher altitude areas, the boiling time should be prolonged, and the boiling time can be increased by 3-4 minutes per altitude1000 m. Chemical disinfection. Disinfectants include dichlorosulfamic acid, iodide, halasone, etc. Put 2 pieces of dichlorosulfamic acid into 1 liter water and let it stand for 15-30 minutes to achieve the purpose of disinfection. Without this medicine, 8- 10 drops of iodine can be dropped per liter of water. If you want to kill bacteria, you must use one of the following methods: water purification tablets are the easiest to use. Before entering the desert, you can buy some from the drugstore and use them according to the instructions of the tablets. You need them not only in self-help and danger avoidance, but also in cars and planes. Generally speaking, 1 water purification tablet is enough to purify 1 liter of clean water, and 2 tablets can purify 1 liter of turbid water. Before using pure water, let it settle for 30 minutes. Add 3 drops of iodine per liter of clear water and double the amount of turbid water. After settling for 30 minutes, add 2 drops of household bleach (5.25% sodium chlorite) to each liter of clean water. Use after settling for 30 minutes. Bleached water has a very light chlorite smell. Boiling water can also be purified in 3-5 minutes. Add a little carbon to the water and boil it to remove the abnormal color. Stir the water to cool it and restore its taste or add a pinch of salt. 2. Find the water source (1). Finding and purifying drinking water is very important for human survival. As the saying goes, water is more important than food to some extent. 1983, several college students got lost in Emei Mountain Cave and couldn't get out. They only drank mountain spring water for more than ten days, and were finally found and rescued. During the Spring and Autumn Period and the Warring States Period, Qi sent troops to the lonely bamboo country. When they returned to China smoothly, it was already the middle of winter, the rivers dried up and the people were thirsty. The army cannot March. Minister Peng Ji suggested to the King of Qi: "It is said that ants live in the shade of mountains in summer and in the sunshine of mountains in winter. There must be water near the ant nest, so that the soldiers can go to the south of the mountain separately to find the ant nest and dig deep. " The King of Qi adopted this suggestion and found water and saved the whole army. This story tells us the growth and distribution of vegetation, birds and animals in various regions. Where Populus euphratica forest grows, it is pointed out that the groundwater level is only 5 ~ 10 meters from the surface; Achnatherum splendens shows that the groundwater is about 2 meters below the surface; Lush reeds show that the groundwater level is only about 1 m; If you find plants like King Diane Dai and Malanhua, you can know that you can find groundwater by digging about 50 cm or 1 m here. We can also learn about the quality of groundwater from plants. If you see plants such as Malania and Hibiscus, you can conclude that there is fresh water not too deep. In the south, deep-rooted bamboo forests not only grow on river banks. It often grows in karst cracks and water tunnels related to underground rivers. For example, many karst valleys in Guangxi, clusters or independent bamboo forests, often have signs of big water caves. Some of these water tunnels can see water directly at the entrance, and some can't see water at the entrance, but as long as you go deep, you can often find groundwater. In addition, where the groundwater is shallow, the soil is wet, ants, snails and so on. In winter, frogs and snakes like to hibernate here; On summer nights, mosquitoes usually fly around in droves because of the humidity and coolness. You can also test the depth of the groundwater level. Dig a small hole in the ground, buckle it at the bottom with a plate and cover it with some grass. When there are small drops of water on the plate in the morning, the groundwater level is high. Dig a pit of 1 m and ignite the smoking vegetation in the pit. If the smoke column rises in an arc, the groundwater level is high. Because water is in nature, under normal circumstances, it is difficult to ensure that the water source is not polluted. If you have a map, you should pay attention to whether there are mines upstream of the water source. If there are mines, the water source may be polluted by minerals. If the stones in the river are unusually tea red or yellow, it is best not to drink the river water here. If there are no fish or other living things, you should be more careful. Rainwater can be drunk directly at ordinary times. When it rains, you can use ponchos and plastic sheets to collect a lot of rainwater. Use empty cans, cups, helmets and other containers to collect. You can put it on a clean stone, not on the ground. If it rains heavily, the soil on the ground will splash into the water receiving container. In the absence of reliable drinking water and inspection equipment in the wild, we can roughly identify the quality of water according to its color, taste, temperature and traces. Pure water is colorless and transparent when it is shallow, and light blue when it is deep. You can use a glass or a white porcelain bowl to hold water for observation. Usually, the clearer the water, the better. The more turbid the water is, the more impurities it contains. The color of water changes with pollution. For example, humus is yellow, low-valent iron compounds are light green and blue, high-valent iron or manganese is yellowish brown, and hydrogen sulfide is light blue. Generally speaking, clean water is tasteless, while polluted water often has some peculiar smell. For example, water containing hydrogen sulfide smells like rotten eggs, salty water tastes salty, water with high iron content tastes like metal rust, and water containing magnesium sulfate tastes bitter. Water containing organic matter is rotten, smelly, moldy, fishy and medicinal. In order to accurately identify the smell of water, you can use a clean small bottle, fill it with half a bottle of water, shake it a few times, and smell it with your nose immediately after opening the cork. You can also put the bottle of water in hot water at about 60℃ and smell it, so you can't drink it. The temperature of surface water (rivers and lakes) depends on the temperature. The water temperature is low and constant. If the water temperature rises suddenly, it is mostly caused by organic pollution. After industrial wastewater pollutes the water source, it will also raise the water temperature. You can also use a piece of white paper to dry the water droplets on it and observe the water traces. Clean water is spotless; Spots indicate that there are many impurities in the water and the water quality is poor. In the wild, it is best not to drink water from weeds, but to drink clear water from cliff cracks or rocks. When drinking river or lake water, you can dig a small pit in the sand one or two meters away from the water. The water seeping out of the pit is cleaner than the water directly extracted from rivers and lakes. The less suspended solids and colloidal substances in drinking water, the better. Otherwise, long-term drinking will easily lead to diseases. Drugs such as drinking water disinfection tablets, bleaching powder tablets and alum can be used to purify water. In the wild, due to the limited conditions, some wild plants containing mucus can also be used to purify turbid drinking water, such as the roots and stems of Osmunda japonica, the bark, leaves and roots of elm, the branches and leaves of kapok, the whole grass of cactus and overlord whip, and the branches and leaves of hibiscus. They all contain carbohydrate polymers. These plants are combined with metal salt solutions of metals such as calcium, iron, lead and magnesium above the second order to form flocs, which can adsorb suspended solids and sink to the bottom of the water in the process of precipitation, thus playing a role in purifying muddy water. Among the wild plants mentioned above, cactus and bawangbian are edible plants, and the amount used for purifying water is very small, and the flocs generated can precipitate, so it is the most ideal to purify drinking water with them. Mash and grind. When in use, put about 4g of plant paste into a bucket of water, stir for 3 minutes, and then let it stand for 10 minute, and the turbid water will be clarified. Plant purified water can remove some bacteria and microorganisms during flocculation precipitation, but it has no disinfection effect. Therefore, it is best to add a little bleaching powder to the drinking water for disinfection. If there is no bleaching powder, a few drops of dilute hydrochloric acid or iodine can also play a disinfection role. In the virgin forest, many streams and rivers look clear and clean, but in fact they contain many harmful bacteria. Once people drink them, they will get serious diseases, such as dysentery and malaria. Secret service, 1943 fought in Myanmar in February and trudged more than 300 kilometers in the jungle. Because of the water problem, in just two months, one third of his team members died or got sick, so they couldn't move on. Finally, the British army must not cancel the scheduled long-range infiltration operation. Remember, no matter how thirsty you are, don't drink unclean water to prevent germs from entering the body through drinking water. This is especially important in tropical jungle areas. As a last resort, you must boil water before drinking. 3. Desalination of coastal seawater and saline-alkali water. If there is no ion exchange resin desalter, you can use a pot to boil seawater and collect distilled water to desalt seawater. When boiling seawater, stick a towel on the inside of the pot cover. Absorb the distilled water from the towel and screw it into a big shell or other container. In this way, you can get the fresh water you need. In World War II, some China and British sailors made a lot of fresh water on a desert island in a similar way, and they survived for 76 days until they were discovered by British planes. In winter, seawater can freeze in containers. When seawater freezes, most of the salt dissolved in the water will crystallize out of the water, so the ice cubes are basically desalinated. The unfrozen water, that is, concentrated brine, is heated in a pot, boiled to dryness to obtain crystallized salt, and then spread on paper to remove bitterness to obtain salt. In the vast desert Gobi in the northwest of China, where there are plants, there is usually 4-5 meters of hidden groundwater. Water is filtered by sand layer, which is generally clear and transparent, but it is not drinkable. If there is no ion exchange resin desalter, the above seawater desalination method can be used. Residents in the desert area of northwest China use local pepper grass to treat brackish water. 0. 1 ~ 1.9 g of dried pepper grass was added to 1 kg of brackish water containing 0.37% ~ 0.72% minerals and boiled together, although the bitterness could not be removed. But it can prevent abdominal pain, abdominal distension and diarrhea. In places with wet sand or brackish water, fresh water can be obtained by a simple solar distiller. The method is to dig a bunker with a diameter of 1.5 m and a depth of 1 m, cover it with a transparent plastic film, fix it with sand or stones around it, and put a pebble in the middle. Make the plastic film into an inverted cone. Put a water container under this cone in advance. Sunlight will evaporate the water in the silo through the plastic film, and the water vapor will condense into water droplets when it meets the plastic film, and the water droplets will drip into the container along the top of the cone. By this method, about 1.5 liters of distilled fresh water can be obtained every day. Whether you can drink seawater as a last resort is controversial at present. Some people think that the salinity of seawater is four times higher than that of human body. Drinking seawater will increase the total osmotic pressure in the body. Although it can temporarily quench thirst, it will soon urinate a lot, resulting in a large loss of water in the body. But many people think that a small amount of seawater in a short time will help to prolong life. Some people try to drink seawater from the first day of falling into the sea, 1 every half hour, 50 ml each time, only 500 ml a day, or even 4-5 times. The metabolism of the experimenter quickly returned to normal. Alain bhombal, a French doctor who is known as the "model of the navy", said: "If you have fresh water, add seawater to prolong your water supply time under the condition of strictly controlling the proportion; If you don't have fresh water, drink seawater to save your life until you can get rain, get a fish squeezed into fish juice or wait for the lifeboat to arrive. "Alan bhombal does not advocate drinking seawater, but emphasizes that drinking seawater should be strictly controlled in a life-and-death emergency. Alan bhombal's experience is that the ratio is 2: 1, that is, drinking two parts of fresh water and one part of seawater together will generally not endanger people's health. But it will greatly prolong the lives of the victims at sea, because only by gaining time can we gather our strength to fish and collect rainwater, and then we can continue to sail and send a signal to the rescue ship. Bouriaud, a famous French naval doctor, wrote in a recent book: "The victims can drink a small amount of seawater, up to 800 ~ 900 ml per day, and don't wait until they are completely dehydrated. "In the Second World War, three sailors were killed. They drank sea water to quench their thirst. One of them drank it for 34 days. He can only moisten his throat with bitter and astringent sea water two days ago, and then have a drink or two. On the third day, he was very thirsty and drank a lot, about 2000 ml a day and a night. However, he survived. It seems that drinking a small amount of seawater is also an emergency measure in the absence of fresh water.