The Earth's atmosphere is formed by a vast amount of gas that accumulates under the planet's gravitational pull, stretching thousands of kilometers into space. As altitude increases, the density of this gas gradually decreases. Even at 3,000 kilometers above the surface, sounding rockets have detected a very thin layer of atmosphere. Some scientists suggest that the upper limit of the atmosphere could extend as far as 6,400 kilometers from the ground.
At sea level, the average atmospheric pressure is 1 atmosphere, which equates to about 1,034 grams of air pressing down on every square centimeter of the Earth's surface. With a total surface area of approximately 510 million square kilometers, the entire atmosphere weighs roughly 5.2 × 10¹ⵠtons—just a tiny fraction (about one-millionth) of the Earth's total mass. Most of the atmosphere’s mass, around 50%, is found within 30 kilometers of the surface. Above 100 kilometers, the air becomes so thin that it accounts for only a small portion of the total atmospheric mass.
The air near the Earth's surface is a mixture of gases: approximately 78% nitrogen, 21% oxygen, 0.93% argon, and 0.03% carbon dioxide. Other components include trace amounts of neon (0.0018%), along with inert gases, ozone, water vapor, and dust particles. However, due to human activities and pollution, the atmosphere now also contains harmful gases such as sulfur dioxide, nitrogen oxides, and carbon monoxide.
Dry air has a molecular weight of 28.96 and a density of 1.293 grams per cubic meter at 0°C and standard atmospheric pressure (760 mmHg). When air is compressed, it becomes compressed air, and the devices used to produce it are known as air compressors. Humans have been using compressed air for centuries, and today it plays a vital role in both industry and daily life. As modern industries continue to evolve, the demand for high-quality compressed air has grown significantly, leading to rapid advancements in drying technologies to meet these needs.
Source: http://news.chinawj.com.cn
Editor: Hardware Business Network Information Center
HDT Vicat softening temperature Tester
The HDT Vicat Softening Point Apparatus is a testing instrument used to determine the softening point of a material. It is commonly used in the plastics industry to evaluate the heat resistance and thermal stability of polymers.
The apparatus consists of a heating bath, a test specimen holder, and a needle or a flat-ended plunger. The test specimen is placed in the holder and immersed in the heated bath. The temperature is gradually increased at a specified rate, and the needle or plunger is applied to the specimen at regular intervals.
The softening point is determined by observing the point at which the needle or plunger penetrates a specified distance into the specimen. This indicates the temperature at which the material starts to soften and lose its dimensional stability.
The HDT Vicat softening point apparatus is designed to meet international standards, such as ISO 306 and ASTM D1525. It provides accurate and reliable results, allowing manufacturers to assess the suitability of materials for various applications and ensure product quality.
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