John Dalton

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Synopsis
Chemist John Dalton was born September 6, 1766, in Eaglesfield, England. During his early career, he identified the hereditary nature of red-green color blindness. In 1803 he revealed the concept of Dalton’s Law of Partial Pressures. Also in the 1800s, he was the first scientist to explain the behavior of atoms in terms of the measurement of weight. Dalton died July 26, 1844 in Manchester, England. CONTENTS

* Synopsis
* Early Life and Career
* Dalton's Law
* Atomic Theory
* Later Life
* Death and Legacy
Early Life and Career
British chemist John Dalton was born in Eaglesfield, England, on September 6, 1766, to a Quaker family. He had two surviving siblings. Both he and his brother were born color-blind. Dalton's father earned a modest income as a handloom weaver. As a child, Dalton longed for a formal education, but his family was very poor. It was clear that he would need to help out with the family finances from a young age. After attending a Quaker school in his village in Cumberland, when Dalton was just 12 years old he started teaching there. When he was 14, he spent a year working as a farmhand, but decided to return to teaching--this time as an assistant at a Quaker boarding school in Kendal. Within four years, the shy young man was made principal of the school. He remained there until 1793, at which time he became a math and philosophy tutor at the New College in Manchester. While at New College, Dalton joined the Manchester Literary and Philosophical Society. Membership granted Dalton access to laboratory facilities. For one of his first research projects, Dalton pursued his avid interest in meteorology. He started keeping daily logs of the weather, paying special attention to details such as wind velocity and barometric pressure--a habit Dalton would continue all of his life. His research findings on atmospheric pressure were published in his first book, Meteorological Findings, the year he arrived in Manchester. During his early career as a scientist, Dalton also researched color blindness--a topic with which he was familiar through firsthand experience. Since the condition had affected both him and his brother since birth, Dalton theorized that it must be hereditary. He proved his theory to be true when genetic analysis of his own eye tissue revealed that he was missing the photoreceptor for perceiving the color green. As a result of his contributions to the understanding of red-green color blindness, the condition is still often referred to as "Daltonism." Dalton's Law

Dalton's interest in atmospheric pressures eventually led him to a closer examination of gases. While studying the nature and chemical makeup of air in the early 1800s, Dalton learned that it was not a chemical solvent, as other scientists had believed. Instead it was a mechanical system composed of small individual particles that used pressure applied by each gas independently. Dalton's experiments on gases led to his discovery that the total pressure of a mixture of gases amounted to the sum of the partial pressures that each individual gas exerted while occupying the same space. In 1803 this scientific principle officially came to be known as Dalton's Law of Partial Pressures. Dalton's Law primarily applies to ideal gases rather than real gases, due to the elasticity and low particle volume of molecules in ideal gases. Chemist Humphry Davywas skeptical about Dalton's Law, until Dalton explained that the repelling forces previously believed to create pressure only acted between atoms of the same sort, and that the atoms within a mixture varied in weight and complexity.

The principle of Dalton's Law can be demonstrated using a simple experiment involving a glass bottle and large bowl of water. When the bottle is submerged under water, the water it contains is displaced, but the bottle isn't empty; it's filled with the invisible gas hydrogen instead. The amount of pressure exerted by the hydrogen can be...
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