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Thomas Graham (20 December 1805 – 11 September 1869) was a Scottish chemist known for his pioneering work in dialysis and the diffusion of gases. Graham's law, formulated in 1848, states that the rate of diffusion or effusion of a gas is inversely proportional to the square root of its molecular weight. This law was a result of Graham's experiments with gases, where he slowed down the process to study it quantitatively. He also studied the diffusion of substances in solution, discovering that some apparent solutions are actually suspensions of particles too large to pass through a parchment filter. Graham's law has since been used to find the approximate molecular weight of a gas and was even used in the Manhattan Project to separate uranium-235 from uranium-238.
| Characteristics | Values |
|---|---|
| Name | Thomas Graham |
| Born | 20 December 1805 |
| Birthplace | Glasgow, Scotland |
| Education | University of Glasgow, University of Edinburgh |
| Known For | Pioneering work in dialysis, diffusion of gases, and colloid chemistry |
| Notable Contributions | Graham's Law of diffusion and effusion of gases, study of colloids and crystalloids, separation of uranium isotopes |
| Formulation of Graham's Law | Triggered by German chemist Johann Döbereiner's observations, Graham experimentally studied the diffusion of gases through various methods and formulated his law in 1848 |
| Graham's Law Equation | Rate of effusion is inversely proportional to the square root of the molar mass of gas particles |
| Applications | Used in the Manhattan Project to separate uranium isotopes, provides insights into gas behaviour and kinetic theory |
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What You'll Learn
Thomas Graham's research on the diffusion of gases
Thomas Graham (20 December 1805 – 11 September 1869) was a Scottish chemist known for his pioneering work in dialysis and the diffusion of gases. He is regarded as one of the founders of colloid chemistry and is often referred to as "the father of colloid chemistry".
Graham's research on the diffusion of gases was triggered by his reading about the observations of German chemist Johann Döbereiner, who noted that hydrogen gas escaped from a small crack in a glass bottle faster than the surrounding air entered to replace it. This led Graham to investigate the rate of diffusion of gases through plaster plugs, fine tubes, and small orifices. By slowing down the process, he was able to study it quantitatively. In 1831, he stated that the rate of effusion of a gas is inversely proportional to the square root of its density, and later in 1848, he showed that this rate is also inversely proportional to the square root of the molar mass. Graham's law of effusion, or diffusion, states that the rate of diffusion or effusion of a gas is inversely proportional to the square root of its molecular weight.
Graham's work on the diffusion of gases built upon the earlier studies of gas behaviour by scientists such as Daniel Bernoulli and Amedeo Avogadro. Bernoulli suggested in 1738 that heat increases proportionally to the velocity and kinetic energy of gas particles. Avogadro proposed in 1811 that equal volumes of different gases contain equal numbers of molecules, which provided a basis for later theoretical work by James Clerk Maxwell. Graham's research on the diffusion of gases led to his formulation of Graham's law, which relates to the diffusion of gases and has important applications, such as its use in separating uranium-235 from uranium-238 during the Manhattan Project.
In addition to his work on gas diffusion, Thomas Graham made significant contributions in other areas of chemistry. He studied the three forms of phosphoric acid, which led to the development of the concept of polybasic acids. He also investigated the properties of the water of crystallization in hydrated salts and obtained definite compounds of salts and alcohol, known as "alcoholates". Furthermore, Graham's study of colloids and crystalloids resulted in his ability to separate them using a "dialyzer", a technology that laid the foundation for modern kidney dialysis machines.
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The rate of effusion of a gas
Thomas Graham (20 December 1805 – 11 September 1869) was a Scottish chemist known for his pioneering work in dialysis and the diffusion of gases. Graham's research on the diffusion of gases was triggered by his reading about the observations of German chemist Johann Döbereiner. Döbereiner observed that hydrogen gas escaped from a small crack in a glass bottle faster than the surrounding air entered to replace it. This observation led Graham to study the rate of diffusion of gases through plaster plugs, fine tubes, and small orifices.
Graham's law of effusion, formulated in 1848, states that the rate of effusion of a gas is inversely proportional to the square root of the molar mass of its particles. This means that if the molecular weight of one gas is four times that of another, it will effuse through a pinhole or porous plug at half the rate of the lighter gas. Graham's law can be used to determine the approximate molecular weight of a gas if the rate of effusion and the molar mass of another gas are known.
To study the rate of effusion, Graham used an apparatus consisting of a glass tube sealed at one end with plaster. The plaster had holes large enough for gas to enter or exit the tube. By filling the tube with hydrogen gas, Graham observed that the level of water in the tube rose slowly because the hydrogen molecules escaped through the holes in the plaster faster than air molecules could enter the tube. This allowed Graham to collect data on the rate at which different gases mixed with air.
Graham's work on the diffusion and effusion of gases contributed significantly to the field of colloid chemistry, and he is considered one of its founders. Graham's law played a crucial role in the Manhattan Project, where it was used to separate uranium-235 from uranium-238 in the process of creating the first atomic bomb.
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The inverse relationship between gas density and rate of diffusion
Thomas Graham, a Scottish chemist born in Glasgow, Scotland, is known for his work in dialysis and the diffusion of gases. Graham's research on the diffusion of gases was inspired by German chemist Johann Döbereiner's observations that hydrogen gas escaped from a small crack in a glass bottle faster than the surrounding air moved to replace it. Graham's law of effusion, also known as Graham's law of diffusion, was formulated by him in 1848.
Graham's law states that the rate of diffusion or effusion of a gas is inversely proportional to the square root of its molecular weight. This means that if one gas has a molecular weight four times that of another, it will diffuse through a porous plug or escape through a small pinhole in a vessel at half the rate of the other gas. Heavier gases diffuse more slowly. Graham's law can be used to determine the approximate molecular weight of a gas if the rate of diffusion or effusion of another gas with a known molecular weight is known.
Graham's experiments involved measuring the rate of diffusion of gases through plaster plugs, fine tubes, and small orifices. By slowing down the process, he was able to study it quantitatively. He discovered that the rate of effusion of a gas is inversely proportional to the square root of its density. This relationship became known as Graham's law of diffusion. Graham's work on the diffusion of gases and his development of Graham's law were significant contributions to the field of chemistry.
Graham's law has practical applications, such as in the Manhattan Project during World War II. The United States government built a gaseous diffusion plant to separate uranium-235 from uranium-238 found in natural uraninite (uranium ore). This process was essential for creating the first atomic bomb. Graham's law and the kinetic theory of gases, which explains the properties of gases as collections of particles moving through space, have contributed significantly to our understanding of gas behaviour and have practical applications in various fields.
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Graham's law of effusion
Thomas Graham (20 December 1805 – 11 September 1869) was a Scottish chemist known for his pioneering work in dialysis and the diffusion of gases. Graham's research on the diffusion of gases was triggered by his reading about the observations of German chemist Johann Döbereiner, who noted that hydrogen gas escaped from a small crack in a glass bottle faster than the surrounding air entered to replace it.
In 1831, Graham stated that the rate of effusion of a gas is inversely proportional to the square root of its density. Later, in 1848, he showed that this rate is also inversely proportional to the square root of the molar mass. Graham's law of effusion, also called Graham's law of diffusion, was thus formulated.
Mathematically, Graham's law can be stated as:
Rate1/Rate2 = √(M2/M1)
Where Rate1 is the rate of effusion for the first gas (volume or number of moles per unit time), Rate2 is the rate of effusion for the second gas, and M2 is the molar mass of gas 2.
Graham's law states that the rate of diffusion or effusion of a gas is inversely proportional to the square root of its molecular weight. This means that if the molecular weight of one gas is four times that of another, it will diffuse through a porous plug or escape through a small pinhole in a vessel at half the rate of the other gas. This is because heavier gases diffuse more slowly.
Graham's law was significant in the development of the kinetic theory of gases, which later provided a complete theoretical explanation for the law. The law also has practical applications, such as in the separation of uranium-235 from uranium-238 during the Manhattan Project.
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The separation of colloids and crystalloids
Thomas Graham was a Scottish chemist known for his work in dialysis and the diffusion of gases. Graham's research on the diffusion of gases was triggered by his reading about the observations of German chemist Johann Döbereiner. Döbereiner found that hydrogen gas escaped a small crack in a glass bottle faster than the surrounding air entered to replace it. Graham's study of colloids resulted in his ability to separate colloids and crystalloids using a "dialyzer". This technology is considered a forerunner of the machines used in modern kidney dialysis.
In 1829, Thomas Graham used an apparatus to study the diffusion of gases—the rate at which two gases mix. The apparatus consisted of a glass tube sealed at one end with plaster that had holes large enough to allow a gas to enter or leave the tube. When the tube was filled with H2 gas, the level of water in the tube slowly rose because the H2 molecules inside the tube escaped through the holes in the plaster faster than the molecules in the air could enter the tube. By studying the rate at which the water level in this apparatus changed, Graham was able to obtain data on the rate at which different gases mixed with air.
Graham found that the rates at which gases diffuse are inversely proportional to the square root of their densities. This relationship eventually became known as Graham's law of diffusion. Graham's law can also be used to find the approximate molecular weight of a gas if one gas is a known species. Graham's law was the basis for separating uranium-235 from uranium-238 found in natural uraninite (uranium ore) during the Manhattan Project.
From examining the diffusion of one liquid into another, Graham divided particles into two classes: crystalloids, such as common salt, having high diffusibility; and colloids, such as gum arabic, having low diffusibility. Graham's study of colloids resulted in his ability to separate colloids and crystalloids.
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Frequently asked questions
Graham's Law, formulated by Scottish chemist Thomas Graham, states that the rate of diffusion or effusion of a gas is inversely proportional to the square root of its molecular weight.
Thomas Graham was inspired to study the diffusion of gases after reading about German chemist Johann Döbereiner's observations that hydrogen gas escaped from a small crack in a glass bottle faster than air diffused in to replace it.
Thomas Graham measured the rate of diffusion of gases through plaster plugs, fine tubes, and small orifices. He used an apparatus consisting of a glass tube sealed at one end with plaster that had holes large enough for gas to enter or leave the tube. By studying the rate at which the water level in this apparatus changed, he obtained data on the rate at which different gases mixed with air.
Graham's Law was significant as it allowed for the separation of uranium-235 from uranium-238 during the Manhattan Project. It also has applications in understanding the behaviour of gases, such as the relationship between temperature and kinetic energy.
