anode rays experiment by eugen goldstein

• Structure of Atom

Canal Ray Experiment

Canal Ray experiment is the experiment performed by German scientist Eugen Goldstein that led to the discovery of the proton. The discovery of proton which happened after the discovery of the electron further strengthened the structure of the atom . In the experiment, Goldstein applied high voltage across a discharge tube which had a perforated cathode. A faint luminous ray was seen extending from the holes in the back of the cathode.

Table of Contents

Apparatus of the experiment, procedure of the experiment, explanation, frequently asked questions – faqs.

The apparatus of the experiment incorporates the same apparatus as of cathode ray experiment which is made up of a glass tube containing two pieces of metals ions at the different end which acts as an electrode. The two metal pieces are connected with an external voltage. The pressure of the gas inside the tube is lowered by evacuating the air.

• Apparatus was set up by providing a high voltage source and evacuating the air to maintain low pressure inside the tube.
• High voltage was passed to the two metal pieces to ionise the air and make it a conductor of electricity.
• The electricity started flowing as the circuit was complete.
• When the voltage was increased to several thousand volts, a faint luminous ray was seen extending from the holes in the back of the cathode.
• These rays were moving in the opposite direction of cathode rays and were named canal rays.

When very high voltage is applied, it ionises the gas and it is positive ions of gas that constitutes the canal ray. It is actually the nucleus or kernel of the gas that was used in the tube and hence it has properties different from the cathode rays which were made up of electrons.

• Unlike cathode rays, canal rays depend upon the nature of gas present in the tube. It is because the canal rays are composed of positive ionised ions formed by ionisation of gas present in the tube.
• The charge to mass ratio for the particles of the ray was found to be different for different gases.
• The behaviour of particles in an electric and magnetic field was opposite to that of cathode rays.
• Some positively charged particles carry multiples of the fundamental value of the charge.

Who discovered the canal rays?

Dempster was one of the first spectrometers to use such sources of ions. He never succeeded in using magnetic bending. By the light, they released while travelling through gases and by the fluorescent patch they created on the discharge tube wall, Goldstein had discovered canal rays.

Why anode rays are called canal rays?

These rays are particle beams that travel in a direction opposite to the “cathode rays,” which are electron waves that move through the anode. These were called canal rays because they passed through the holes or canals in the cathode

What was Goldstein experiment?

In the 1870s, Goldstein conducted his own discharge tube experiments and named Kathodenstrahlen, or cathode rays, the light emissions examined by others. He found some major cathode ray properties, which led to their subsequent discovery as the electron, the first subatomic particle.

What is the difference between cathode rays and canal rays?

Cathode rays are charged negatively, while Canal Rays are charged positively. Cathode rays emanate from the cathode, while the rays of the canal do not emanate from the anode, but are produced inside the chamber by the collision of gas molecules. In an electric field, cathode rays are drawn to positive electrodes.

How canal rays are produced?

The electrons emitted from the cathode collide with the gas atoms found in the tube, knocking one or two additional electrons out of each of these atoms. These collisions leave behind ions which are positively charged. The produced positive ions travel towards the cathode. Any of the positive ions pass through the perforations that create canal rays in the cathode disc. Both electric and magnetic fields deflect the channel rays in the same direction from the cathode rays.

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Eugen Goldstein

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Eugen Goldstein (born Sept. 5, 1850, Gleiwitz , Prussia—died Dec. 25, 1930, Berlin) was a German physicist known for his work on electrical phenomena in gases and on cathode rays; he is also credited with discovering canal rays.

Goldstein studied at the University of Breslau (now in Wrocław, Pol.), where he received his doctorate in 1881. His career was spent at the Potsdam Observatory. He was primarily interested in electrical discharges in moderate to high vacuums. In 1886 he discovered what he termed Kanalstrahlen, or canal rays, also called positive rays; these are positively charged ions that are accelerated toward and through a perforated cathode in an evacuated tube. He also contributed greatly to the study of cathode rays; in 1876 he showed that these rays could cast sharp shadows, and that they were emitted perpendicular to the cathode surface. This discovery led to the design of concave cathodes to produce concentrated or focused rays, which became fundamental to numerous experiments.

Eugen Goldstein

The Raisin Pudding Model of the Atom (Eugen Goldstein)

In 1886 Eugen Goldstein noted that cathode-ray tubes with a perforated cathode emit a glow from the end of the tube near the cathode. Goldstein concluded that in addition to the electrons, or cathode rays, that travel from the negatively charged cathode toward the positively charged anode, there is another ray that travels in the opposite direction, from the anode toward the cathode. Because these rays pass through the holes, or channels, in the cathode, Goldstein called them canal rays.

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Source: © The Board of Trustees of the Science Museum

The discovery of mass spectrometry

By Mike Sutton 2022-10-03T08:28:00+01:00

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Mike Sutton traces how Francis Aston’s mass spectrograph shook up chemistry

The award of the 1922 Nobel chemistry prize to Francis Aston may have surprised some of his contemporaries, as his most significant research was in an area generally regarded as a branch of physics. Yet with a century’s worth of hindsight, the decision seems appropriate. Aston’s work was to have a substantial impact on the next hundred years of chemistry.

Francis William Aston was born in 1877, in Harborne, a village near Birmingham. This region of the English midlands was renowned for its skilled metal-workers, who made nails and needles, buttons and buckles, spurs and stirrups, and thousands of other essential items. Although factories flourished there, much work was still outsourced to small companies, and even to individual artisans with back-yard forges. Both Francis’s grandfathers came from farming backgrounds, but established successful metal-working businesses. And his father – while still owning a farm – became a metal merchant, supplying materials to local manufacturers.

Aston’s work was to have a substantial impact on the next hundred years of chemistry

Francis’s interest in science flowered in this dynamic environment. As a schoolboy he had his own attic laboratory, and in 1893 he entered Birmingham’s Mason College to study for London University’s external examinations. After graduating in 1898 he became a research student there , helping chemistry professor Percy Frankland investigate optically active substances.

From 1900, Aston was employed as a chemist by a nearby brewery, but continued doing research in his home lab. He was fascinated by the luminous phenomena generated when electrical discharges passed through partially evacuated glass tubes. Earlier investigators – including Michael Faraday, Heinrich Geissler, Julius Plücker, Wilhelm Hittorf and William Crookes – had all obtained intriguing results, and Wilhelm Röntgen’s 1895 discovery of x-rays aroused further interest, but many puzzles remained unresolved.

Expert skills

This research was technically demanding. Making complex glass vessels that could protect a near-vacuum against the atmosphere’s pressure was difficult enough. When these containers were pierced by electrical wires – and by valves for admitting and removing gases – maintaining their integrity became even more challenging. But Aston was an expert glass-blower, and had mastered the necessary skills by 1903, when he returned to the college – now part of the new University of Birmingham – as a research assistant to physics professor John Poynting.

Aston’s tasks there included making and operating electrical discharge tubes. He also investigated their peculiarities on his own initiative, and discovered a phenomenon now called the Aston dark space. In 1908, however, a substantial legacy from his father enabled him to spend a year’s holiday travelling around the world via Australia, New Zealand, Canada and the US. While visiting Hawaii, he became one of the first Europeans to try surfing.

In January 1910, he moved to the University of Cambridge’s Cavendish Laboratory, as technical assistant to J J Thomson

Sports were always important to Aston – he performed creditably in tennis tournaments, enjoyed skiing and mountaineering, and once cycled two hundred miles in a day. In later life he often partnered Ernest Rutherford on the golf course, and although the professor’s famously erratic drives must have tried Aston’s patience sorely, the two remained friends. Aston was also an accomplished musician and a skilled photographer – further activities that required an intense concern for precision.

In the autumn of 1909 Aston returned to the University of Birmingham as a science lecturer, but it soon became obvious that he was unsuited to this new career. In January 1910 – on Poynting’s recommendation – he moved to the University of Cambridge’s Cavendish Laboratory, in the more familiar role of technical assistant to J J Thomson. Thomson was a titan of theoretical physics – a Nobel laureate himself, he taught or supervised several further Nobel prize-winners. However, he lacked manual dexterity and needed specialist technicians to build and maintain his apparatus. This was Aston’s function at the Cavendish – until his experimental skills and theoretical insight earned him recognition as an independent investigator.

Rays to ratios

One of Thomson’s major achievements had been proving (in 1895) that the cathode rays produced in discharge tubes were streams of negatively-charged particles – later to be named electrons. Thomson then investigated the analogous anode rays – first observed by Eugen Goldstein in 1886, and shown by Wilhelm Wien in 1897 to consist of positively charged ions. In 1910 Aston joined this project.

Source: © The Board of Trustees of the Science Museum, London

Aston’s original mass spectrometer – now in the Science Museum’s collection – looks quite different…

The particles they studied were repelled by the anode of an almost-evacuated discharge tube. Having passed through the tube’s perforated cathode, they were diverted by electrical and magnetic fields before hitting a photographic plate or fluorescent screen. In Thomson’s apparatus, the electrical and magnetic fields were applied to the particle-stream at the same point, but at right angles to each other. Under these conditions, the paths of ions having the same charge/mass ratio but different velocities diverged, since the slower-moving ones were more strongly affected by the electrical field. The result was a roughly parabolic line on the detecting medium.

When ions with different charge/mass ratios coexisted in the particle stream, they were steered into a sequence of roughly parallel curves on the detecting medium creating what became known as a mass spectrum. When Aston and Thomson put neon gas into this instrument in 1912, they expected to see lines representing the ions Ne + and Ne 2+ . They did – but close to the Ne + line there was a faint trace they could not explain.

Isotopic intuition

A clue to this anomaly was provided by the English chemist Frederick Soddy, who proposed that the atoms of some elements did not all have identical masses. Soddy eventually succeeded in adding the word isotope to science’s vocabulary – the word was suggested to him by pioneering female doctor Margaret Todd – but initially his suggestion encountered some opposition. Thomson himself was sceptical, though Aston thought their results could indicate the presence of two neon isotopes. However, attempts at separation – by fractional distillation and by gaseous diffusion – were unsuccessful. As Aston stated in his Nobel lecture: ’When the war interrupted the research, it might be said that several independent lines of reasoning pointed to the conclusion that neon was a mixture of isotopes, but none of these could be said to carry absolute conviction.’

Aston spent the first world war at Farnborough, helping the Royal Aircraft Factory improve its aeroplanes, and was fortunate to escape unharmed when one of them crashed. Occasionally, he discussed physics with colleagues there – including Frederick Lindemann, who mistrusted Soddy’s isotope concept, and thought Aston’s neon was probably contaminated by some compound whose ionised molecule had a charge/mass ratio close to that of Ne + .

While Aston worked on military aircraft, the Canadian physicist Arthur Dempster was pursuing isotopes at the University of Chicago in the US. Dempster competed his PhD in 1916, and in 1918 built an instrument differing somewhat from Thomson and Aston’s. Initially, Dempster’s results made less impact. But he persevered with the research, and his eventual identification of a uranium isotope with atomic mass 235 would prove to be a vital step towards the exploitation of nuclear energy.

Aston quickly confirmed that neon had isotopes with atomic masses 20 and 22

By the time Aston returned to Cambridge in 1919, Soddy’s isotope concept had been vindicated by measurements of the atomic masses of different lead samples (including radioactive decay products). Nevertheless, to confirm that two neon isotopes did exist, a better instrument was needed. Aston built one, increasing the precision of its measurements from one part in a hundred to one part in a thousand – and eventually, beyond one part in ten thousand.

One of Aston’s improvements to Thomson’s earlier mass spectrograph was to narrow the beam, by passing the positive ions through consecutive slits. Also significant was his decision to divert this beam in one direction by an electrical field, before bending it back in the opposite direction with a magnetic field. The intensities of these fields were adjusted so that particles having the same mass/charge ratio but differing velocities were focussed to a point, rather than tracing a line.

Aston quickly confirmed that neon had isotopes with atomic masses 20 and 22, in proportions that were compatible with neon’s overall atomic mass of 20.2. He also identified two chlorine isotopes having atomic masses of 35 and 37, and further discoveries followed as heavier gases – and eventually solid elements – were ionised and analysed. This work established Aston’s scientific reputation – he became a fellow of Cambridge’s Trinity College in 1920, was elected to the Royal Society in 1921, and received the Nobel Chemistry Prize in 1922. An impressive career trajectory for a former brewery chemist!

A weighty problem

Aston’s discoveries raised profound issues in physics, chemistry and cosmology. Chemists had often wondered why the atomic masses of so many elements were so close to being integers. Now, the discovery of isotopes with (apparently) integral atomic masses suggested new possibilities. In his 1922 Nobel lecture, Aston declared:

’By far the most important result of these measurements is that, with the exception of hydrogen , the weights of the atoms of all the elements measured, and therefore almost certainly of all elements, are whole numbers to the accuracy of experiment, namely, about one part in a thousand.’ [Emphasis added]

This uniformity was more obvious because Aston took one sixteenth of the atomic mass of the oxygen-sixteen isotope – rather than hydrogen’s atomic mass – as his basic unit of measurement. But he also recognised that hydrogen’s anomalous status resulted from the inter-convertibility of mass and energy, in accordance with Einstein’s famous equation.

Aston’s discoveries raised profound issues in physics, chemistry and cosmology

It seemed clear that in the nuclei of all elements – except hydrogen – the mutual repulsion of protons must be resisted by a powerful attractive force if their atoms were to remain stable. Others had already attributed this force to the conversion of a tiny portion of nuclear mass (later called the ‘mass defect’) into binding energy. But the hydrogen nucleus – a lone proton – needed no binding energy, and was therefore proportionally more massive. By 1922 Aston fully appreciated the implications of this fact, stating in his Nobel lecture that

‘… we may consider it absolutely certain that if hydrogen is transformed into helium a certain quantity of mass must be annihilated in the process. The cosmical importance of this conclusion is profound and the possibilities it opens for the future very remarkable, greater in fact than any suggested before by science in the whole history of the human race. … Should the research worker of the future discover some means of releasing this energy in a form which could be employed, the human race will have at its command powers beyond the dreams of scientific fiction.’

Weighing the future

During the 1920s and 30s Aston continued improving his mass spectrograph. But its ever-increasing precision eventually revealed that the atomic masses of isotopes did not, after all, have exactly integral values – each one had its own individual ‘mass defect’. Aston described the ratio of an isotope’s mass defect to its mass number as its ‘packing fraction’, and showed that for any isotope, the size of this fraction was indicative of the relative stability of its nucleus.

Source: © Science Photo Library

…to its modern-day counterparts in labs around the world

In 1932, however, the picture was further complicated when Aston’s Cambridge colleague, James Chadwick, discovered another nuclear particle – the neutron. Soon afterwards, the use of neutron bombardment to split atomic nuclei opened up exciting new possibilities for physicists. But Aston was not involved in these developments, and he ceased doing research following the outbreak of the second world war in 1939.

During the 1940s mass spectrometry advanced rapidly, due to its vital role in the development of nuclear physics (and of nuclear weapons). Its utility was greatly enhanced after the photographic plates employed by earlier investigators were replaced by electronic detectors, permitting more precise measurements of the components of an ion beam.

Since those pioneering days, the mass spectrometer has contributed significantly to many areas of chemical and biological research. It is employed as an analytical tool in numerous industries, and it can extract valuable information from archaeological finds. Recent advances have enabled researchers to vaporise – and ionise – some large and relatively fragile organic molecules, and then subject them to mass spectrum analysis, generating fresh ideas about how such molecules might function in living systems. Further advances may be expected in the years ahead.

Francis Aston died in November 1945. Unmarried and childless, he left substantial bequests to Trinity College and to various scientific institutions – but his greatest legacy was the instrument he had done so much to develop.

Mike Sutton is a historian of science in Newcastle, UK

• Analytical chemistry
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1. Introduction

Eugen Goldstein (5 September 1850 – 25 December 1930) was a German physicist. He was an early investigator of discharge tubes, the discoverer of anode rays or canal rays, later identified as positive ions in the gas phase including the hydrogen ion or proton. [ 1 ] He was the great uncle of the violinists Mikhail Goldstein and Boris Goldstein.

Goldstein was born in 1850 at Gleiwitz Upper Silesia, now known as Gliwice, Poland, to a Jewish family. He studied at Breslau and later, under Helmholtz, in Berlin. Goldstein worked at the Berlin Observatory from 1878 to 1890 but spent most of his career at the Potsdam Observatory, where he became head of the astrophysical section in 1927. He died in 1930 and was buried in the Weißensee Cemetery in Berlin.

In the mid-nineteenth century, Julius Plücker investigated the light emitted in discharge tubes (Crookes tubes) and the influence of magnetic fields on the glow. Later, in 1869, Johann Wilhelm Hittorf studied discharge tubes with energy rays extending from a negative electrode, the cathode. These rays produced a fluorescence when they hit a tube's glass walls, and when interrupted by a solid object they cast a shadow.

In the 1870s, Goldstein undertook his own investigations of discharge tubes and named the light emissions studied by others Kathodenstrahlen , or cathode rays. [ 2 ] He discovered several important properties of cathode rays, which contributed to their later identification as the first subatomic particle, the electron. He found that cathode rays were emitted perpendicularly from a metal surface, and carried energy. He attempted to measure their velocity by the Doppler shift of spectral lines in the glow emitted by Crookes tubes.

In 1886, he discovered that tubes with a perforated cathode also emit a glow at the cathode end. Goldstein concluded that in addition to the already-known cathode rays, later recognized as electrons moving from the negatively charged cathode toward the positively charged anode, there is another ray that travels in the opposite direction. Because these latter rays passed through the holes, or channels, in the cathode, Goldstein called them Kanalstrahlen , or canal rays. They are composed of positive ions whose identity depends on the residual gas inside the tube. It was another of Helmholtz's students, Wilhelm Wien, who later conducted extensive studies of canal rays, and in time this work would become part of the basis for mass spectrometry.

The anode ray with the largest e/m ratio comes from hydrogen gas (H 2 ), and is made of H + ions. In other words, this ray is made of protons. Goldstein's work with anode rays of H + was apparently the first observation of the proton, although strictly speaking it might be argued that it was Wien who measured the e/m ratio of the proton and should be credited with its discovery.

Goldstein also used discharge tubes to investigate comets. An object, such as a small ball of glass or iron, placed in the path of cathode rays produces secondary emissions to the sides, flaring outwards in a manner reminiscent of a comet's tail. See the work of Hedenus for pictures and additional information. [ 3 ]

• C. E. Moore; B. Jaselskis; A. von Smolinski (1985). "The Proton". Journal of Chemical Education 62 (10): 859–860. doi:10.1021/ed062p859. Bibcode: 1985JChEd..62..859M. http://dbhs.wvusd.k12.ca.us/webdocs/AtomicStructure/Proton.pdf. 
• E. Goldstein (May 4, 1876) "Vorläufige Mittheilungen über elektrische Entladungen in verdünnten Gasen" (Preliminary communications on electric discharges in rarefied gases), Monatsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin (Monthly Reports of the Royal Prussian Academy of Science in Berlin), 279-295. https://books.google.com/books?id=7-caAAAAYAAJ&pg=PA279#v=onepage&q&f=false
• 3.0.CO;2-7. Bibcode: 2002AN....323..562M.  https://dx.doi.org/10.1002%2F1521-3994%28200212%29323%3A6%3C567%3A%3AAID-ASNA567%3E3.0.CO%3B2-7" id="ref_3">M. Hedenus (2002). "Eugen Goldstein and his laboratory work at Berlin Observatory". Astronomische Nachrichten 323 (6): 567–569. doi:10.1002/1521-3994(200212)323:6 3.0.CO;2-7. Bibcode: 2002AN....323..562M.  https://dx.doi.org/10.1002%2F1521-3994%28200212%29323%3A6%3C567%3A%3AAID-ASNA567%3E3.0.CO%3B2-7

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Canal Ray Experiment

What are Canal Rays?

A Canal ray (also known as a positive or anode ray) is described as a positive ions' beam, created by certain gas-discharge tube types. These rays were observed in 1886 in Crookes tubes when the German scientist named "Eugen Goldstein performed experiments." 

Later on, anode rays work by the scientist Wilhelm Wien and J. J. Thomson led to the mass spectrometry development. So, it is said that Dempster is the one who discovered canal rays. He was also one of the first spectrometers to use such ions’ sources.

The canal rays experiment is the one that led to the discovery of the proton. The proton discovery has happened after the electron discovery has further strengthened the structure of the atom . In this experiment, Goldstein happened to apply a high voltage across a discharge tube that had a perforated cathode. Also, a faint luminous ray was seen extending from the holes of the back of the cathode.

Apparatus of the Experiment

The apparatus of this experiment includes the same cathode-ray experiment, made up of a glass tube containing two metal ion pieces at different ends that acts as an electrode. These two metal pieces are further connected with an external voltage. The air evacuation lowers the pressure of the gas present inside the tube.

The Procedure of the Experiment

Let us discuss more details about the procedure of the experiment, as listed below.

As the apparatus is set up by evacuating the air and giving a high voltage source for maintaining a low pressure inside the tube.

The high voltage is passed to the two metal pieces to ionize the air by making it an electricity conductor.

Thereby, the electricity starts to flow as the circuit is complete.

When the voltage was increased to thousands of volts, a faint luminous ray was seen, extending from the holes present behind the cathode.

These rays moved in the opposite direction facing the cathode rays and were called canal rays.

Explanation

When a higher voltage is applied, the experiment ionizes the gas, and it is the positive ions of gas that constitute the canal ray. It is the kernel or nucleus of the gas that is used in the tube, and thus, it has different properties to that of the cathode rays, made up of electrons.

Differences between Cathode and Anode Rays

Basically, in the first Canal ray experiment, William used the Crookes tube supplying high voltage and gradually reduced the pressure within the tube chamber from 0.01 to 0.001 atm. Also, he noticed a certain beam of light starting to emanate from the tube's cathode, and this travelled throughout the tube upon reducing the pressure further.

Then, the light emitted from the ray was passed via the strong electric field formed between two plates, charge positive and negative. The light beam was found to curve towards the positive plate and was thus charged negatively. It was named Cathode Rays because it originated from the Cathode of the Tube.

After that, using a perforated Cathode (Cathode with fine pores), he conducted another experiment. Even this time, too, he saw the light, but now, starting from the middle of the tube. Upon increasing the voltage and reducing further pressure, the beam went towards the cathode. The beam bent towards the negative plate when the light beam was placed in between an electric field, and hence, these rays were charged positively.

But we cannot call them Anode Rays since they weren't emitted from the AnodeAnode. Therefore, they were known as Canal Rays because they formed light 'canals' when they left the cathode's perforations.

Production of Anode Rays

When a high range of voltage is applied to the tube, the electric field accelerates the small ions count (electrically charged atoms) that are always present in the gas, created by natural processes like radioactivity. These collide with the gas atoms by knocking the electrons off of them and creating added positive ions. These electrons and ions strike more atoms, in turn, creating added positive ions in a chain reaction . Then, all the positive ions get attracted to the negative cathode, and a few of them pass through the holes in the cathode if any. These are known as the anode rays.

Unlike the cathode rays, canal rays will depend upon the nature of gas that is present in the tube. This is due to the canal rays being composed of positive ionized ions formed by the ionization of gas present in the tube.

The charge to the ratio of mass for the ray particles was different for different gases.

The particle's behavior in the magnetic and electric fields was opposite compared to the cathode rays.

Besides, a few particles that are charged positively carry multiples of the fundamental value of the charge.

E. Goldstein also concluded that apart from the cathode rays that pass from the negatively charged electrode to the positively charged electrode, there is another set of rays that move exactly in opposite directions which is from a positively charged electrode to a negatively charged electrode and these rays are canal or anode rays. They were further analyzed and it led to the discovery of a positively charged subatomic particle called “Proton”. 

FAQs on Canal Ray Experiment

1. What is meant by the Goldstein experiment?

E. Goldstein was the person who conducted an experiment in which he passed electricity through two electrodes that were placed on either side of the glass or vacuum chamber. Then the electrodes were connected to an external electricity source. When the electricity was passed through the electrodes, the positively charged ions were emitted from the positive electrode and these rays were known as the canal rays. Goldstein conducted discharge tube experiments on his own in the 1870s named Kathodenstrahlen, or the cathode rays, which are light emissions, examined by others. He found a few major properties of the cathode ray, which led to their subsequent discovery as the electron, which is the first subatomic particle. Finally, he concluded that in addition to the cathode rays or ions that travel from the negatively charged electrode towards the positively charged electrodes, other rays travelled in opposite directions which is from the positively charged electrode to the negatively charged electrode. These rays deflected oppositely when they were subjected to magnetic and electric fields.

2. Why are the anode rays referred to as canal rays?

The anode rays are the particle beams that travel in the opposite direction to the "cathode rays," the electron waves, which move through the Anode. These positive rays were referred to as Kanal Strahlen, by Goldstein, "canal rays" or "channel rays," because the channels or holes in the cathode formed them. Canal rays have positively charged ions that move from a positive electrode towards a negative electrode in a glass chamber through a gas. They deflect in an opposite direction that cathode rays deflect when both of them are subjected to magnetic and electric fields. By further analyzing these rays, positively charged subatomic particles also known as protons were discovered. Canal rays, also known as anode rays, travel in a straight line but have lesser velocity than the cathode rays and can penetrate through thin metal plates. 

3. Describe some differences between canal and cathode rays?

Canal rays are also known as anode rays, they are positively charged ions that travel through a gas chamber to reach the negatively charged electrode. These rays were discovered by E. Goldstein when he was conducting an experiment and further analysis of these rays has led to the discovery of positively charged protons. On the other hand, cathode rays are negatively charged electrons that travel from the negatively charged electrode to the positively charged electrode. Both the rays deflect in opposite directions when they are brought under the effect of the magnetic and electric fields. Cathode rays travel in straight lines, thus they cast a sharp image or reflection. Unlike the anode rays, the properties of the cathode rays are not dependent on the gas present in the vacuum tube. Phosphorus is an element that glows when the cathode rays fall on it. Similar to the anode rays, cathode rays also penetrate through thin metal plates. These rays are lighter than the lightest element that is hydrogen. J.J Thomson discovered a subatomic particle related to the cathode rays in 1897, they are  known as “electrons”

Cathode rays are negatively charged, whereas the Canal Rays are positively charged. 

Cathode rays emanate from the cathode but the canal rays do not emanate from the Anode, and they are produced inside the chamber by the gas molecule's collision. 

Cathode rays are drawn to positive electrodes in an electric field.

4. Explain the Production of Canal Rays.

Canal rays also known as the anode rays were discovered by E. Goldstein when he was experimenting. These rays are positively charged ions that pass through a chamber of gas to reach the negative electrode also known as a cathode. The apparatus required to produce the canal rays is a glass tube having two metal ion pieces on either side and further connected to an external circuit.  The metal piece acts as an electrode. The air is evacuated to reduce the pressure on the gas, the electricity is passed through the electrodes and in this process, the gas gets ionized. 

Electrons, which are emitted from the cathode, collide with the gas atoms present in the tube by knocking either one or two additional electrons out of each atom. These collisions leave behind ions that are charged positively. The positive ions that are produced travel towards the cathode. And, any of the positive ions pass via perforations that create canal rays in the cathode disc. Both magnetic and electric fields deflect the channel rays in a similar direction to the cathode rays.

5. What are the characteristics of canal or anode rays?

Canal rays also known as the anode rays were discovered by E. Goldstein when he was experimenting. They are positively charged rays that move towards the negative electrode also known as a cathode in a discharge tube when high voltage electricity is passed through the tube. Following are the applications of canal or anode rays:

They are positively charged ions that move in an enclosed place along with the gas.

They are oppositely deflected to the deflecting direction of cathode rays due to magnetic and electric fields. 

They travel at a lower velocity compared to the cathode rays and travel unidirectionally.

Anode rays affect the photographic rays and also produce fluorescence and ionize the gas through which they pass. Positively charged protons are discovered after analyzing the anode rays. 

Distillations magazine

Positive effect.

Meet J. J. Thomson, who disproved Einstein’s dictum that the man “who has not made his great contribution to science before the age of thirty will never do so.”

Albert Einstein once remarked that “a person who has not made his great contribution to science before the age of thirty will never do so.” J. J. Thomson represents a glaring contradiction to this sentiment. After receiving the Nobel Prize in physics days before his 50th birthday in 1906, Thomson embarked on a new line of research, arguably invented mass spectrometry, and published the field’s foundational text, Rays of Positive Electricity and Their Application to Chemical Analyses , exactly 100 years ago this year.

Thomson’s starting point—the “rays of positive electricity’’ from his title—was in a sense the opposite of the electrons (then known as cathode rays) he had won fame for discovering. Originally called Kanalstrahlen , Thomson’s rays had first been described by Eugen Goldstein in 1886. They were produced by drilling channels ( Kanäle , or canals) in the cathode of a cathode-ray tube (a sealed glass tube with almost all its air removed and with a cathode and anode added). As the flow of electrons left the cathode, unknown particles flowed in the opposite direction, passing through the holes. At first the rays were enigmatic, since unlike electrons they were not affected by a magnetic field. But researchers soon found that a stronger magnetic field deflected the rays, implying that they were charged particles like electrons but immensely more massive.

Little was known about the nature of these particles until Thomson began a series of improvements to the apparatus. First, he collimated the rays, lining them up by extending the hole in the cathode into a long, narrow tube. Then he developed various techniques to record the faint impression the rays made when they hit the wall of the tube after being deflected by powerful magnetic and electric fields. Ultimately, placing a photographic plate inside the vacuum tube itself proved most effective. Finally, when Thomson reduced the minuscule air pressure inside the tube even further, spots produced by the canal rays suddenly separated and resolved themselves into a series of parabolic smears.

Thomson knew that electric and magnetic fields applied to the rays would cause particles with the same charge-to-mass ratio to deflect as a family, smearing into a unique parabola on the screen. Particles with any other charge-to-mass ratio would make up a distinct family that would form its own parabola. Thomson’s improved apparatus now allowed him to identify the canal rays as positively charged ions with a distinct atomic or molecular mass. He could take the ions of whatever gases were in the tube and spread them across the screen by mass, making a mass spectrum.

Thomson immediately saw an application to chemical analysis. He wrote, “I feel sure that there are many problems in Chemistry which could be solved with far greater ease by this than by any other method. The method is surprisingly sensitive—more so even than that of Spectrum Analysis, [and] requires an infinitesimal amount of material.” The method excelled, for instance, in revealing trace constituents of a sample.

Much of the credit for improving the original apparatus must go to Thomson’s assistant, the talented experimenter Francis William Aston, who joined Thomson’s lab in 1910. Thomson credits Aston early in the book with creating a clever means of photographing the mass spectra but hardly mentions him after that. Ironically, Rays of Positive Electricity does contain the seeds of Aston’s later claim to fame. The last plate of the book includes a photograph of a mass spectrum with an unidentifiable feature corresponding to atomic mass 22 just under the strong line corresponding to neon, which has an atomic mass of 20. “It must, I think, be a new element,” Thomson writes. Aston reappears as Thomson recounts a series of painstaking experiments to separate this new element from the neon so close by. Alas, unable to separate the two because they are so close in weight and physical properties, Thomson voices a suspicion that “the two gases, although of different atomic weights, may be indistinguishable in their chemical and spectroscopic properties.” Aston received his own Nobel Prize in 1922 for the discovery of isotopes, the first of which was neon-22.

Editor’s note: Francis William Aston received his 1922 Nobel Prize for the discovery of non-radioactive isotopes.

James R. Voelkel is the curator of rare books at the Science History Institute and a senior advisory editor to the Chymistry of Isaac Newton project.

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Anode ray explained

An anode ray (also positive ray or canal ray ) is a beam of positive ion s that is created by certain types of gas-discharge tube s. They were first observed in Crookes tube s during experiments by the German scientist Eugen Goldstein , in 1886. [1] Later work on anode rays by Wilhelm Wien and J. J. Thomson led to the development of mass spectrometry .

Anode ray tube

Goldstein used a gas-discharge tube which had a perforated cathode . When an electrical potential of several thousand volts is applied between the cathode and anode, faint luminous "rays" are seen extending from the holes in the back of the cathode. These rays are beams of particles moving in a direction opposite to the " cathode ray s", which are streams of electron s which move toward the anode. Goldstein called these positive rays Kanalstrahlen , "channel rays", or "canal rays", because these rays passed through the holes or channels in the cathode.

The process by which anode rays are formed in a gas-discharge anode ray tube is as follows. When the high voltage is applied to the tube, its electric field accelerates the small number of ion s (electrically charged atom s) always present in the gas, created by natural processes such as radioactivity . These collide with atoms of the gas, knocking electrons off them and creating more positive ions. These ions and electrons in turn strike more atoms, creating more positive ions in a chain reaction. The positive ions are all attracted to the negative cathode, and some pass through the holes in the cathode. These are the anode rays.

By the time they reach the cathode, the ions have been accelerated to a sufficient speed such that when they collide with other atoms or molecules in the gas they excite the species to a higher energy level . In returning to their former energy levels these atoms or molecules release the energy that they had gained. That energy gets emitted as light. This light-producing process, called fluorescence , causes a glow in the region behind the cathode.

Anode ray ion source

An anode ray ion source typically is an anode coated with the halide salt of an alkali or alkaline earth metal . [2] [3] Application of a sufficiently high electrical potential creates alkali or alkaline earth ions and their emission is most brightly visible at the anode.

• Canal ray experiments

External links

• Rays Of Positive Electricity by J.J. Thomson Proceedings of the Royal Society , A 89, 1-20 (1913)
• The Goldstein canal ray tube at The Cathode Ray Tube site

Notes and References

• Book: Grayson, Michael A. . Measuring mass: from positive rays to proteins . Chemical Heritage Press . Philadelphia . 2002 . 4 . 0-941901-31-9 .
• Book: Thomson . J. J. . Rays of positive electricity, and their application to chemical analyses (1921) . 1921 . 142 . 2013-04-22.
• Book: Kenneth Tompkins Bainbridge . Alfred Otto Nier . Relative Isotopic Abundances of the Elements . 21 April 2013 . 1950 . . 2– . NAP:16632.

This article is licensed under the GNU Free Documentation License . It uses material from the Wikipedia article " Anode ray ".

Except where otherwise indicated, Everything.Explained.Today is © Copyright 2009-2024, A B Cryer, All Rights Reserved. Cookie policy .

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Did JJ Thomson know about Eugen Goldstein’s experiment discovering canal rays?

We learn that JJ Thomson discovered the electron in 1897. Several years EARLIER in 1886, Eugen Goldstein performs the same experiment but with the anode and cathode switched to produce positively charged canal rays. My question is, did JJ know about Goldstein’s experiment? I’m surmising he did not, as it wouldn’t have taken such a leap to conclude that Goldstein’s was a positive particle as well as the negative electron JJ discovered. Does anyone know the history who can confirm this is true or prove it is false?

• history-of-chemistry
• atomic-structure

• 3 $\begingroup$ Stack Exchange History of Science and Mathematics will get you the response. Secondly have you tried looking at the original paper of JJ and does he cite Goldstein using Google Scholar? Most likely he does. $\endgroup$ –  ACR Commented Jan 6, 2021 at 6:40
• 1 $\begingroup$ See the original paper. web.lemoyne.edu/~giunta/thomson1897.html#footnote . The charge of cathode "rays" was determined by Perrin not by JJ. $\endgroup$ –  ACR Commented Jan 6, 2021 at 8:13

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ResearchTweet

Discovery of protons: model, discovery, and experiment.

• Reading time: 5 mins read

What are Protons?

The three different sub-atomic particles present in the nuclei of an atom are called, protons, neutrons, and electrons and they were discovered in the nineteenth and twentieth century.

Discovery of Protons

The nucleus of the atom was discovered by a scientist named Ernest Rutherford in the year 1911 in his well-known gold foil experiment. He stated that all the positively charged particles present in an atom were concentrated in a singular core and that maximum of the atom’s volume was empty.

He also stated that the total number of positively charged particles present in the nucleus of an atom is always equal to the total number of negatively charged electrons present around it.

The finding of the proton is credited to Ernest Rutherford, who showed that the nucleus of the hydrogen atom (that is a proton) is present in the nuclei of all atoms in the year 1917. But, the presence of a positively charged particle found in an atom had been first noticed by E. Goldstein in the year 1886 based on the concept that atoms are generally electrically neutral which means that they have the same number of positive and negative charges.

He performed a series of experiments and detected that when high voltage electricity was passed through a cathode tube which was fitted with a perforated cathode (pierced disk) and thus contained gas at low pressure then a new type of ray was produced from a positive electrode or commonly called as the anode which moved towards the cathode.

These new rays he named as canal rays, positive rays, or anode rays. Further, the canal Ray experiment is the experiment that was performed by German scientist Eugen Goldsteinin that led to the discovery of the proton. The discovery of proton occurred after the discovery of the electron which further supported the structure of the atom.

The Canal Ray Experiment

• The apparatus as shown above in the figure is set by providing a very high voltage source and emptying the air to preserve low pressure inside the tube.

• High voltage is thus passed to the two metal pieces as shown to ionize the air and hence making it a conductor of electricity.

• The electricity started to flow as the circuit completes.

• When the voltage was increased further to several thousand volts, then a faint luminous ray was observed extending from the holes in the back of the cathode.

• The rays thus observed were moving in the opposite direction of cathode rays and were termed as canal rays.

Conclusion of Canal Ray Experiments

• As compared to cathode rays, canal rays depend upon the nature of gas present in that tube. It is because of the fact that the canal rays consisted of positive ionized ions which were formed by the ionization of gas present in the tube.

• The behavior of particles present in an electric and magnetic field was thus the opposite to that of cathode rays.

Protons Characteristic

Protons are referred to as the positively charged subatomic particles of an atom. It is represented by the symbol p or p + .

A hydrogen atom comprises of one proton and one electron, so when an electron is removed from the hydrogen atom then a proton is produced. This is the reason why the proton is also represented as H + .

It thus possesses +1e (or 1.60 10 -19 coulomb) positive electric charge.

The word Proton is a Greek word that means ‘First’. It was initially used by Ernest Rutherford in the year 1920. The subatomic particles protons and neutrons are collectively known as nucleons.

What is The Mass of Protons?

The mass of the proton is 1.67 10 -24 gram or 1.67 10 -27 kg.

The mass of an electron is equal to 9.1 10 -28 consequently the mass of a proton is 1836 times the mass of an electron. Though the mass of a proton is almost always equal to the mass of a neutron present in the nuclei of an atom.

The number of protons present inside the nucleus of an atom is always equal to the atomic number (Z) of the atom.

Mathematically,

Number of Protons = Atomic Number

For instance, the atomic number of the Krypton (Kr) atom is equal to 36. Henceforth, the nucleus of the Krypton atom consists of 36 protons.

Properties of Protons / Positive Rays / Anode Rays

1. They are positively charged ions.

2. They travel in straight lines and thus can cast a shadow of the thing located in their path.

3. These positive rays are also deflected by electric as well as a magnetic field.

4. Mass of proton is equal to 1.672 x 10 -24 g.

5. The charge on the proton is equal to +1.602 x 10 -19 coulombs.

Discovery of Neutrons: Model, Discovery, and Experiment

Protons citations.

• Discovery of new proton emitters 160Re and 156Ta. Phys Rev Lett . 1992 Mar 2;68(9):1287-1290.
• Particle therapy and treatment of cancer. Lancet Oncol . 2006 Aug;7(8):676-85.

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