History of Science - 7

History of Science - 7.

Joseph Black.

James Watt.

Joseph Priestley.

Henry Cavendish.

Carl Scheele.

Antoine Laurent Lavoisier.

Historians refer to the period following the renaissance as the enlightenment.

The basic feature of enlightenment was a belief of the superiority of reason over superstition.

The success of Newtonian physics in providing the mathematical description of an ordered world,

played a big part in the flowering of enlightenment in the 18th century.

It encouraged rationalist philosophers, chemists and biologists, to explain the natural world,

on the basis of simple laws.

It is probably not a coincidence that the industrial revolution took place in England,

between 1740 and 1780, before spreading to the rest of Europe.

There are many factors which contributed to this revolution.

One of them was the geological circumstance of Britain being an island of coal.

Another factor was the early flowering of democracy.

Another factor was that the Newtonian mechanistic world view became firmly established in his homeland.

The industrial revolution gave a huge boost to science.

Topics such as heat and thermodynamics stimulated interest,

because of its commercial importance in the steam age.

Science provided the tools for investigation of the world.

Chemistry was lagging behind, astronomy, physics and botany in science.

Astronomy could be carried out with the human eye.

Physics involved studying objects such as balls rolling down, or the swing of pendulums.

Botanists and zoologists could work with simple magnifying glasses.

What the chemist needed was a reliable and controllable source of heat, to encourage chemical reactions.

Even into the 19th century chemists had to use candles or sprit lamps,

to obtain a localised source of intense heat.

Fahrenheit invented the alcohol thermometer in 1709.

He developed a temperature scale, now named in his honour.

This was just 2 years after Thomas Newcomen completed,

the first practical steam engine to pump water from mines.

What was wrong in Newcomen’s design was more important than what was right,

in stimulating the progress of science.

There was a large gap between the time of Boyle, who laid the ground rules of chemistry,

to the people, who actually made chemistry scientific at the time of the industrial revolution.

From 1740 onwards progress of science in chemistry was rapid.

Joseph Black was born in 1728 a year after Newton died.

Joseph Black’s father John Black had 13 children, all of whom, unusual for the time,

grew to adulthood.

Joseph was educated by his mother till the age of 12.

After that he was sent to school in Belfast.

He entered the university of Glasgow in 1746.

At first Joseph studied languages and philosophy, and later switched to medicine and anatomy.

He studied medicine under William Cullen, whose classes included chemistry.

Cullen proved that very low temperatures could be achieved when water or other fluids evaporated.

By using an air pump to produce cold by evaporating liquids at low pressure,

Cullen, in effect invented the first refrigerator.

Joseph graduated in 1752 and moved to Edinburgh to carryout research,

leading to the award of a doctor’s degree.

At that time there was a great deal of concern, in the medical profession,

about the use of quack remedies to cure stones in the urinary system.

This involved drinking powerful concoctions, such as caustic potash.

It became popular, when the then Prime Minister of Britain endorsed this remedy.

When Joseph was a medical student a milder alkali, milk of magnesia, was introduced to medicine,

to treat acidic stomach.

Joseph decided to investigate whether white magnesia could be used for treatment of stones.

This did not workout.

But his investigations led him to discover carbon dioxide.

He showed for the first time, that air is not a single substance, but a mixture of gases.

In his time mild alkalis could be converted into caustic alkalis, by boiling them with slaked lime.

Slaked lime was produced by slaking quicklime with water.

Quicklime was produced by heating limestone in a kiln.

It was thought that some fire stuff from the kiln got into the lime, and eventually made it caustic.

Joseph discovered that white magnesia lost weight when it was heated.

He realised that this could happen only if air had escaped from the material.

He then found out that all mild alkalis effervesce when treated with acids,

but the caustic alkalis did not.

He inferred that mild alkalis have ‘fixed air’ which can be liberated, while caustic alkalis did not have.

In other words caustic properties are not the result of the presence of fire stuff.

This lead to experiments in which everything was weighed at every step.

From the changes in the weight, Joseph could calculate the weight of the fixed air, gained or lost.

The air released by the mild alkalis was found to extinguish a lighted candle.

Joseph showed that it is different from ordinary air, but must be present in it.

In other words air is a mixture of gases.

This was a dramatic discovery at that time.

Joseph published his findings in 1756, and received a doctorate for it.

He became well known with the scientific world as a leading chemist.

He became a professor of medicine, and lecturer of chemistry in Glasgow,

with a private medical practice on the side, at the age of 28.

Joseph’s lectures attracted students from all over Britain, Europe and even America.

He was a major influence on the next generation of scientists.

Joseph showed among other things that ‘fixed air’ is produced by respiration of animals,

the process of fermentation, and by burning charcoal.

By 1760, he started turning his attention to physics.

Joseph’s other major contributions to science concerned the nature of heat.

Heat at that time was fascinating, because of its role in the burgeoning industrial revolution.

The development of the steam engine is an obvious example.

The whisky industry in Scotland, used large amounts of fuel to turn liquid into vapours,

and to remove large amount of heat from the vapours, as they condensed back into liquid.

He described the heat which the solid absorbed, while melting to liquid with the same temperature,

as latent heat.

It was this heat that made the water liquid instead of solid.

He made the crucial distinction between the concepts of heat and temperature.

Joseph also investigated the latent heat associated with the transition of liquid water into vapour.

He also gave the name ’specific heat’ to the amount of heat required to raise the temperature,

of a certain amount of substance, by a certain temperature.

If a pound weight of water at freezing point of 32 degrees Fahrenheit, is added to a pound of water,

at the boiling point of 212 degree Fahrenheit, the result is 2 pounds of water at 122 degree Fahrenheit,

which is half way between the two extremes.

The specific heat of iron is less than that of water.

If a pound of water at 212 degrees Fahrenheit is poured to a pound of iron at 32 degree Fahrenheit,

the temperature of iron would increase by more than 90 degree Fahrenheit.

These findings were given in Joseph’s lectures, but never published.

James Watts was an assistant to Joseph, and they became good friends.

Joseph was quite pleased, when James Watt became rich and famous, for his work on steam engines.

Joseph became the professor of chemistry in Edinburgh.

He was the physician and friend to Adam Smith, David Hume, and James Hutton.

He never married.

He died in 1799, at the age of 71.

James Watt was born in 1736.

His father was a ship builder and merchant.

His mother bore 5 children, and 4 of them died.

He had a good basic education.

He suffered from migraines and was regarded as physically delicate.

He was more interested in his father’s workshop, than school.

He made working models of different machines, including a barrel organ.

His father wanted him to take over the ship building business, and did not send him to university.

The business however suffered a succession of failures.

James in his teens, had to make his own living.

In 1755, he went to London and had an apprenticeship, with one of the best instrument makers.

He returned to Glasgow and became a mathematical instrument maker to the university.

Watt could just about make a living in his new position.

He found some time to do some experiments in steam power.

In 1763, he was asked by the university to repair a model of a Newcomen engine.

Thomas Newcomen built the first successful steam engine in 1712.

It was used to pump water out of a mine.

Watt realised that the model of the Newcomen engine had a problem, called the scale effect.

Newton had pointed out that a small object loses heat more rapidly than a large object.

Watt investigated to see whether he could improve the efficiency of the Newcomen engine.

He realised that the solution was to have two cylinders.

One which was kept hot all the time, and one which was kept cold all the time.

Watt made many other improvements including having a separate condenser.

He independently came to know about latent heat, as he was unaware of Joseph’s work,

which was never published.

Joseph helped him to further improve his engine.

Watt noticed that if a small amount of steam is bubbled through cold water, it makes the water boil.

This is due to the latent heat released as steam condenses to water.

Watt patented his steam engine in 1769.

It was not an immediate commercial success.

He married his 1st wife in 1763, who died in 1773, leaving two sons.

In 1774, he moved to Birmingham, where he became part of a scientific group, called Lunar society.

The members included Joseph Priestly, Josiah Wedgwood, and Erasmus Darwin.

He entered into partnership with Mathew Boulton,

which led to the commercial success of his steam engines.

He married again in 1775.

He retired from his steam engine business in 1800, at the age of 64.

He continued inventing till he died in 1819.

The importance of steam in the industrial revolution, encouraged further study of the connection between,

heat and motion, or thermodynamics, in the 19th century.

Joseph Priestley was born in 1733.

His mother bore 6 children in 6 years, and died in the unusual severe winter of 1739.

At the age of 8 he went to live with his aunt, who had no children.

He had a good education in Latin and Greek.

After completing his education, Priestley became a minister.

He was an Arian.

He married Mary Wilkinson in 1762, sister of John Wilkinson.

John Wilkinson made a fortune out of armaments.

He taught at Warrington academy.

It was one of the first educational institution in England, to replace the study of classics,

with lessons in history, science and literature.

Priestley’s intellectual interests were wide ranging.

In his early writings, he made a biographical chart of the chronological relationship,

between important figures from history, from 1200 BC to the 18th century.

For this he was awarded the ‘Doctor of Laws’, by the university of Edinburgh, in 1765.

Priestley met Benjamin Franklin and other scientists interested in electricity.

He suggested among other things, that electricity obeys an inverse square law.

This work got him elected as a fellow of the Royal society in 1766.

He published a history of electricity in 1767.

He developed an interest in chemistry.

He made various publications in scientific and non scientific subjects, which made him famous.

A politician called Lord Shelburne, invited him to become his librarian, at a salary of 250 pounds a year.

This gave him plenty of time for other scientific work, and other interests.

Shelburne became secretary of state in 1766, and tried to push through a policy of conciliation,

with the Americans.

For this he was dismissed by King George III.

The King’s disastrous policy resulted in the defeat of Britain, in the American war of Independence.

The King was forced to recall Shelburne, to carry out the difficult task,

of establishing peace with former colonies.

Priestley was an outspoken religious dissenter.

For this he was retired as a librarian by Shelburne, with the pension of 150 pounds a year.

He became an active member of the Lunar society.

He supported the American colonists, and was an outspoken supporter of the French revolution.

For his views, his opponents organised a mob, which destroyed his house, his library, manuscripts,

and his scientific equipments, but Priestley escaped.

In 1794, Priestley who was 61 years old, emigrated to North America.

He published 30 more works before he died in 1804.

Priestley was a great experimenter but a lousy theorist.

When he started his work, only two gases were known, air and carbon dioxide.

Hydrogen was discovered by Henry Cavendish in 1776.

Priestley identified 10 other gases, including ammonia, hydrogen chloride, nitrous oxide,

and sulphur dioxide.

His greatest discovery was oxygen.

However his model to explain combustion with oxygen was wrong.

He did not make the connection between combustion and oxygen.

It was initially thought, in his model, that something called phlogiston,

left the substance that was being burnt.

It was the French scientist Antoine Lavoisier, who made the connection,

between combustion and oxygen.

Priestley began his experiments involving air, while in Leeds, where he lived close to a brewery.

The air above the surface of the brew was identified as carbon dioxide.

Priestley found that this air could extinguish a candle.

He mixed carbon dioxide and water and produced a pleasant sparkling drink.

This led to a craze for ‘soda water’, which spread across Europe.

He did not seek financial reward for his innovation.

It was because of this soda water, that lord Shelburne heard of Priestley.

Shelburne encouraged Priestley’s chemical experiments, which led to the discovery of oxygen.

He found that the ability of air to sustain life, could be used up in respiration,

making the air unfit to breathe.

He found that the unfit air could be made respirable by the presence of plants.

This was the first hint of photosynthesis, in which carbon dioxide is broken down, to release oxygen.

In 1774, he heated mercuric oxide, using the focused rays of the sun.

He found that a gas was released, and mercuric oxide was reverted to mercury.

He discovered that a lighted candle exposed to the released gas, flared up with unusual brightness.

He did experiments with mice, and concluded over time, that the gas released,

was 5 times as good as common air.

This corresponds to the fact that 20% of the air we breathe is actually oxygen.

Another Swedish scientist Carl Scheele had discovered that air is a combination of two substances,

one which promotes combustion, and one which prevents it.

He did not publish his work till 1777.

Scheele made many other important discoveries, but he published only one book.

He died young at the age of 43, and not so well known as the others.

We now associate Priestley with the discovery of oxygen.

This is one of the examples of the contributions of many other scientists being over looked,

and who are now unknown.

Many scientists have carried out experiments to satisfy their curiosity, but never bothered to publish it

We never hear about them in science books.

Henry Cavendish published many works, which made him an important figure,

in the development of chemistry.

He did not publish a wealth of other works, which was rediscovered by other scientists, later on.

Cavendish came from two of the most wealthy and influential aristocratic families in England.

Both families had scientific interests.

Henry Cavendish’s father Charles Cavendish was keenly interested in science.

He gave up the role of aristocratic politics for science.

He invented in 1857, thermometers which showed the highest and lowest temperatures.

Charles Cavendish had an income of 2000 pounds a year.

This was at a time, when 50 pounds a year, was enough to live,

and 500 pounds was enough for a gentlemen to live comfortably.

Henry Cavendish was born in 1731.

His mother died soon after.

Henry went to Cambridge in 1749, when he was 18.

He left 3 years later without taking a degree, like many aristocratic young men.

Henry had no interest in politics, but was fascinated by science.

He devoted his life to science, initially in collaboration with his father.

Some members of his family thought that it was not decent for Henry, an Aristocrat,

to be involved in laboratory experience.

Henry received an allowance of 120 pounds a year.

Henry had no interest in money.

One incident illustrates his attitude to money.

After his father died, his banker visited him and told him that,

he had 80000 pounds accumulated in his current account.

He urged him to do something with the money.

Henry initially was not interested in such trivial matters.

His banker persuaded him to invest at least half the amount.

Henry agreed and told him not to bother him again.

By the time he died, the investment was worth more than a million pounds.

When Henry died in 1810, he left his fortune to close relations, mainly to George Cavendish.

Henry was referred to as the richest of the wise, and the wisest of the rich.

One of George descendants, his grandson, was William Cavendish.

William Cavendish increased his wealth by businesses including iron and steel.

He provided the endowment for the construction of the Cavendish laboratory in Cambridge in 1870’s.

The Cavendish laboratory was in the forefront of research in the 19th and 20th century.

Henry had no social life, except to meet the other scientists.

He was painfully shy and hardly went out to scientific gatherings.

Henry was elected as a Fellow of the Royal Society in 1760.

He became a member of the Royal Society club.

He attended nearly every weekly club dinners, for the next 50 years.

Much of Henry’s scientific work was never published in his life time.

The published work was mostly in chemistry.

He developed a method for preparing arsenic acid, which is still in use today.

Henry published for the first time, the ‘philosophical transactions’ in 1766, when he was 35 years old.

His significant discovery was the gas given off when metals reacted with acids.

Henry called it inflammable air.

This gas is now called as hydrogen.

He thought that the gas was released by the metals,

though we now know that it is released from the acids.

He also investigated Joseph’s carbon dioxide.

He turned his attention to electricity, and published a theoretical model,

based on the idea of electricity as a fluid, in 1771.

Though he discovered Ohm’s law, he never published it.

Ohm independently rediscovered the law.

Henry discovered that electricity force obeys the inverse square law, now known as Coulomb’s law.

He also investigated oxygen discovered by Joseph.

He however thought that combustion involved adding what was called as phlogiston to air,

where as combustion is really taking oxygen out of the air.

He carried out an experiment wherein, a mixture of hydrogen and oxygen, in a sealed vessel,

was exploded using an electric spark.

He weighed everything before and after the explosion.

This technique was invented by Volta.

At that time it was thought that the heat that escaped, had weight.

Though he noticed that some dew formed after the explosion,

he did not realise that it was a combination of hydrogen and oxygen.

Henry showed that water is not an element, but a combination of two other substances.

This paved the way for future research by other scientists.

Watt on the basis of experiments of others, arrived at the idea of the compound nature of water,

which was published in 1784.

Henry did experiments by sparking of nitrogen and oxygen, providing a variety of oxides of nitrogen.

He noticed that after all the nitrogen and oxygen was used up, there was a small bubble remaining.

He did not know what it was.

A century later in 1894, William Ramsay and Lord Rayleigh discovered that it was argon.

This work led to the award of two of the first Nobel prizes.

Rayleigh received the award for physics, and Ramsay received it for chemistry.

The Nobel prize was never awarded posthumously.

If it was Henry would have been awarded the Nobel prize, for his work 120 years earlier.

John Michell was a friend of Henry.

He conceived the idea of weighing the Earth.

He built an apparatus to do so, in Cambridge, but died before he could complete the experiment.

The apparatus was passed on to Henry, who rebuilt it.

The setup was called torsion balance.

Using this he could work out the mass of the Earth.

It was also possible with this experiment to calculate the Gravitational constant, ‘G’.

Though he never measured G, it could be inferred from his data.

He did not calculate the mass of the Earth, but did calculate the density of Earth,

as 5.45 times the density of water.

The modern value of the mean density of Earth is 5.52 times the density of water,

which is just about 1% more than what he calculated.

Henry died in 1810.

Joseph Black, Joseph Priestly, Carl Scheele and Henry Cavendish laid the foundation,

of chemistry as science.

Antoine Laurent Lavoisier was born in 1743 in France.

He was brought up in middle class comfort.

His mother died in 1748, and he and his sister, Emille lived with the maternal grandmother.

Antoine attended college and excelled in classics and literature.

He also began to learn about science.

In 1761, he entered the school of law, intending to follow the traditional family career.

He graduated in 1764, with a bachelor of law, and a licentiate of law.

He also attended courses in astronomy, mathematics, botany, geology and chemistry.

He became more interested in science than law.

His grandmother died and left most of her ample wealth to him.

In 1766, he was awarded a gold medal, by the royal academy of sciences, on behalf of the king,

for an essay on the best way to light, the streets of a large town.

He became well known in scientific circles,

and was elected as a member of the royal academy of sciences, in 1678, at a young age of 25.

The French academy of sciences, unlike the royal society in England,

was funded by the French government.

The members were expected to carry out scientific work for the government.

The French taxation system at that time was unfair, incompetent and corrupt.

Nobles were exempted from paying tax.

This was a major factor in the discontent that led to the French Revolution.

Lavoisier invested in a Tax farm, which means in effect, he became a tax collector.

The right to collect taxes was farmed out to groups of financiers, known as Tax farmers.

The Tax farmers paid the government for the privilege.

They made a profit from the tax they collected, after paying the government.

Tax farmers had to provide sinecures for members of the royal family,

who would draw an income, without doing any work.

Lavoisier entered into arranged marriage with Marie Anne,

the 13 year old daughter of a fellow tax farmer.

Marie was keenly interested in science, an worked as Lavoisier’s assistant.

Lavoisier carried out experiments building on Joseph Black’s meticulous approach to chemistry.

By heating diamonds using sunlight concentrated with a huge lens,

he proved that diamond is combustable.

He established that sulphur gains weight when it it burnt.

It was the first step in the modern understanding of combustion,

involving a process in which oxygen from the air combines with the substances being burnt.

In 1774, after his discovery of oxygen,

Priestley met Lavoisier and gave him the early results of his experiments with oxygen.

Lavoisier carried out his own experiments and in 1775 he published a paper,

describing how oxygen combined with metals, during combustion.

The way gun powder was supplied to the army and navy was privatised, inefficient and corrupt.

When Louis XVI became the king in 1774, he wanted to reform this.

He effectively nationalised the gun powder industry.

He appointed 4 commissioners to do it.

One of them was Lavoisier.

Lavoisier moved into the Paris Arsenal, and worked diligently.

He did further experiments on combustion, and in 1779 gave oxygen,

which was called ‘Pure air’ till then, its modern and current name, ‘oxygen’.

He carried out experiments which showed that oxygen from the air is converted to carbon dioxide,

by animals including humans, during respiration.

At that time carbon dioxide was referred to as ‘fixed air’.

He concluded that humans and animals maintain body temperature,

by the conversion of oxygen into carbon dioxide.

He carried out an experiment along with a friend, Laplace, with a guinea pig, placed in a container of ice.

After 10 hours the warmth of the animal’s body melted a measured amount of ice.

They compared it with, how much charcoal was needed to melt that much ice.

They measured how much carbon dioxide the guinea pig breathed out in 10 hours,

and compared it with the amount of carbon dioxide produced by burning charcoal.

This confirmed the idea that animals keep warm by converting carbon,

from their food into carbon dioxide, by combining it with oxygen in the air, which they breathe in.

They concluded that respiration is a combustion, like the burning of charcoal.

This was the key step in settings humans in the right context, where they obey the same laws of nature.

In 1786, he published in Memoires of the academy, demolishing the Phlogiston model.

He also set out very clearly, the conditions in which combustion takes place.

Henry Cavendish had arrived at the composition of water.

This became known to Lavoisier.

Lavoisier published his own works, where he established that water,

was a combination of hydrogen and oxygen.

Lavoisier summed up his life’s work in chemistry, in the book ‘Elements of Chemistry’,

which was published in 1789, the same year as the storming of the Bastille.

There were many translations and editions of the book, which laid the foundation for chemistry,

as a scientific discipline.

Chemists regard this book, as the equivalent of Newton’s Principia to physics.

It provided extensive descriptions of the techniques of chemistry, including the apparatus used.

Importantly it provided the clearest definitions of a chemical element.

This consigned the four ‘elements’ of the ancient greeks to the dustbin of history.

It gave the first table of the then known elements.

It stated clearly the law of conversation of mass.

It gave logical names to elements like hydrogen and oxygen, and compounds like sulphuric acid,

nitrates, etc,.

It was a turning point, when chemistry got rid of its last vestiges of alchemy,

and became a scientific discipline.

Lavoisier was 46 when the book was published.

Lavoisier was elected the provincial assembly of Orleans as a representative of the third estate.

The other two were the clergy and the nobles.

Politically he would now be called as a liberal and a reformer.

However, he was tainted with the widespread hatred of tax farmers.

He played an important role in reforming the French educational system.

He was a member of the commission, which eventually introduced the metric system.

In spite of all this, unfortunately, since he was a former tax farmer,

he was guillotined, by the Jacobin government in 1794.

It was the end of an era in chemistry.