Sceptical Chymists

Program 24

Lesson 4.2

Text References

Speilberg & Anderson, none

Booth & Bloom 225-226; 227-233

Coming Up

Before we are done with this program we will have seen the transition from alchemy to chemistry as the reigning paradigm on the nature of matter and changes which it undergoes. We will see the role of two transitional characters and the influence they had on the development of chemistry as a science distinct from alchemy and its spiritualism. We will see how a speculative, but essentially correct, book changed the paradigm virtually overnight by defining what is meant when we speak of an "element". We will examine two competing theories on the nature of combustion and see how the concept of the weight of atoms led to a revolution in chemistry. Finally we will briefly examine the role of electricity, newly discovered and little understood, in the discovery of new chemical elements.

Questions

1. Describe the major factors which led to a transition from alchemy to chemistry in the seventeenth and eighteenth centuries.

2. Who was Paracelsus and what did he contribute to the science of chemistry.

3. Who was van Helmont and why is he sometimes called "the First Chemist"

4. What did Robert Boyle contribute to our modern concept of "element".

5. Simplify the distinction between the concept of element as envisioned by Aristotle, Alchemy, and Boyle

6. How did Boyle's concept of "element" differ from that of Aristotle and from an alchemist's?

7. What is phlogiston and what were its properties thought to be?

8. Why was Lavoisier's weighing of substances important?

9. Why is Lavoisier remembered as the "father" of chemistry?

10. How did Lavoisier determine that a substance was not an element?

11. Who discovered oxygen, Priestly or Lavoisier? Explain.

12. Why was the invention of the battery important in the history of chemistry?

13. Who was Humphrey Davy, and what did he do?

Objectives

1. Characterize the transition from alchemy to chemistry through the concept of element

2. Compare and contrast the views on matter of Paracelsus, van Helmont and Boyle

3. Describe the phlogiston theory of combustion

4. Specify the contributions of Lavoisier to the chemical revolution

5. Describe the role of the battery in the discovery of chemical elements

1. Alchemy to Chemistry

1.1. Aristotle's theory of form and matter led logically to the belief that every chemical change was a transmutation

1.1.1. reaction products completely new

1.1.2. nothing remained of the old substance (reactant) except a "virtue" or hidden quality

1.2. properties of matter were thought to be due to "substantial forms and real qualities" where elements were believed to be actual entities attached to matter

1.2.1. a substance was white because it contained "form of whiteness"

1.2.2. substances were endowed with personality: they loved and hated (affinities)

1.3. Seventeenth century saw rapid growth of chemical knowledge as well as physical as the old ideas were challenged

1.4. first half of the seventeenth was a period of increasing precision

1.4.1. quantitative studies come to chemistry

1.4.2. indestructibility of matter realized

1.4.3. nature of acids and bases and their salts began to be understood

1.5. first scientific societies in allowed results and methods to be reported

1.6. theoretical development of chemistry was in a chaotic state

1.7. every chemist had a theory of matter

1.8. most theories did not survive the century

1.9. theories arose because of challenge to old theories

1.10. new discoveries demanded better explanation that offered by occult and mystical forces

1.11. A new paradigm arose: purity of substance

1.12. electricity enters chemistry

1.13. coincided with rapid expansion of knowledge in other areas

1.14. many substances thought to be elements were shown not to be

1.15. fifteen new elements discovered in 18th, twenty five more in nineteenth

2. Paracelsus 1493 - 1541

2.1. real name: Phillippus Theophrastus Bombastus von Hohenheim

2.2. called himself Paracelsus to indicate his superiority to the second century Roman physician and writer, Celsus

2.3. Swiss physician, alchemist, mystic and drunk

2.3.1. slept on the floor of taverns

2.3.2. coined the word "alcohol"

2.4. promoted the use of specific remedies and authored many medical and occult works

2.5. stressed the use of chemicals to cure disease

2.6. views brought him nearer to modern concept of chemistry than anyone before him

2.7. Most controversial and certainly the weirdest figure in the history of medicine and chemistry

2.7.1. publicly burned the works of Galen to show his contempt for orthodox medical opinion

2.7.2. considered the views of Aristotle and Galen to be those of heathens and heretics

2.7.3. known for original ideas and violence of temper

2.7.4. wandered around Europe engaging in stormy controversies with physicians who followed the theories of Galen

2.7.5. lectured in vernacular Germans rather than Latin

2.7.6. aroused such violent opposition that his writings could not be published until twenty years after his death

2.8. writings are marred by mysticism, strange terminology and by a confused style of writing

2.8.1. it is not altogether clear exactly what his ideas were in many cases

2.9. main outlines of his chemical theories are well established

2.9.1. alchemy meant any process in which natural products were mad fit for a new end, processes such as working iron and baking bread

2.9.2. held that the macrocosm (the universe) and the microcosm (man) behaved similarly, so human digestion was also a human process

2.9.3. controlled by an alchemist spirit he called "the Archaeus"

2.9.4. The Archaeus separated poisonous substances from nutritious ones in the body

2.9.5. the most important goal of alchemy was the preparation of medicines called "arcana" which could restore bodily balance disturbed by disease

2.9.6. believed in transmutation, but not as the primary goal of alchemy

2.10. subjected large number of metals to a standardized set of reactions

2.10.1. grew up in mining district with good knowledge of metallurgy

2.10.2. obtained a series of salts of various metals in solution

2.10.3. called them "oils"

2.10.4. thus generalized chemical reactions instead of considering every process as an individual treatment of a separate substance

2.10.5. greatly increased the number of remedies available, although some were distinctly dangerous to the patient

2.11. iatrochemistry (use of chemicals for remedies) strongly modified older theories of medicine

2.11.1. ideas encountered strenuous opposition by physicians, ideas were spread by a large group of followers

2.12. important theoretical contribution

2.12.1. added salt to tradition of mercury and sulfur as components of metals

2.12.2. concrete expression of the idea of soul, spirit, and body (gas, liquid, solid)

2.12.3. added body to complete the triangle

2.12.4. air (called "chaos" by Paracelsus) had given way to fire as the prime principle

2.12.5. sulfur embodied fire, mercury embodied liquidity, salt embodied earth

2.12.6. when wood burns "that which burns is sulfur, that which vaporizes is mercury, that which turns to ashes is salt."

2.12.7. fitted so well with observations that it completely replaced the sulfur mercury theory

2.12.8. Paracelsus still considered the four elements of Aristotle as basic, but placed little emphasis on them and that his sulfur, mercury, and salt were not the common substances but rather their more abstract essences. The four elements appeared in bodies as three principles of salt, sulfur, mercury

2.12.8.1. everything had its own particular kind of salt, mercury and sulfur

2.12.8.2. salt: principle of fixity and incombustibility: earthiness

2.12.8.3. mercury: principle of fusibility and volatility: metalness

2.12.8.4. sulfur: principle of combustibility

2.12.9. medical substances were composed from the four elements, which formed receptacles or matrices for the universal qualities of the tria prima or three prime qualities

"The world is as God created it. He founded this primordial body on the trinity of mercury, sulfur and salt and these are the three substances of which the complete body consists. For they form everything that lies in the four elements, they bear them all the forces and faculties of perishable things.

3. Johann Baptista van Helmont (1579-1644)

3.1. represents the transition from alchemy to chemistry

3.2. influential and highly respected physician

3.3. many erroneous theories, but large influence on later chemists

3.4. harsh criticism of the conventional medicine of his time made him many enemies and retarded the general acceptance of his views

3.5. denounced as heretic by Spanish inquisition, spent most of his life under house arrest

3.5.1. Spain was in control of what is now Belgium

3.6. posthumous writings brought him fame, like Paracelsus

3.7. claimed to have witnessed a transmutation of base metal into gold

3.8. a disciple of Paracelsus, but disagreed and modified

3.9. called himself a "philosopher by fire"

3.10. strongly anti-Aristotelian

3.11. rejected four elements, but also rejected tria prima

3.12. Boyle: "an author more considerable for his experiments than many learned men are pleased to think him"

3.13. two first beginnings of bodies: water and active organizing principle called a "ferment"

3.14. the other element was air which was purely physical whereas water could be molded into the variety of substances on earth

3.15. fire was a transforming agent, not an element

3.16. earth was created by the action of ferments on water

3.17. carefully documented the weight of water used compared with the weight gain of a tree

3.17.1. planted tree in weighed amount of earth

3.17.2. watered it for 5 years

3.17.3. tree gained 164 pounds, weight of earth remained the same

3.17.4. concluded that wood was made from water alone

3.18. recognized that air was not element, but mixture of gases

3.19. water glass

3.19.1. fused a weighed amount of sand with alkali to form water glass

3.19.2. water glass liquefied when exposed to air, obviously a conversion of earth to water

3.19.3. water could be reconverted to earth by treatment with acid and the amount of earth (silica) recovered was the same as the original amount

3.20. thinking was much more modern than his predecessors

3.20.1. quantitative: routing weighing of reactants, hinted at conservation of mass

3.20.2. theory of the elements: when water evaporates it gives rise to an airlike substance, so do many chemical reactions. These could not be air, so represent a new class of materials. The product of evaporation of water easily returned to water, so Van Helmont considered it a type of vapor. Other substances were more permanent so he gave them a name.

"I call this spirit, unknown hitherto, by the new name of Gas, which can neither by contained by vessels, nor reduced into a visible body . . ."

3.20.3. 'gas' comes from 'chaos'

3.20.4. gas was subtler than a vapor, but denser that elementary air

3.20.5. chemical reactions can produce gas powerful enough to explode a closed glass container, used it to explain the effects of gunpowder.

4. Robert Boyle (1627-1691)

4.1. founder of Royal Society of London

4.2. contemporary of Newton

4.3. wealthy

4.4. practiced science as hobby

4.5. performed experiments rather than just observing and speculating

4.6. discovered gas law

4.6.1. pressure is inversely proportional to volume

4.7. Worked to establish a mechanistic chemistry

4.8. The Sceptical Chymist published in 1661

4.8.1. a dialogue between supporters of the older theories and Boyle, who needed to be convinced by more that medieval speculations

4.8.2. presented convincing arguments to destroy most of the former beliefs

4.8.3. did not present a substitute for the ideas which were cast aside

4.8.4. led some to believe that he was a complete skeptic

4.8.5. supported corpuscular theory of matter

4.8.5.1. conceived of small, solid, physically indivisible particles tat were the building blocks of nature. These were associated into larger groups which often acted as units through a number of chemical reactions. Size and shape of these units gave physical properties to substances, but their motion was equally important, and a change of motion resulted in a change in properties. Attraction and affinity were explained by the mutual fitting together of moving particles.

4.8.6. defined modern view of element, although he still believed in transmutation by rearranging corpuscles

4.8.6.1. did not make connection between corpuscles of matter and purity of elements

4.8.7. "I now mean by elements . . . certain primitive and simple or perfectly unmingled bodies, which not being made of any other bodies or of one another, are the ingredients of which all those perfectly mixt bodies are immediately compounded and into which they are ultimately resolved."

4.8.8. Began dialogue on modern concept of element

4.8.8.1. much as Galileo did with motion

4.8.8.2. dispelled alchemists notion of element

4.8.8.3. elements as purity of substance replaced substances as "purveyors of elemental principles"

4.8.9. Boyle was not clear on how to distinguish elements from other substances

4.8.9.1. listed no possible candidates

4.8.9.2. 17th century techniques were crude

4.8.9.3. many "elements" were really "compounds"

4.8.9.4. how could a chemist tell if a material was "unmingled" or "mixt"?

4.9. Three Views of Elements

4.9.1. Aristotle: purity of quality

4.9.2. Alchemy: quality of substance

4.9.3. Modern: purity of substance

5. Phlogiston Theory

5.1. phlogiston was thought to be a primary substance (one of three 'earths') which was contained in all matter

5.2. an incorrect theory of combustion

5.3. in eighteenth century chemical interests turned to the nature of combustion and the forces that held chemical compounds together

5.4. obvious that fire was escaping from a burning object

5.5. analogy between calcification and combustion

5.6. idea grew that air was needed if combustion was to occur

5.6.1. combustion ceased when air became saturated with phlogiston

5.6.2. combustion ceased when substance "ran out of" phlogiston

5.6.3. phlogiston was removed from air by plants which were eaten by animals

5.6.4. a phlogiston cycle

5.7. smelting infused ores with phlogiston

5.8. explained calcination as loss of phlogiston from a metal

5.9. explained combustion as loss of phlogiston from a substance

5.10. phlogiston explained acidity and alkalinity, colors and odors of plants, chemical reactivity and composition

5.11. obvious today that heating metals creates a heavy calx, a process called calcination

5.11.1. weight is a physical process which was thought to be separate from chemical changes

5.11.2. not so obvious to 17th and 18th century chemists

5.11.3. high temperatures attained with lenses actually vaporized some of the calx so weight gain was not apparent

5.12. problems arose in 1760s when the gaseous state was studied

5.12.1. phlogiston as incorporeal, ethereal fire, substance with negative weight, lightest known substance

5.12.2. too many problems arose, signaled eventual end of the theory

6. Antoine Lavoisier (1743-1794)

6.1. Father of modern chemistry

6.1.1. unfortunate association with a company organized to collect taxes for King Louis

6.1.2. died at guillotine (of no use to the New Republic of France)

6.1.3. headless body buried in unmarked grave

6.2. Showed conservation of mass in chemical reactions

6.2.1. invented precise scale to weigh small amounts of matter

6.2.1.1. accurate to 0.0005 grams

6.2.1.2. about 1/100 of a drop of water

6.2.2. mass of all reactants = mass of all products

6.2.3. cannot create matter from nothing, can only change form

6.2.4. matter is not created from nothing, only changes form during chemical reactions

6.3. freed thinking from phlogiston theory

6.3.1. Priestly's Dephlogisticated Air

 

6.3.2. Lavoisier's Oxygen

6.3.3. showed that products of combustion weighed more than combustible materials

6.3.4. combustion is a process of addition rather than subtraction

6.3.4.1. involves combination with oxygen in air

6.3.5. "discovered" oxygen (recognized it as a substance)

6.4. Showed a way to distinguish between unmingled and mixt

6.4.1. If a reaction produces a product that weighs more than the reactant then the product cannot be an element

6.4.2. smaller weight represented the uncombined substance

6.4.3. recall Boyle's definition of an element

6.5. Showed nitrogen was inert gas in air, not involved in combustion

6.6. Published first textbook of chemistry

6.6.1. Traite Elementair de Chimie (1789)

6.6.2. made clearly defined list of elements based on Boyle's criteria

6.6.3. put discoveries of others in coherent form for the first time

6.6.4. took mystery out of chemistry

6.6.5. many errors but great advancement of concept and method

6.7. Hinted at the law of constant proportions (thought water was 7:1)

7. Electrolysis &New Elements

7.1. Cavendish and hydrogen

7.2. Invention of battery (1800)

7.2.1. by Alessandro Volta (1745-1827)

7.2.2. allowed continuous supply of electricity

7.2.3. from Galvani's observation

7.2.3.1. dead frogs twitching

7.2.3.2. hung on wire, touching lower wire

7.2.3.3. Galvani reasoned a new kind of life energy

7.2.3.4. Volta recognized reaction between two metals mediated by electrolyte

7.2.4. Voltaic Pile: The First Battery

7.3. William Nicholson (1753-1815) used battery to electrolyze water

7.3.1. decomposed water into hydrogen and oxygen

7.3.2. more current and more time = more water decomposed

7.3.3. recombined to form water again

7.3.4. showed water is not an element

7.3.5. related electricity to chemistry

7.4. Humphrey Davy (1778-1829) decomposed other substances

7.4.1. electrolyzed molten salts

7.4.2. discovered potassium, sodium, barium, strontium, calcium, magnesium

7.4.3. all are shiny and reactive metals, reacted rapidly with air or water

7.4.4. became an invalid at age 33 due to habit of sniffing and tasting chemicals

8. Summary & Conclusions

In this program we saw how the superstitions and animism of alchemy gradually became more scientific. Paracelsus was one of the earliest physicians to use specific chemicals as a cure for disease. Although deeply rooted in the mysticism of alchemy he systematically tested different substances and their reactions another particular substance.

The first truly quantitative chemistry on record is that of van Helmont. A contemporary of Galileo, van Helmont's main contribution is the careful weighing of products and reactants. Van Helmont represents the transition from Alchemy to Chemistry. It is interesting to note that van Helmont and Galileo were contemporaries, and working on similar problems albeit in different areas and with different intentions.

Robert Boyle is remembered not only for founding the Royal Society of London and his law of pressure and volume of gases. He stated a definition of a chemical element which defined our modern paradigm and caused a revolution in chemistry, although he hadn't a clue how to identify an element. Rarely has there been a single more influential statement in the history of science.

On the stream of events and scientists we took a brief side trip to study the theory of combustion know as Phlogiston Theory. We studied this concept to illustrate the way in which quantitative studies can help where qualitative speculation fails. Qualitatively Phlogiston made sense, but quantitatively the theory fell apart.

Lavoisier has been called the father of chemistry. Largely because of his quantitative methods he was the first chemist to classify substances and their properties the way we do today. He showed that mass conserved in chemical reactions, disproved the phlogiston theory, and discovered a way to identify elements according to Boyle's definition. He also published the first textbook of chemistry which contained the first list of elements in the modern sense. Although it contained many errors, the techniques and insights of Lavoisier mark the beginning of modern chemistry.

Many new elements were discovered using Lavoisier's techniques, aided tremendously by the invention of the battery. This invention marked the beginning of what some believe to be the most significant technological achievement of our species, the control of electricity. The connection between chemistry and electricity will provide one more link in our chain of paradigms: Newtonian physics, heat and energy, chemistry, electricity.