Chemistry 125: Lecture 19October 13, 2010

Oxygen and the Chemical Revolution Lavoisier’s Analysis (1789)

Chronological treatments of organic chemistry often begin with Lavoisier, the father of

modern chemistry. But his “Chemical Revolution” depended upon discoveries like those of

Scheele, the Swedish apothecary who discovered oxygen and prepared the first pure

samples of organic acids. Lavoisier’s “Traité Élémentaire de Chimie” launched modern

chemistry with its focus on facts, ideas, and words. Lavoisier weighed gases and measured

heat with a calorimeter, as well as clarifying chemical language and thought. Lavoisier’s key

concepts were conservation of mass for the elements, and “oxidation”, which could convert

a “radical” or “base” into an acid. Elemental analysis was the technique for determining the

composition of organic compounds. Lavoisier's early combustion and fermentation

experiments showed a new, though naïve, attitude toward handling experimental data.

For copyright notice see final page of this file

http://webapp1.dlib.indiana.edu/newton/index.jsp

Carl Wilhelm

Scheele (1742-1786)

Prerevolutionary Pharmacist

Carl Wilhelm

Scheele (1742-1786)

Scheele's Acids

BenzoicO

OH

H

H

H

H

H

UricN

N N

N

O

O

O

H

HH

H

CitricH

H O

OHH

HO

O

H

OH

O OH

LacticH

OH O

OH

H3C

OxalicO

OH

HO

O

Gum Benzoin

Rhubarb (?)

Lemon

Milk

Urine

(purified as heavy-metal salts)

Bismuth, cobalt, antimony, tin, mercury, silver, and gold were attacked by lactic acid either by digestion or by boiling. After standing over tin the acid caused a black precipitate to form in a solution of gold in aqua regia.

7)

Lead dissolved after several days of digestion. The solution acquired a sweet, tart taste but did not crystallize.

10)

With copper our solution first took on a blue color, then green, finally dark blue, but it did not crystallize.

9)

Iron and zinc were dissolved with formation of flammable air. The iron solution was brown and gave no crystallization, but the zinc solution crystallized.

8)

On Milk and its Acid (1780) 19 pp.

!

Tartaric H

OH O

OHHO

HO

O

H

Tartar(wine cask residue)

e.g. "Oxymoron"

"Oxy" = Sharp

What's sharpabout Rhubarb?

Acidic taste

"acre" to be sour

root "ac-" sharp

sharp dullness(self-contradiction) Latin "acidus”; Greek

(oxus)

Scheele's Acids (purified as heavy-metal salts)

Benzoic

Oxalic

Citric

Lactic

Uric

Tartaric

O

OH

H

H

H

H

H

N

N N

N

O

O

O

H

HH

H

H

H O

OHH

HO

O

H

OH

O OH

H

OH O

OH

H3C

H

OH O

OHHO

HO

O

H

O

OH

HO

O

Gum Benzoin

Rhubarb

Lemon

Milk

Urine

Tartar (Wine Casks)

vs. Carboxylic Acid

Alcohol pKa ~16 Carboxylic Acid pKa ~5

AlcoholCarbonyl

High HOMO Stabilized

C

O

O H

C

O

O H

C

O

O H

Higher HOMO More Stabilized

C

O

O

C

O

O

C

O

O

(Note: there will be more to this story involving "inductive effects")

pKa depends on energy difference between A-H and A- H+

Scheele's Acids (purified as heavy-metal salts)

Benzoic

Oxalic

Citric

Lactic

Uric

Tartaric

O

OH

H

H

H

H

H

N

N N

N

O

O

O

H

HH

H

H

H O

OHH

HO

O

H

OH

O OH

H

OH O

OH

H3C

H

OH O

OHHO

HO

O

H

O

OH

HO

O

Gum Benzoin

Rhubarb

Lemon

Milk

Urine

Tartar (Wine Casks)

?

Uric Acid

Two C=O LUMOs stabilize the High HOMO of N

N

N N

N

O

O

O

H

HH

HN

N N

N

O

O

O

H

HH

HN

N N

N

O

O

O

H

HH

H

Two C=O LUMOs stabilize the Higher HOMO of N-

N

N N

N

O

O

O

H

HH

N

N N

N

O

O

O

H

HH

N

N N

N

O

O

O

H

HH

pKa 5.8 (vs. 38 for NH3 NH2- + H+)

tung sten

7 Elements Discovered or Codiscovered by Scheele

nitrogen

chlorine

manganese

molybdenum

barium tungsten

oxygen

gases

heavy stone (Swedish)

Scheele (1771)

Feuerluft "fire air"

Ag + O2

> 340°C

Ag2CO3

Ag2O + CO2

…since I have no large burning glass, I beg you to try with yours…

Genealogy Top

The Chemical Revolution 1789

WeradRadix

Latin

Licorice(glukos + rhiza)

Greek

RutabegaSwedish

WortOld English

Mathematics (16th Cent)

Race?RazzaItalian

Eradicate

WurzelGerman

Chemistry (18th Cent - France)

Politics (18th Cent - England)

Radish Radical: Going to the root or origin

= Root

1787: Radical Introduced as a Political Term

"The necessity of a substantial and radical reform in the representation..."

J. Jebb

September 17, 1787

byLouis Bernard

Guyton de MORVEAU(1737-1816)

"Radical"Introduced as aChemical Term

1787

age 50

Méthode de Nomenclature Chimique1787

Antoine François de FOURCROY

(1755-1809) age 32Claude Louis BERTHOLLET

(1748-1822) age 39

AntoineLaurent

Lavoisier(1743-1794)

age 45

7,000 pounds (~$300,000)

TraitéÉlémentairede Chemie

(1789)

Weighing a Gas

vacuum

HgPatm - Pgas

"Lavoisier in his Laboratory

Mme. Lavoisier taking his dictation

(After a sepia drawing

by Mme. Lavoisier)"

Lavoisier'sPneumatic Trough

Elementary Treatiseof Chemistry

1789

PRESENTED IN A NEW ORDERAND ACCORDING TO MODERN DISCOVERIES

With Figures

Preliminary Discourse (1789)

I had no other object, when I began the following Work, than to extend and explain more fully the Memoir which I read at the public meeting of the Academy of Science in the month of April 1787, on the necessity of reforming and completing the Nomenclature of Chemistry. While engaged in this employment, I perceived, better than I had ever done before, the justice of the following maxims of the Abbé de Condillac, in his System of Logic, and some of his other works:

Preliminary Discourse (1789)

"We think only through the medium of words.

--Languages are true analytical methods.

--Algebra, which is adapted to its purpose in every species of expression, in the most simple, most exact, and best manner possible, is at the same time a language and an analytical method.

--The art of reasoning is nothing more than a language well arranged."

Preliminary Discourse (1789)

Thus, while I thought myself employed only in forming a Nomenclature, and while I proposed to myself nothing more than to improve the chemical language, my work transformed itself by degrees, without my being able to prevent it, into a treatise upon the Elements of Chemistry.

Preliminary Discourse (1789)

The impossibility of separating the nomenclature of a science from the science itself, is owing to this, that every branch of physical science must consist of three things; the series of facts which are the objects of the science, the ideas which represent these facts, and the words by which these ideas are expressed. Like three impressions of the same seal, the word ought to produce the idea, and the idea to be a picture of the fact.

Preliminary Discourse (1789)And, as ideas are preserved and communicated by means of words, it necessarily follows that we cannot improve the language of any science without at the same time improving the science itself; neither can we, on the other hand, improve a science, without improving the language or nomenclature which belongs to it. However certain the facts of any science may be, and, however just the ideas we may have formed of these facts, we can only communicate false impressions to others, while we want words by which these may be properly expressed.

Clarity:

Facts Ideas

Words

“impressions of the same seal”

New Order

1) Doctrine

2) Nomenclature

3) Operations

Elements…if by the name of elements we mean to desig-nate the simple, indivisible molecules that make up substances, it is probable that we do not know what they are :

but if, on the contrary, we associate with the name of elements, or of the principles of substances, the idea of the furthest stage to which analysis can reach, all substances that we have so far found no means to decompose are elements for us…they behave with respect to us like simple substances.

TraitéÉlémentairede Chimie

(1789)

Table ofElements

imponderable

Lavoisier-Laplace Calorimeter (1782)

Flame

3 Feet

Inner CanCompletelySurrounded

by InsulatingIce

Lamp into

BucketBucket into Cage

Cage into Can

FlameCompletelySurroundedby Melting

Ice

Melted by Flame Only!

Elementary Treatiseof Chemistry

1789

PRESENTED IN A NEW ORDERAND ACCORDING TO MODERN DISCOVERIES

With Figures

1) Doctrine

2) Nomenclature

3) Operations

New OrderIdeas

Words

Facts

Facts: Analysis

Analysis

Since the chemical properties of the part of atmospheric air that does not support respiration were not well known, we were content to deduce the name of its base from the property of its gas to take the life of animals that breathed it : so we have named it azote, from the Greek privative, and from (zoe) life, thus the unbreathable part of air would be azotic gas.

besides it has been shown to enter also into nitric acid compounds; so one could be just as properly name it the nitrigen principle. Ultimately we had to reject a name which conveyed a systematic idea, & decided to avoid this risk of fooling ourselves by adopting the names azote and azotic gas, which expresses only a fact, or better a property, that of taking the life of animals that breathe this gas.

We have given to the base of the portion of air that supports respiration the name of oxygen, deriving it from two Greek words (oxus), acid, & (geinomai), to cause to be, because in fact one of the most general properties of this base is forming acids by combining with most substances. We shall thus call oxygen gas the combination of this base with caloric.WORD

FACT

THEORY

Caloric+

Base or Radical

Gas

Oxy-gen+

Base or Radical

Acid

we find ourselves forced to give a name. Nothing seems more convenient to us than hydrogen, that is to say, the generating principle of water, from (hydor) water, & from , (geinomai), to cause to be. We shall call the combinate of this principle with caloric hydrogen gas, & the word hydrogen alone will stand for the base of this same gas, the radical of water.

TraitéÉlémentairede Chimie

(1789)

?

The word gas is thus for us a generic name that designates the ultimate degree of saturation of whatever substance by caloric.

Lavoisier'sCompound

Radicals

ScheeleAcids

Oxidation States

Radical1°

"oxide"2°

"-ous" acid3°

"-ic" acid

4°"oxygenated

-ic" acid

Risky Prediction

Elemental Analysis by Oil Combustion

Air Supply

Oil Supply

H2OCollector

CO2

Collector

Lamp

H2OCollector

How to analyze a substance that will not burn cleanly?

e.g.grape sugar

Everyone knows how wine, cider and mead are made…

Plate X: Fermentation Apparatus

H2OAbsorptionby CaCl2

CO2

Absorption by NaOH soln.

any other Gas

Foam catcher

Sugar/Yeast/Water

I can consider the materials subjected to fermentation and the products of fermen-tation as an algebraic equation; and by in turn supposing each of the elements of this equation to be unknown, I can derive a value and thus correct experiment by calculation and calculation by experi-ment. I have often profited from this way of correcting the preliminary results of my experiments.

Fermentation

it can furnish a meansof analyzing sugar

Oxidationhad failed with

AirOxygen

Sulfuric AcidMercuric Oxide

etc.because of incomplete combustion (charring)

Lavoisier’s Bookkeeping

72 grains = 1 gros8 gros = 1 ounce = 28.35 g

Proximate

Ultimate

End of Lecture 19Oct. 13, 2010

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