Illusztrációk az Általános Kémia Előadáshoz, 2010. ősz

ÁLTALÁNOS KÉMIA

I. éves Kémia BSc évf.

 Cél, feladat:

 

A kémiai fogalomrendszer, gondolkodásmód bemutatása, s ezzel a tételes tárgyak előkészítése.

Alapfogalmak: rendszeresen, precízen

Bonyolultabb fogalmak: halljanak róla, szokjanak a gondolathoz, még akkor is, ha nem ért(het)ik pontosan.

Tartalom:

I. A kémia atomi - molekuláris alapjai

II. Az anyag makroszkopikus megjelenése

III. A termodinamika alapjai

IV. Elektrokémia

V. Reakciókinetika

Vizsga:

írásbeli (belépő) + szóbeli (egy A, egy B tétel)

A kémia felosztása különböző lehetEgy könyvkiadó: WileyEurope > Chemistry

 Browse Chemistry subjects

Analytical Chemistry Biochemistry Chemical Engineering Computational Chemistry & Molecular Modeling Electrochemistry Environmental Chemistry General Chemistry 

Industrial Chemistry Inorganic Chemistry Organic Chemistry Physical Chemistry Polymer Science & Technology Special Topics Spectroscopy

WileyEurope > Chemistry Analytical ChemistryBiochemistryChemical EngineeringComputational Chemistry & Molecular ModelingElectrochemistryEnvironmental ChemistryGeneral ChemistryIndustrial ChemistryInorganic ChemistryOrganic ChemistryPhysical ChemistryPolymer Science & TechnologySpecial TopicsSpectroscopy 

ACS Divisions Agricultural & Food Chemistry Agrochemicals Analytical Chemistry Biochemical Technology Biological Chemistry Carbohydrate Chemistry Cellulose, Paper & TextileChemical Toxicology Colloid & Surface Chemistry Computers in Chemistry Environmental Chemistry Fluorine Chemistry Fuel Chemistry Geochemistry Industrial & EngineeringChemistry Inorganic Chemistry Medicinal Chemistry Nuclear Chemistry &Technology Organic Chemistry Petroleum Chemistry Physical Chemistry Polymer Chemistry Polymeric Materials: Rubber

A kémia felosztása különböző lehet

Kémia mindenhol

TOP 50 CHEMICALS: Rank Billions of lb1995 1994 1995 19941 1 Sulfuric acid 95.36 89.632 2 Nitrogen 68.04 63.913 3 Oxygen 53.48 50.084 4 Ethylene 46.97 44.605 5 Lime(b) 41.23 38.376 6 Ammonia 35.60 34.517 7 Phosphoric acid 26.19 25.588 8 Sodium hydroxide 26.19 25.119 10 Propylene 25.69 23.9410 9 Chlorine 25.09 24.3711 11 Sodium carbonate(c) 22.28 20.5612 18 Methyl tert-butyl ether 17.62 13.6113 14 Ethylene dichloride 17.26 16.7614 12 Nitric acid 17.24 17.2215 13 Ammonium nitrate(d) 15.99 17.0316 16 Benzene 15.97 15.27

22 20 Carbon dioxide(f) 10.89 11.80

27 26 Hydrochloric acid 7.33 7.47

33 33 Acetic acid 4.68 3.98

42 42 Titanium dioxide 2.77 2.7643 43 Acetone 2.76 2.66

50 49 Bisphenol A 1.62 1.70

Top 50 Chemical Companies in 1999Rank Company Total sales Chemical sales Chemical operating profits

Rank Company Total sales Chemical sales Chem. Oper. profits  1999   1998 1999  ($ M) 1999  ($ M) % of 1999  ($ M) %

total1 1 BASF (Germany) 34,689.4 31,250.3 90.1% 1,350.9 4.32 2 DuPont (U.S.) 29,740.0 27,688 .0 93.1 2,961.0 10.73 3 Bayer (Germany) 29,106.7 20,192.5 69.4 3,024.7 15.04 4 Dow Chemical (U.S.) 18,929.0 18,600.0 98.3 2,732.0 14.75 8 Exxon Mobil (U.S.)b 185,527.0 13,777.0 7.4 1,354.0 9.86 6 ICI (U.K.) 13,671.5 13,671.5 100.0 923.9 6.87 5 Shell (U.K./Netherlands) 149,706.0 12,886.0 8.6 885.0 6.98 19 Akzo Nobel (Netherlands) 15,375.9 12,323.5 80.1 819.3 6.69 35 Degussa-Hüls (Germany)c 13,157.7 10,085.8 76.7 544.6 5.410 11 BP Amoco (U.K.) 101,180.0 9,392.0 9.3 1,100.0 11.711 28 Total (France)c 42,069.0 9,343.6 22.2 643.5 6.912 10 Elf Aquitaine (France) 37,872.8 9,272.2 24.5 540.2 5.813 13 Sumimoto Chemical (Japan) 8,342.9 8,136.5 97.5 588.9 7.2

16 18 Henkel (Germany) 12,104.0 7,324.6 60.5 604.1 8.2 

Nemzeti jövedelmekhez hasonlítva:

Comparative economic indicators, 2000Hungary Slovenia Slovakia

GDP (US$ bn) 45.6 18.1 19.2GDP per head (US$ at PPP) 9,035 14,250 8,718

March 12, 2002 : The survey, published in a recent issue of the Society's publication, Chemical & Engineering News (C & EN), ranks the global top 50 by their chemical sales. It also charts their total sales, chemical operating profits and capital spending

Kémia a háztartásban

http://consumerlawpage.com/article/household-chemicals.shtmlTOP "10" HAZARDOUS HOUSEHOLD CHEMICALSBy Richard Alexander

AIR FRESHENERS: Most air fresheners interfere with your ability to smell by coating your nasal passages with an oil film, or by releasing a nerve deadening agent. Known toxic chemicals found in an air freshener: Formaldehyde: Highly toxic, known carcinogen. Phenol: When phenol touches your skin it can cause it to swell, burn, peel, and break out in hives. Can cause cold sweats,convulsions, circulatory collapse, coma and even death.

AMMONIA: It is a very volatile chemical, it is very damaging to your eyes, respiratory tract and skin.

BLEACH: It is a strong corrosive. It will irritate or burn the skin, eyes and respiratory tract. It may cause pulmonary edema or vomiting and coma if ingested. WARNING: never mix bleach with ammonia it may cause fumes which can be DEADLY. NH2Cl, klóramin keletkezhet

DISHWASHER DETERGENTS: Most products contain chlorine in a dry form that is highly concentrated.# 1 cause of child poisonings, according to poison control centers.

DRAIN CLEANER: Most drain cleaners contain lye, hydrochloric acid or trichloroethane. Lye: Caustic, burns skin and eyes, if ingested will damage esophagus and stomach. Hydrochloric acid: Corrosive, eye and skin irritant, damages kidneys, liver and digestive tract. Trichloroethane: Eye and skin irritant, nervous system depressant; damages liver and kidneys.

contnd,.

FURNITURE POLISH: Petroleum Distillates: Highly flammable, can cause skin and lung cancer. Phenol: (see Air fresheners, Phenol.) Nitrobenzene: Easily absorbed through the skin, extremely toxic.

MOLD AND MILDEW CLEANERS: Chemicals contained are: Sodium hypochlorite: Corrosive, irritates or burns skin and eyes, causes fluid in the lungs which can lead to coma or death. Formaldehyde: Highly toxic, known carcinogen. Irritant to eyes, nose, throat, and skin. May cause nausea, headaches, nosebleeds, dizziness, memory loss and shortness of breath.

OVEN CLEANER: Sodium Hydroxide (Lye): Caustic, strong irritant, burns to both skin and eyes. Inhibits reflexes, will cause severe tissue damage if swallowed.

ANTIBACTERIAL CLEANERS: may contain: Triclosan: Absorption through the skin can be tied to liver damage. (Ált. fertőtlenítőszer – kórházak :

LAUNDRY ROOM PRODUCTS: Sodium or calcium hypocrite!? nyilván hypochlorite: Highly corrosive, irritates or burns skin, eyes or respiratory tract. Linear alkylate sulfonate: Absorbed through the skin. Known liver damaging agent. Sodium Tripolyphosphate: Irritates skin and mucous membranes, causes vomiting. Easily absorbed through the skin

TOILET BOWL CLEANERS: Hydrochloric acid: Highly corrosive, irritant to both skin and eyes. Damages kidneys and liver. Hypochlorite Bleach: Corrosive, irritates or burns eyes, skin and respiratory tract. May cause pulmonary edema, vomiting or coma if ingested. Contact with other chemicals may cause chlorine fumes which may be fatal

Mi mindent tud a kémia?

VÁLOGATÁSOK KURRENS EREDMÉNYEKBŐL

INHIBITORS TARGET KEY TB ENZYME

Iminosugars may provide leads for new class of tuberculosis drugs

Scientists in England have designed and synthesized the first inhibitors of an enzyme that is essential for the survival of the tuberculosis bacterium [Org. Biomol. Chem., 2, 2418 (2004)]. The compounds might lead to better treatments for TB, which annually infects 8 million to 10 million people and kills 2 million to 3 million. e and kills 2 million to 3 million.

2004

Gyógyszerek, bioaktív anyagok

The proteasome—the cell’s garbage disposal for proteins—could become a target for new tuberculosis drugs, biologists report. A team led by Carl Nathan of Weill Cornell Medical College has found that some oxathiazolone compounds kill tuberculosis-causing bacteria by selectively inhibiting mycobacterial proteasomes without affecting human proteasomes (Nature, DOI: 10.1038/nature08357).

September 21, 2009 Volume 87, Number 38, p. 8

New Tuberculosis Drug Target

September 3, 2007 Volume 85, Number 36 , p. 7

When Organics Fail, Try WaterLadder polyethers form readily from epoxides in water

Complex ladder polyether natural products, so named for their runglike structure, are the active toxins found in the harmful algal blooms known as red tides. Red tides cause devastating ecological damage, so scientists hope that by studying this water-promoted cascade reaction, they will gain a better understanding of how and why these toxins form

Fantázia a természetben és a laborban: molekuláris létrák

In infants, EPO is produced mostly in the liver, but the kidneys become the primary site of EPO synthesis shortly after birth. EPO production is stimulated by reduced oxygen content in arterial blood in the kidneys. Circulating EPO binds to receptors on the surface of erythroid progenitor cells that in turn mature into red blood cells.….. contnd

Understanding the function of endogenous hormones and putting them to good use to treat diseases has been one of the great accomplishments of modern medicine. One natural hormone that has turned out to be a blockbuster drug--but not without some controversy--is erythropoietin (EPO).

Ezt is tudjuk …… EPO

EPO is a glycoprotein (protein-sugar conjugate) that serves as the primary regulator of red blood cells (erythrocytes) in mammals. It stimulates bone marrow stem cells to differentiate into red blood cells and controls hemoglobin synthesis and red blood cell concentration. Human EPO is a 30,400-dalton molecule containing 165 amino acids and four carbohydrate chains that incorporate sialic acid residues. There are several forms of EPO, designated by Greek letters, that differ only in the carbohydrate content.

Human EPO was first isolated and later purified from urine in the 1970s. Interest in developing clinical uses for EPO led to the discovery of the gene encoding EPO, and several groups devised recombinant DNA methods to produce EPO by the mid-1980s.

Recombinant EPO quickly made it to market to treat anemia resulting from a host of conditions, primarily kidney failure, HIV infection in patients treated with AZT, and cancer chemotherapy. Doses of EPO are given by injection one or more times per week to maintain a normal hematocrit level, the ratio of red blood cell volume to total blood volume. Generally, EPO might be prescribed for any condition where blood oxygen levels are depressed and to help eliminate the potential need for blood transfusions.

……

Enzyme immunoassays can provide a measure of serum EPO levels, but the tests can't determine if the EPO is natural or produced recombinantly and injected by unscrupulous athletes. The World Anti-Doping Agency has now developed combination urine and blood tests that can detect EPO abuse by athlets.

Mercury FulminateResearchers finally determine X-ray structure of infamous explosive

Wolfgang Beck and Thomas M. Klapötke, professors at Ludwig Maximilians University in Munich, Germany, and their colleagues report that, as expected, the molecule Hg(CNO)2 is

nearly linear, with the nitrogens carrying a positive charge and the oxygens a negative charge. The mercury atom is bound to two carbon atoms, with the bonding arrangement O–N C– Hg–C N–O (Z. Anorg. Allg. Chem. 2007, 633, 1417). This connectivity and linear structure was predicted by a number of groups, including Beck's and Klapötke's. Other groups, however, had predicted that the O atoms were bound to Hg.Mercury fulminate is sensitive to friction, heat, and shock, and it decomposes violently

the super-sensitive explosive with a nefarious 300-year history, has been so difficult to handle in the lab that only now have scientists finally determined its crystal structure.

ROBBANTGATUNK?

October 3, 2007 Also appeared in print Oct. 8, 2007, p. 11

Inorganic ChemistryMercury Tetrafluoride SynthesizedElusive Hg(IV) species has been prepared in solid argon, neonJyllian KemsleyMercury, a group 12 element with a valence electron configuration of s2d10, is generally considered to be limited to the +1 and +2 oxidation states. Theoretical work, however, has long predicted that mercury could be stable in the +4 oxidation state. In a fundamental advance that opens new possibilities for mercury compounds, that prediction has now been confirmed with the successful synthesis of HgF4 using matrix isolation techniques (Angew. Chem., DOI:

10.1002/anie.200703710).

SCIENCE & TECHNOLOGY

 RDX LINKS RUSSIAN CRASHES

Powerful explosive found in the debris of two planes that crashed

 

 

 

Traces of RDX, a common military explosive that is also known as hexogen or cyclonite, were found at the crash sites of two Russian planes that went down within minutes of each other on Aug. 24, Russian authorities report. RDX was also used in a suicide bombing at a Moscow metro station on Aug. 31, news reports say. "RDX is a very powerful explosive," says Jimmie C. Oxley, a professor of chemistry at the University of Rhode Island. "A terrorist wouldn't need to conceal very much." RDX has an explosive power considerably greater than that of TNT, is chemically stable, and is more susceptible than TNT to shock detonation.

2004 Sept.

January 12, 2009 Volume 87, Number 2p. 38

High-Nitrogen Anion Exceeds The Power Of RDX

German chemists report the synthesis of a collection of explosive azidotetrazolate (CN7

–) saltsRachel A. Petkewich

                  

In the quest for environmentally friendlier and more powerful explosives , researchers at Ludwig Maximilians University, in Munich, report the synthesis of a collection of azidotetrazolate (CN7

–) salts that take a step toward

both goals (J. Am. Chem. Soc., DOI: 10.1021/ja8077522). Thomas M. Klapötke and Jörg Stierstorfer synthesized the CN7– anion

by deprotonating 5-azido-1H-tetrazole. The new salts have the highest nitrogen content reported for tetrazolate compounds. For example, the hydrazinium salt, N2H5CN7, is 88.1% nitrogen by mass. These nitrogen-rich molecules are considered "greener"

than traditional explosives because they generate fewer carbon-based by-products that can damage artillery gun barrels and the environment. The researchers' calculations indicate that N2H5CN7 has the highest detonation pressure and velocity of the new

compounds—values that exceed those of the powerful explosive RDX. Although hydrogen bonds help render N2H5CN7

thermally stable at room temperature, the compound is still too sensitive to impact and friction for field use. Klapötke says adding a methyl group to the anion may reduce its sensitivity enough for it to be used safely.

2009 Sept.

"Molekuláris giroszkóp"

Gyönyörűszép Molekulák

One example, reported by Bryan W. Eichhorn's group at the University of Maryland, is the [As@Ni12@As20]3–

ion. This cluster consists of an As20 pentagonal dodecahedron that encapsulates a Ni12 icosahedron, which contains an

arsenic atom at its center. The As20 cage is related to the smallest fullerene, C20 C&EN May 5, 2003

2003

Játék, vagy tudomány? Klatrátok (zárványvegyületek)

ION RECOGNITION

System exploits weak interactions to attract anion to cation in capsuleA new approach to anion recognition that uses electrostatic and hydrogen-bonding interactions has been developed by chemists at the University of Missouri, Columbia. "For the first time, we have utilized a single molecule to completely encapsulate an ion pair in polar media," chemistry professor Jerry L. Atwood tells C&EN. "We envision that resins incorporating these capsules could be used in anion sensing in environmental applications."Atwood and postdoc Agnieszka Szumna embedded a tetramethylammonium cation in the pocket of a resorcin[4]arene molecule functionalized with bulky amide substituents. The complex selectively binds to a chloride anion in solvents such as methanol [Chem. Comm., 2003, 940].

Source: C&EN/ April 14, 2003

May 11, 2009 Volume 87, Number 19 | p. 7 |SAFETY

Negligence Caused UCLA DeathState safety and health agency faults university for training lapses, unsafe practices

When the incident occurred, Sangji was drawing approximately 20 mL of 1.7 mol/L tert-butyllithium in pentane into a 60-mL syringe when the syringe plunger was either ejected or pulled out of the syringe. An undetermined amount of the liquid splashed onto her hands, arms, and torso. The ensuing fire burned more than 40% of her body. One of the postdoctoral researchers used his lab coat to extinguish the flames and called for help. Sangji died of her injuries

A kémia veszélyes tevékenység .....

A modern kémia megszületése

A modern kémia a 18. sz. második felében, s a 19. sz. elején alakul ki, de kezdetei már a 17. sz.-ban láthatók

Robert Boyle (1627–1691) was born at Lismore Castle, Munster, Ireland, the fourteenth child of the Earl of Cork. As a young man of means, he was tutored at home and on the Continent. He spent the later years of the English Civil Wars at Oxford, reading and experimenting with his assistants and colleagues. This group was committed to the New Philosophy, which valued observation and experiment at least as much as logical thinking in formulating accurate scientific understanding. At the time of the restoration of the British monarchy in 1660, Boyle played a key role in founding the Royal Society to nurture this new view of science.

Although Boyle's chief scientific interest was chemistry, his first published scientific work, New Experiments Physico-Mechanicall, Touching the Spring of the Air and its Effects (1660), concerned the physical nature of air, as displayed in a brilliant series of experiments in which he used an air pump to create a vacuum. The second edition of this work, published in 1662, delineated the quantitative relationship that Boyle derived from experimental values, later known as "Boyle's law": that the volume of a gas varies inversely with pressure.

Robert Boyle at the age of thirty-seven, with his air pump in the background. François Diodati reengraved this image from an engraving by William Faithorne, Opera varia (1680)

Courtesy Edgar Fahs Smith Memorial Collection, Dept. of Special Collections, University of Pennsylvania Library. Robert Boyle (25 January 1627 – 31 December 1691) was a natural philosopher, chemist, physicist, inventor, and gentleman scientist, also noted for his writings in theology. He is best known for the formulation of Boyle's law.[2] Although his research and personal philosophy clearly has its roots in the alchemical tradition, he is largely regarded today as the first modern chemist, and therefore one of the founders of modern chemistry. Among his works, The Sceptical Chymist is seen as a cornerstone book in the field of chemistry.

Boyle was an advocate of corpuscularism, a form of atomism that was slowly displacing Aristotelian and Paracelsian views of the world. Instead of defining physical reality and analyzing change in terms of Aristotelian substance and form and the classical four elements of earth, air, fire, and water—or the three Paracelsian elements of salt, sulfur, and mercury—corpuscularism discussed reality and change in terms of particles and their motion. Boyle believed that chemical experiments could demonstrate the truth of the corpuscularian philosophy. In this context he defined the term element in Sceptical Chymist (1661): " . . . 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 called perfectly mixt bodies are immediately compounded, and into which they are ultimately resolved."

Robert Boyle: The Skeptical Chemist, 1661 (!)  "Én megpróbáltam a kémiát más szempontok szerint művelni, nem úgy, ahogy az eddigi kémikusok tették, hanem ahogy egy tudóshoz illik." .... "Bár viselnék az emberek inkább a tudományok előrehaladását szívükön, mint önző érdeküket, akkor könnyen belátnák, hogy nagyobb szolgálatot tennének a világnak, ha minden erejüket kísérletek végzésére és megfigyelések gyűjtésére fordítanák, ahelyett hogy kísérleti alapozás nélküli elméleteket állítanának fel. "

Joseph Priestley (13 March 1733 (Old Style) – 6 February 1804) was an 18th-century English theologian, Dissenting clergyman, natural philosopher, educator, and political theorist who published over 150 works. He is usually credited with the discovery of oxygen, having isolated it in its gaseous state, although Carl Wilhelm Scheele and Antoine Lavoisier also have a claim to the discovery.[2]During his lifetime, Priestley's considerable scientific reputation rested on his invention of soda water, his writings on electricity, and his discovery of several "airs" (gases), the most famous being what Priestley dubbed "dephlogisticated air" (oxygen). However, Priestley's determination to defend phlogiston theory and to reject what would become the Chemical Revolution eventually left him isolated within the scientific community.

Priestley

Lomonosov, 1753:“Today I made an experiment in hermetic glass vessels in order to determine whether the mass of metals increases from the action of pure heat. The experiment demonstrated that the famous Robert Boyle was deluded, for without access of air from outside, the mass of the burnt metal remains the same."

Mikhail Lomonosov (1711-1765), a polymath and writer of Imperial Russia Polymath : polihisztor.

Lavoisier

The Burning lenses

Calcination of a piece of metal with the burning lenses

Állandó súlyviszonyok törvénye Többszörös súlyviszonyok törvénye

Joseph Louis Proust(1754 – 1826)

John Dalton(1766 – 1844)

In 1811 Avogadro hypothesized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. From this hypothesis it followed that relative molecular weights of any two gases are the same as the ratio of the densities of the two gases under the same conditions of temperature and pressure. Avogadro also astutely reasoned that simple gases were not formed of solitary atoms but were instead compound molecules of two or more atoms. (Avogadro did not actually use the word atom; at the time the words atom and molecule were used almost interchangeably. He talked about three kinds of "molecules," including an "elementary molecule"—what we would call an atom.) Thus Avogadro was able to overcome the difficulty that Dalton and others had encountered when Gay-Lussac reported that above 100oC the volume of water vapor was twice the volume of the oxygen used to form it. According to Avogadro, the molecule of oxygen had split into two atoms in the course of forming water vapor. Curiously, Avogadro's hypothesis was neglected for half a century after it was first published. Many reasons for this neglect have been cited, including some theoretical problems, such as Jöns Jakob Berzelius's "dualism," which asserted that compounds are held together by the attraction of positive and negative electrical charges, making it inconceivable that a molecule composed of two electrically similar atoms—as in oxygen—could exist. In addition, Avogadro was not part of an active community of chemists: the Italy of his day was far from the centers of chemistry in France, Germany, England, and Sweden, where Berzelius was based. Avogadro was a native of Turin, where his father, Count Filippo Avogadro, was a lawyer and government leader in the Piedmont (Italy was then still divided into independent countries). Avogadro succeeded to his father's title, earned degrees in law, and began to practice as an ecclesiastical lawyer. After obtaining his formal degrees, he took private lessons in mathematics and sciences, including chemistry. For much of his career as a chemist he held the chair of physical chemistry at the University of Turin.

Amedeo Avogadro.

Joseph Louis Gay-Lussac’s law of combining volumes (1808) (when two gases react, the volumes of the reactants and products—if gases—are in whole number ratios) tended to support Dalton’s atomic theory. Dalton did not in fact accept Gay-Lussac's work, but the Italian chemist Amedeo Avogadro (1776–1856) saw it as the key to a better understanding of molecular constituency.

Avogadro EREDETI CIKKÉBŐL! : http://web.lemoyne.edu/~giunta/avogadro.html

Essay on a Manner of Determining the Relative Masses of the Elementary Molecules of Bodies, and the Proportions in Which They Enter into These CompoundsJournal de Physique 73, 58-76 (1811) [Alembic Club Reprint No. 4] I. (fordítás franciából)

M. Gay-Lussac has shown in an interesting Memoir (Mémoires de la Société d'Arcueil, Tome II.) that gases always unite in a very simple proportion by volume, and that when the result of the union is a gas, its volume also is very simply related to those of its components. But the quantitative proportions of substances in compounds seem only to depend on the relative number of molecules which combine, and on the number of composite molecules which result. It must then be admitted that very simple relations also exist between the

volumes of gaseous substances and the numbers of simple or compound molecules which form them. Kiemeles FG: The first hypothesis to present itself in this connection, and apparently even the only admissible one, is the supposition that the number of integral molecules in any gases is always the same for equal volumes, or always proportional to the volumes. Indeed, if we were to suppose that the number of molecules contained in a given volume were different for different gases, it would scarcely be possible to conceive that the law regulating the distance of molecules could give in all cases relations as simple as those which the facts just detailed compel us to acknowledge between the volume and the number of molecules. On the other hand, it is very well conceivable that the molecules of gases being at such a distance that their mutual attraction cannot be exercised, their varying attraction for caloric may be limited to condensing the atmosphere formed by this fluid having any greater extent in the one case than in the other, and, consequently, without the distance between the molecules varying; or, in other words, without the number of molecules contained in a given volume being different. Dalton, it is true, has proposed a hypothesis directly opposed to this, namely that the quantity of caloric is always the same for the molecules of all bodies whatsoever in the gaseous state, and that the greater or less attraction for caloric only results in producing a greater or less condensation of this quantity around the molecules, and thus varying the distance between the molecules themselves. But in our present ignorance of the manner in which this attraction of the molecules for caloric is exerted, there is nothing to decide us à priori in favour of the one of these hypotheses rather than the other; and we should rather be inclined to adopt a neutral hypothesis, which would make the distance between the molecules and the quantities of caloric vary according to unknown laws, were it not that the hypothesis we have just proposed is based on that simplicity of relation between the volumes of gases on combination, which would appear to be otherwise inexplicable.