John Dalton Quotes

When we consider that all elastic fluids are equally expanded by temperature, and that liquids and solids are not so, it should seem that a general law for the affection of elastic fluids for heat, ought to be more easily deducible and more simple than for liquids, or for solids.—There are three suppositions in regard to elastic fluids which merit discussion.
1. Equal weights of elastic fluids may have the same quantity of heat under like circumstances of temperature and pressure.
The truth of this supposition is disproved by several facts...
2. Equal bulks of elastic fluids may have the same quantity of heat with the same pressure and temperature.
This appears much more plausible... But... considerations... render this supposition extremely improbable, if they do not altogether disprove it. ...
3. The quantity of heat belonging to the ultimate particles of all elastic fluids, must be the same under the same temperature and pressure.
It is evident the number of ultimate particles or molecules in a given weight or volume of one gas is not the same as in another... The only answer that can be given... is this.—The particles will condense their respective atmospheres of heat, by which their mutual repulsion will be diminished, and the external pressure will therefore effect a proportionate condensation in the volume of air: neither an increase nor diminution in the quantity of heat around each molecule, or around the whole, will take place. Hence the truth of the supposition, or... proposition, is demonstrated.
Corol. 1. The specific heats of equal weights of any two elastic fluids, are inversely as the weights of their atoms or molecules.
Corol. 2. The specific heats of equal bulks of elastic fluids, are directly as their specific gravities, and inversely as the weights of their atoms.
Corol. 3. Those elastic fluids that have their atoms the most condensed, have the strongest attraction for heat; the greater attraction is spent in accumulating more heat in a given space or volume, but does not increase the quantity around any single atom.
Corol. 4. When two elastic atoms unite by chemical affinity to form one elastic atom, one half of their heat is disengaged, &c. And in general, when m elastic particles by chemical union become n; the heat given out is to the heat retained as m-n is to n.

Now it is one great object of this work, to shew the importance and advantage of ascertaining the relative weights of the ultimate particles, both of simple and compound bodies, the number of simple elementary particles which constitute one compound particle, and the number of less compound particles which enter into the formation of one more compound particle.

A pure elastic fluid is one the constituent particles of which are all alike, or in no way distinguishable. Steam, or aqueous vapour, hydrogenous gas, oxygenous gas... and several others are of this kind. ...Whatever ...may be the shape or figure of the solid atom abstractedly, when surrounded by such an atmosphere it must be globular; but as all the globules in any small given volume are subject to the same pressure, they must be equal in bulk, and will therefore be arranged in horizontal strata, like a pile of shot.

1. Small particles called atoms exist and compose all matter; 2. They are indivisible and indestructible; 3. Atoms of the same chemical element have the same chemical properties and do not transmute or change into different elements.

When we attempt to conceive the number of particles in an atmosphere, it is somewhat like attempting to conceive the number of stars in the universe; we are confounded with the thought. But if we limit the subject, by taking a given volume of any gas, we seem persuaded that, let the divisions be ever so minute, the number of particles must be finite; just as in a given space of the universe, the number of stars and planets cannot be infinite.

Chemical analysis and synthesis go no farther than to the separation of particles one from another, and to their reunion. No new creation or destruction of matter is within the reach of chemical agency. We might as well attempt to introduce a new planet into the solar system, or to annihilate one already in existence, as to create or destroy a particle of hydrogen. All the changes we can produce, consist in separating particles that are in a state of cohesion or combination, and joining those that were previously at a distance.

Philosophers are generally persuaded, that the sensations of heat and cold are occasioned by the presence or absence, in degree, of certain principle or quality denominated fire or heat... It is most probable, that all substances whatever contain more or less of this principle. Respecting the nature of the principle, however, there is a diversity of sentiment : some supposing it a substance, others a quality, or property of substance. Boerhaave, followed by most of the moderns, is of the former opinion; Newton, with some others, are of the latter; these conceive heat to consist in an internal vibratory motion of the particles of bodies.