Harden, New View of the Atomic Theory (1896), have shown, from a study of Dalton's manuscript notes, that we do not owe his atomic theory to such experiments.
Following Newton, he believed a gas to be made up of particles or atoms, From Dalton's Hydrogen Gas.
He drew simple diagrams, three of which, taken from Dalton's New System of Chemical Philosophy, part ii.
The table here given contains some of Dalton's diagrams of atoms. They are not all considered to be correct at the present time; for example, we now think that the ultimate particle of water is made up of two atoms of hydrogen and one of oxygen, and that that of ammonia contains three atoms of hydrogen to one of nitrogen.
But these differences between Dalton's views and our present ones do not impair the accuracy of the arguments which follow.
Thus if Dalton's diagram for the molecule, propor- or compound atom, of water be correct, it follows that in all samples of water the total number of the hydrogen atoms is equal to that of the oxygen atoms; consequently, the ratio of the weight of oxygen to that of hydrogen in water is the same as the ratio of the weights of an oxygen and a hydrogen atom, and this is invariable.
If we compare Dalton's diagrams of the two oxides of carbon or of the three oxides of nitrogen that are given in the preceding table, we at once see the necessity of this law; for the more complex molecule has to be formed from the simpler one by the addition of one or more whole atoms. In the oxides of carbon the same weight of carbon must be combined with weights of oxygen that are as 2, and in the oxides of nitrogen a fixed weight of nitrogen must be in union with weights of oxygen that are as 1: 2: 2, which are the same ratios as 2: 4: r.
To see how this law follows from Dalton's theory let us consider his diagrams for the molecules of water, ethylene and the oxides of carbon.
Berzelius saw at once that it afforded an admirable test for the correctness of Dalton's views, and he made numerous experiments expressly designed to test the law.
Similarly, Dalton's diagram for ammonia, together with the fact that ammonia contains 4.67 parts of nitrogen to one of hydrogen, at once leads to the conclusion that the atomic weight of nitrogen is 4.67.
The laws of chemical combination were solved, in a measure, by John Dalton, and the solution expressed as Dalton's " atomic theory."
The value of Dalton's generalizations can hardly be overestimated, notwithstanding the fact that in several cases they needed correction.
Torbern Olof Bergman used an elaborate system in his Opuscula physica et chemica (1783); the 1 Dalton's atomic theory is treated in more detail in the article Atom.
In the development of the atomic theory and the deduction of the atomic weights of elements and the formulae of compounds, Dalton's arbitrary rules failed to find complete acceptance.
Dalton's idea that elements preferentially combined in equiatomic proportions had as an immediate inference that metallic oxides contained one atom of the metal to one atom of oxygen, and a simple expansion of this conception was that one atom of oxide combined with one atom of acid to form one atom of a neutral salt.
Hence we have Dalton's law: constituents if each alone were present.
Mendeleeff also devoted much study to the nature of such "indefinite" compounds as solutions, which he looked upon as homogeneous liquid systems of unstable dissociating compounds of the solvent with the substance dissolved, holding the opinion that they are merely an instance of ordinary definite or atomic compounds, subject to Dalton's laws.
But the most important of all Dalton's investigations are those concerned with the Atomic Theory in chemistry, with which his name is inseparably associated.
But from a study of Dalton's own MS. laboratory notebooks, discovered in the rooms of the Manchester society, Roscoe and Harden (A New View of the Origin of Dalton's Atomic Theor y, 1896) conclude that so far from Dalton being led to the idea that chemical combination consists in the approximation of atoms of definite and characteristic weight by his search for an explanation of the law of combination in multiple proportions, the idea of atomic structure arose in his mind as a purely physical conception, forced upon him by study of the physical properties of the atmosphere and other gases.
See Henry, Life of Dalton, Cavendish Society (1854); Angus Smith, Memoir of John Dalton and History of the Atomic Theory (1856), which on pp. 253-263 gives a list of Dalton's publications; and Roscoe and Harden, A New View of the Origin of Dalton's Atomic Theory (1896); also Atom.
After satisfying himself of Rolle's sanity, Dalton's father provided him with food and shelter and a hermit's dress.
See Colonel Dalton's Ethnology of Bengal, 1872.
De Chimie, 1802) he showed that different gases are dilated in the same proportion when heated from o° to ioo° C. Apparently he did not know of Dalton's experiments on the same point, which indeed were far from accurate; but in a note he explained that "le cit.
The relative lowering of the vapour-pressure can be easily measured by Dalton's method of the barometer tube for solvents such as ether, which have a sufficient vapour-pressure at ordinary temperatures.