"(...) all the bodies of perceptible sizes,
also liquid and solid, consists of
a great number of very small particles or
atoms of matter (...)
No chemical process can create or annihilate
- John Dalton
The 18-th century is the time of many changes (political, industrial, cultural). Also physics developed fast. Scientists used Newton's laws to describe their discoveries, but they also created new theories and laws for better understanding of nature. Scientists researched chemistry. It's also the time of researching electricity. Occurrences of electricity were known even in ancient times (Thales described the electrical influence of amber electrified by rubbing) but it wasn't discern researched till 18-th century. All that led to better understanding of laws in microstructure. Scientists, no more hesitating, were using data from experiments, and for many experiments became the most important scientific instrument.
Daniel Bernoulli, who lived in the years 1700-1782 starting with the idea of atom proved Boyle's law, assuming that gas pressure is atoms colliding with the walls of the vessel, inside which is the gas. It was the first time when the hypothesis of atoms were used to quantitative and experimental verifiable calculations.
Beniamin Franklin lived in the years 1706-1790. He worked over the problems of electricity. He introduced the idea of the positive and negative electricity. He maintained that electrifying bodies consists in electricity's flow. He formulated the electric charge's conservation law. He explained electrostatic induction.
Rudjer Josip Boscowich, who was born in 1711 in Dubrovnik and died in 1787, created some interesting theories about world's microstructure. Although he knew Newton's works he didn't accept the law of universal gravitation completely. He though that it might not be the rule in atomic scale, where attractive force could be always equilibrate by the repulsive force. He postulated the subsistence of the field of force which could be described using geometry. He also said that atoms are particles without any dimension; they were reduced to geometric points.
Charles Augustin de Coulomb lived in the years 1736-1806. He worked over electrostatics and magnetism. He created torsion balance. Thanks to it he could evaluate forces precisely. He showed that forces between charges are inversely proportional to the square of the distance between that charges. He also discovered that monomial charges repulse and different charges attract.
Antoine Laurent Lavoisier was the great French chemist, who lived in the years 1743-1794. Chemistry as a science, at the beginning of the 18-th century, was an assemblage of different, not arranged rules. The same was with chemical nomenclature. Lavoisier arranged chemical nomenclature basing on the names of simple substances when giving names to complicated substances composed of that simple ones. But before he could systematise chemical nomenclature he had to make changes in chemistry. He proved that all elements can occur in three states of aggregation: gaseous, liquid and solid. He showed that while burning down substances bind with oxygen. He also proved that water can't change into other substances like many scientists though. He thought that precipitate left after boiling water didn't come from the water but from the pot. After longer researches he managed to prove that water consists of oxygen and hydrogen. Decomposing water he discovered that always weight ratio between oxygen and hydrogen was 8:1. It was a direction telling that world consisted of atoms. Lavoisier believed in it but he didn't evolve his atomistic outline. He arranged chemistry, so next scientists could easier fathom its mysteries, penetrate chemical secrets.
Alessandro Volta, who lived in the years 1745-1827 was the originator of the first galvanic cell (in 1800). It was made of zinc and silver electrodes immersed in sea water. He built also an electrometer to measure.
John Dalton, who lived in the years 1766-1844 was the first chemist who in explaining different occurrences used the theory of atomistics. He researched gases. He discovered the law of partial pressures. Dalton's law says that pressure of not reacting gaseous mixture is equal to a sum of pressures of each, separate element of the mixture put in the same volume as the mixture has. Another Dalton's discovery, which he did in 1804, was showing that if two elements make more than one combination, then weight amounts of one of them belonging to unchanging amount of the second one are staying in relations of small integers (the law of multiplied proportions). For example, for chlorine oxides (Cl2O, Cl2O6, Cl2O7) masses of oxygen belonging to chlorine unit are staying in proportions 1:6:7. Dalton noticed that results he got could be simply explained using the conception of atom. Expanding atomistic ideas the assumed that chemical combinations became by combining the atoms of different elements. He was of the opinion that atoms of different elements had different mass; as mass unit he took the mass of one atom of hydrogen. He laid the foundation of modern atomistics and he described world's microstructure explaining most of occurrences know those days. After over two thousand years, finally there were so many proofs of atom's subsistence, that hypothetical till then atoms became real (although Dalton's particles were not the same as Democritus's ones because it appeared they were not finally components of matter).
Researches on world of atoms which took place in 18-th century brought many researches but also many questions. Finally, thanks to Dalton's works there were enough proofs of atoms' subsistence that it became a public admitted scientific conception. It also appeared that there subsist two kinds of molecules- the positive ones and the negative ones. Some secrets of electricity were explained but mostly it still was a puzzle which scientist tried to unriddle in the next century.
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If you want to read about the 16-th and 17-th centuries atomists click here:
THE 16-TH AND 17-TH CENTURIES