Hydrogen (inflammable air) and nitrogen were discovered. The differences between acids, bases, and salts and their relationship to one another became understood. There was some theoretical as well as empirical knowledge about metals, e.g. in boiling points, intermetallic compounds, and changes in properties.
In 1742, Benjamin Frankin invented the Franklin stove, which greatly improved heating efficiency. As a freestanding cast-iron fireplace, it supplied heat in all directions instead of only from the one direction of the usual wall fireplace. Also, the heat absorbed by its cast-iron sides provided warmth even after the fire went out.
Static electricity was being discerned. It had been noticed that shaking a mercury barometer produced a strange glow in its "vacuum". Experiments showed that a glass rubbed in vacuo would shine brightly and that an exhausted glass globe rapidly whirled on a spindle and rubbing against the hand produced a brilliant glow. And further, as Newton wrote: "if at the same time a piece of white paper or white cloth, or the end of ones finger be held at the distance of about a quarter of an inch or half an inch from that part of the glass where it is most in motion, the electric vapor which is excited by the friction of the glass against the hand, will by dashing against the white paper, cloth, or finger, be put into such an agitation as to emit light, and make the white paper, cloth, or finger, appear lucid like a glowworm". In the study of electricity, conductors and insulators were recognized. There were demonstrations of electrical phenomena such as seeing the ignition of brandy by a spark shooting from a man's finger and the feeling the transfer of an electrical impulse created from a rubbed glass globe among a circle of people by their holding hands. In 1733, Frenchman Charles DuFay discovered that there are two types of static electric charges, and that like charges repel each other while unlike charges attract, linking electricity to magnetism.
In 1750, Benjamin Franklin "caught" lightning with a sharp pointed wire attached to the top of a kite which led down to a key at the other end. When a thunder cloud electrified the kite, a charge was seen coming from the key to an approaching finger. This charge was then stored in an early type of capacitosr, a1745 Leyden jar, and then reproduced to create the same feeling of transfer of electrical impulse among a circle of hand-holders, thereby illustrating that it was the same phenomenon as electricity. This countered the theological belief that thunder and lightning were signs of divine displeasure or the work of the devil. Franklin invented the lightening rod, which was then used to protect buildings. About ten years later, the first lightening rod on an English church was erected, which showed the church's acceptance of his theory. Franklin theorized that there were electric charges everywhere and designated them as positive or negative. He observed that opposite charges attracted each other, but that like charges repelled each other. In 1766, Joseph Priestly did an experiment suggested by Franklin and showed that electrical force follows the same law as gravitational force; that is, that the attraction or repulsion between two electrical charges varies inversely in proportion to the square of the distance between them.
Joseph-Louis LaGrange from France developed differential equations. Natural history museums were established. A group split off from the Royal Society to show collections of curiosities.
In 1754, a self-educated mechanic founded the Society for the Encouragement of Arts, Manufactures, and Commerce. It had sections on agriculture, manufactures, mechanics, chemistry, liberal arts, and trade and colonies. It sponsored contests at which prizes were given, such as that in 1761 for the best invention of a machine that would spin six threads of wool, flax, cotton, or silk at one time with only one person attending it.
Machines still mostly relied on human, animal, and water power.
Abraham Darby was a Quaker and millwright who made large cooking pots of iron, which cost less than bronze. Around 1709, he experimented with various substances to take the place of wood charcoal in iron smelting. Coal was a remote possibility. In forging or working metals coal had more or less the same qualities as wood charcoal, but this was not the case in smelting ores, especially iron ore. Coal contained sulphur compounds which caused the iron ore to deteriorate. So he controlled the burning of coal to burn out these impurities, which produced coke. His son took over after his death and improved the methods of coking, strengthened the bellows, and added ore limestone and other reagents to the mixture. By 1756, his large blast furnace using both pit coal and wood charcoal was very productive. He made iron goods of such quality as those imported.
In 1767, Richard Reynolds replaced the wooden rails connecting a blast furnace to mines with cast iron rails. He had apprenticed as a grocer and then became a partner in a large ironworks of Darby with a man whose daughter he married. After Darby died and before Darby's sons became of age, Reynolds was in charge of the ironworks. He cast cylinders of the early steam engines.
In 1749 John Roebuck, a physician and son of a prosperous manufacturer of Sheffield goods, found a cheaper way to manufacture sulphuric acid. He did this by using leaden chambers instead of glass globes to collect the vapor from burning nitre and sulphur over water. This reduced the cost of sulfuric acid to one-fourth of its previous cost, so that sulfuric acid came to be used to bleach linen instead of sour milk. He also made cast iron into malleable iron by smelting iron using coke from pit-coal instead of charcoal. But flooding in his mines and further ventures resulted in his ruin and bankruptcy.