Imponderable fluids

In spite of the apparent acceptance of the particulate nature of solid matter, the imponderable fluids of heat, magnetism, and electricity of Newtonian tradition were still indispensable instruments of discussion. In chemistry, phlogiston and the matter of heat, later called caloric, were typically treated as continuous fluids. John Dalton, who finally made the atomic idea functional for chemistry, continued to utilize heat or caloric as a fluid atmosphere that surrounded each atomic particle in the gaseous state. Though he did speak of the caloric as having particles, he always treated those particles collectively, never as discrete entities as he did the atomic particles of ponderable matter. Hence, early in the nineteenth century the vocabularies of both particulate and continuous views of matter remained in simultaneous usage. 

The phenomena of heat require explanation, however, and he expresses himself in favor of the material theory of heat—as an imponderable fluid pervading all space, which condensing in the pores of a substance accounts for the various phenomena of absorption or evolution of heat. The physicists, in fact, were divided for a long time after Lavoisier upon the nature of heat—whether it were a mode of motion or an imponderable fluid. An English writer, Metcalfe, in a two volume work on caloric, 1837, presents the material theory about as strongly as possible. 

The notion of imponderable fluid substances was common in the eighteenth century. Lavoisier s quantifying approach was distinctive. See Chapter 6. 

When two similar bodies are equally hot or cold to the touch, they have the same temperature, which remains unaltered if we bring the bodies into contact. On the other hand, a gradual change in temperature takes place if we bring into contact two or more similar bodies which do not feel equally hot or cold, i.e. have not the same temperature. The bodies which were hotter at the beginning cool down, while the colder bodies become warmer, until, ultimately, all have attained the same temperature. We conclude from this that the colder bodies take up heat, and that the warmer bodies give out heat, or that, heat flows from places of high temperature to places of low temperature. For this reason, heat was considered to be fluid in nature for many years. It was looked upon as a substance with the properties of an imponderable fluid, which permeated... 

Imponderable fluid A substance that cannot be weighed or otherwise measured but whose existence can be inferred from chemical activity. Phlogiston and caloric were imponderable fluids. The concept was discarded as unscientific in the 1800s. 

Lavoisier s vision of the mathematization of chemistry placed him in the Newtonian tradition of ethers and imponderable subtle fluids. In shifting the focus of the Chemical Revolution away from the originality of Lavoisier s experiments on combustion and towards the power, fruitfulness and intellectual context of his basic chemical concepts and categories, postpositivist scholars undermined the positivist-Whig notion of Lavoisier s crucial year and any clear sense of its cruciality . ... 

Instruments and Audiences in French Chemistry Lissa Roberts and Bernadette Bensaude-Vincent developed constructivist analyses of the Chemical Revolution which related Lavoisier s use of the ice-calorimeter and the balance to the rhetorical, experimental and theoretical practices that accompanied them and the audiences for which they were intended. The proliferation of imponderable substances - in the form of electrical and magnetic fluids, phlogiston and the matter of heat, or caloric- in physics... 

A second problem was Lavoisier s postulation of the element caloric —a kind of imponderable heat fluid. In certain ways, caloric was a substitute for the... 

Berzelius himself made experiments on contact electricity. He thought that electricity (the nature of which is unknown), seems to be the first cause of the activity all around us in nature. He preferred the two-fluid to the one-fluid theory. In the first edition (1808) of his Ldrbok he explained the development of heat and light on combustion by Lavoisier s caloric theory (see Vol. Ill, p. 422) and added light, electricity, and magnetism to caloric to form a group of imponderable elements. The ponderable elements are divided into metals and non-metals, the latter being called metalloids this name had been used by Erman for the metals of the alkalis and earths later it was applied to semi-metals like arsenic. 

The 1840 edition of the Encyclopaedia Britannica noted that "there is no branch of science more likely to reward the diligence of the young investigator than that which treats of the electric fluid in animal and vegetable life, its effects upon inorganic matter and its connection with the imponderable agents of light and heat". (48)... 

Joseph Black was the first to distinguish between the quantity of heat and the intensity of heat (temperature) and to recognize latent heat absorbed or given off in phase transitions. However, Black believed in the caloric theory of heat, which incorrectly asserted that heat was an imponderable fluid called caloric. This incorrect theory was not fully discredited until several decades after Black s death. 

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