---
title: "History of experiments"
chunk: 2/3
source: "https://en.wikipedia.org/wiki/History_of_experiments"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:11:05.503097+00:00"
instance: "kb-cron"
---

The experiments of Antoine Lavoisier (1743–1794), a French chemist regarded as the founder of modern chemistry, were among the first to be truly quantitative. Lavoisier showed that although matter changes its state in a chemical reaction, the quantity of matter is the same at the end as at the beginning of every chemical reaction. In one experiment, he burned phosphorus and sulfur in air to see whether the results further supported his previous conclusion (Law of Conservation of Mass). In this experiment, however, he determined that the products weighed more than the original phosphorus and sulfur. He decided to do the experiment again. This time he measured the mass of the air surrounding the experiment as well. He discovered that the mass gained in the product was lost from the air. These experiments provided further support for his Law of Conservation of Mass.
One of Lavoisier's experiments connected the worlds of respiration and combustion. Lavoisier's hypothesis was that combustion and respiration were one and the same, and combustion occurs with every instance of respiration. Working with Pierre-Simon Laplace, Lavoisier designed an ice calorimeter apparatus for measuring the amount of heat given off during combustion or respiration. This machine consisted of three concentric compartments. The center compartment held the source of heat, in this case the guinea pig or piece of burning charcoal. The middle compartment held a specific amount of ice for the heat source to melt. The outside compartment contained packed snow for insulation. Lavoisier then measured the quantity of carbon dioxide and the quantity of heat produced by confining a live guinea pig in this apparatus.  Lavoisier also measured the heat and carbon dioxide produced when burning a piece of charcoal in the calorimeter. Using this data, he concluded that respiration was in fact a slow combustion process. He also discovered through precise measurements that these processes produced carbon dioxide and heat with the same constant of proportionality. He found that for 224 grains of "fixed air" (CO2) produced, 13 oz (370 g). of ice was melted in the calorimeter.  Converting grains to grams and using the energy required to melt 13 oz (370 g). of ice, one can compute that for each gram of CO2 produced, about 2.02 kcal of energy was produced by the combustion of carbon or by respiration in Lavoisier's calorimeter experiments. This compares well with the modern published heat of combustion for carbon of 2.13 kcal/g. This continuous slow combustion, which Lavoisier and Laplace supposed took place in the lungs, enabled the living animal to maintain its body temperature above that of its surroundings, thus accounting for the puzzling phenomenon of animal heat.  Lavoisier concluded, "La respiration est donc une combustion," That is, respiratory gas exchange is combustion, like that of burning a candle.
Lavoisier was the first to conclude by experiment that the Law of Conservation of Mass applied to chemical change. His hypothesis was that the mass of the reactants would be the same as the mass of the products in a chemical reaction. He experimented on vinous fermentation, determining the amounts of hydrogen, oxygen, and carbon in sugar. Weighing a quantity of sugar, he added yeast and water in measured amounts, allowing the mixture to ferment.  Lavoisier then measured the mass of the carbonic acid gas and water that were given off during fermentation and weighed the residual liquor, the components of which were then separated and analyzed to determine their elementary composition.  In this way he controlled a couple of potential confounding factors. He was able to capture the carbonic acid gas and water vapor that were given off during fermentation so that his final measurements would be as accurate as possible. Lavoisier concluded that the total mass of the reactants was equal to the mass of the final product and residue. Moreover, he showed that the total mass of each constituent element before and after the chemical change remained the same. Similarly, he demonstrated via experimentation that the mass of products of combustion is equal to the mass of the reacting ingredients.

== Louis Pasteur ==