in 1807 the English chemist Humphrey Davy passed an electric current through molten potassium hydroxide and isolated a bright, shiny reactive substance. He claimed the discovery of a new element, which he names potassium. In those days, before the advent of modern instruments, what was the basis on which one could claim that a substance was an element.

Characteristic metallic properties similar in character to sodium (couldn’t be broken down further).

Well, back in the day, before fancy instruments and all, chemists had to work with what they had. They relied on a combination of clever observations and good ol' trial and error. If a substance behaved in a consistent and unique way, showing distinct properties and characteristics, they might have thought they stumbled upon a new element. It was a bit like detective work, but with more explosions and less Sherlock Holmes.

In the early days before modern instruments were available, there were a few criteria or methods by which chemists could claim the discovery of a new element. Here are a few key factors that were taken into consideration:

1. Persistence of the substance: Chemists would examine if the substance remained unchanged under various experimental conditions. If the substance remained the same, it indicated that it was a pure element.

2. Inseparability: Chemists attempted to separate the substance into simpler components using various chemical reactions. If the substance could not be broken down further, it suggested that it was an indivisible element.

3. Unique properties: Chemists would look for distinct properties exhibited by the substance. Elements have characteristic properties that differentiate them from other substances. These properties could include color, luster, reactivity, conductivity, melting point, boiling point, etc.

4. Comparison with known elements: Chemists would compare the properties of the newly discovered substance with those of existing elements. If it did not match any known element, it indicated the possibility of a new element.

5. Replication: Researchers would perform the experiments multiple times to ensure the consistency of results. If the substance consistently displayed the same properties, it reinforced the claim of a new element.

It's worth noting that while these methods were helpful in identifying new elements, they were not foolproof. The advent of more advanced instruments, such as spectroscopy, allowed for a more precise understanding of elements by analyzing their atomic structure and spectra.

In the early days of chemistry, before the advent of modern instruments, determining whether a substance was an element was primarily based on several important factors:

1. Observational Purity: The substance had to be isolated in a pure form, free from any impurities. This was often achieved by various chemical techniques, such as separation methods or purification processes.

2. Chemical Reactivity: Elements possess unique chemical properties. They react with other substances in characteristic ways. Chemists would perform experiments to test the reactivity of a substance and compare it to known elements.

3. Consistency across sources: If a substance is consistently found in different samples from various sources, it suggests that the substance is an element. Consistency in physical and chemical properties across different samples would strengthen the case for an element.

4. Indestructibility: An element cannot be broken down into simpler substances by chemical means. If a substance was found to be resistant to decomposition or unable to be further broken down, it was more likely to be considered an element.

Humphrey Davy's claim that he had discovered a new element, potassium, was based on these principles. He was able to isolate potassium in a pure form and observe its unique chemical reactivity. By comparing its properties to other known substances and establishing consistency across various samples, he concluded that he had indeed discovered a new element.