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Difficulty: MediumInferences and Implicit Meaning

Although eighteenth-century chemist Joseph Priestley famously isolated what is now known as oxygen gas in 1774, his adherence to phlogiston theory led him to conceptualize the substance as 'dephlogisticated air.' According to phlogiston doctrine, combustible materials contained an invisible weight-bearing principle, phlogiston, which was released into the surrounding atmosphere during combustion until the air became saturated. Priestley observed that a candle burned far more brilliantly and a mouse survived significantly longer in a sealed container filled with his newly isolated gas than in ambient atmospheric air. Rather than interpreting this as evidence of a distinct elemental constituent of air that actively combines with burning matter—as Antoine Lavoisier would subsequently propose—Priestley inferred that the isolated gas was entirely devoid of phlogiston, thereby enabling it to absorb phlogiston emitted by burning bodies far more rapidly than ordinary air could. Consequently, while Priestley's meticulously documented experimental protocols provided the empirical bedrock for Lavoisier's chemical revolution, Priestley himself remained convinced until his death that his observations validated, rather than undermined, the traditional phlogiston framework.

Based on the passage, which of the following can be inferred regarding Priestley's interpretation of his 1774 combustion experiments?

  1. A
    He concluded that ordinary atmospheric air contained a higher concentration of elemental oxygen than the gas isolated in his sealed containers.
  2. He believed that the enhanced combustion of a candle in the isolated gas occurred because the gas possessed a greater capacity to absorb released combustion byproducts than ordinary air did.Answer
  3. C
    He ultimately abandoned phlogiston theory after failing to measure the weight of the invisible principle released during candle combustion.
  4. D
    He argued that Lavoisier's chemical revolution was based on flawed empirical data gathered from inaccurate experimental protocols.
  5. E
    He maintained that the duration of a mouse's survival in a sealed container depended primarily on the total volume of atmospheric air present rather than its chemical purity.

Answer

Priestley believed that the enhanced combustion of a candle in the isolated gas occurred because the gas possessed a greater capacity to absorb released combustion byproducts than ordinary air did.
The passage states that Priestley believed combustible items release phlogiston into surrounding air until the air becomes saturated. Because he thought his isolated gas contained no phlogiston ('dephlogisticated'), he inferred it could absorb phlogiston emitted during combustion much faster and more effectively than ordinary air could. This directly supports the choice stating that he believed the gas had a greater capacity to absorb released combustion byproducts.

Step-by-Step Solution

1
Locate the passage section discussing Priestley's inference regarding the isolated gas.
The text states Priestley inferred the gas was 'entirely devoid of phlogiston, thereby enabling it to absorb phlogiston emitted by burning bodies far more rapidly than ordinary air could.'
Inference questions require identifying claims that logically follow from explicit passage premises without extrapolating beyond them.
2
Match Priestley's theoretical concept (phlogiston absorption) to the option descriptions.
Phlogiston was posited as a substance released into air during combustion (a combustion byproduct). Being devoid of phlogiston meant the gas had a higher capacity to absorb more of it during burning.
Rephrasing 'dephlogisticated air absorbing emitted phlogiston' yields 'a greater capacity to absorb released combustion byproducts'.
3
Eliminate options that contradict text facts or make unwarranted claims.
Options claiming Priestley abandoned phlogiston theory, accused Lavoisier of using flawed data, or misread oxygen concepts are unsupported or directly contradicted by the text.
Valid GRE inferences must be strictly supported by the text and avoid extreme or out-of-scope assumptions.

Key Concept

Drawing Valid Inferences from Implicit Theoretical Premises in Reading Comprehension
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Topics

Inferences and Implicit Meaning

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