Boyle's Law
Properties of Matter

Boyle’s unusual laws

Stories from Physics for 11-14 14-16 IOP RESOURCES

Marriage policy 
Robert Boyle was the fourteenth child and seventh son of aristocratic Irish parents. Boyle’s father, Richard, was described as “immensely rich” and “the greatest landlord in Ireland”. Robert’s siblings were forced to make often disastrous marriages to secure the social standing of the family and Robin (as he was known to his family), narrowly escaped a forced marriage.

Perhaps because of his siblings’ unhappy experiences, Boyle never married, a decision he reported was “at first out of Policy afterwards more Philosophically”. He argued that:

…yet I have observed so few Happy Matches, and so many Unfortunate ones; and have so rarely seen men love their wives at the rate they did, whilst they were their Mistresses, that I wonder not, that Legislators thought it necessary to make marriages Indissoluble, to make them Lasting.

Day of Judgement 
Boyle was a studious boy. At Eton, one of his masters reported that: “His delight is in his learning, he takes noe pleasure in playing with boyes nor running abroad.” He was also devoutly religious - whilst on a tour of Europe, a severe thunderstorm made him reflect on his unreadiness for his own Day of Judgement and he wrote tracts against swearing and make-up. In Florence with his brother, it is reported that:

Nor did he sometimes scruple, in his Governor’s Company, to visit the famousest Bordellos; whither resorting out of bare Curiosity, he retain’d there an unblemish’t Chastity, & still return’d thence as honest as he went thither. Professing that he never found any such sermons against them, as they were against themselues.

Solving transmutation 
An adherent of alchemy, Boyle attempted to experimentally demonstrate the transmutation of elements. In a publication in 1625, he claimed that whilst mixing mercury and gold in the palm of his hand, the mixture had become hot, and he reported he was approaching a solution to the problem of transmutation.

Mercurial discovery 
Boyle is perhaps best known for his eponymous law. He investigated the relationship between pressure and volume in a gas using a J-shaped tube filled with mercury. The shorter limb of the tube was around 30 cm high and sealed. The longer side was 2.4 m tall, so Boyle was forced to carry out the experiment in a stairwell. The tube was filled with mercury which trapped a volume of air in the shorter end of the tube. Boyle poured mercury into the longer limb and used a small mirror behind the tube to measure the height of the mercury against a scale marked in sixteenths of an inch on a piece of paper. Decimals were not in common usage at the time and Boyle reported the length of the trapped gas as fractions which seem awkward by today’s standards, for example, “107 13/16 inches” and “107 7/13 inches”. In addition, the graphical display of numerical data was not usual practice and Boyle did not include a graph showing the relationship between variables in his paper.

The pressure of mercury could cause the tube to crack so he placed the tube in a wooden box to prevent the loss of any of the expensive mercury in the case of fracture. He attempted to investigate the effect of temperature on volume and reported that he had heated the shorter side of the J-tube with a candle “so that we scarce doubted, but that the expansion of the air would, notwithstanding the weight that opprest it, have been made conspicuous, if the fear of unseasonably breaking the glass had not kept us from increasing the heat”.

Hopes for the future  
In the 1660s, Boyle wrote a to-do list he hoped science might achieve in the future:

  •  The Prolongation of Life
  •  The Recovery of Youth, or at least some of the Marks of it, as new Teeth, new Hair colour’d as in Youth
  •  The Art of Flying
  • The Art of Continuing long under water, and exercising functions freely there
  •  The Cure of Wounds at a Distance
  •  The Cure of Diseases at a Distance, or at least by Transplantation
  •  The Attaining Gigantick Dimensions
  •  The Emulating of Fish without Engines by Custome and Education only
  •  The Acceleration of the production of things out of Seed • The Transmutation of Metalls
  •  The makeing of Glass Malleable
  •  The Transmutation of Species in Mineralls, Animals, and Vegetables
  •  The Liquor Alkaest and Other dissolving Menstruums
  •  The making of Parabolicall & Hyperbolicall Glasses
  •  The making of Armour Light, and extremely hard.

An apology 
Despite his achievements, Boyle seems to have struggled with paperwork and had various mishaps with his correspondence. On one occasion, he claimed that “highly corrosive Liquor” destroyed some papers, whilst in another case “a kindl’d coal unluckily landed on your Letter”. Ultimately, his misadventures with paperwork led him to publish a general apology:

An Advertisement of Mr Boyle, about the Loss of many of his Writings: Address’d to Mr J.W. to be communicated to those Friends of His, that are Virtuosi, which may serve as a kind of Preface to most of his Mutilated and Unfinish’d Writings




Boyle's Law
is expressed by the relation (p_1)(V_1)=(p_2)(V_2)
can be used to derive Ideal Gas Law
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