00:00:01 What a beautiful day for fishing. Yeah, but it's a shame we haven't caught any fish. Yeah, but so what? The view's great. Look at the trees and the mountains, even the river.

00:00:28 It's so pretty around here. It's one of the reasons that the people that built that big house back there came to live in Northumberland. How do you know that? I took a tour through it once. The house is fixed up to look like it did a long time ago and has a small museum. Can we go in? Sure, let's go.

00:00:58 Joseph Priestley was born in 1733 in Yorkshire, England, and became a minister of a dissenting church at the age of 22. In 1761, he became a teacher of language and literature.

00:01:24 He was a friend of Benjamin Franklin and supported both the American Revolution and the French Revolution. Priestley's religious and political talks made some people in England very angry with him. During a riot in 1791, the mob burned his house, forcing Priestley and his wife Mary to flee.

00:01:46 Priestley's elder sons moved to the new country of America in 1793 to become farmers in Pennsylvania. Priestley thought that in America he could speak more freely about his religion.

00:02:01 Mary Priestley found that she liked the Susquehanna River Valley very much. She wrote to a friend,

00:02:10 I am happy and thankful to meet with so sweet a situation and so peaceful a retreat as the place I now write from. Dr. Priestley also likes it and of his own choice intends to settle here, which is more than I hoped for at the time we came up.

00:02:33 This country is very delightful, the prospects of wood and water more beautiful than I have ever seen before, and the people plain and decent in their manners.

00:02:50 Mary and Joseph Priestley started to build this house in 1794. Mary enjoyed planning the house, but she died before it was finished. In recent years, the Pennsylvania Historical and Museum Commission has restored the Priestley house so that it looks like it did when Joseph Priestley lived in it.

00:03:10 Many of the floors and walls have been restored, and the furniture now in the house is typical of the era during which the Priestleys lived. Priestley lived in this house from 1794 until his death in 1804. He used fireplaces for heat and candles for light.

00:03:32 The ceilings of the house were made ten feet high so that the house would be cooler in the summer. This beautiful staircase leads upstairs to the bedrooms. Blankets for the beds were hand quilted and stored in cedar chests.

00:03:49 Anyone in the house who was sick would be moved downstairs to a small room just off the kitchen, where it was warm and more convenient to care for the sick. In the kitchen, the cooking was done on a fireplace. Water had to be carried into the house in buckets.

00:04:08 Joseph Priestley enjoyed the game of chess, and his chess set is on display in the parlor. Also in the parlor is a jib door, which leads from the house to Priestley's laboratory.

00:04:24 The top half of the jib door has shutters that fold back out of the way to reveal a window. The window opens and is held open by a pin. The lower section of the door then opens into a small hallway, leading to the laboratory where Dr. Priestley performed many experiments.

00:04:44 As a small boy, Joseph Priestley liked to do experiments, and when he became a teacher in his twenties, he encouraged his students to do experiments as well. Priestley later did many experiments with electricity, using the various equipment then available. He wrote letters about these experiments to Benjamin Franklin. Priestley also wrote the first book on the history of electricity.

00:05:14 Joseph Priestley was so dedicated to his experiments that he had the laboratory built before the rest of the house. The restoration of the laboratory includes glassware replicas made especially for the Priestley house, based on the original glassware now at the Smithsonian Institute in Washington, D.C.

00:05:34 The laboratory has two ventilation shafts, which from the outside of the house look like chimneys, but were used to remove bad air or fumes from the laboratory and to let outside air into the laboratory.

00:05:49 In this laboratory, Dr. Priestley continued to do experiments like those he had done in England. He had a stove for heating chemicals in crucibles, glass vessels for his experiments, a balance for weighing chemicals, as well as other kinds of equipment.

00:06:08 Joseph Priestley is most famous for his study of gases, which he called airs. He knew that in some airs, mice could live, but that in other airs, mice died. Priestley hoped that his study of airs would someday help people.

00:06:27 He used a large water tub called a pneumatic trough to investigate various airs or gases. A tube full of water will remain full of water even when inverted, as long as the open end of the tube remains underwater. The water can, however, be displaced by a gas bubbling up through the water.

00:06:48 Priestley found that by dripping acid onto chalk, he could generate a gas he called fixed air. Marble chips and chalk are both made of calcium carbonate. When hydrochloric acid is poured onto chalk or marble chips, a gas is generated. This gas goes through the tubing and bubbles up to fill the test tube. The gas is called carbon dioxide.

00:07:19 The chemical equation is calcium carbonate plus hydrochloric acid yields calcium chloride, water, and carbon dioxide. Priestley also discovered that the air above fermenting wine or beer is this same fixed air, carbon dioxide.

00:07:38 Today we know that during the fermentation of wine, some of the sugars in the grapes react to form alcohol and carbon dioxide. Priestley found that if he used a machine to increase the pressure, fixed air dissolved in water, giving it a pleasant taste. The bubbles in soda pop are carbon dioxide.

00:08:03 Dr. Priestley and others thought that fixed air might help prevent scurvy, a disease sailors often got in those days. Water containing fixed air was used aboard a ship, but it did not help the sailors.

00:08:18 Priestley found that a mouse in a glass of fixed air died quickly, and that a candle would not burn in this fixed air. However, he found that plants did not die in fixed air, and furthermore, that if he put a sprig of mint in a tube containing fixed air for several days, a candle could burn in the new air, or a mouse could live in it.

00:08:44 Priestley called this new gas deflogisticated air. Today we call this gas oxygen.

00:08:53 In his most famous experiment, Joseph Priestley used a magnifying glass, which he called a burning lens, to focus sunlight on a red powder he called mercurus calcinatus.

00:09:05 Today we know the red powder as mercuric oxide, and can use a propane torch to heat it. When the mercuric oxide gets hot enough, 500 degrees Celsius, it begins to turn black, and a gas is generated that can be collected over water in a pneumatic trough.

00:09:24 This gas is oxygen, the same deflogisticated air plants give off. As more heat is applied to the mercuric oxide, mercury is deposited on the side of the test tube. The chemical equation is mercuric oxide yields mercury metal plus oxygen gas.

00:09:47 Because oxygen is the same, whether it comes from mercuric oxide or from green plants, candles burn brightly in it, and mice can live in it. One day, Dr. Priestley breathed this gas himself. He wrote to a friend.

00:10:03 The feeling of it in my lungs was not sensibly different from that of common air, but I fancied that my breast felt peculiarly light and easy for some time afterwards. Who can tell but that in time this air may become a fashionable article in luxury. Hitherto, only two mice and myself have had the privilege of breathing it.

00:10:24 Priestley's deflogisticated air, oxygen, is used in hospitals all over the world to help people who have trouble breathing. Joseph Priestley died in 1804. He is most famous for his discovery of oxygen.

00:10:39 In 1874, 77 chemists met at the Priestley House to celebrate the 100th anniversary of the discovery of oxygen. They decided to form a society, now called the American Chemical Society, the largest professional association in the country.

00:10:59 Chemists have gathered at the Priestley House several times to recall the discovery of oxygen. In 1983, they gathered here to celebrate the first day of issue of a commemorative stamp honoring Joseph Priestley by the United States Post Office.

00:11:14 The Priestley House in Northumberland, Pennsylvania is administered by the Pennsylvania Historical and Museum Commission. The house is open for people to come and remember the work of Joseph Priestley, minister, teacher, and scientist.

00:11:44 The house is a popular place for people to come and remember Joseph Priestley, minister, teacher, and scientist.

00:11:59 The house is a popular place for people to come and remember Joseph Priestley, minister, teacher, and scientist.

00:12:14 The house is a popular place for people to come and remember Joseph Priestley, minister, teacher, and scientist.

00:12:44 The house is a popular place for people to come and remember Joseph Priestley, minister, teacher, and scientist.