Monday, November 29, 2010
This weekend we visited the Thomas Edison National Historical Park in West Orange, New Jersey. I used to love visiting there as a kid, and I hadn't been there in many years. They recently completed an extensive renovation of the laboratories, so I was anxious to see it again.
Edison built this lab later in his life. It was in this lab that he perfected the phonograph which he had previously invented, and invented the motion picture camera and the alkaline storage battery. He also built factories around the laboratories, to manufacture his various inventions.
Much of the equipment displayed in the Chemistry Laboratory is what Edison was using on his last project, which was incomplete at the time of his death. Edison was asked by his close friend Henry Ford to help find a plant that could be grown in the United States that could provide latex to make rubber. The plant that is commonly used to make natural rubber, the Para Rubber Tree, only grows in tropical climates. Ford needed a stable, inexpensive source of rubber to make tires for his growing automobile business.
Latex is a material produced by about 10% of flowering plant species, and it is believed to serve as a defense against insect infestation. The latex is stored in cells just underneath the outer layer of each part of the plant. If you have ever picked a dandelion and seen the milky white substance "bleeding" from the stem, that is latex. Tiny particles of a natural rubber polymer (polyisoprene) are suspended in this latex.
Edison tested thousands of different species of plants to try to find the ones that made the best quality rubber. He finally settled on a particular species of goldenrod, which he then cultivated to grow taller and with a greater rubber yield. This goldenrod was later named after him, Solidago edisoniana. The photo above is from the National Park Service collection showing Edison (on the left) with his namesake goldenrod.
And here is a piece of machinery in the Chemistry Lab that Edison used to crush the various plant fibers during his experiments and extract their latex.
This is what "crude" goldenrod rubber looks like after the polymer particles have been coagulated and separated out of the latex, which is mostly water.
This sample is dated 1933, which was two years after Edison's death. Edison's wife and employees continued the search for a while, but finally abandoned it when it became clear that synthetic rubber based on petroleum was going to be the material of choice for automobile tires.
Here is a strip of goldenrod rubber, compounded with carbon particles for strength, ready to be formed into a tire.
One of the most intriguing things our tour guide pointed out in the Chemistry Lab was this bottle on one of the shelves.
Here is a closeup of the label.
In case you have trouble reading it, it says "Sanguin Dragonis / Dragons Blood". The tour guide told us they didn't know what "Dragon's Blood" was, and we joked that maybe Edison was a Harry Potter fan. But when I got home I found out pretty quickly on Google that Dragon's Blood is the common name for the red resin produced from several different species of plants.
Maybe Edison had collected this Dragon's Blood to see if he could make rubber from it. Dragon's Blood has been put to various uses over the years, including a varnish and a wood stain. Many of Edison's phonographs came in beautiful wood cases, so this use would make sense as well. Dragon's Blood has also been used as an herbal cure for many ailments including stomach ailments, which Edison suffered from. Maybe someone gave this to him to take as a medicine.
Or maybe Edison just couldn't resist having a bottle of something called Dragon's Blood. He prided himself on having his stockroom filled with every type of material and substance that might possibly be needed for his far flung investigations. Dragon's Blood must surely have been useful for something.
You will be happy to know that I am kind of curious about this, and have emailed the National Park Service to find out. Either the NPS historians do not check Google when doing their research, or maybe our tour guide missed the memo. But I will get to the bottom of this and report back to you!
at 8:57 PM