I am a chemist's daughter. Let that be the backstory.
2nd, THIS illustration from a chemical website is not really correct. There needs to be a "C" in the middle of the junction of the three "O"s for the Carbon atom and the sodium atoms (the NAs) need to be next to the two "O"s at the bottom, where they are bonded. How do I know? Because I was home this weekend and my father explained it all!
3rd: This is the first of an on-and-off series with a completely different focus (and, no doubt more esoteric, less search-engine friendly than the one on creative jumpstarts).
Let me explain: Last week I read a book called: Twinkie, Deconstructedby Steve Etlinger.
Each chapter explains the history, chemistry, manufacture, etc. of one of the ingredients (in order) of the famous snack cake -- it was a totally fascinating read for a foodie. Lurking in the depths of, hmm, maybe chapter 12, sodium carbonate appears as a predecessor of sodium bicarbonate, (baking soda) component of double acting baking powder. I read it not only as an erstwhile Twinkie eater, but as an erratic baker, as well as an artist/frequent user of sodium carbonate (sodium carbonate/soda ash) the catalyst for the chemical reaction between reactive dyes and natural fibers, allowing for the chemical bond that colors the cloth.
I had so much fun reading Etlinger's book ,that I have decided to do my own abbreviated version of the natural history/chemical history of some of the common "ingredients" that I use in my art work, borrowing heavily (with due credit and links) from other sources far more technically inclined than I. Obviously, if you read Etlinger's book, one could do this right, with travels and interviews across the nation to track down all the relevant sources. I will take the easy way out and just find what I can on the internet and in print. Recently, several of the internet groups lists that I lurk about have had much discussion of chemicals, health hazards and potential unpleasant interactions between the pigments, discharge agents, resists, etc that many of us art cloth makers regularly use. That won't be my focus, but some of the information from those sources may bleed out into this blog at times. Thus said, Starting with:
SODA ASH
Here's what one online definition from the Columbia Encyclopedia says:
Sodium Carbonate is a colorless, transparent crystalline compound commonly called sal soda or washing soda. Because seaweed ashes were an early source of sodium carbonate, it is often called soda ash or, simply, soda. Sodium carbonate chemical compound, Na 2 CO 3 , is soluble in water and very slightly soluble in alcohol. Pure sodium carbonate is a white, odorless powder that absorbs moisture from the air, has an alkaline taste, and forms a strongly alkaline water solution. It is one of the most basic industrial chemicals.Basic industrial chemical means that sodium carbonate is used in such varied industrial and manufacturing applications from toothpaste to detergents, glass making (its largest and most important use arguably), brick-making, to give ramen noodles their characteristic look and texture, and in our swimming pools as a ph increaser. The name comes from one of the earliest known sources: the ashes of seaweed. But deposits of soda ash mixed with naturally occurring sodium bicarbonate (known as natrum) have been were used in ancient Egypt in the preparation of mummies, as well as in early glass manufacture.
Most likely, the soda ash you use in dyeing comes from the world's largest known trona deposit in Wyoming.
Etlinger explains that the U.S. produces most (much, much, much) of our soda ash from this huge mineral deposit in Wyoming. These mined deposits, trona mines, provide the rocks that are refined into soda ash -- a relatively simple and inexpensive process compared to the Solvay industrial process used by much of the world.
From Wikipedia:
sodium bicarbonate carbonate (Na3HCO3CO3·2H2O), is mined in several areas of the United States and provides nearly all the domestic sodium carbonate. Large natural deposits found in 1938, such as the one near Green River, Wyoming, have made mining more economical than industrial production in North America.
The Wyoming trona mines are huge -- the largest with more than 2000 miles of tunnels producing as much as 900 tons of minerals an hour. These giant ancient lake deposits of sodium bicarbonate carbonate have made the U.S. enormously wealthy in soda ash, and keeps the price cheap for our industrial production. Other trona deposits in California are strip mined, with huge trenches mined for deposits from other ancient lake beds.
As far as hazards (we do eat sodium carbonate in minute quantities in various processed foods), the principle problem is with inhalation and skin irritation from exposure and breathing the dust. WEAR YOUR DUST MASK AND GLOVES! From the MSDS date sheet:
Inhalation:
Inhalation of dust may cause irritation to the respiratory tract. Symptoms from excessive inhalation of dust may include coughing and difficult breathing. Excessive contact is known to cause damage to the nasal septum.
Ingestion:
Sodium carbonate is only slightly toxic, but large doses may be corrosive to the gastro-intestinal tract where symptoms may include severe abdominal pain, vomiting, diarrhea, collapse and death.
Skin Contact:
Excessive contact may cause irritation with blistering and redness. Solutions may cause severe irritation or burns.
Eye Contact:
Contact may be corrosive to eyes and cause conjuctival edema and corneal destruction. Risk of serious injury increases if eyes are kept tightly closed. Other symptoms may appear from absorption of sodium carbonate into the bloodstream via the eyes.
Chronic Exposure:
Prolonged or repeated skin exposure may cause sensitization.
As far as its use in Procion Mx dyeing - Soda Ash is a catalytic agent -- ie, it doesn't become part of the chemical bond between dye and natural fiber molecule, but it facilitates the bonding by making increasing ph and making the fiber molecules of cotton more available for chemical bonding with the dye molecules. For more on the specifics of dye chemistry vis a vis sodium carbonate, the best source I know of is Paula Burch's excellent website on dyeing.