It is really a curious thing, sometimes, where you find inspiration and knowledge. In this case, it started with my dishwasher. It had accumulated a lot of “scale” and it just wasn’t cleaning any more. Really, not at all. In some parts. There was a Very Clean strip of dishes on one axis, and dirty ones on each side.
This lead me to discover that the screen in the bottom, a circle about the size of a dinner plate full of tiny holes, was effectively a solid. Oops.
That restricted water flow enough that the “spinning squirters” were not spinning, just squirting weakly in place. Thus the clean stripe.
I started with removal and mechanical debridement. Some bits flaked cleanly, some were tougher. Then I advanced to soaking in a dish tub of vinegar. A gallon or so later and some brushing and flexing and the disk was once again usable. That, then, left inspection of the rest of the machine. Taking about a 1/2 cup of “scale” from the pump sump under the screen, I began to realize that my water (full of Ca and Mg ions) was clearly reacting with the soap to make a lot of scale. Inspection of the dispenser flap was also enlightening. It had become “finicky” about closing and staying closed, then opening on time. The tiny latch was being blocked by scale on the backside of the recess it was supposed to use. The sides of the door were wedging on scale in the recess they were supposed to slide into as well. Below it, in the ‘drop area’ was a thick buildup of scale. OK, lots of vinegar washing…
Skipping way down the line… After 2 days of some scraping, some washing with full strength vinegar, some “running it with vinegar” and a bottle of CLR (that is other organic acids) used per directions: I had pretty much gotten the worst of the scale gone from most of the places where it was an issue.
It was at that point I discovered that there were two kinds of scale. A simple to dissolve, most likely carbonate scale, and a clearer glassier scale that looked like a silicate. Hmmmm… Reading the Cascade bottle ingredients, it includes Sodium Silicate. Waterglass.
But doesn’t waterglass form a solid silicate on heating? Can’t it react with other things, like calcium ions, to form complex silicates over time? Even if very very slowly, it does react in a highly alkaline environment, and dishwasher soap is highly alkaline.
So I’m pondering if my dishwasher has solved the mystery of DIY silicate geopolymer formation… Mix CaO or Ca(2 CO3) with Sodium Silicate and add water. Ancient Egypt had the skill needed to make those things. Burn lime and you get CaO. Use Natron and some lye and some silicate and you can make waterglass. I’d tried to buy a can of waterglass at Home Depot about a year back for just that experiment, but it was special order so I skipped it and moved on to other projects. Yet here in front of me was what looked like an existence proof of making a geopolymer via sodium silicate and alkaline carbonates.
OK, some more chipping and a few more runs of CLR and Vinegar later, including some direct application to the layer of white glossy stone like stuff, and it still is just sitting there. This isn’t any carbonate. But the washer works OK. (It did take a few runs with pauses to tweeze and needle chips out of the upper spinning squirter nozzles to get it all spinning right, but now seems clear end to end in the plumbing.)
Yet the idea of ongoing application of Sodium Silicate seemed like maybe “not a good idea”.
Off To The Store
A trip to the store to inspect bottle and box labels followed. Hmmm… Most have now got Sodium Silicate in them. I see no reason to have it, but there it is. Oh for the days of Phosphate and TSP cleaners that worked great and didn’t gunk up the machine. That was when Cascade had become my standard and I’d not addressed the issue of brands until forced to, now.
The “Finish” brand didn’t have it. It seemed mostly Sodium Carbonate and Sodium PERcarbonte. What is Sodium Percarbonate, I wondered… Didn’t have that in chem class…
Sodium percarbonate is a chemical, an adduct of sodium carbonate and hydrogen peroxide (a perhydrate), with formula 2 Na2CO3 · 3 H2O2. It is a colorless, crystalline, hygroscopic and water-soluble solid. It is used in some eco-friendly cleaning products and as a laboratory source of anhydrous hydrogen peroxide.
“Eco-friendly” eh? Well, as long as it works… Then that “source of hydrogen peroxide” caught my eye. Wait a mo… this stuff is just like a solid solution of fixed molar ratios of sodium carbonate and H2O2. H2O2 is useful with acetone (nail polish remover) to make a fairly unstable but effective explosive, favorite of Islamic Terrorists. Has anyone pondered this? I wonder…
Off To Boom Land
The wiki hints at it, but doesn’t address it directly:
As an oxidizing agent, sodium percarbonate is an ingredient in a number of home and laundry cleaning products, including non-chlorine bleach products such as OxyBoost, OxiClean, Tide laundry detergent, and Vanish. Dissolved in water, it yields a mixture of hydrogen peroxide (which eventually decomposes to water and oxygen) and sodium carbonate (“soda ash”).
2 Na2CO3·3 H2O2 → 2 Na2CO3 + 3 H2O2
Many commercial products mix a percentage of sodium percarbonate with sodium carbonate (washing soda). The average percentage of an “Oxy” product in the supermarket is 65% sodium percarbonate and 35% washing soda. The “ultra boosters” seen on infomercials may contain as much as 80% sodium percarbonate. However, sodium percarbonate is less expensive in its pure form and can be adjusted to any percentage the user desires.
Sodium percarbonate can be used in organic synthesis as a convenient source of anhydrous H2O2, in particular in solvents that cannot dissolve the carbonate but can leach the H2O2 out of it. A method for generating trifluoroperacetic acid in situ for use in Baeyer–Villiger oxidations from sodium percarbonate and trifluoroacetic anhydride has been reported; it provides a convenient and cheap approach to this reagent without the need to obtain highly concentrated hydrogen peroxide.
Well, one quick web search turned up someone who got a $bucket to study this and figured out it works pretty good.
VI. LEVERAGING OF RESOURCES
The DHS project has been instrumental in building new relationships with companies, local and federal agencies. We have built a good relationship with MRI Global (Kansas City, MO) and have received approximately $500K for CBRNE research and training workshops.
Gee, and I’d do it just for a guarantee not to be arrested doing the experiments ;-)
Well, that and a nice lab with lots of protective equipment, some distance operated mixing equipment, lots of blast shields, really good ear protection, and maybe a few Grad Students to do the actual work ;-)
F1-A1: Synthetic routes to new and improvised high explosives
Abstract — The project deals with alternative routes for synthesis of triacetonetriperoxide (TATP) without the use of liquid peroxides. The research aims to explore commonly available chemicals which can be used as precursors along with ‘over the counter’ materials which have the ability to produce TATP. One of the most promising chemicals for the synthesis of TATP are percarbonates giving yields higher than with liquid peroxides Commonly available cleaners containing percarbonates were investigated. Full analytical characterization of these materials; x-ray diffraction (XRD), nuclear magnetic resonance (NMR), mass spectrometry, thermo-gravimetric analysis (TGA) is being conducted. This effort will be conducted in close collaboration with ALERT partners. We are also closely coordinating with industrial contacts from the United States, Canada (University of Alberta), and Europe (Cambridge University). Transition and accomplishments of previous efforts will also be described. The relevance to the DHS for this work is to readily identify new precursors for the synthesis of illicit explosives.
Since sodium percarbonate is basic and the formation of TATP is acid catalyzed, its use as a peroxide source in the preparation of TATP requires that it first be neutralized and then acidified. Here hydrochloric acid was used. After dissolution, neutralization, and acidification of the sodium percarbonate in aqueous solution, addition of acetone resulted in the precipitation of a fine white powder with energetic properties. NMR spectroscopy confirmed the identity of the species as TATP. Examination of the powder X-ray diffraction (PXRD) pattern revealed this material to be a phase pure specimen, by comparison to the PXRD patterns calculated from single-crystal X-ray structures. Figure 1 shows the PXRD patterns from the TATP synthesized. The material synthesized is shown in the top pattern. 1a-b are database structures with 1a being the most stable. It is important to note that there are 6 polymorphs of TATP. Our material matches a less stable form (1b), which is surprising, but is hypothesized to be due to the ionic strength. This might be a useful tool for source attribution of TATP since synthesis protocols appear to determine the polymorph generated.
They do find that with excess of sodium carbonate the reaction does not proceed, so expect to eventually see your “Oxy” cleaners and bleaches made less functional as they get diluted into very eco-friendly non-functional forms… I’d say “rinse and repeat”, but that would be too cheeky… Maybe they will let me have my phosphate cleaners back then.
We have also confirmed that the TATP synthesis works when using Oxy-boost as a commercial oxidant. Oxy-boost is available for discrete purchase online (20 lbs/$60.00). LA’s Totally Awesome Oxygen Based Cleaner and Oxiclean Baby Stain Soaker did not generate TATP, even though these cleaners worked for the organic reaction described in the J. Chem. Ed. Paper, which indicates that the TATP synthesis may require a substantially potent oxidant to work effectively. Figure 2 shows the pictures of the cleaners used. Increasing the ratio of Na2CO3 : Na2CO3 ½ H2O2 renders the synthesis of TATP unsuccessful. Since all the cleaners are not pure sodium percarbonate, rather they are a mixture of with sodium carbonate, we hypothesized that a critical amount of sodium percarbonate was necessary to produce TATP. This was tested by both testing the TATP formation by both synthesis from the commercial cleaners for which the carbonate/percarbonate ratio is reported and also by mixing different ratios of carbonate/percarbonate in the laboratory. The yields of the lab mixed percarbonate:carbonate ratios match those of the neat compounds well. This indicates that TATP synthesis may be mitigated by the use of an adulterant material such as sodium carbonate. See Table 1 for carbonate/percarbonate ratios and corresponding TATP yields.
So if Oxyboost mysteriously disappears from the stores, or suddenly doesn’t work as well, you will know why.
The paper goes on to build the basis for another grant, stating that looking for ways to dissolve out the carbonate while leaving the percarbonate wasn’t explored. I did a bit of looking, and while it would be dangerous (due to the oxidizer in the H2O2 wanting to make rocket fuel with organics) I suspect a very frigid solution of methanol might work. Alternatively, I’d look to do some kind of cold precipitation from water. It would likely take a while, but it looks like there is enough differential solubility in water to work, just keep it cold so the percarbonate doesn’t break down.
I’d speculate some other solvents might also work, but finding a non-flammable non-water solvent might be a bit of work. Even ammonia liquid is flammable. Perhaps some polar group stuck onto a fluorocarbon… (It might be fun to watch for shacks in the desert blowing up as various jihadis run the experiments to find the right solvents and conditions ;-)
At present, it looks like “neat” sodium percarbonate is sold on line for about $24 / 10 lbs. so it will likely “be a while” before concentration as a DIY process is needed.
So that’s how “being green” supports your local terrorist. It also demonstrates how cleaning the dishwasher can lead to answers about geopolymer formation and even how to make DIY explosives. Just follow the question trail and who knows where any given “Dig Here!” might lead.
I didn’t set out to learn about DIY explosives. I have NO interest in peroxide / acetone based mixes. The things are hideous widow makers and highly unstable. They are not very good weapons materials either. Too wet and they don’t work or squib. Too dry and they detonate “just because they can” and at the most unpleasant times…
Yet an innocent desire to know what I was putting in my dishwasher, and would it gunk the thing up, lead me there. Oh Well. Hope it didn’t put me on a terrorist watch list for being curious about home appliances and knowing too much chemistry…
FWIW, I’m now exploring Boraxo as a scale reducer, still trying to figure out how to remove what is almost certainly a silicate scale remnant, and really wishing I could just use phosphate based cleaners that worked and didn’t have these problems. Oh Well… The dish washer is working again, I’ve re-cleaned all the dishes in the cupboards, and it looks like using a non-silicate cleaner at least isn’t adding any deposits. We’ll see if, over time, the remaining scale reduces under that regimen. IF it ever acts up again, I have a cleaning procedure worked out, and I can explore silicate chemistry more, then, if needed.
I also know to avoid mixing nail polish remover & discarded dishwasher soap in the trash…