April 20, 2020

Household chemicals and a dubious infographic

Source - James Kennedy's blog

I searched James Kennedy's blog for the original source of this graphic, and I can't find it at all.

I searched for bleach and vinegar and household and a whole bunch of other terms that are listed here, but the graphic - still hosted on his site - and its original post is entirely missing from his site. The graphic's host address suggests that it was posted sometime in 2013, and I've been through every on of his 2013 posts (he claims to have read and reviewed 103 books in that year, and I scanned every single one of this review posts, blech).

I'm curious as to why he might've taken the graphic down, and I have an idea.

The graphic is woefully undersourced and possibly dangerous.

To quote the graphic...
This chart summarizes how people in internet forums are using various combinations of household chemicals to make stuff on their own. Sources include YouTube, Yahoo! Answers, and countless niche internet forums. Because all the information was gleaned from the Internet, I cannot accept any responsibility for its accuracy or efficacy.

This table is provided for viewing only. Do not use attempt [sic] any of the household chemistry on this chart. I accept no responsibility for damage incurred as a result of using the information provided in this chart.
Admittedly that's a much easier way to post an infographic: say that it might or might not be correct and claim that nobody can sue you if they get hurt using the information you provided. That seems incredibly irresponsible and foolish coming from someone who claims to be somewhat of an expert in the chemistry field (and whose work I've posted before).

I'm not going to make any claims as to the veracity of the infographic up there. In fact, I'm going to say flatly that I don't trust it because there aren't any sources presented.

Some of the 'answers' - the water line, the bleach/ammonia combo, the bleach/soap combo - are most assuredly correct. Others - the hydrogen peroxide/liquid soap, salt/vinegar, whatever 'washing up liquid' is - are partially but certainly not entirely correct. And others are almost assuredly wrong - rubbing alcohol/cornstarch makes shampoo?

Today's lesson is that just because something is written and presented neatly, it isn't automatically correct.

April 13, 2020

CERAMIC COATINGS - How It Works | SCIENCE GARAGE



First off, thanks to Eric Moorman who sent me this video. Mad love for Eric.

Let's go through the material science awesomeness in this video about how to get the most durable, prettiest finish on your car.

  • The first four minutes or so are all about the causes of the tiny scratches on car surfaces and how to clean the car before applying a finish coating of either wax or ceramic.
  • At 4:10 we get a discussion of wax, and the host even uses the word hydrophobic, explaining how the water beads up because of the hydrophobic nature of the wax.
  • At 5:10, we finally get to the ceramics, "a non-metallic solid material making up an inorganic compound of metal and nonmetal (or metalloid) atoms primarily held in ionic and covalent (?) bonds." The host explains that those atoms can be crystalline (in various ways) or even vitrified.
  • There's an explanation of the Moh's hardness scale, and a mention that there are other ways to measure hardness like via measuring scratch resistance.
  • Heck, he even shows a very simplified version of covalent bonding with shared pairs of electrons.
  • We get into using nanotextures to increase the hydrophobic character of a surface, increasing the contact angle between a drop and the surface - with a nice diagram, too - explaining super hydrophobic coatings.
Admittedly, I had no idea such coatings existed for cars.

April 3, 2020

Things not to mix


TL; DR - The first two are bad. The third and fourth are very minor worries.

I came across this graphic online and thought I'd take a moment to check the chemistry involved.

Let's go in order, and I'll cite sources as I find them...

From ThoughtCo.com...regarding bleach + vinegar

What Happens When Bleach and Vinegar Are Mixed 
Chlorine bleach contains sodium hypochlorite or NaOCl. Because bleach is sodium hypochlorite dissolved in water, the sodium hypochlorite in bleach actually exists as hypochlorous acid: 
NaOCl + H2O ↔ HOCl + Na+ + OH-
Hypochlorous acid is a strong oxidizer. This is what makes it so good at bleaching and disinfecting. If you mix bleach with an acid, chlorine gas will be produced. For example, mixing bleach with toilet bowl cleaner, which contains hydrochloric acid, yields chlorine gas: 
HOCl + HCl ↔ H2O + Cl2 
Although pure chlorine gas is greenish-yellow, gas produced by mixing chemicals is diluted in air. This makes it invisible, so the only way to know it's there is by the smell and negative effects. Chlorine gas attacks mucous membranes in the eyes, throat, and lungs—these attacks can be deadly. Mixing bleach with another acid, such as the acetic acid found in vinegar, yields essentially the same result: 
2HOCl + 2HAc ↔ Cl2 + 2H2O + 2Ac- (Ac : CH3COO) 
There is an equilibrium between the chlorine species that is influenced by pH. When the pH is lowered, as when adding toilet bowl cleaner or vinegar, the ratio of chlorine gas is increased. When the pH is raised, the ratio of hypochlorite ion is increased. Hypochlorite ion is a less efficient oxidizer than hypochlorous acid, so some people will intentionally lower the pH of bleach to increase the oxidizing power of the chemical even though chlorine gas is produced as a result.
So, I'd say that one checks out.

Next up, bleach and ammonia...again, from h2g2.com...
When these two compounds are combined, the following reaction takes place:
2 NaOCl + 2 NH3 --> 2 NaONH3 + Cl2
...
Another potential reaction, which occurs when a greater amount of bleach is added than ammonia, is this:
3 NaOCl + NH3 --> 3 NaOH + NCl3
That's sodium hydroxide and nitrogen trichloride. Nitrogen trichloride is a very toxic chemical to humans, and even if you did get close enough to ingest it, it would probably explode in your face first, as it is also a very volatile explosive.
...
Still another reaction - in three parts this time - can occur, producing hydrazine, N2H4, a component of rocket fuel) if you have more ammonia than bleach:
NH3 + NaOCl --> NaOH + NH2Cl
These two products then react with ammonia as follows:
NH3 + NH2Cl + NaOH --> N2H4 + NaCl + H2O
One last reaction occurs to stabalise the reagents:
2 NH2Cl + N2H4 --> 2 NH4Cl + N2
That last equation is of particular interest because of the amount of heat it produces. The heat is so great that it usually leads to an explosion.
Again, I'm okay with staying you definitely shouldn't mix those two. I did, however, struggle to find a source with reactions that I trusted. The first two I found - this and this - didn't make sense in a few places, having missing mass in various places in their reactions.

Now, bleach + rubbing alcohol...

I'm a little less sure about this one. I found a lot of sources that say this one produces "chloroform, (CHCl3), hydrochloric acid (HCl), and other compounds, such as chloroacetone or dichloroacetate." but I can't find the exact chemistry anywhere.

The only reaction I could find, however, in all of the articles was of acetone with bleach.
3 NaClO + C3H6O --> CHCl3 + 2 NaOH + NaOCOCH3
Acetone and isopropyl (rubbing) alcohol certainly aren't the same thing. So I'm going to leave this one as a maybe as I also found a fair number of sources that said any reaction between isopropyl alcohol and bleach would be fairly slow and likely would need a catalyst to see significant product production at room temperature.

The last combo is hydrogen peroxide with vinegar (acetic acid). From wikipedia...
[Peracetic acid] forms upon treatment of acetic acid with hydrogen peroxide with a strong acid catalyst.
H2O2 + CH3CO2H ⇌ CH3CO3H + H2O
From cooksinfo.com
If you mix the two together in one bottle, a weak form of peracetic acid is formed. Peracetic Acid ( aka peroxyacetic acid) is a mixture of acetic acid and hydrogen peroxide. Peracetic Acid is primarily used for deactivation of a large variety of pathogenic micro-organisms in the industrial food industry, medical supplies and to prevent biofilm formation in paper pulp industries. It is usually produced in concentrations of 5 – 15%. This industrial formulation is toxic by inhalation, ingestion or if absorbed through skin; caustic and corrosive at concentrations > 10%; irritant at concentrations below 2%. Retail vinegar is a mixture of acetic acid and water composed of 4 to 8% acetic acid. Hydrogen peroxide at 3 % and retail versions of vinegar are an extremely diluted form of peracetic acid. Mixing the diluted form of acetic acid (known as vinegar) with 3% hydrogen peroxide forms a weak form of peracetic acid that may cause some reaction to those who are very sensitive to it – another reason, besides effectiveness, that applying the two solutions separately is recommended.
So this one I'm going to say is true but a minor issue.

Seriously, though, the first two combos - bleach with either vinegar or ammonia - are bad combos and are to be avoided. The other two, maybe less so...maybe.