Basic Chemistry

basic

The other end of the pH scale.

When you start writing a blog it’s hard to predict what people will find most interesting. Inevitably, it’s not what you expected. For example, two of The Chronicle Flask’s most-read posts are about rhubarb and lemons. Perhaps people are more interested in fruit than I ever imagined. Or perhaps I’m getting a lot of hits from people mistakenly looking for recipes.

Or maybe it’s because both feature the ever-interesting topic of acids. In which case, I should probably write something else about acids.

So, this is a post about bases.

Just in case this spectacular bit of contrariness isn’t immediately obvious, bases – some of which are called alkalis (I’m coming to that in a minute) – are at the other end of the pH scale to acids. Acids are the things with a pH value of less than 7, and bases have pH values of more than 7. So basically (hoho), they’re the opposites of acids.

whysoblueI’m using the word base deliberately, and not just because of all the brilliant chemistry puns you can make with it. The more familiar word is probably alkali, but while all alkalis are bases, not all bases are alkalis.

Alkalis are often described as soluble bases. More precisely, alkalis are produced from the metals in group 1 (the ‘alkali’ metals) and group 2 (the ‘alkaline earth’ metals) of the periodic table. The more general term, base, applies to anything that can neutralise an acid. Chemists have another definition: a base is a proton (H+ ion) acceptor, while acids are proton donors (actually chemists have yet another definition, but the proton acceptor one is the one that gets trotted out most often).

The distinction between alkalis and bases does matter to chemists and the two types of substance usually look quite different – bases tend to come in solid lumps or powders (baking soda, for example) and alkalis are more likely to arrive as a solution in a bottle – but in terms of chemistry they both get involved in the same type of chemical reaction, which is neutralising acids.

Indigestion tablet advertWe make use of this all the time, whether we realise it or not. For example if you’re suffering from acid indigestion you probably reach for the indigestion tablets. An advertising campaign for a particular brand of these says that they “turn excess acid into water and other natural substances”. Those ‘natural substances’ are salts – presumably it was decided that the word ‘salt’ had too many negative connotations (which is probably true: how many people would pop a pill that promised to turn into salt in their tummy?) The main ingredient in the tablets in question is calcium carbonate; a base that reacts with stomach acid to produce calcium chloride. Which is definitely a salt, if not the one most people think of when they hear the word.

Tangentially, calcium chloride is also a food additive with the E number E509. It falls into the category of anti-caking agents, which is sort of funny when you think about it.

Anyhoo, that’s one place you use a base (rhyming now as well as punning, sorry). You’re actually making one yourself every time you eat, because your liver produces a substance called bile (bloggers love bile) which helpfully neutralises the acid your stomach produces. If it didn’t, your intestines would get damaged by that acid, so it’s important stuff.

Interestingly, in a lot of the older medical traditions (you know, swallow three leeches with meals, turn around three times under a full moon and bury a toad under a horseradish in a mock turtle) the body’s health depended on the balance of four ‘humors’, or vital fluids: blood, phlegm, ‘yellow bile‘ (choler), and ‘black bile‘. If you had too much of the last two, it was supposed to cause aggression and depression, and in fact the Greek names for them are the root of the words cholera and melancholia.

It’s interesting that in the 21st century many people are obsessed with ‘alkalinizing‘ the body (just check out the comments on that lemons post) when for thousands of years people have understood that too much alkali is probably a bad thing. Public understanding of science has really moved on hasn’t it?

soapBile does something else that’s really quite important in the body, it helps you to digest fats. Bases are generally really good at breaking down fats. This is another thing that’s been known for quite a while, ever since soap was first discovered about (sources vary quite considerably on this) six thousand years ago. Soap is made by a process of saponification, in which fats react with a strong base, usually sodium hydroxide (otherwise known as caustic soda, or sometimes lye). This breaks apart the fat molecules to make glycerol and carboxylate salts (they’re the soap bit). Because of this use, sodium hydroxide features in a famous, and rather gruesome scene, in the film Fight Club.

firediamondNaOH

The fire diamond for NaOH

Because bases are so good at breaking down fats they’re actually surprisingly (or not, if you’ve just watched that Fight Club clip)dangerous, especially because they’re also quite good at breaking down proteins. Your skin is mostly fat and protein, so they can do quite a bit of damage. Remember fire diamonds? The one for sodium hydroxide has a 3 in the blue box, which means that short exposure could cause ‘serious temporary’ or ‘moderate residual’ injury – yikes.

Corrosive hazard symbol

Corrosive hazard symbol

The European hazard symbol is even more alarming, featuring a hand with holes being burned through it. Of course, acids have symbols like these too, but people sort of expect acids to do this kind of stuff. Whereas they’re often (unless they’re chemists) strangely unaware of the dangers of alkalis. For example there’s the a famous, and gruesome, story of the serial killer John George Haigh, who famously dissolved the bodies of his victims in oil drums full of concentrated sulfuric acid. It worked quite well, but he was caught eventually when the police searched his workshop and found sludge containing three human gallstones and part of a denture.

Sulfuric acid is a particularly powerful acid, and is undoubtedly incredibly dangerous stuff, but sodium hydroxide is not much safer. It will cause instantaneous and serious burns, and solid sodium hydroxide gets incredibly hot if it’s added to water. In fact, the water will quickly boil if you’re not careful.

In May last year American Carmen Blandin Tarleton was in the news because she had just received a face transplant. She needed it because her estranged husband had doused her with concentrated sodium hydroxide six years previously. She had undergone fifty-five operations before she made the decision to get the transplant. The pictures are really quite horrific. I won’t reproduce one here; you can see the result of the attack if you follow the link above. Tarleton has also written a book about her experiences. She was left blind and horribly disfigured, with burns to 80% of her body. Doctors described it as “the most horrific injury a human being could suffer”. Sodium hydroxide is not nice stuff.

It’s surprisingly, shockingly, easy to buy sodium hydroxide. Because it’s used in soap-making, you can get it quite easily. It’s even available on Amazon. And of course it’s an ingredient in lots of drain cleaners available in supermarkets. When they say you should wear gloves to handle this stuff, it’s definitely not health and safety gone mad. You really should. Even I would (and I’m really bad about wearing gloves).

So spare a thought for bases. They’re just as interesting, and certainly no nicer or safer than their acidic cousins. In fact, they’re so good at breaking down fat and protein that they could arguably be more dangerous. And next time you’re cleaning out your oven, do remember to wear your gloves.

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8 thoughts on “Basic Chemistry

  1. Even though I have a chemistry degree, I’m always learning and refreshing. Your blogs are written in a simplified way that still ends up being very informative and easy to read.

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  2. Kat
    Totally agree with you about this. I am the chemistry adviser at CLEAPSS and you only have to look at how the level of dilution affects the hazard classification to realise the corrosive activity of sodium hydroxide and other alkalis compared to that of acids. The term corrosive is a problem as well as the general public think this refers to metals and not, as we chemists realise in the hazard sense, to the destruction of the human cell. Then there is the “log-scale” problem of the pH scale. I was once at a luvvies meeting of actors (a hobby) commented that the pH of the carbonated water was pH4, the same as acid rain and not pH7.5, that of tap water. From then on, I had all the fizzy water.
    Now how about that other neglected term “ions”. Everyone from the age of 5 (including my granddaughter) hears the words atoms and molecule and the words become established in their memory banks. By the time our students reach 14 years-old and have to understand about ions, it is so difficult to add that word to their memory banks. And then ions get all sorts of mumbo-jumbo pseudo medicine surrounding them. You either use ions at KS1 and 2 teaching or leave out particle theory out altogether. I prefer the former but include the word ions. Just mention the word, there is no need to explain it unless the child asks.
    Bob

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    • You know, that’s a good point about ions. Part of the problem is the sound of the word: ion vs iron. Then the idea of ‘charged’ particles, as many people struggle with the idea of charges. I think you’re right though that the answer is probably to introduce these terms earlier, not later.

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