White Yeti - 3-9-2011 at 15:46
A friend of mine, who's name shall remain unspoken, has foolishly used a relatively powerful cleaning product without gloves and now has fingerprints
that are barely visible and very difficult to identify.
But he/she used what's called "non TSP cleaner", which is supposed to be less dangerous than TSP itself, and yet still as powerful against grease and
other things you find in a McDonalds kitchen. I looked at the package and said it contained sodium metasilicate, better known as sodium silicate, or
water glass.
So here's the question, has sodium silicate saponified the skin on my friend's fingers (rendering the fingerprints unidentifiable)?
It seems like sodium silicate cannot be as powerful as TSP, and yet, the company claims that their product is just as powerful a cleaner as TSP.
Any thoughts?
bbartlog - 3-9-2011 at 16:18
Saponification is a reaction specific to fats, no? Skin on fingertips is mostly composed of other stuff. But yes, of course sodium silicate is a
plenty strong base and can give you chemical burns. 'Saponification' just isn't the right word to describe them.
magnus454 - 3-9-2011 at 18:55
He burned off his finger prints, saponification is when fats get turned into soapy like substances.
Endimion17 - 4-9-2011 at 03:20
Yeah, saponification was in order. Silicate anions hydrolize to give hydroxide anions and silicic acid. Hydroxide anions reacted with lipids in his
skin.
Bases are a hell lot more dangerous for skin than acids. They penetrate better and deeper. He should visit a dermatologist because his skin still
might not be safe. Fingerprints will grow back, but the skin layers need to be healed properly.
It's weird how he used it without gloves... wasn't there a "corrosive" sign?
White Yeti - 4-9-2011 at 07:50
Thank you all so much for the info.
Magnus454, when fats become saponified, they get washed away with water, thus explaining the fact that the fingerprints are no longer visible.
I had no idea that sodium silicate was that powerful. It's sometimes sold in crystal growing kits without any warning signs. There are no warning
signs on the package, but they do say "harmful if swallowed, avoid eye contact" and "may cause burns". Reading a little more, they say "wear gloves
and protective clothing". Interestingly enough, they didn't say their product was "corrosive" per say.
I know that saponification specifically refers to trigycerides, but (from personal experience) I also know that even dilute solutions of strong bases
can saponify the phospholipid bilayer cell membranes on the cells of the epidermis. I had an accident at school when I was performing a titration
reaction, and the valve of the burette came loose and about 50mL of dilute calcium hydroxide spilled all over my hands. They felt all slippery, and
the teacher explained that the cell membranes on the epidermis had been saponified.
Ozone - 4-9-2011 at 08:20
TSP = trisodium phosphate. It is only a problem (E.G. IN THE us) when phosphates have been controlled or eliminated/banned for environmental reasons
(e.g. algal proliferation, dead-zones, etc.).
Sodium silicate is a solution of silica in sodium hydroxide. The sodium hydroxide catalyzes the addition of water to the fats in you skin to yield
fatty acid sodium salts (e.g. sodium strearate, myristate, laurate, etc). These compounds are soaps, and are why alkaline solutions feel slippery on
the skin--the slickness is soap made from you. Because these lipids are structural, removing them destroys the tissue (lipid bylayers, etc.) leaving a
chemical burn.
See also DCM or other defatting solvents which dissolve out the lipid from you skin with similar result.
FWIW, they removed the TSP from our dish washer detergent, and it began to leave spots (and buildup scale clogging the drain line), etc. I now fortify
my detergent with <2 % w/w TSP acquired OTC (DAP, hardware store) and it works great 
.
Endimion17 - 4-9-2011 at 08:36
In an elementary school jargon, a salt made of a weak acid and strong base will be basic. Sodium hydroxide is one hell of a base, and silicic acid is
a very, very poor acid (compare: pK<sub>a</sub>(HI) = -9.5, pK<sub>a</sub>(HNO3) = -1.4,
pK<sub>a</sub>(H<sub>2</sub>S) = 7,
pK<sub>a1</sub>(H<sub>4</sub>SiO<sub>4</sub>
= 9.84, pK<sub>a2</sub>(H<sub>4</sub>SiO<sub>4</sub> =13.2