[time-nuts] LCD display connector

Chuck Harris cfharris at erols.com
Tue Jan 4 06:16:53 UTC 2011

gary wrote:
> They mix in stuff like wintergreen oil. The FDA doesn't have an issue
> with so-called inert ingredients. Inert for use on the body, not inert
> in electronics or optics. Most prescription drugs are full of inert
> materials. They don't have to be listed.

Actually, they do have to be on the list as inert ingredients.  The label
that goes on the customer's bottle is never a complete label.  The pharmacist
has that and will give you a copy if you ask....sometimes even if you don't.
That list will indicate if inert ingredients exist.

Wintergreen oil, or mineral oil, or any other skin conditioner added to rubbing
alcohol would be considered to be an active ingredient (it is preventing skin
irritation), and would have to be listed to avoid potential allergic reactions.

> Generally you need reagent grade to get something pure. When you do
> chemistry, you need to know exactly what you are using. Surprises are
> not cool in chemistry. There are even grades of reagent grade.

A very well known little factoid, but we aren't doing chemistry here, we are
cleaning electronics.  Specifically a silly little rubber connector.

> There is plenty of stuff on the denaturing chemicals on the net, though
> it has long been known in the industry that drug store alcohol off the
> shelf isn't suitable for electronics or optics.

Denaturing chemicals only apply to ethanol, also known as grain alcohol.
We are talking about propanol, or isopropanol, which is synthesized from
coal, and generally sold as propyl, or isopropyl alcohol.  It doesn't
need denaturing chemicals because you wouldn't be able to stand to drink
it... and if you did, it certainly wouldn't be pleasant, and might even
kill you.

Having spent many years working in a laser, and optics laboratory, I
have done all of the standard tests on many different batches of drug
store, and grocery store 91%, and 99% isopropyl alcohol, and I have found
that it leaves no visible residue.  I use it for cleaning optics, and for
cleaning electronics assemblies routinely without problem.

-Chuck Harris

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