Re: sodium (perforate)/ Carbonate / Tetraborate decahydrate

[Kay Lancaster <kay@xxxxxxxx>]

On Fri, 27 Jun 2003, Jennifer Hein wrote:

> Then,  any chemist??? Does anyone know the difference or similarity of
> Sodium carbonate Arm & Hammer Washing Soda),

Sodium carbonate is Na2CO3, washing soda, or sal soda.  It typically has
10 molecules of water attached it in crystal form, which makes it
sodium carbonate decahydrate.

Written out in chemist-ese, it looks like Na2CO3 * 10H2O , sort of
(since ascii doesn't let you do the subscripts for the 2 and 3 in Na2CO3
and H20.  The * sign is what I'm using for the raised dot that chemists
use to visually tie the 10 waters to the Na2CO3.  And if that makes no
sense to you, I apologize profusely (it's been a very long week, and
it's going to be longer), and direct you to
http://www.bartleby.com/65/so/sodiumca.html, where it's written out
properly on the 4th line of the encyclopedia entry.

> Sodium Tetraborate decahydrate (20 Mule Team Borax)

That's what's generally just called borax, Na2B407 * 10 H20;
also written B4O7Na2 * 10 H20.  Also known as disodium tetraborate
decahydrate, sodium tetraborate decahydrate and sodium pyroborate
decahydrate.  http://chemistry.about.com/library/weekly/aa091002a.htm

What's the difference?  Well, they are both sodium salts, and they're
both used as laundry aids, and they're both pretty basic (alkaline)
when dissolved in water, and they've already got some water attached
to their crystal structure.  Washing soda will release the carbonate
ion when it's dissolved in water; borax will release the borate
ion when it's dissolved in water.  Both will require a fair amount
of rinsing to get all the residue out of the fabric.

There's a pretty good introduction to the chemistry of bleaching at:
http://library.thinkquest.org/27034/chem.html?tqskip1=1&tqtime=0627

Sodium perborate (different from sodium borate)  is probably the most
commonly available "non chlorine bleach" on the laundry shelves, at
least to my casual survey, but there are a lot of sodium percarbonate
(different from sodium carbonate) bleaches around, too.  The "per"
bit in the chemical names lets you know that this is an oxidizing agent,
and they break down in water to make hydrogen peroxide (like you put
on cuts or bleach hair with), which does the actual bleaching.
Borax, washing soda, sodium perborate and sodium percarbonate are all
too alkaline (basic) to use on wool or silk...

Speaking *strictly* as an amateur here, and apparently the designated
mender and cleaner of family textile treasures, I usually try hydrogen
peroxide as a bleach instead of sodium perborate or percarbonate... just
because hydrogen peroxide breaks down to water -- no borate or carbonate
residue to rinse and rinse and rinse.  My first resort if it has to be
wet cleaned, though, is just a good long soak in detergent and water and
lots of rinses.  Note, though, that I'm dealing with stuff like 50 year
old baby bibs Aunt Myrtle embroidered, not a Worth gown or 17th century
tapestry fragment!

Perhaps the professional conservationists here could comment on
bleaches for us amateurs.  Am I off-track in preferring hydrogen
peroxide over perborate or percarbonate bleaches?

Many thanks.

Kay Lancaster  kay@xxxxxxxx