adjust pH with LABSA - Chemists Corner

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adjust pH with LABSA

Posted by esmail on March 26, 2019 at 5:45 am

hello every one

i’m trying to make dish
wash liquid and after neutralization LABSA with NaOH when i add CDEA the
pH goes up to about 9. for adjusting pH to 7.5 could i add excess LABSA
and make the solution acidic so after adding CDEA pH attains to 7.5(is
this make sense?) or shlold neutralize LABSA completely and then adjust
the pH in final steps with citric acid(i know this is the regular
procedure)?

does free LABSA molecules makes problem in final product(ingredints: LABSA NaOH SLES CAPB CDEA fragrance dye and preservative)?

esmail replied 5 years, 7 months ago 4 Members · 8 Replies
8 Replies

ozgirl

Member
March 27, 2019 at 9:10 pm

The CDEA contains free diethanolamine (usually 4- 8%) so if you add extra LABSA you are actually neutralising this free DEA to give the DEA salt of LABSA. This is an acceptable way of achieving your final pH.

You could also just try reducing the NaOH rather than adding extra LABSA.
esmail

Member
March 28, 2019 at 12:00 pm

@ozgirl thanks for your comment. knowing “The CDEA contains free diethanolamine” is very useful point to me.

ozgirl said:

You could also just try reducing the NaOH rather than adding extra LABSA.

actually i do that. calculate appropriate amount of NaOH need to neutrlize completely my desired amount of LABSA then add slightly less than calculated NaOH.
Gunther

Member
March 29, 2019 at 6:59 pm

Besides CDEA containing diethanolamine as @ozgirl pointed out,
LABSA molecular weight varies a little bit from batch to batch, so it needs a slightly different NaOH amount to neutralize each time.

The last 5% or so of the NaOH solution should be added slowly, stepwise, checking pH every time.
esmail

Member
March 30, 2019 at 5:48 am

thanks for your attention

Gunther said:

LABSA molecular weight varies a little bit from batch to batch, so it needs a slightly different NaOH amount to neutralize each time.

The last 5% or so of the NaOH solution should be added slowly, stepwise, checking pH every time.

yes that right. i make titration for each new purchased barrel(or made small test batch).

Gunther said:

Besides CDEA containing diethanolamine as @ozgirl pointed out,

is that basic nature of CDEA because of some diethanolamine in it? if yes, could we say the pH of CDEA sample is indication of % diethanolamine in that sample?
Fekher

Member
March 30, 2019 at 1:25 pm

@esmail i suggest to add CDEA before Naoh why? because it will be easier to find adequat amount of Naoh so you just make 20% solution of soude and add littel by littel then check ph to reach wanted one.
esmail

Member
March 30, 2019 at 2:02 pm

Fekher said:

@esmail i suggest to add CDEA before Naoh why? because it will be easier to find adequat amount of Naoh so you just make 20% solution of soude and add littel by littel then check ph to reach wanted one.

yes you right, thank you for this suggestion.

but

the high pH medium after adding NaOH doesnt ruin CDEA structure?
Fekher

Member
March 31, 2019 at 1:37 pm

@esmail adding adequat amount of NaOh will not affect CDEA this order is proposed to know exactly how much you need NaOh without adding LABSA or citric acid .
esmail

Member
March 31, 2019 at 2:21 pm

ok. thanks