SDS becoming yellow - (Mar/31/2006 )

Hello,
I have a problem. I want to do a SDS 10% stock solution, but the solution is becoming yellow until the powder is dissolved. I don't understant why , I never had this problem.
If somebody have an idea it will be welcome

on applichem bottle of 20% SDS it's written :

appearance of the solution : clear-yellowish (pH6.5 -8.0). our solution is white (pH3.0) and precipitates all the time (because of pH3.0). could your SDS be closer to pH8.0 ?

It was not the first time I prepared SDS 10%. In the past I never saw that yellow color. Maybe it's the pH but i can't check it because i don't keep this yellow solution, the people around me tell me i should better don't use it.

Yes, if it's the first time it's yellow, you would't trust it neither.

.. I remember, something, once I found a yellow NaOH 10N solution in the closet, freshly prepared.
strange.