Yeah what I've got is "Arm & Hammer Super Washing Soda" and I gave it a sniff. A few sneezes later, I can confirm this stuff too has a pretty soapy smell.
I dunno ... sounds like a question for those RC guys.
This is my bookmark of where I first heard of the homemade buffer idea ... it references two threads on RC about it. So, maybe from here we can get an idea of someone we can pose the question to ...
Homemade Buffer