Quote Originally Posted by gainer View Post
The highest grade I have seen from Rio Tinto specs is NF, a pharmaceutical grade, which lists only heavy metals at <20 ppm. The difference between Rio Tinto Tech granular and powder is ONLY in the water insoluble particles, which are <400 ppm in the granular and none in the powder. The variance in measurement of percent borax decahydrate is in the water content, which will vary with storage conditions due to changes in humidity. the same variance can occur in any grade, including AR.

Your AR grade assay was for a particular sample of known hydration
Pat - Did does Rio Tinto Technical Grade Powder really say "none" for the insoluble particles? That surprises me as there should be a limit of some sort - i.e a value given in parts per million. As an analytical chemist, I can say that there is always going to be a little of something in most everything... unless you are talking about homeopathic medicine. Did it really say None detected or something, and that is based on the method of analysis, but really doesn't mean that there is "none". Just that that test can't detect any.

The AR grade assay had absolutely nothing to do with a "known hydration". Infact, I doubt the hydration was even tested for. It was an "assay", a measurement of the material of interest.