This aluminum driving me nuts

[pippo]

People,

 

Been sellling aluminum for years- a 11,000ppm solution- simple- aluminum nitrate dissolved in a dilute nitric solution. Never a problem. Now, Im finding the solution is not stable for even 3 months. It looses about say, 2% strength/month, give/take. Just checked a stock bottle from december and its down 10% or so to about 10,000ppmAl.

 

What is going on?? Where is the aluminum dissappearing?? Bottles always tightly capped.

Oh- the way I test it is by classic titration- in ACS Reagents manual, if youre familiar with it. basically, its an EDTA back- titration, with dithizone indicator. very pH sensitive- gotta be 4-5.

[John Cuthber]

What's the bottle made of?

Glass bottles leach alkali and that would ppt the Al.

 

More fundamentally, what has changed?

Have you moved lab, bought a bottling machine, changed your nitric acid supplier, moved to the Arctic?

There has to be something.

[pippo]

What's the bottle made of?

Glass bottles leach alkali and that would ppt the Al.

 

More fundamentally, what has changed?

Have you moved lab, bought a bottling machine, changed your nitric acid supplier, moved to the Arctic?

There has to be something.

 

Not sure what "leach alkalai" means. The solution is acidic.

 

I know, John- theres got to be an answer other than some mideival reasoning, like the gods are not happy with me as a sinner. Same polyethylene HDPE bottle, same shelf, same bldg, same supplier - but wait- I believe its a different lot from a few yrs ago. I couldcal them to "explain". Doubt they would know, as all tey would say is maybe "havnt had any other complaints".

 

I use ACS grade, too. Not tech grade garbage.

[pippo]

this morning (yeah, on a Sunday) I restandardized it. Left it a tad strong, but within limits. We';ll see what happens in 2 months or so.

[John Cuthber]

If you put clean water in a glass bottle and leave it, the water becomes alkaline as silicates leach out of the glass.

[pippo]

If you put clean water in a glass bottle and leave it, the water becomes alkaline as silicates leach out of the glass.

you mean like pure DI? Didnt know that, John. If so, probably not much to worry about, especially since the solution is not buffered- woyuldnt take much silica to raise pH in non buffered medium.