It's hard to keep up in the blog world when your trying to move. I mean moving to a different residence. You always forget how much of a pain it is. I've got everything packed up in I-CHEM boxes swiped from work. Well they're not really swiped, they were getting thrown away.
Anyways, anyone know how to clean an extraction lens or re-install instrument controlling software without getting a headache?
Friday, July 21, 2006
Wednesday, July 05, 2006
Silver crashes
The other day I took on the rather long task of making a multi-element solution. A multi-element solution is exactly what it sounds like, a solution (a mixture of dissolved stuff), the dissolved stuff being many different elements. This particular solution was to be composed of 27 different metal elements such as chromium, arsenic, and manganese. One way to start making this solution is to dissolve different metallic salts, like As2O3, into a diluted acid (HNO3 or nitric acid) solution. But, I don't have to do that, we buy the metals already dissolved in acidic solutions.
So all I have to do is successfully pipette certain amounts like 10mL, 1mL, or 0.1mL. Then dilute the solution to 1 or 2L in a class A volumetric flask. It's not that hard if you got good lab technique, but you do have 27 chances to accidently add the wrong amount. Anyways, silver is always a little tricky to get into a solution. It always wants to precipitate out. I think it forms AgCl. The Cl anions come from the HCl I add to the solution along with the HNO3 to stabilize the metals. One way to prevent precipitation is to add the HCl last after the silver has already been added and is diluted throughout everything else. But in general, silver can't be put in a multi-element solution above 500ppb. Well for some reason I forgot everything I knew for 30 seconds and messed up the entire solution on the 27th metal, silver. As soon as I pipetted 0.5mL of a 1000ppm silver solution into about 1L of other dissolved metals + acid + water it crashed out into a white haze in the flask and eventually combined into what looks like normal table salt at the bottom of the volumetric flask, but I wouldn't put that salt on my fries.
So all I have to do is successfully pipette certain amounts like 10mL, 1mL, or 0.1mL. Then dilute the solution to 1 or 2L in a class A volumetric flask. It's not that hard if you got good lab technique, but you do have 27 chances to accidently add the wrong amount. Anyways, silver is always a little tricky to get into a solution. It always wants to precipitate out. I think it forms AgCl. The Cl anions come from the HCl I add to the solution along with the HNO3 to stabilize the metals. One way to prevent precipitation is to add the HCl last after the silver has already been added and is diluted throughout everything else. But in general, silver can't be put in a multi-element solution above 500ppb. Well for some reason I forgot everything I knew for 30 seconds and messed up the entire solution on the 27th metal, silver. As soon as I pipetted 0.5mL of a 1000ppm silver solution into about 1L of other dissolved metals + acid + water it crashed out into a white haze in the flask and eventually combined into what looks like normal table salt at the bottom of the volumetric flask, but I wouldn't put that salt on my fries.
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