[kerelu]

Hi,

 I am trying to find out the solid content of a suspension. I know this can easily be done by drying the suspension and recording the mass intermittently till there is no mass change. However, my suspension is in sulphuric acid. So my question is: can I dry a suspension containing sulphuric acid in an oven? Thanks.

[Zyklonb]

Well, yeah you could. Sulfuric acid has a very high boiling point though. If you have a torch or hotplate use that.

[Arkcon]

Here is a Canadian mirror of an older version of the USP, available on-line.  The test for residue is in the National Formulary Monograph.  Briefly, like Zyklonb: said, you simply have to get the sulfuric acid hot enough, for long enough, to volatilize it away from any impurities.  The USP seems to think it can just go in the muffle furnace, once dry enough.  Seems like that would work, but I'd be sure it was mostly gone before I let someone put it int my workplace muffle furnace.  I wouldn't want residual sulfur trioxide vapor to hit the electric heating element.  Might work a few times, or maybe a few dozen times, but eventually, the wire will corrode, and then you're out a few thousand dollars.  Anyway, the link, check the relevant blue hyperlinks in the document if you need more info: http://www.pharmacopeia.cn/v29240/usp29nf24s0_m80000.html

[kerelu]

Thank you for your replies.