Concentrating Ammonia

[javagamer]

Hi,

I'm planning on making some concentrated ammonia solution and I'm a little confused as to the math. I plan on heating some store bought ammonia, which I already determined is 10%, and bubbling the gas through water. What I'm confused about is how to convert from w/v since the density of water changes depending on how much ammonia is dissolved. Do I need to know the density of 10% and 35% (that's saturated, right?) to figure this out?

Anyways, any help is appreciated.

 

Edit: I think some of the trouble I'm having is from wikipedia's article on ammonium hydroxide. It says "At 15.5556 °C, the density of a saturated solution is 0.88 g/mL and contain 35% ammonia by mass, 308g/L w/v, (308 grams of ammonia per litre of solution) ...". I was confused because I thought if it's 35% then there would be 35g/100ml, though now I see that it's at 15.6 °C so that probably clears that up.

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Alright, I think I figured most of it out. 10% solution means there's 10g of ammonia in 100ml FINAL solution. Now I just need to know how to go the reverse, figure out how many grams of ammonia I need to dissolve in a given volume of water to get a given percentage solution. Anyone able to help?

Edited January 17, 2010 by javagamer

[JGK]

Edit: I think some of the trouble I'm having is from wikipedia's article on ammonium hydroxide. It says "At 15.5556 °C, the density of a saturated solution is 0.88 g/mL and contain 35% ammonia by mass, 308g/L w/v, (308 grams of ammonia per litre of solution) ...". I was confused because I thought if it's 35% then there would be 35g/100ml, though now I see that it's at 15.6 °C so that probably clears that up

 

The "by mass" term means that the % data is w/w not w/v so 35% will be 35 g ammonia per 100g solution. At a density of 0.88 g/mL that will be the equivalent of 35 g ammonia in a volume of 113.6 mL at 15.5556 °C. this data gives you the 308 g/L you list above

[thrival]

I've been distilling urine into ammoniated water to extract its salt. To increase the ammonia concentration, when I distill again, should I throw out the first water or the last? In other words does the ammonia gas come over in the beginning of the distillation, at the end, or equally throughout? I've seen the above posting, et al, I just want to keep this simple, not go out for long distillation trains, columns, equipment, etc. Thanks.

Edited May 28, 2013 by thrival