Magpie
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ammonium hydroxide
I purchased some Ace brand janitorial ammonium hydroxide today. The label says it contains 10% ammonium hydroxide. I decided to titrate it, both to
verify the strength and to prove out a method for determining the strength of a more concentrated solution. I plan to beneficiate this OTC to a lab
grade 30% ammonium hydroxide. 
Assuming a sp. gr. of 0.98 I calculated the normality as (0.98)(1000)(0.10)/35.05 =
2.8 N.
For my 1st titration I used some 0.171N potassium acid phthalate that I had on hand and a methyl orange indicator (color change 3.1-4.4 pH). This
didn't work as the pH wouldn't drop enough as I believe phthalic acid is too weak. On my next attempt I used 4.3N HCl. This was successful
but I got a normality for the ammonium hydroxide of 5.1!
Although I'm not complaining about the higher than expected (2.8N) concentration I'm wondering if I've missed something. Have any of
the rest of you had this experience - or have an explanation for my strange results?
The single most important condition for a successful synthesis is good mixing - Nicodem
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woelen
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If the stuff is 10%, then I would expect a concentration of approximately 5.5 mol/l. Actually, you did your measurements quite well!!
Ammonium hydroxide is a very bad name. Just call it solution of ammonia (NH3) in water. The percentage is given as percentage NH3 and not as
percentage NH4OH.
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Magpie
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Woelen you are probably right. If so this is just sloppy labeling. I don't know what the convention is for stating the strength of ammonia for
cleaning. Perhaps it is "% ammonia."
The single most important condition for a successful synthesis is good mixing - Nicodem
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vulture
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For the manufacturer it is beneficial to use the mass percentage of NH4OH (although EVERY serious chemist knows this is wrong) as this will be higher
than the mass percentage of NH3...
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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woelen
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I cannot agree with that. I have purchased ammonia many times in all kinds of concentrations (ranging from 5% to 32%), but I've never seen it
specified as weight percentage NH4OH, always as NH3.
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vulture
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| Quote: |
The label says it contains 10% ammonium hydroxide
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Magpie's apparently does...Maybe the chemistry Gestapo is more active in Europe 
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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woelen
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Vulture, things are even better at the other side of the ocean, the label says 10% ammonium hydroxide, but it is 10% ammonia!!! That's more than
twice the amount of NH4OH. So, in fact for each bottle of ammonium hydroxide you buy, you get one for free as well  . You only have to take your own water .
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((Blasta))
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15%-20% NH4OH found..cheap too
I get my stuff from Janitors Supply huts... I get 4L for $12.50 CANADIAN
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Magpie
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My attempt to upgrade janitorial ammonium hydroxide (5.2N) to reagent grade (16N) had very limited success. Using simple sparging of ammonia at a few
inches of water pressure for 1 hr it only reached 7.0N.
I am thinking the ammonia dissolution will have to be done under pressure. For this I will make some liquid ammonia according to the method of
Eleusis. This will give me gaseous ammonia at 114 psig. To contain the liquid I will need to buy a lecture bottle, or homemake one out of black iron
pipe and a valve.
Questions, comments, or suggestions?
[Edited on 19-10-2005 by Magpie]
[Edited on 20-10-2005 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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chloric1
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Question: Who is Eleusis?
Ammonia like any gas is more soluble in cold than warm solvents. WHy can't you cool Janitorial Ammonia with dry ice to -40 degrees C or colder
and then add ammonia. I was adding dry ice to ammonia once to make ammonium carbonate to do an improvized Solvey process and after a pound of dry
ice was added to 600 ml of ammonia the liquid was so cold that 1 cm thick ice form on the beakers outside from the humidity! And the dewpoint was
about 10 Degrees C that day! THe point is the aqueous solution did not freeze.
Fellow molecular manipulator
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Magpie
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Eleusis is the name of someone who posted the method on the internet.
I cooled the ammonia gas with an ice-water cooled condenser and the janitorial ammonia was kept in a 100 mL graduate cylinder immersed in an ice-bath.
The freezing point of my janitorial ammonia would be about -14C per CRC handbook. I'm skeptical that lowering the temperature to -14C would help
much since at 0C the absorption capability of water for ammonia is around 47 wt%! Therefore I think it is more of a mass-transfer rate problem than
an absorption capability problem.
The single most important condition for a successful synthesis is good mixing - Nicodem
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garage chemist
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How did you generate the gaseous ammonia and how much of it was bubbled through the aqueous NH3?
Concentrating the ammonia to 30% should pose no problem.
The only important thing is to generate enough of the gaseous NH3.
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Magpie
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I generated the ammonia using about 300 mL of janitorial ammonia placed in a 500mL RBF, gently heated. The evolved ammonia was led through the
ice-water cooled condenser then to a sparge tube with an aquarium air sparge stone on the end. This was fully immersed in the 100 mL grad cylinder,
immersed in ice-water. I sparged for 1 hr with a steady stream of bubbles until the source petered out.
The single most important condition for a successful synthesis is good mixing - Nicodem
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