separation of acids.

[New2this]

There is a concrete etching chemical made by Sika that I saw today at my local Home Depot it is a transparent liquid with a slight yellow tint. Ingredients Contains Phosphoric Acid, Nitric Acid.. I would assume water as well and hopefully no detergents. Is there a way to separate these acids? My first guess was to boil them off at a specific temp. leaving the h3po4 behind which decomps at 316F.

[YT2095]

be very careful doing this, hot phosphoric acid eats glassware!

[New2this]

My user name says it all.. what is hot phosphoric acid? as in at what point does it become dangerous to the glassware (id assume when you say "glassware" is lab safe pyrex or equiv) Also I am having trouble finding the boiling point of nitric acid at an unknown concentration. Anybody familiar with this concrete etching formula?

[frosch45]

look up an msds for your particular product. you should be able to find one online, and it will give you the concentrations of the acids.

[New2this]

well i got the msds... but still have to make sense of it, take a walk with me will ya. http://www.sikaconstruction.com/msds-cpd-sikagardheavydutycleanandetch-us.pdf

 

so it seems out of the gallon jug it is 65%-75% acids, maybe the rest water, still unknown.

further breakdown:

percentage by weight:

 

nitric 15-35%

phosphoric 15-35%

(not sure if that means the mixture is equal parts of the 2 or not)

 

i am not sure if it is a redundancy but it goes on to say NITRIC ACID (7697-37-2) 15 - 35 %..... (not sure if of the 15-35% of the nitric in the jug, is actually composed of a nitric that has a 15-35% purity)

 

my goal was to be able to use this product as a source for both acids, as for now my HCL is easy to obtain, the sulfuric can be pricey with unknown purity, so making nitric with use of sulfuric may be a little more hazardous than the process is already.

[frosch45]

read the back of the bottle, sometimes it tells you if anything else is added. Is it just a sort of clearish liquid?

 

as for separating them, thats gonna be tough if you want to keep both of the acids in tact. the first thing that comes to mind is distillation.... do you have a distillation set?

 

if not, maybe freezing would work. it would certainly concentrate the acids in the process. it depends on the melting points for the purity/grade that you have, as well as if there are any other add-ins. I don't know, but one of the freezing points could be -50 degreese

[New2this]

Ok i did some more leg work on the freezing theory, yet again the freezing points are based on purity/concentration.

 

according to the online Britannica:

(HNO3), colourless, fuming, and highly corrosive liquid (freezing point -42° C [-44° F], boiling point 83° C [181° F])

 

and as for the phosphoric that left me scratching my head, i don't know alot about supercooling besides, a liquid going below it's freezing point void of crystallization.

 

http://www.jcichem.com/jcipages/prodpgs/PhosphoricA.html

 

-17.5°C

with a small note " *Freezing points are theoretical values since the acids possess the property of supercooling without crystallizing "

 

these temps are obtainable but it seems it would be much like the distillation in reverse. I am trying to build a method, so distill off most of the water then freeze and separate?

 

Whats the chances that since this chemical is mostly used in construction that there might be a antifreeze additive?

[frosch45]

Hmm, well, a few things

 

1) If you freeze your solution, you will effectively purify it to nearly 100% because water freezes at 0 degreese celcius and will be solid.

 

2) Supercooling just means that a liquid goes below its freezing point without freezing. It can happen somewhat easily. To solve this, you just need to add some teflon or glass chips (search boiling chips in google and look at those) and it will provide a nucleation site for the crystals to fall out of the solution at the proper freezing point.

 

3) As for the methanol, I can't see why that would be added. It would just be more expensive to produce, and the MSDS says that it is not at all flammable, so I don't think that it would have any in it. That too, however, if added, would freeze out at a certain temperature (or just be left as a liquid after the nitric solidified).

[John Cuthber]

"If you freeze your solution, you will effectively purify it to nearly 100% because water freezes at 0 degreese celcius and will be solid"

No it won't.

If you freeze the mixture there's every chance that you will get a eutectic mixture rather than a pure component. In any event the stuff won't freeze anywhere near 0C.

Page 8 of this

http://www.charis.wlc.edu/publications/symposium_spring02/hansen_a.pdf

gives the phase diagram for nitric acid/water. The addition of phosphoric acid would make it more complicated still.

Adding a fuel like methanol to a strong oxidant like nitric acid wouldn't be a good idea and since the mixture won't freeze in ordinary weather I doubt they will have added any antifreeeze.

Distillation would be the way to go but you need a still that will cope with this rather corrosive mixture and that's not going to be easy.

[YT2095]

you could try and find a suitable metal or metal salt to add to this and exploit the fact that all Nitrates are soluble, and a few phosphates (particularly those of the heavier metals) aren`t very soluble.

and work from that point

[John Cuthber]

I wondered about that, but I think the fact that nitric acid is a rather stronger acid would mess things up.

[frosch45]

"If you freeze your solution, you will effectively purify it to nearly 100% because water freezes at 0 degreese celcius and will be solid"

No it won't.

If you freeze the mixture there's every chance that you will get a eutectic mixture rather than a pure component. In any event the stuff won't freeze anywhere near 0C.

Page 8 of this

http://www.charis.wlc.edu/publications/symposium_spring02/hansen_a.pdf

gives the phase diagram for nitric acid/water. The addition of phosphoric acid would make it more complicated still.

 

you're right, I don't have much excuse for it either

 

anyway, the reson I didn't suggest distillation was because when you heat those things up, its pretty tough to control, and your setup would have to be pretty tough to withstand that power!

[nitric]

He could use vicor:D

[New2this]

from what i am getting here, is that it is more work than it is worth. The antifreeze i was thinking was like car antifreeze which isn't a methanol base. So getting both acids is near out of the question. Anybody have a method for targeting one of the 2... preferably the nitric, considering it is much harder to find. At least then ill be able to determine how much acid and of what type is in there. I thought i found gold but this is more like a piece of granite.

[frosch45]

you can also buy it....

 

http://www.trinitylabsupply.com/chemicals.htm

 

or

 

store.hvchemical.com

[New2this]

65% NITRIC ACID 1 GALLON (in HDPE).....$113.34

[frosch45]

or at the hvchemical

 

NITRIC ACID 70%/GLASS 2.5 LT REA/ACS 515712-2.5 $46.88 + $25 HAZMAT fee...

[New2this]

or at the hvchemical

 

NITRIC ACID 70%/GLASS 2.5 LT REA/ACS 515712-2.5 $46.88 + $25 HAZMAT fee...

 

thats a little savings. but if this acid is generally that expensive i might then conclude that the percentage of nitric in the concrete etching chemical is alot less than i thought. Considering the under $20 price tag. I was a little shocked to see nitric as the second ingredient, you don't see that everyday.

[nitric]

you should trust the msds.as you can see alot of the price is hazmat

[New2this]

I looked at the bottle again today. no new info on it, just happened to be in the home depot for some cabinet hardware. As i was looking at the bottle, i had a thought.... if this bottle contained just those two acids and water, wouldn't that be like pre-made nitrocellulose in a bottle? I have heard that sulfuric isn't the only acid that can be used in this process, i had a little chuckle on that thought.

[hermanntrude]

to be honest with you, i'd suggest not trying to separate these two chemicals, since to do it you'd probably have to get one of them to 100% purity, which would be impossible and/or incredibly dangerous.

[New2this]

This question was way to complicated for me to look up with my seemingly infantile understanding of these acids. So avoiding any specifics i am going to ask this as vague as possible.

 

Problem: 1 gallon of nitric and phosphoric acid diluted in water

Is there anything that i can add to this mix that will produce a reaction converting one of the two acids into something else that also is not reactive to the remaining acid and or water? preferably a gas, h2O, or a solid that is not water soluble...

 

If i don't have the equipment i can borrow it, or buy it, i have a vacuume pump, and seemingly limitless argon, nitrogen, oxygen the HVAC business gives me options.. oh yeah that also brings me to the r 22 r 134 r 410 and assorted. not sure what i could do with CHClF2 C2HF5 besides give you a lower freezing temp than the average joe.. But that would also give me a nice fine if somebody saw me vent it to quick freeze something.

 

this topic has shifted in a few directions for sure, if there is a better place for this question and others previously mentioned other than the current section, inorganic chemistry, please let me know and I will do my best to either keep the questions focused or not clutter the wrong sections with unrelated content.