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Diluting nitric acid


#1

Hi, How do I make a “30% nitric acid solution” for etching silver?
The nitric acid I have is 69.9%.

Thanks,
Rick
www.elkinjewelers.com


#2

69% to 70% is the best Nitric Acid Chemical for etching non-ferris
metals. By mixing a 1/3 Nitric Acid to 2/3 Water solution, you will
have the BEST etching mordant. Other chemicals, added to this Nitric
strength will etch ferris metals.

Good Luck.
Mary Ann Scherr


#3

Hi Rick,

How do I make a "30% nitric acid solution" for etching silver? The
nitric acid I have is 69.9%. 

The following is a very useful formula for dilution which I’ve
posted before. Note it down, it’s useful for many situations.

You are starting with 69.9% nitric acid and want to achieve a
concentration of 30%. In my example below, I’m using a starting
volume of 10 ml but this can be changed. You need to choose a
starting volume, but the formula will tell you how much water to add
to make the concentration of choice.

ORIGINAL CONCENTRATION X ORIGINAL VOLUME = FINAL CONCENTRATION X
FINAL VOLUME

Substituting:

0.699 (69.9%) X 10 (ml) = 0.3 (30%) x FINAL VOLUME (our unknown)

FINAL VOLUME = 0.699 X 10/0.3
FINAL VOLUME = 6.99/0.3
FINAL VOLUME = 23.3 ml

This is the total volume you will end up with. You therefore need to
subtract the 10 ml from the answer to find the volume of water you
need to add.

Therefore, 23.3 ml - 10 ml = 13.3 ml water to be added.

As I said, you can choose a different starting volume - it doesn’t
matter - the formula still works. But don’t forget to subtract your
original acid volume from your final volume, to determine how much
water is needed.

HOWEVER, always remember to add acid to water, not the other way
round.

This formula works for any kind of dilution problem where you know
your starting concentration of a solution and want to make a
different concentration. It also works if you’re trying to work out a
concentration from known volumes. It doesn’t matter what’s being
diluted (the solute) and with what (the solvent).

Helen
UK
http://www.hillsgems.co.uk
http://helensgems.ganoksin.com/blogs/


#4

hi all

well today i managed to find my first batch of nitric acid so i can
try and etch some silver, on the label it says NH03 % 55.5% ±1 (i
couldnt get the plus and minus to be on top of each other like they
are on the label) and seein the rest of the label is in polish and i
myself am not polish i guess that means its around 55.5% ? all the
posts i did manage to read said about different percentages of acid
and ratios of water needed. I know to some they might think “not
another how much water do i add” question but my maths aint good so
i would be greatful if someone could tell me how much water i would
need to add to say 50ml of this acid to get the right mix and would
that make enough to etch a average size pendant as i dont really
want to have massive amounts or it layin around

i would be greatful for any help
regards
jason


#5

Hey Jason, Always Add Acid to water not the other way around as it
can cause a violent reaction. I don’t etch so can’t help you with
the math.

Be safe, have a good one. Jim Doherty


#6

Concerning keeping safe with acid dilution–always ADD THE ACID TO
THE WATER! This is important. Don’t pour water into concentrated
acid!

When water and concentrated acid are mixed, a lot of heat is
produced. If water is poured into acid, the first bit of water to hit
the acid can be heated to produce steam, enough to spray acid over
your face, hands or whatever is close. Concentrated nitric acid is
particularly strong and caustic. It immediately burns skin and will
blind you if it hits your eyes.

Wear safety goggles and gloves when handling Nitric and other
concentrated acids. You may ignore this warning at your peril.

There are a number of mnemonic devices used to help one remenber
this and my favorite one is “Drop Acid Not Water”. Just google
"mixing nitric acid and water". You will find a bunch of recipes for
making dilutions and lots of warnings stronger than mine about doing
it in the right order.

I wish you well.

Gerald Vaughan

(To those who might question it, I do not mean that one should drop
LSD before diluting HNO3. Please.)


#7

hello Jason, first its fine to store a solution of nitric acid in
water for a few months. second, always add acid to water-and you will
need to add about one part (70 % reagent grade) to 3 parts distilled
water for sterling. For steel, one part to 6 parts distilled water,
and for base metals, one part acid to one part water. If you wabnt to
know what the Polish translates to- simply install the translate
buttion in Firefox or on the google toolbar and type the characters
as you see them printed then hit translate Polish to English- and you
should get a reasonable translation of the bottle’s or
at least a part of it relevant to your needs. Regarding the
solution:Use in a glass dish with a low center of gravity so it can’t
get easily knocked over or spilled. Acid solutions can be used many
times before enough metal is dissolved in them to inhibit the
effectiveness ( before the solution is used up!). Keep different
solutions for different metals separate (don’t use a solution to etch
copper that you have used for steel- keep them all dedicated or you
will get strange and unpredictable results). If a new solution seems
to be working too slowly add a small amount of used solution to the
mix to give it a jump start. Don’t use a mason type jar with a metal
lid as the lid will corrode if you attempt to store pre-mixed
/slightly used solutions in them.,rer


#8

Jason,

First off, please don’t add water to acid, ever. Add the acid to
the water, and do it carefully. If the solution bumps, it’s a lot
better to have it blowing up in your face if you’ve only managed to
add a little acid to a lot of water, versus the other way 'round.

Next, it’s just a matter of percentages and simultaneous equations,
but since you’d probably rather just get the answer, here’s a site
that you’ll find useful for that.

http://www.handymath.com/calculators.html

The specific link you want on that page is

http://www.handymath.com/cgi-bin/chemcalc4.cgi?submit=Entry

It’s in the "Chemical Calculators section, maybe halfway down, and
the entry is “Chemical Mixing Calculator for Adjusting the Active
Ingredient Concentration of a Batch”.

You didn’t specify how much, or what the final percentage was, but
if you have 20 grams of the 55% and want to get it down to 20%…
well, here’s how that example would work out:

Weight of Initial Mixture                       20
Percent Active Ingredient in Initial Mixture    55
Percent Active Ingredient in Adjustment Mixture  0    
Percent Active Ingredient in Final Mixture      20
Weight of Adjustment Mixture                    35
Weight of Final Mixture                         55

So, you’d take 35ml (that’d be 35 grams) of water, and add,
carefully, 20 grams (probably less than 20ml) of your 55% solution
to it. The final weight would be 55 grams, with a concentration of
20%.

Use your own numbers to get the results you really need.

Loren
http://www.golden-knots.com


#9

Okay Jason, I’ll post it again. The following is a VERY simple
formula for working out dilutions of anything. But to answer your
question more simply first, I tend to find that a 25% solution works
best, so using my calculation, you would need to add your 50 ml of
acid to 60 ml of water (remember to always add the acid to the
water).

original concentration X original volume = final concentration X
final volume

Remember to be consistent with where your decimal point should be.
For 55%, I’m using 0.55, and for 25%, I’m using 0.25. For 50 ml, I’m
using 0.05 (of a litre), but if you wanted to use ml, then just make
sure you use ml both sides of the equation.

Substituting:

0.55 X 0.05 = 0.25 X final volume
final volume = 0.0275 / 0.25
final (total) volume = 0.11 litres (which equals 110 ml)
110 ml - 50 ml (volume of your acid) = 60 ml water.

Hope this helps. The formula works for all such problems, and it
works any way round.

Helen
UK
BTW, where are you in the UK?


#10

Oh this first time I see someone going to use nitric acid, could you
tell me where did you purchase it from, I am having trouble finding
them.

Anna from Canada


#11

Jason,

I hope I am not the only one to bring this up, but regardless of the
quantities of water and acid to mix in order to achieve the strength
that you will need, NEVER add water to acid. Always add acid to
water. Adding water to acid can result in a a violent reaction which
can splash the concentrated acid onto your face and hands.

happy etching
John Bowling


#12
There are a number of mnemonic devices used to help one remember
this and my favorite one is "Drop Acid Not Water". 

You must be mighty old! I doubt there are many people on Orchid who
even remember the phrase to “drop acid”.


#13

Concerning keeping safe with acid dilution–always ADD THE ACID TO
THE WATER! This is important. Don’t pour water into concentrated
acid! " There are a number of mnemonic devices used to help one
remenber this and my favorite one is “Drop Acid Not Water”. And then
there is: “May his rest be long and placid, he put the water in the
acid”

Jerry in Kodiak


#14

Hi all

firstly thanks for the help, secondly i think you got the wrong idea
when i said about how much water to add to 50ml of nitric, what i
ment was how much water would i need, yes i know to add the acid to
water and NOT the other way around so im sorry for the mix up.

Helen, the reason why i ask this question was because i was told by
somebody to use 25ml of water with 100ml of acid which i thought was
no that much water but seeing i had never done it before i thought i
would ask just to make sure it wasnt to strong

Anna, i bought it from a local chemical supplier

Gerald, as far as safety goes, apart from doing it outside just so
the nitric fumes dont get chance to hang around i will be doing it
outside so there will be massive amounts of fresh air (and because i
dont want to risk any affects on my tools or rolling mill), no doubt
if any people happen to see me they will think i am mad but i will
also have acid resistant boots, apron and long acid resistant gloves
with another pair of gloves inside (i found these to be better then
the shorter ones as there is no chance to get any on your arms as
they are more or less up to your armpit), safty goggles aswell as a
full face mask and a respirator ( although i do need to buy some new
filters before i start). i did once work at a company who had
massive acid baths so i know the risks and that is another reason
why a thin pairs of gloves are a good idea as i have seen the damage
caused by people missing an hole in the glove when they check them

thanks again to everyone for the advise and im sorry if i didnt
explain things right the first time, i do seem to babble on at times
and then i losetrack

regards
jason


#15

Hi Jason,

the reason why i ask this question was because i was told by
somebody to use 25ml of water with 100ml of acid which i thought
was no that much water but seeing i had never done it before i
thought i would ask just to make sure it wasnt to strong 

As I keep saying when someone asks this question, it depends
entirely what concentration of acid you’re using - it’s not enough
for people to say "add X amount of acid to Y amount of water, without
taking into account the concentration of acid being used, and the
concentration you want to end up with. Using 25 ml of water with 100
ml of your acid will give a different end result to whoever
recommended that, if they’re using a different concentration of acid.
That’s why I did the calculation based on what you told me was your
concentration, and what I have found to be an ideal end
concentration. You asked a specific question, I worked it out for
you, told you how to work it out in the future for any other dilution
problems, and provided a specific answer. I hope it was helpful.
People seem to be so scared of doing the maths, but the formula is SO
simple to use and it works every time if used correctly. I’ve posted
longer, more detailed posts on it in the past if more is
needed (but some folks got bored with me saying it), or else I’m
happy to answer any questions offline.

Helen
UK


#16
You must be mighty old! I doubt there are many people on Orchid
who even remember the phrase to "drop acid". 

I remember Dr.Timothy Leary – “Turn on, tune in, drop out” Don’t
have to be so old–I’m still only 18. The trouble is, I’m stuck in a
sixty-two year-old body!

David Stitt
North Canton, Ohio