Sciencemadness Discussion Board

Problem Nitrating Cotton

rrkss - 21-4-2010 at 19:47

I am running into problems nitrating cotton. I am running the nitration of 0.5 g of cotton (certified 100% cotton) using 10 mL of 96.5% H2SO4 and 5 mL of 52% HNO3. This is done in a 50 mL beaker and not cooled down by ice or anything. I let this cotton sit in the solution for 10 minutes and stir every minute. After that I rinse in tapwater and neutralize with baking soda.

When the cotton dries, it burns like regular cotton. Any ideas why this is happening?

kclo4 - 21-4-2010 at 20:04

My guess is that you are either not using pure enough acids, or not letting it sit long enough.
Try using more sulfuric acid, and both in excess to the cotton. Also let it sit longer. Perhaps after the two acids have been added, wait a while before you add the cotton.

Make sure it is completely dry when you go to ignite it.







[Edited on 22-4-2010 by kclo4]

rrkss - 21-4-2010 at 20:08

The sulfuric is ACS reagent grade and the nitric was distilled from ACS grade KNO3 and the sulfuric. Unfortunately I added a little bit too much water when I distilled it giving me 52% (Tested with titration). I will try nitrating a little bit longer but it does give me the a fuming mixture which gives off white fumes when I mix the two acids. How long should I leave it to nitrate?


Edit: Tried rerunning the reaction with a slight bit more of sulfuric acid (7 mL of HNO3 and 16 mL of H2SO4) and the cotton completely disintegrated. It turned from a nice fluffy cotton ball to a millions of tiny pieces that were impossible to wash out and rinse. If I want any hope of recovering them I would need to vacuum filter.

[Edited on 22-4-2010 by rrkss]

a_bab - 21-4-2010 at 22:57

It may be not cotton at all? Try with a better source of cotton, like a cotton thread. There are many fakes nowadays. A good cotton source would be white toilet paper, unscented :)

woelen - 22-4-2010 at 00:57

I used white cellulose wadding for this experiment, using 53% HNO3 with 96% H2SO4 and this works like a charm. I left the piece of wadding in the acid mix for 15 minutes or so and occasionally took the piece of wadding apart with a pair of glass rods, allowing freesh acid mix to come in contact with the wadding. I did not use cooling, but I waited till the mix of acids cooled down again.

I also tried nitrating tissue paper and that did not work (it either charred and disintegrated, or no nitration occurred). So, indeed as a_bab suggests, you must have real cotton. Paper-like stuff does not work.

rrkss - 22-4-2010 at 06:32

The package claims it is 100% cotton, but I will go ahead and try a different source of cotton and report back to you. The nitric acid is yellow due to dissolved NO2. This shouldn't have any ill effects right?

quicksilver - 22-4-2010 at 06:35

The best I've used was toilet tissue from a VERY plain-wrap off brand. That went into nitration damn well and it was easy to measure. You'd pull the tube out and weigh, then use a sharp knife to cut what you need & the accuracy is pretty fine.
I've tried or read about just about everything someone attempted to nitrate. The most unique was horn from sheep to make picric acid. I tried it and it really works but you have to deal with a smell that would curl your hair. There is also a prep that needs to be followed. Wool is easier but still stinks but the picric acid is of a very standard quality.

Nitrating raw cotton is really interesting if you can get it. It appears to work well but has "weight" to it, that refined cotton does not have. Paper-pulp also has the same quality to it. It seems "heavy" and burns very, very fast and fierce.

The WiZard is In - 22-4-2010 at 06:35

Quote: Originally posted by rrkss  
I am running into problems nitrating cotton. I am running the nitration of 0.5 g of cotton (certified 100% cotton) using 10 mL of 96.5% H2SO4 and 5 mL of 52% HNO3. This is done in a 50 mL beaker and not cooled down by ice or anything. I let this cotton sit in the solution for 10 minutes and stir every minute. After that I rinse in tapwater and neutralize with baking soda.

When the cotton dries, it burns like regular cotton. Any ideas why this is happening?


This from a page removed from a chemistry book by
me maybe 50 years ago. It has been kitchen tested
a number of times.

In a 250-cc beaker mix carefully [For saftey
sake do as you ought'r - add the acid to the water.], exactly
10 cc of water 68 cc. of concd. sulfuric acid, and 30 cc. of concd. nitric
acid. Cool the solution to 30o and introduce 1 g of absorbent
cotton, in a single piece. Stir the mixture from time to time
and maintain at a temperature of 30o for twenty minutes.
At the end this time remove the nitrate cotton by means
of a glass rod and transfer immediately to a large volume of
cold water. Wash thoroughly with cold water, and finally
warm water, until washings do not show an acid reaction
to litmus paper. Squeeze ad dry as possible and spread out
to dry in the air, at room temperature. The product
obtained in this way contains about 11.0 per cent nitrogen.

NB - The litmus test is close to useless. If you intend (though
I don't know why you would) store it. Either boil it for several
day changing water several times or treat it with urea.

I recommend doing this out of doors, the fumes \
emitted are annoying.

Checking Google.com/books, I believe this was extracted
from Laboratory experiments in organic chemistry
By Roger Adams, John Raven Johnson, Charles F. Wilcox.
Numerous editions.

[Edited on 22-4-2010 by The WiZard is In]

simply RED - 22-4-2010 at 07:09

50% HNO3 is not concentrated enough for nitration! You may get some material (poorly nitrated) but no way to get decent yield. Use at least 65%! I was disappointed from the yields with 65% too, by the way!

Use 65-90% HNO3 and 98%H2SO4. 1 volume part HNO3 - 1.5 volume parts H2SO4. 1 gram cellulose - 10 ml mixed acids. 12-15 degrees celsius ; 20-25 minutes nitration. Works fine, tried hundred times!

50% HNO3 is like NOx smelly water - useless for nitration

hissingnoise - 22-4-2010 at 07:20

Yes, if you're preparing NC it's as well to cram in as many NO3s as possible.
Collodion isn't enough!
Use the strongest mixed acid. . .

rrkss - 22-4-2010 at 07:50

ok, then I will redistill my acid with H2SO4 and boost the concentration up. I will report on my results when I am finished. Thanks for the responses.

The WiZard is In - 22-4-2010 at 08:12

Quote: Originally posted by hissingnoise  
Yes, if you're preparing NC it's as well to cram in as many NO3s as possible.
Collodion isn't enough!
Use the strongest mixed acid. . .



For the highest degree of nitration - phosphoric acid is
added to the brew (it serves the same purpose as the
H2SO4 - removing water). There is another method, however,
I have to hit la road so I'll post it latter.

hissingnoise - 22-4-2010 at 08:48

Phosphoric? You mean its anhydride?
H2SO4 is fine - or Ac2O in my dreams. . .



The WiZard is In - 22-4-2010 at 14:43

Quote: Originally posted by hissingnoise  
Phosphoric? You mean its anhydride?
H2SO4 is fine - or Ac2O in my dreams. . .



Good catch— and the crowd goes wild.

TWENTY YEARS' PROGRESS IN EXPLOSIVES

[With 9 plates.]
By OSCAR GUTTMANN, M. Inst. C. E., F. I. C., F. C. S.
ANNUAL REPORT SMITHSONIAN INSTITUTION. 1908
Reprinted, by permission, with abridgment by the author, from Journal of the
Royal Society of Arts, London, Nos. 2927, 2928, 2929, Vol. LVII, December
25, 1908, January I and 8, 1909, and from volume " The Manufacture of
Explosives. Twenty Years' Progress." Whittaker & Co., London and New
York, 1909.

It was somewhat of a surprise when Arthur Hough, of New York, [British
patent No. 12627, of 1904.] announced that he could nitrate starch so as to
contain at least 16 per cent of nitrogen. You will remember that Hoitsema ["
Zeitschrift ftir angewandte Chemle," 1898, p. 273.] has already studied the
possibility of producing higher cellulose nitrates than hexanitrocellulose by
keeping up the strength of the acid with phosphoric anhydride. Hough seems
to have found the practical solution. This nitro-starch has been utilized in the
manufacture of smokeless powders, and I understand that it is used to a
certain extent in the United States Army.


However, I was not completely wrong, just incomplete.

This from Ullmann's 5th ed (I cannot afford the current ed.)

A5 430
The nitric acid/phosphoric acid system is of special interest
in a 1:1 ratio with 2.5% phosphorus pentoxide added, with
winch an almost completely nitrate product of great stability
was achieved. (14.08 - 14.14 % Nitrate content.)

... nitric acid/acetic acid/acetic anhydride system in a
ratio of 43:32:25 at 0o C. 14.08-14.14.

NC using magnesium nitrate (11.9% N) see US Patents
2 776 9656 and 3 063 981.

N2O5 14.14%
N2O5 in CCl4 14.14
HNO3 in nitromethane 14.0
&c., &c.


/djh/
The Chymists are a strange Class of Mortals, impelled
by an incomprehensible Impulse to take their Pleasure
amid Smoke and Vapour, Fume and Flame, Poison and
Poverty - Yet among all these Evils, I seem to live so
sweetly that may I die if I would change places with the
Persian King! Johann Beccher
Physica Subterranea, 1703

hissingnoise - 23-4-2010 at 03:18

There's also the handy expedient of using a large excess of MA and swirling until the cows come home. . .