SHlTnipplesmadeofeggs - 1-10-2018 at 06:48
I know I know there are a ton of posts on this, but here's yet another.
TL;DR Nitration of cellulose using acid + nitrate salt yielded less NC than starting C. What gives?
First of all, I read through and used the instructions in the paper in the 1st reply here.
1.5 moles of nitrate (NH4NO3) per hydroxyl group of organic material (cellulose, so 9 mols to 1 mol) was used. I don't remember the exact calculations
but I do remember 50g of cellulose was used in the form of cotton balls. A rather large jar with a replaceable lid was used which allows you to shake
every so often since a magnetic stirrer wasn't available (it's still in the construction phase)
The nitrate salt was added to about 500ml of H2SO4 (Rooto so presumable around 93%) cooled in freezer and cooled in between additions in a ice/NaCl
bath in the freezer. The cap of the jar prevents most smell from NOx and of course temp helps too.
50g of cellulose was added, and as you can imagine and was expected, there wasn't enough liquid to effectively cover everything. As per the paper
frozen distilled water was added (about 150ml) since the paper says that the H2SO4 could be diluted down to around 70% and that for some compounds
there may even be an advantage to this.
The cellulose still wasn't completely covered so an unmeasured amount of sulfuric acid was added until it was.
After it cooled again from the addition of the cellulose, the jar was left to rise to room temperature and the cellulose sat in the nitrating mix for
close to 24 hours, with periodic shaking.
The jar was placed back in the freezer to cool and then the contents were dumped into a strainer with something to catch the acid so it could be
reused (rather large excess of H2SO4). The now NC was rinsed and neutralized and so on..
Here is where the bewilderment comes in, once it was neutralized and squeezed as dry as possible, the damp ball was weighed - 50g. Wtf? It was then
picked apart and dried. Several pieces were tested (not sure of the weight). They burned with almost no residue (a really small amount). After drying
and burning a bit, the product was weighed - 20g.
I don't understand how this would happen? Was it nitrated too long and was destroyed/dissolved in the acid bath? The product was good, but I expected
the yields to be higher than the starting amount.
This is still a continuing trial, as afterwards, using the recycled acid that should still have nitronium ions floating around, 15g more cellulose was
added. Same process was used except for a 6-8 hour nitration at room temp with virtually no shaking as the experimenter was sleeping.
It was weighed after neutralization as a damp ball and it came out to 14g. It's currently being dried and I will report back what the experimenter
tells me.
What do you all think the problem could be here? I could understand the experimenter getting a product without all the hydroxyls being replaced, but I
don't understand how they could get less NC than the C that was put in. There was a very small amount stuck to the screen that was so small that it
both was not easy to remove and not worth the effort, but that amount would've measured at most at 500mg.
I will report back once the second product has dried on whether it is fully/mostly nitrated and depending on its nitrogen content more cellulose may
be added, or more nitrate salt may be added to see how much the acid can be recycled so as to document this for anyone else who may want to take try
recycling the acid.
Herr Haber - 2-10-2018 at 03:28
Did you take the cotton balls straight from their packet and into the nitration bath ?
Any impurities will get oxydized. You'll lose N and therefore have a reduced yield. And if the temperature climbs hight enough your yield will suffer
even more.
SHlTnipplesmadeofeggs - 2-10-2018 at 10:20
I'm thinking it's the length of nitration as I put some old, partially nitrated NC from my very first attempt and let it sit overnight/part of the
morning. When I poured it out, the acid had turned yellow (who knows) and when I went to rinse what I thought was NC, it turns out whatever it was was
water soluble and went down the drain. The screen was rather fine so I don't think it simply slipped through it.
Still confused as to what exactly happened. Could the cellulose have been broken down into glucose? That would explain the lost material. But I think
on my next trial I will definitely nitrate for a shorter period of time and see how recycling the acid does with that.
Herr Haber - 3-10-2018 at 02:59
30mn should be more than enough. The yellow color is due to Nitrogen oxides. They may be responsible for oxidizing your cellulose.
Get Urbansky's books from the library. 60 pages alone on the choice of cellulose. A lot more about it's nitration 