Gun Cotton
Guncotton Henri Braconnot discovered in 1832 that nitric acid, when combined with starch or wood fibers, would produce a lightweight combustible explosive material which he named xyloïdine. A few years later, 1838 another French chemist Théophile-Jules Pelouze (teacher of Ascanio Sobrero and Alfred Nobel) treated paper and cardboard in the same way. He obtained a similar material he called nitramidine. Both substances were highly unstable, and were not practical explosives.
Christian Friedrich Schönbein, a German-Swiss chemist, discovered a more practical solution around 1846. As he was working in the kitchen of his home in Basle, he spilled a bottle of concentrated nitric acid on the kitchen table. He reached for the nearest cloth, a cotton apron, and wiped it up. He hung the apron on the stove door to dry, and as soon as it was dry there was a flash as the apron exploded. His preparation method was the first to be widely imitated - one part of fine cotton wool to be immersed in fifteen parts of an equal blend of sulfuric and nitric acids. After 2 minutes , cotton was removed and washed in cold water to set the esterification level and remove all acid residue. It was then slowly dried at a temperature below ~ 100°C.
The process uses the nitric acid to convert the cellulose into cellulose nitrate and water:
2HNO3+ C6H10O5 → C6H8(NO2)2O5 + 2H2O
The sulfuric acid is present to prevent the water produced in the reaction from diluting the concentrated nitric acid.
ENG: Nitrocellulose.
Nitrocellulose (also: cellulose nitrate, flash paper) is a highly flammable compound formed by nitrating cellulose through, for example, exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton.
The power of guncotton made it suitable for blasting. As a projectile driver, it has around six times the gas generation of an equal volume of black powder and produces less smoke , less heating. However the sensitivity of the material during production led the British, Prussians and French to discontinue manufacture within a year.
Further research indicated that the key is the very careful preparation of the cotton: unless it was very well cleaned and dried, it was liable to explode spontaneously. The British, led by Frederick Augustus Abel, also developed a much lengthier manufacturing process at the Waltham Abbey Royal Gunpowder Mills, patented in 1865, with the washing and drying times each extended to 48 hours and repeated eight times over. The acid mixture was also changed to 2 parts sulfuric acid to 1 part nitric.
Guncotton remained useful only for limited applications. For firearms, a more stable and slower burning mixture would be needed. Guncotton-like preparations were eventually prepared for this role, known at the time as smokeless powder.
Guncotton, dissolved at approximately 25% in acetone, forms a lacquer used in preliminary stages of wood finishing to develop a hard finish with a deep luster. It is normally the first coat applied, sanded, and followed by other coatings that bond to it..
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Nitratul de celuloza (Fulmicoton sau Piroxilina)
Obtinere
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Substante necesare:
- 1 parte celuloza (Vata higroscopica)
- 0,89 parti Acid azotic
- 3,26 parti acid sulfuric
Amestecul acizilor se face pe o baie de gheata, mentinindu-se o temperatura
de ÷20øC (se toarna acid sulfuric peste acid azotic agitinduse continuu).
Dupa ce s-a pregatit solutia , se raceste complet cu gheata, dupa care se
adauga celuloza. Se ridica temperatura amestecului la 60-70 øC, si se
amesteca continutul cu ajutorul unei baghete de sticla. Dupa ÷10 minute se
scoate vata, se soala cu apa rece, se usuca pe hirtie de filtru si apoi intr-o
capsula de portelan asezata pe o baie de apa la fierbere.
Contine 13-13,6% azot, este o substanta exploziva, deoarece arde intr-un timp
foarte scurt si degaja o mare cantitate de gaze. Se foloseste ca exploziv de
mina.
Reactia are loc in prezenta de acid sulfuric ce are rolul deshidratarii:
H2SO4 | / ONO2 |
[C6H7O2(OH)3]n + 3n HONO2 —–> | C6H7O2 — ONO2 |
| \ ONO2 |n
