“Nitrocellulose–cellulose’s combustible sibling” experiment

How to make cotton wool burn in a few seconds

In this in­ter­est­ing and dan­ger­ous ex­per­i­ment, we will re­veal an­oth­er se­cret of ma­gi­cians – how do they set fire to cot­ton wool in their hands with­out get­ting burnt?

Safe­ty pre­cau­tions

Wear pro­tec­tive gloves, a mask and glass­es, and work in a well-ven­ti­lat­ed room. Ob­serve safe­ty rules when work­ing with con­cen­trat­ed acids, fire and flammable sub­stances.

Warn­ing! Don’t try to re­peat this ex­per­i­ment at home. This ex­per­i­ment is sup­posed to be con­duct­ed only by a pro­fes­sion­al.

Reagents and equip­ment:

  • cot­ton wool;
  • con­cen­trat­ed ni­tric acid;
  • con­cen­trat­ed sul­fu­ric acid;
  • ice;
  • tweez­ers;
  • con­cen­trat­ed so­lu­tion of sodi­um bi­car­bon­ate;
  • beaker;
  • lighter;
  • two glass bowls.

Step-by-step in­struc­tions

Put ice in the first glass bowl, and place a beaker in which we put the cot­ton wool, then pour sul­fu­ric and ni­tric acids in the ra­tio of 2:1. Wait 30 min­utes. Then move the ni­tro­cel­lu­lose that has formed to the sec­ond glass bowl, which is filled with the so­lu­tion of sodi­um bi­car­bon­ate, to neu­tral­ize the re­mains of the acid. Wring out the ni­tro­cel­lu­lose and leave to dry for about half an hour. Light it.

Pro­cess­es de­scrip­tion

Cot­ton wool main­ly con­sists of cel­lu­lose, a nat­u­ral poly­mer from which a very in­ter­est­ing sub­stance can be ob­tained – ni­tro­cel­lu­lose, which is a com­plex ether of cel­lu­lose and ni­tric acid. For ex­am­ple, it is used to make ping pong balls, and is found in ex­plo­sive mix­tures, smoke­less gun­pow­der, and is used by ma­gi­cians as a swift-burn­ing com­po­nent. It was also used in the past as a mount for cam­era and cin­e­ma film, but be­cause of its flamma­bil­i­ty it was re­placed by safer ma­te­ri­als.

It burns up so quick­ly that it doesn’t burn the hand, but non-pro­fes­sion­als should still not at­tempt this ex­per­i­ment:

(C₆H₁₀O₅)n + HNO₃ + H₂­SO₄ = [C₆H₇(NO₂)₃O₅]n + H₂­SO₄ + nH₂O

Sul­fu­ric acid acts as a de­hy­drat­ing agent and cat­a­lyst of this re­ac­tion.