754 



GUN-COTTOST 



GUST-WOOD. Eucalyptus piperata, or blue-gum tree of New South Wales. The 

 wood is sent over in large logs and planks; the colour of dark Spanish mahogany, 

 with a blue and sometimes a greyish cast. See EUCALYPTUS. 



GUN BARRELS. See FIRE ARMS. 



GUN COTTON. (Syn. Pyroxylins ; Fitlmicoton, Fr.) In 1833 M. Braconnot 

 discovered that starch, by the action of monohydrated nitric acid, became converted 

 into a peculiar substance which dissolved in excess of the acid, and was re -precipitated 

 ina gramilar state on the addition of water. This substance, known as xyloidine, 

 when washed and dried, was found to explode on contact of a light, and even if heated 

 to 356. It also exploded if subjected to a smart blow. The subsequent researches of 

 31. Pelouze indicated this singular body to be starch, C 12 H'0 10 (C fi H'O 5 ), in which 

 one equivalent of hydrogen is replaced by peroxide of nitrogen, or hyponitric acid. 



The formula of xyloidine would consequently be ^Q 4 lo 10 [C fl H 1) (iro 2 )O 5 ]. On 



the supposition of this being the correct formula, 100 parts of starch should yield 1277 

 of xyloidine, and M. Pelouzo obtained from 128 to 130. About thirteen years subse- 

 quently to the discovery of-xyloidino, M. Schonbein announced his discovery of gun- 

 cotton. Chemists immediately saw the analogy between the two substances, for while 

 xyloidine appears to be 'derived from starch by the substitution of one equivalent of 

 hyponitric acid for one of hydrogen, gun-cotton is derived from cellulose, C I2 H I0 10 

 (C b H'O 3 ), isomeric with starch, by the substitution of two or three equivalents of 

 hyponitric acid for the same number of equivalents of hydrogen. 



4 ounces pure dry nitre in fine powder. 



30 drams (fluid measure) sulphuric acid, sp. gr. 1'845. 



120 grains of well-carded cotton. 



The cotton is to be well pulled out and immersed in the mixture of the nitre and 



