38 Cellulose 



cellulose regenerated by saponification retains the film form, 

 shows no tendency to be further hydrolysed by the alkaline 

 solutions used for saponifying, and is unaffected by boiling with 

 alkaline cupric oxide. The analyses of this acetate show satis- 

 factory concordance of numbers with those calculated fora 

 tetracetate : /*[C 6 H 6 O.(O.C 2 H 3 O)4]. 



The specific gravity of this acetate is 1*210. It is soluble 

 in acetone, methyl alcohol, glacial acetic acid, and nitrobenzene. 

 It dissolves in concentrated nitric acid (as do the cellulose 

 acetates generally), and is precipitated on dilution, apparently 

 without change. 



This compound is of ' critical ' value in elucidating the con- 

 stitution of cellulose. If the above formula be established by 

 further and exhaustive investigation, the cellulose ' unit ' must 

 be C 6 H 6 O.(OH) 4 ; this is consistent with a cyclic arrangement 

 of the carbon nuclei, and probably a symmetrical disposition 

 of the OH groups. This question will be referred to subse- 

 quently. 



Cellulose and Nitric Acid. Cellulose Nitrates or 

 Nitro-Celluloses. The action of nitric acid on starch 

 was investigated to some extent by Braconnot in 1833, who 

 found that a very rapidly burning body was produced, and 

 which was called xyloidine. Pelouze further investigated 

 this substance in 1838, and also similar bodies from paper, 

 linen, &c. which he held to be identical with the one 

 from starch. Schonbein is generally credited with the 

 discovery of gun cotton in 1846. It appears to have been 

 almost simultaneously discovered by Bottger, and also by 

 Otto. 



Whenever cellulose, in any form, is brought into contact with 

 concentrated nitric acid at a low temperature a nitro-product, or 

 a nitrate, is formed. The extent of the nitration depends upon 

 the concentration of the acid ; on the time of contact of the 



