The penta-nitrate may be obtained in a pure state by the following process, devised by Eder:--The gun-cotton is dissolved in concentrated nitric acid at 90 deg. C., and reprecipitated by the addition of concentrated sulphuric acid. After cooling to 0 deg. C., and mixing with a larger volume of water, the precipitated nitrate is washed with water, then with alcohol, dissolved in ether-alcohol, and again precipitated with water, when it is obtained pure. This nitrate is soluble in ether-alcohol, and slightly in acetic acid, easily in acetone, acetic ether, and methyl-alcohol, insoluble in alcohol. Strong potash (KOH) solution converts into the di-nitrate C_{12}H_{18}O_{8}(NO_{3})_{2}. The hexa-nitrate is not soluble in acetic acid or methyl-alcohol. The lower nitrates known as the tetra- and tri-nitrates are formed together when cellulose is treated with a mixture of weak acids, and allowed to remain in contact with them for a very short time (twenty minutes). They cannot be separated from one another, as they all dissolve equally in ether-alcohol, acetic ether, acetic acid, methyl-alcohol, acetone, amyl acetate, &c. As far as the manufacture of explosive bodies is concerned, the two forms of nitro-cellulose used and manufactured are gun-cotton or the hexa- nitrate (once regarded as tri-nitro-cellulose), which is also known as insoluble gun-cotton, and the soluble form of gun-cotton, which is also known as collodion, and consists of a mixture of several of the lower nitrates. It is probable that it chiefly consists, however, of the next highest nitrate to gun-cotton, as the theoretical percentage of nitrogen for this body,. the penta-nitrate, is 12.75 per cent., and analyses of commercial collodion-cotton, entirely soluble in ether-alcohol, often give as high a percentage as 12.6. We shall only describe the manufacture of the two forms known as soluble and insoluble, and shall refer to them under their better known names of gun-cotton and collodion-cotton. The following would, however, be the formulae[A] and percentage of nitrogen of the complete series:-- Hexa-nitro-cellulose C_{12}H_{14}O_{4}(NO_{3})_{6} 14.14 per cent. nitrogen. Penta-nitro-cellulose C_{12}H_{15}O_{5}(NO_{3})_{5} 12.75 per cent. nitrogen. Tetra-nitro-cellulose C_{12}H_{16}O_{6}(NO_{3})_{4} 11.11 per cent. nitrogen. Tri-nitro-cellulose C_{12}H_{17}O_{7}(NO_{3})_{3} 9.13 per cent. nitrogen. Di-nitro-cellulose C_{12}H_{18}O_{8}(NO_{3})_{2} 7.65 per cent. nitrogen. Mono-nitrocellulose C_{12}H_{19}O_{9}(NO_{3}) 3.80 per cent. nitrogen. [Footnote A: Berthelot takes C_{24}H_{40}O_{20} as the formula of cellulose; and M. Vieille regards the highest nitrate as (C_{24}H_{18}(NO_{3}H)_{11}O_{9}). _Compt. Rend._, 1882, p. 132.]