(140° F.), with 5 parts HNO_{3} is 60 per cent. only, showing that in the process of isolation some of the cellulose itself is attacked and converted into soluble products. Schulze’s method of isolating cellulose from wood, and from the ligno-celluloses generally, consisted in macerating them for 12 to 14 days with 8⁠/⁠10 their weight of potassium chlorate dissolved in 12 parts by weight of nitric acid (sp. gr. 1·10), and completing the resolution by afterwards boiling with dilute ammonia. By the action of a more concentrated acid, 50 per cent. HNO_{3}, at 80° C. (176° F.), a soluble derivative is obtained which has the composition (C_{25}H_{40}NO_{25}). It is a syrupy, highly acid body, dyeing animal fibres a deep yellow shade, and giving with the earthy bases salts of the formula (C_{25}H_{32}NO_{25}M_{4}), which are precipitated by alcohol from their aqueous solution in the form of bright yellow flocks that dry to a yellow powder. _Dilute Alkalis._—The action of boiling dilute solutions of the caustic alkalis upon the ligno-celluloses is similar to that of the dilute acids, viz., purely hydrolytic, causing no essential change in the composition of the fibre substance. _Water at High Temperatures._—The ligno-celluloses undergo a profound modification when heated with water at elevated temperatures. They are to a great extent converted into soluble products, of which a large proportion are the volatile bodies, acetic and formic acids and furfural. The residual fibre is found to be more or less disintegrated, and of a dark-brown colour, but preserving many of the chemical features of the original. A similar disintegration is caused by exposing the ligno-celluloses in a dry state to an atmosphere of superheated steam, the effect being much increased if the ligno-cellulose be previously bleached by any of the ordinary {22} processes, i.e., under oxidising conditions. In these decompositions oxidation, as well as hydration, plays an important part. It is found that the presence of small quantities of reducing agents, e.g., sulphites, exerts a remarkable effect in retarding and often entirely preventing these changes. It is probable that they act in obviating an initial change, which, with a cumulative reaction on the fibre, effects the profound resolutions above described. (See p. 71.)