A solution of ammoniacal cupric oxid is one of the best solvents for cellulose. The solution should contain from ten to fifteen per cent of ammonia and from two to two and a half of cupric oxid. In the preparation of this reagent, ammonium chlorid is added to a solution of cupric salt and then sodium hydroxid in just sufficient quantity to precipitate all of the copper as hydroxid. The precipitate is well washed on a linen filter, squeezed as dry as possible and dissolved in ammonia of 0.92 specific gravity. The cellulose is readily precipitated from the solution in cuprammonium by the addition of alcohol, sodium chlorid, sugar, or other dehydrating agents. Solutions of cellulose are used in the arts for many purposes.[225] =275. Qualitive Reactions for Detecting Cellulose.=—Cellulose may be identified by its resistance to the action of oxidizing agents, to the halogens and to alkaline solutions. It is further recognized by the sirupy or gelatinous solutions it forms with the solvents mentioned above. The cellulose hydrates precipitated from solutions have in some instances the property of forming a blue color with iodin. A characteristic reaction of cellulose is secured as follows: To a saturated solution of zinc hydrochlorate, of 2.00 specific gravity, are added six parts by weight of potassium iodid dissolved in ten parts of water and this solution is saturated with iodin. Cellulose treated with this reagent is at once stained a deep blue violet color.[226] For the characteristics of cellulose occurring in wood the researches of Lindsey may be consulted.[227] =276. More Rarely Occurring Carbohydrates.=—It is not possible here to give more space to the rarer forms of carbohydrates, to which the attention of the agricultural analyst may be called. Nearly a hundred kinds of sugars alone have been detected in the plant world. For descriptions of the properties of these bodies and the methods of their detection and determination, the standard works on carbohydrates may be consulted.[228] AUTHORITIES CITED IN PART THIRD. [170] Vines; Physiology of Plants. Nägeli; Beiträge zur näheren Kenntniss der Stärkegruppe. [171] Bulletin 5, Department of Agriculture, Division of Chemistry, pp. 191 et seq.: Bulletin 25, New Hampshire Experiment Station. [172] Spencer; Handbook for Sugar Manufacturers, p. 31. [173] Vid. op. cit. supra, pp. 102, 108. [174] Journal of the American Chemical Society, Vol. 16, p. 677. [175] Botanical Gazette, Vol. 12, No. 3. [176] Bulletin de l’Association des Chimistes de Sucrerie et de Distillerie, Tome 13, p. 133. [177] Journal of Analytical and Applied Chemistry, Vol. 4, p. 381. [178] Spencer’s Handbook for Sugar Manufacturers, pp. 30 et seq. [179] Bulletin de l’Association des Chimistes de Sucrerie et de Distillerie, Tome 13, p. 292. [180] Vid. op. cit. supra, Tome 2, p. 369. [181] Dosage du Sucre Cristallisable dans la Betterave, pp. 117 et seq.: Journal of the American Chemical Society, Vol. 16, p. 266.