al and Applied 265 



processes. In experiments where sulphuric acid is added as the 

 hydrolysing acid, the solution should be distilled and the volatile 

 acid estimated. 



(e) Alkali oxidations. Study the continued action of hypo- 

 chlorite of sodium and of hypobromite, continuing the action until 

 the specific reactions of the fibre disappear and a residue of 

 cellulose is obtained. 



(/) Sulphite processes. For these the experiments must be 

 conducted in sealed glass tubes or in a lead-lined digester. The 

 fibre is sealed up with 7 or 10 times its weight of a solution of 

 bisulphite of lime, and heated for 8 hours, raising the temperature 

 gradually to 140 in the case of jute, or 160 in the case of woods. 

 The products are thrown out into a dish and the insoluble cellulose 

 filtered off, and the soluble products may be examined for the 

 reactions described on p. 200. If neutral sulphite is used, take a 

 5 p.ct. solution of crystalline salt, and in this case raise to 160. 



(5) Furfural Estimations. --The method used has been subject 

 to extensive investigations, as stated in the text, the details 

 finally adopted being those of Flint and Tollens (Landw. Vers.- 

 Stat. 1893, 42, 381-407). The fibre is boiled with hydro- 

 chloric acid, of i *i sp.gr., in a flask attached to a condenser. 

 The volume is kept constant by the addition of acid of this 

 strength to the flask. The furfural which distils is converted into 

 hydrazone in the neutralised solution, and estimated as such, with 

 careful attention to all the precautions given in the paper above 

 cited. The results are uniform, and the method is an important 

 one for the student to master. 



(6) Methoxyl Determinations. The fibre -substance is boiled 

 with concentrated hydriodic acid. Methyl iodide is formed, and is 

 carried forward by a stream of carbonic acid through a special 

 apparatus. The full details of the method are given in the original 

 paper of Zeisel (Monatshefte f. Chem. 1885, vi. 989), and is also 

 described in Vortmann's Anleitung 2. Chem. Anal. Org. Stoffe. 

 (Leipzig, 1891). This method is of growing importance in the 

 investigation of vegetable substances, and should be thoroughly 

 mastered by the student. 



(7) Nitration. The * nitrating ' acid is a mixture of equal volumes 

 of nitric acid (1-5 sp.gr.) and sulphuric acid (1*83), previously 

 mixed and cooled. The weighed quantity of the fibre-substance, 



