Experimental and Applied 263 



coal-tar dyes in great variety (simply dyeing or staining phe- 

 nomena). 



(2) Solutions of the Lignocelluloses. In cuprammonium, in zinc 

 chloride (saturated aqueous solution), and zinc chloride in HC1 ; 

 partial solution under the thiocarbonate reaction. This reaction 

 should be carefully followed up with the microscope, more 

 especially the extraordinary combination which takes place with 

 water on covering the fibre, after the reaction, with water. 



(3) Hydrolytic Agents. (a) Concentrated solutions of caustic 

 soda (10-25 P- ct ' NaOH) in the cold. This reaction should 

 be studied quantitatively, and should be also followed up with a 

 microscopic observation of the fibre under action. 



(b] Dilute alkali solutions. These constants, quantitatively 

 determined in terms of loss of weight, are important. The usual 

 conditions are a I p.ct. solution of caustic soda in large excess ; the 

 specimen being boiled for 10 minutes, and a second for 60 minutes, 

 keeping the volume of the solution constant. The fibre is then 

 washed off and treated with a little dilute hydrochloric acid, again 

 washed, and dried. 



(c) Dilute acids. The observation of the action of boiling 

 dilute sulphuric acid (i p.ct. H.^SO,) is of use in differentiating 

 one lignocellulose from another. The fibre may be boiled for 60 

 minutes with an excess of I p.ct. acid, keeping the volume of 

 the solution constant. The fibre is washed free from acid, dried, 

 and weighed. 



(4) Cellulose Estimations. On this subject see Cross and 

 Bevan, J. Chem. Soc. 1882. The following methods should be 

 worked : 



(a) Bromine method. The fibre is boiled in dilute alkali, washed, 

 and placed in saturated bromine water and left for some hours, 

 afterwards washed and boiled in dilute ammonia. The fibre is 

 then washed and returned to the bromine water, and again boiled, 

 after digestion, in ammonia. The treatment is repeated so long 

 as any residues of a yellow colour are seen in the boiling alkaline 

 solution. The cellulose is finally washed with dilute acid and then 

 with water, dried, and weighed. 



(b) Chlorine method. This involves not only a determination 

 of cellulose, but of the amount of chlorine disappearing in reaction, 

 and also the amount of hydrochloric acid (Read, Cross, and 



