254 Cellulose 



acetylation, which is a measure of the OH groups rendered 'free' 

 or reactive by the process. A systematic series of observations 

 embracing these points would be a useful contribution to our 

 knowledge. 



1 Toughening ' Action of Nitric Acid upon Papers. The student 

 should read the original paper of Francis (J. Chem. Soc. 47, 183) 

 and repeat his observations on the toughening of filter paper by 

 this process. 



Preparation of Hydrocellulose. This reaction may also be 

 studied by the student statistically. A given weight of a pure 

 bleached cellulose fabric, preferably in the form of rag, is exposed, 

 in the air-dry condition, to hydrochloric acid gas in a closed vessel. 

 The reaction is complete when the fabric breaks down on slight 

 pressure to an impalpable powder. It may, however, be more 

 conveniently washed in the original form of cloth, which it will 

 retain sufficiently notwithstanding the disintegration which has 

 taken place to withstand a current of wash water, carefully ad- 

 mitted to the bottom of the vessel. The product when pure may 

 be dried and weighed, and its properties and reactions determined. 



The student should convert the product into the corresponding 

 nitrates. One part of the product (dried at 105 C. and cooled in 

 a dry atmosphere) is gradually stirred into 5 parts of concentrated 

 nitric acid (HNO 3 of i'5 sp.gr. and colourless). The gummy solu- 

 tion of the nitrate may be treated in various ways for the separa- 

 tion of various products. 



(a) It may be diluted with a small proportion of water, gradually 

 stirred in so as to keep the product dissolved ; the solution then 

 poured on to a glass plate, and the acid evaporated at a temperature 

 of 40 C. in a free draught of air. The product is then washed, and 

 detached as a film from the glass. 



(b) The concentrated or somewhat diluted solution may be 

 poured into water or spread on a glass plate, which is then plunged 

 beneath water contained in a suitable vessel. 



(c) The precipitation may be effected by sulphuric acid the 

 acid being added drop by drop to the concentrated solution, or 

 the solution poured into the sulphuric acid. In either case the 

 mixture must be carried out without sensible rise of temperature. 



Preparation and Diagnosis of Oxycelluloses. The student of 

 cellulose technology will find it necessary to study the original 



