The Typical Cellulose and the Cellulose Group 27 



cellulose by spontaneous shrinkage, was removed at intervals. 

 Original volume of solution, 100 c.c. 



Time in days 



Coagulation . . 8th day 

 First appearance 

 of liquid . . 



Vol. of cellulose 

 hydrate 



Diff. from TOO c.c. 

 =vol. expressed 



The shrinkage from a 5 p.ct. to a 10 p.ct. coagulum of cellu- 

 lose hydrate is therefore extremely slow and fairly regular ; 

 from 10-12 p.ct. there is considerable retardation; and at 

 12-15 p.ct. the coagulum may be considered as a hydrate, 

 stable in a moist atmosphere. It follows from these observa- 

 tions that if a 10-12 p.ct. solution be allowed to coagulate 

 spontaneously, the resulting cellulose hydrate will undergo very 

 small shrinkage if kept in a moist atmosphere. These obser- 

 vations indicate the uses which can be made of the solution in 

 preparing cellulose casts and moulds. 



As regards the problem of hydration and dehydration of 

 the cellulose there are, of course, other methods of approxi- 

 mately determining the 'force ' by \\hich the water molecules 

 are held. It is a problem of wide significance, by reason of the 

 important part played by such hydrates in the economy of 

 plant life. Further investigations of the problem, therefore, 

 by the various known methods are being prosecuted. 



(ft) Coagulation by heat. The solution may be evaporated 

 at low temperatures to a dry solid, perfectly resoluble in water. 

 If heated at 70-80, however, the solution thickens ; and at 

 80-90 the coagulation, i.e. decomposition, is rapidly com- 

 pleted. If the solution be dried down at this temperature in 



