456 



ELEMENTARY CHEMICAL MICROSCOPY 



Pyroxylin or Collodion Silk. — (Denitrated Nitro-Cellulose.) Obtained by 

 nitrating cellulose, dissolving in ether-alcohol, filtering and either spinning into 

 filaments or forcing the collodion into water through fine nozzles. The filaments 

 are then denitrated by a suitable compound such as ammonium sulphide. 



Under the microscope the laboratory sample will be found to consist of structure- 

 less transparent flattened filaments, thicker at the edges than at the center. Longi- 

 tudinal striations when present are so faint as to be practically invisible. Edges, 

 straight and smooth. In cross-section the filaments are very irregular in outline, 

 the majority, however, are more or less dumb-bell-like or dumb-bell-like flattened 

 on one side. The filaments polarize strongly and when viewed edgewise give 

 high polarization colors. 



VI. COMMON PAPER FIBERS. 



Papers may be classified as follows: 



B. — Bast fiber papers. 



Linen (including ramie, china grass, etc.) 

 Paper Mulberry (Broussonetia papyrifera) 

 Adansonia (Adansonia digitata) 

 Mitsumata {Edgeworthia papyrifera). 



U. — Palm fiber papers 

 Palmetto 

 Yucca 

 Coconut, etc. 



D. — Grass and Bamboo fiber papers 



Straw (rye, oats, barley, wheat, rice, etc.) 



Maize 



Esparto (alfa grass = Shpa tenacissima) 



Bamboo 



Sugar cane, sorghum. 



E. — Wood fiber papers 



«. 



Coniferous woods. 



Non-coniferous woods . 



spruces 

 firs 

 pines 

 hemlock 



I poplar 

 bass wood 

 birch 



etc., etc. 



r etc., etc. 



J 



