GENERAL MICROSCOPY 



Table 1. Stains for Pulps (Graff C) 



Besides the C stain, stain A as modified by Sutermeister can also be used. This stain is obtained by 

 mixing 45 ml of solution II from stain C with 5 ml solution IV from stain C and storing this in a dark 

 colored bottle, a crystal of I2 being added. Table 2 shows the colors that then occur for the various 

 pulps. In appraising these, however, Graff's color chart is important. 



percentage alongside the other rag fibers. 

 Only large, hardly damaged pieces of flax 

 are clearly recognizable from the displace- 

 ments. It is usually more difficult to identify 

 hemp fibers in paper from their morphologi- 

 cal characteristics. The fiber tends very 

 greatly to fibrillation and little can be seen 

 of the large lumen. For the characteristics 

 of the fibers when unpulped or only slightly 

 pulped see the section on the Morphology 

 of Textile Fibers, p. 350. 



Hard Wood Pulp. The hard woods used 

 for pulp are chiefly poplar, birch, eucalyptus 

 and beech. Chestnut, maple, willow and ash 

 are used to a less extent. Hard wood pulp 

 consists of vessels, vascular tracheides, fiber 

 tracheides, libriform fibers and parenchyma 

 constituents. In the eucalyptus there are also 

 secretion canals. In pulp it is often difficult 

 to distinguish the various parts. Character- 

 istics distinguishing them from other pulps 

 are mainly the large vessels. As far as the 



paper industry is concerned it is usually of 

 importance only to know whether a pulp 

 consists of hard wood or soft wood. Further- 

 more, in the case of a mixed pulp the per- 

 centage of hard wood usually has to be de- 

 termined. The type of hard wood is less 

 important. 



Beech (Fagus sijlvatica). The large vessels 

 are usually fairly long and vary in width 

 from 18 to 80 n. The ends are cut off ob- 

 liquely and are usually digitaliform at one 

 end. The pits are easy to see. The thinner 

 vessels are usually scalariform. The number 

 of scalar rings is 6 to 20. Sometimes the rings 

 are broken, but even with fairly thorough 

 pulping they can still be identified. The types 

 of pits are: 



(1) Simple (small, scattered in medulla) 



(2) Bordered (close together and small — 

 the "border" is usually difficult to distin- 

 guish). 



(3) Large medulla (closely defined and in 

 rows). 



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