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THE JOURNAL OF PHARMACOLOGY. 



From the above it may be seen that, even without resorting to chemical 

 means, lignin can with greatest ease and certainty be distinguished from 

 wood-cellulose. 



Fig. 9. Pine wood showing Tracheids, Medullary Rays and Border Pores. 



12. Hop- Fiber. — This is used principally for the fabrication of the finer 

 qualities of papers. In these, however, the individual fibers are so much 

 destroyed that they are made out with difficulty. 



13. Parchment Paper (Vegetable parchment, phyto-parchment, papy- 

 rine, membranoid) examined under the microscope is seen to consist of 

 much swollen fibers (mostly cotton or flax changed into amyloid) which 

 are directly colored blue by iodine. Parchment paper is therefore easily 

 distinguished microscopically from similar papers and products. 



Examination of the Coloring Matters of Paper. 



Chemists usuall)^ employ macroscopic means to detect the coloring 

 matter of colored papers, i. e., by means of reagents that give certain reac- 

 tions with the various pigments. These reactions may be found described 

 in technological works such as Bolley's, Post's and others. The work of 

 J. Erfurt " Das Flirben des Pap ie r s toff es,'^ Berlin, has special reference to 

 the coloring (tinting) of papers, and on page 164 the means of detecting 

 the coloring matters are given. 



When one has to determine the coloring matter of verj'' feebly tinted 

 papers that usually pass for white, it becomes necessary to apply micro- 

 chemical tests ; the same reactions as above, however, are used. 



White papers usually contain some blue coloring matter which occurs 

 either in small granules or as a coloring of the fiber. The smalts, ultra- 

 marine and also Berlin blue exhibit these granules, whereas anilin blue 

 logwood and indigo color the fiber evenly. 



The reactions which indicate what kind of blue is present in the white 

 paper are as follows : 



{a) Berlin- and Paris-blue are destroyed by alkalies. Chlorinated lime 

 does not change the granular coloring matter. 



