APPENDIX 459 



The sample of paper to be examined is disintegrated, as described above, to 

 such a degree that individual fibers are obtained. This pulp is dried, a large drop 

 of the reagent is placed upon a slide and a little of the dried pulp is introduced 

 into the drop and evenly distributed; a cover glass is carefully laid upon the drop, 

 pressed down gently and the preparation examined under the microscope. 1 



Chlorzinc iodide stains fibers as follows: 



A. RED (Red, Wine red, Violet-red, Brownish pink, Pink.} = Cotton and 



Linen rags, bleached hemp, bleached manila. 



B. BLUE (Dark blue, Light blue, Violet-blue, Blue-violet). = Chemical wood; 



bleached straw, jute, esparto, adansonia. 



C. YELLOW (Greenish yellow, Lemon yellow, Golden yellow, Dark yellow, 



Brownish) = Mechanical wood; raw straw, jute, manila, esparto, ramie, 

 flax. (The larger the amount of lignin (ligno-cellulose, lignone) the 

 yellower will be the preparation.) 



VH. OIL IMMERSION OBJECTIVES AND DARK-FIELD ILLUMINA- 

 TION. See pages 37-46. For specific instructions see Bulletin Board. 



VIII. HANDLING SMALL AMOUNTS OF MATERIAL. 



1. Decantation. page 278. (a) Dissolve a tiny fragment of an aluminum salt 

 in a drop of water, precipitate with NH 4 OH. Decant. 



(b) Precipitate AgCl from a drop of AgNO 3 acidified with HNO 3 , using HC1. 

 Decant. 



(c) Precipitate BaSC>4 from Bads acidified with HC1, using HzSO*, warm gently. 

 Decant. 



2. Filtration. Filter drops prepared as indicated in i, a, b, c, using both the 

 methods of filtration described on pages 285-288. 



3. Sublimation. (a) Make a series of fractional sublimations of Benzoic acid 

 and study the fractions under the microscope. 



(b) Fractionally sublime Phthalic anhydride. Study the fractions under the 

 microscope. 



(c) Make a mixture of approximately equal parts of Benzoic acid and Phthalic 

 anhydride. Fractionally sublime and carefully study the fractions. 



1 The Paper Testing Committee of the Technical Association of the Pulp and 

 Paper Industry gives the following directions for adjusting the Herzberg reagent: 

 " Make up a mixture of about equal parts of bleached soda pulp, bleached sul- 

 phite pulp and rag filter paper .... If the stain is correct then the soda pulp 

 should show a dark blue color, .... the sulphite pulp should show a light blue, 

 .... and the rag fibers will show a red or wine red." If the blue color is more 

 of a violet than a blue, water should be added, a few drops at a time, to the mixed 

 reagent until a pure blue color is obtained with the soda pulp. 



See Clark, F. C.: Paper Testing Methods; Tappi Publishing Corp., N. Y., 1920. 

 Sutermeister, E.: Chemistry of Pulp and Paper Making. Wiley & Sons, N. Y., 

 1920. 



