42 TESTING MISCELLANEOUS SUPPLIES. 



by precipitation with barium chlorid. Dissolve the insoluble residue in hydro- 

 chloric acid and determine iron as described in the preceding section. Or, in 

 case the small amount of platinum (which always goes into solution when 

 iron oxid is dissolved by hydrochloric acid in platinum) causes trouble with 

 the potassium dichromate method, add sulphuric acid, evaporate to fumes, 

 dilute, reduce with zinc, and titrate with potassium permanganate. 



6. Keeping in Ink Wells. 



Allow the bottle of ink to stand perfectly still at room temperature for three 

 days. Carefully remove the stopper without shaking the bottle and draw out 

 about 50 cc with a pipette from the middle of the bottle. Filter this through a 

 <n\v paper, exposing as little as possible to the air, and place 25 cc of the filtrate 

 in a clear glass bottle 140 mm high and 56 mm in diameter, with a neck 32 mm 

 in diameter (an 8-ounce salt-mouth bottle). Cover the top of the bottle with 

 a piece of filter paper, using a small amount of mucilage or paste to fasten the 

 paper firmly across the neck. Let it stand at room temperature and in ordinary 

 daylight in a room free from acid or ammonia fumes for fourteen days, observ- 

 ing from day to day whether mold or any film on the surface forms, and whether 

 any sediment forms on the walls or bottom of the bottle. 



7. Action on Steel Pens. 



Immerse steel pens in the ink and leave them there for seven days. Remove 

 the pens each day, clean them and note whether the metal appears corroded; 

 also whether the ink has become thick. 



8. Streak Tests. 



Procure a supply of uniform good quality white all rag writing paper in sheets 

 2G5X200 mm. Stretch the paper on a smooth board inclined at an angle of 45 

 :m<l let about 0.6 cc of the ink flow from a tube held vertically near the top 

 edge of the paper. For this purpose use a tube -of approximately 3.5 mm bore 

 and 250 mm in length, with a mark 62 mm from the lower end. By drawing 

 (In- ink up to the mark and allowing what will flow out to pass over the paper, 

 uniform streaks can be made. Make streaks with the undiluted inks, and with 

 il ic inks diluted with an equal volume of water. Allow to dry and cut into a 

 number of strips. 



9. Penetration and Fluidity. 



The ink should ponotrnto into the fibers of the paper, but should not pass 

 through ^. This can be best observed on the streaks made for exposure tests. 

 Stickiness should also be observed, and by carefully making the streaks and 

 < MIII|,.IT in- M very good idea of the fluidity can be formed. A normal ink should 

 give an o\;il head to the slteak and the rest should be nearly uniform in width; 

 a very fluid ink gives a wide head and rapidly narrows down. 



10. Resistance to Sunlight and Reagents. 



Cover half of some of the strips with black paper, clamp under glass in a 

 photographic frame, and cxj>ose to sunlight. Expose other strips to the weather 

 uncovered mid keep some strips in ditfnsed daylight in an atmosphere free from 

 laboratory fumes for eight days. I'sc some of these last strips for the tests 



