CANCELING INKS HAVING AN OIL BASE. 4f 



Reweigh the dish at the end of 18 hours, iM hours, 2 days, 3 days, 4 days, 5 

 days, 6 days, 7 days, 14 days, 21 days, and 2s days. Calculate the total per- 

 centage loss of weight at the end of each period of drying. The loss of weight 

 should be gradual and should not exceed 15 per cent during the first 7 days, 

 nor 25 per cent during 28 days. This test shows the absence of highly volatile 

 ingredients and the absence of an excess of matter volatile at the ordiiuiry room 

 temperature. The constituents of a canceling ink should be such that the vola- 

 tile matter will not exceed the above limits when the ink is exposed under the 

 conditions named to a summer temperature of 80 F. and upward. 



3. Determination of Relative Penetrating Power, 

 (a) APPARATUS. 



(a) Homeopathic shell vials about 8 cm long and 2 to 2.5 cm in diameter. 



(6) Strips of white blotting paper, which for a given series of determinations 

 should be cut from the same sheet and of exactly the same dimensions. A con- 

 venient size is 12 mm wide and 25 cm long. 



(c) A pair of dividers with arms 15 cm long or longer. 



(d) A millimeter rule. 



(b) DETERMINATION. 



Place approximately 5 cc of the ink or other material to be tested in one of 

 the " shell vials " described, and if several samples are to be tested arrange the 

 vials in a row. Place 5 cc portions of distilled water in each of two of the vials, 

 and put one of the vials containing water at each end of the row of vials con- 

 taining samples to be tested. Proceeding from left to right, insert a strip of 

 blotting paper in each of the vials, recording the exact time the paper was placed 

 in each vial. The blotting paper should maintain a nearly upright position. 

 The liquids gradually ascend the strips by capillarity; the strips, however, 

 should be in such a position that the liquid does not ascend by capillarity be- 

 tween the edges of the strips and the sides of the vials. 



At the expiration of exactly fifteen minutes from the time each strip is inserted 

 in the vial, measure the height to which the liquid has ascended the strip of 

 paper by means of a pair of dividers and record the distance in millimeters. 

 Make a second set of readings at the end of forty-five minutes. 



After all of the measurements have been recorded reduce the results to the 

 terms of the penetrating power of distilled water, taking the penetrating power 

 of distilled water as 100. This is accomplished by dividing each result by the 

 average of the results obtained for the distilled water contained in the vials 

 and multiplying the quotient by 100. Ten samples may conveniently be tested 

 at one time by working as described. The method gives good comparative 

 results, and has been applied not only to canceling and other stamping inks, 

 but to the liquids used for the manufacture of these inks. 



In observing the penetrating power of a given sample of ink it is important 

 to remember that the value of a canceling or stamping ink depends upon its 

 power to penetrate the paper during the first minute or fraction of a minute 

 following its application to the paper. It is well, however, to keep the tests 

 under observation for several hours, as information can thus be obtained in 

 regard to the extent to which the coloring matter contained in the ink follows 

 the liquid base of the ink as it passes through the paper. In some cases the 

 coloring matters keep pace with the liquid portions of the ink; in others an 

 uncolored band at the top of the portion of the paper which is wet with the ink 

 shows that the coloring matter does not proceed through the paper as rapidly 



