The amount of coloring matter contained in the alcoholic extract can be ascer- 

 tained by spectro-colori metric or by comparative dyeing tests. Both of these meth- 

 ods involve the previous identification of the dyes present by qualitative tests. 



For the quantitative determination of glycerin in canceling inks the Hehner 

 method a was found to be the most satisfactory. In using this method an excess of 

 ferrous ammonium sulphate was added after the completion of the oxidation and 

 this excess determined with standard bichromate solution. In this way a more 

 satisfactory end point was obtained . 



6. RESISTANCE TO LIGHT AND REAGENTS. 



The remarks made above in regard to the investigation of the resistance of cancel- 

 lations made with oil inks apply in general to canceling and other inks for use with 

 rubber stamps. 



III.- METHODS FOR THE INVESTIGATION OF MATERIALS USED FOR 

 THE MANUFACTURE OF CANCELING AND OTHER STAMPING INKS. 



1. VOLATILITY AND PENETRATING POWER. 



The methods which have been described above will be found useful in determin- 

 ing the suitability of liquids for use as bases or constituents of bases of canceling and 

 other stamping inks. 



2. SEDIMENTATION TEST. 



A modification of the sedimentation test described above may be employed with 

 good results for the purpose of ascertaining the suitability of lampblack and other 

 pigments for use in the manufacture of canceling and other stamping inks. The 

 results, of course, are mainly of value for purposes of comparison. 



The conditions of the test may be modified to suit the purposes of the investigation 

 and the character of the materials to be compared. The writer has obtained good 

 results in the comparison of lampblacks and other blacks rich in uncombined carbon 

 by the following method, which was so planned that the results might be applied to 

 stamping inks made with either a water-soluble base or an oil base: 



Mix 0.5 gram of the black to be tested in a mortar with dilute glycerin (87.5 cc of 

 glycerin diluted with water to 1 liter). Rinse the mixture into a 100 cc Nessler cyl- 

 inder and dilute to the 100 cc mark, using the same dilute glycerin. After having 

 prepared a series of tubes, each containing a portion of one of the blacks to be tested, 

 close each tube with a cork and shake thoroughly each tube successively, performing 

 the operation as quickly as possible in order that the time of settling may be approxi- 

 mately the same in the case of each sample. Allow the cylinders to stand at rest in 

 a place free from jar, and record from time to time the height of the sediment formed 

 by the deposition of the blacks. When submitted to this test, a black which is suitable 

 for the manufacture of a canceling or stamping ink should occupy a volume of not less 

 than 25 cc when the sediment has stopped settling. 



3. ASH, ETC. 



Blacks, dyes, and other substances used for the manufacture of canceling and other 

 stamping inks should be carefully examined to insure the absence of considerable 

 percentages of substances which are not essential to the production of an ink of good 

 quality. It can generally be assumed that the presence of considerable quantities 

 of any substance which does not actually contribute to the desirable qualities of the 

 ink will detract therefrom. 



a J. Soc. Chem. Ind., 1889, : 4. 

 [Cir. 12] 



