294 BURTON E. LIVINGSTON AND EDITH B. SHREVE 



COMPOSITE PAPER SLIPS 



In order to bring the cobalt paper slip and those of the two 

 color standards into juxtaposition, and to allow the three to 

 be readily handled in use, a method has been worked out by 

 which they are firmly joined together into a single composite 

 slip, which can be manipulated as a single piece. It is obviously 

 not permissible to join the three pieces by overlapping and pasting, 

 nor should any other material be pasted over the Unes of junc- 

 tion on the surface that is to absorb water. However, on the 

 surface from which observations are made the hues of junction 

 may each be covered by a very narrow strip of thin, non-absorbent 

 material. For this purpose black silk court-plaster has been 

 successfully employed. Each black strip is 1 mm. wide, and 

 covers the line where the two papers adjoin, thus fastening them 

 together. 



In the making of these slips it is found convenient first, to 

 cut the cobalt paper and the permanent blue papers into strips 

 4.5 mm. wide, and about 6 or 8 cm. long. The cobalt strip is laid 

 upon clean glass, a permanent blue strip being laid against each 

 of its long edges, and a court-plaster strip carefully cemented 

 over each of the two lines of marginal contact. Across the 

 composite strip, thus resulting, similar strips of court-plaster 

 are then cemented in a horizontal direction at intervals of 4 mm. 

 After drying between sheets of writing paper, under pressure, 

 these composite strips are cut cross-wise through the center 

 of the horizontal strips of court-plaster, thus producing the fin- 

 ished composite strips, each one being about 9 mm. long and 

 5 mm. wide. Each of the three paper surfaces visible to the 

 observer when the strip is in use is about 4 mm. square, and 

 is surrounded by a black frame 1 mm. wide. It is found in 

 practice, that these composite sUps may be handled in the 

 same manner as are the simple ones. By this arrangement the 

 two standard colors are automatically placed in position when- 

 ever the cobalt shp is applied to any surface to be tested. Of 

 course the standard papers absorb moisture, but their colors 

 are not thereby altered, while the cobalt chloride piece changes 

 from deep blue to nearly white. 



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