Abstracts of Technical Articles from Bell System Sources 



Paper as a Medium for Analytical Reactions} B. L. Clarke and 

 H. W. Hermance. Absorbent paper has long been used in chemical 

 laboratories for filtering suspensions. Paper has also found a special 

 use as a container or holder for certain testing reagents; litmus paper 

 is a common example. In this article and a preceding one {Indus. & 

 Engg. Chem., Anal. Ed., June 15, 1937), are reported exploratory 

 investigations on the extension of the use of absorbent papers in 

 chemical analysis. 



Rapid identification "spot tests" have been described by Feigl in 

 which, by successively placing drops of unknown and reagent solutions 

 on filter paper, characteristic color changes are produced. Methods 

 and apparatus are described in the present articles whereby some of 

 the variables in such tests are controlled. Chief among these innova- 

 tions is the use of semi-soluble instead of soluble reagents, and the 

 precipitation of these compounds directly on the paper fibres to form 

 a more or less permanent test paper. By these changes in technique 

 the sensitivity — the smallest amount of a given metal detectable — 

 is decreased from ten to one-hundredfold. For example, 0.002 

 microgram of copper can be detected by the new method, as compared 

 with 0.2 by the old. 



In another application a very dilute solution of some metal ion is 

 slowly siphoned through a small circular piece of reagent paper 

 suitably mounted. The metal is entrapped on the paper in an in- 

 soluble form strongly adsorbed by the paper. Theoretical analysis 

 indicates that copper, for example, may be removed from a solution 

 in this way so completely that only 8 X 10~^^ microgram will be left 

 in a liter. 



Neutral Particles in Physics.^ Karl K. Darrow. During the 

 early days of science, the elementary particles which scientists and 

 philosophers alike saw fit to postulate were always imagined as 

 chargeless. With the remarkable growth of the understanding of 

 electricity during the nineteenth century, and with the invention of 

 instruments for detecting small charged particles during the twentieth, 

 it became the custom to suppose that the fundamental particles of 



1 Indus. & Engg. Chem., Anal. Ed., October 15, 1938. 

 ^Amer. Phil. Soc. Proc, September 30, 1938. 



246 



