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BELL SYSTEM TECHNICAL JOURNAL 



use directly on latex has been employed as a control during the synthesis of 

 GR-S^^ This test, referred to as the vistex test, consists in adding 1 ml. 

 of the latex sample to be examined to 100 ml. of a solvent having both 

 hydrophobic and hydrophilic properties, such as a mixture of 70 parts (by 

 volume) of xylene with 30 of pyridine, or 60 of benzene and 40 of /-butanol. 

 The clear solution is run through the viscometer in the usual manner and the 

 relative viscositv used as a measure of extent of reaction. The test has the 



Fig. 8. 



-Viscometers and bath used for the determination of diluti' solution viscosity of 

 polymer solutions. 



advantage of great speed, thus providing control of the reaction, step by 

 step. Figure 9 shows the apparatus em[)loyed in the determination of 

 concentrated solution viscosity {CSV)."^ In this measurement a 15 percent 

 solution of the copol3nner in xylene is made by weighing the required 

 quantity of GR-S into a test-tube adding the precise volume of xylene and 

 stoppering. The solution is homogenized by moving a steel armature 

 through it in the test-tube by means of a strong electro-magnet. A trace 

 of acetic acid is added to eliminate thixotropic effects. After complete 

 dispersion has been effected the viscosity is determined by the faUing ball 



