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BELL SYSTEM TECHNICAL JOURNAL 



sufl&ciently high flash point that they would not present a fire hazard. The 

 odor should not cause distress and finally the cost must be reasonable. 



Dr. G. T. Kohman of the Bell Telephone Laboratories has prepared a 

 Hst of such substances that can be mixed, any high one with any low one to 



Fig. 2.39 — The refractoscope 



obtain a fluid satisfactory in all these respects. The following mixtures of 

 substances are taken from his data. 



