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detectable through the yellow or green color of the brom cresol 

 green indicator present lontil the acid has had an opportunity to 

 mix and react with a volume of ambient water containing 0,01 gram 

 molecular weight of sodium carbonate. If the volume of 0.01 gram 

 molecular weight of sulphuric acid solution is l/lOOO as great as 

 the volume of ambient water containing 0.01 gram molecular weight 

 of sodium carbonate solution, the boundary across which the acid 

 ceases to be visible represents a dilution of the acid by a fac- 

 tor of 1000, Thus the color of the acid discharge was character- 

 istic of pH lower than 4.0 and concentrations greater than 1 part 

 in 1000, and invisible if its dilution exceeded this predeter- 

 mined value. The same reasoning applies to the 1 part in 200 

 dilution contour. During operation of the model, samples of the 

 solutions concerned in the bleed water tracer system were titrated 

 repeatedly to end points in both the green and yellow ranges. 

 These values represented the greatest and least measurable dilu- 

 tions respectively of the acid component and served to define 

 numerically the dilution contours represented by color changes 

 in the model. 



The chemical titrations of simulated bleed water against 

 ambient water were referred to a standard sodium carbonate solu- 

 tion of approximately 0.2 normal strength. An intermediate stand- 

 ard sulphuric acid solution of approximately 0,01 normal strength 

 was prepared in order to monitor the concentration of sodium 

 carbonate in the ambient water. The simulated bleed water 



