NSWC/WOL/TR 75-3 5 



4.3.5 Non-specific Measurements 



4.3.5.1 Turbidity 



The turbidity of a water sample can be measured in a 

 turbidimeter (e.g., Kach Model 2100A Laboratory Turbidimeter, $525), 

 which is a true nephelometer . The method is based upon a comparison 

 of the intensity of light scattered by the sample under defined 

 conditions with the intensity of light scattered by a standard 

 reference suspension. The higher the intensity of scattered light 

 the higher the turbidity. The readings are made in the Nephelometric 

 Turbidity Unit (NTU) . 



Samples taken for turbidity measurements should be analyzed as 

 soon as possible. Preservation of samples is not recommended. 



The presence of floating debris and coarse sediments which 

 settle out rapidly will give false high readings. Finely divided 

 air bubbles will also affect the results in a positive manner. 



4.3.5.2 pH 



The pH of most natural waters falls within the range 4 to 9 . 

 The majority of waters are slightly basic due to the presence of 

 carbonate and bicarbonate. A departure from the norm for a given 

 water could be caused by the entry of strongly acidic or basic wastes 

 (HCl in the explosion products) . pH is the logarithm of the 

 reciprocal of the hydrogen ion concentration in moles per liter. 

 The practical pH scale extends from 0, very acidic, to 14, very 

 alkaline, with the middle value (pH 7) corresponding to exact 

 neutrality at 25°C. 



pH can be measured either colorimetrically or electrometrically. 

 The color imetric method requires a less expensive investment in 

 equipment but suffers from severe interferences contributed by color, 

 trubidity, high saline content, colloidal matter, free chlorine, and 

 various oxidants and reductants . 



Electrometrically pH is measured with a pH meter equipped with 

 either a glass electrode in combination with a reference potential 



(saturated calomel electrode) or a combination electrode (glass and 

 reference) . A portable pF meter such as the Micro 50 pH meter 



(Service Tectonics Instrument, Detroit, Michigan, $125) is convenient 

 for field pF measurements. 



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