NSWC/WOL/TR 75-3 5 



4.3.3 Suspended Solids 



4.3.3.1 Suspended Metals 



For the determination of suspended metals a representative 

 volume of sample should be filtered through a 0.45y membrane filter. 

 Transfer the membrane filter containing the particulate matter to a 

 beaker and add 3 ml of HNO3 . Cover the beaker with a watch glass and 

 heat gently. The warm acid will soon dissolve the membrane. Increase 

 the temperature of the hot-plate and digest the material. When the 

 acid has evaporated, cool the beaker and add another 3 ml of HNO3 . 

 Cover and continue heating until the digestion is complete. Add 

 1:1 HCl (2ml) to the dry residue and again warm the beaker to 

 dissolve the material. Filter the sample to remove silicates and 

 other insoluble material. The sample is now ready for analysis by 

 atomic absorption. 



4.3.3.2 Suspended Explosives 



A representative volume of sample is filtered through a . 5 y 

 solvent-resistant filter (membrane or glass fiber) . The particulate 

 matter collected on the filter is washed with several small portions 

 of benzene which is drawn through the filter after each washing. 

 The combined benzene extracts are analyzed for explosives using 

 procedures described in Section 4.3.2.2. 



4.3.3.3 Non-filterable Solids 



a. Total Non-filterable Solid 



Total non-filterable solids are defined as those solids 

 which are retained by a standard membrane filter and dried to 

 constant weight at 103-105°C. 



A known volume of sample is passed through a weighed filter 

 (0.8U). The filter is carefully removed from the filter funnel 

 assembly, placed in a drying oven, and dried at 103-105°C to constant 

 weight. 



b . Particle Measurement 



Particle measurement of the suspended solids can be made by 

 manual microscope methods, but they are tedious and time consuming. 

 Other indirect measuring techniques such as light scattering, sedi- 

 mentation, and electrical field effect are limited by lack of 

 precision. A recently developed Millipore riMC System (Millipore 



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