TOTAL SOLIDS 215 



through a washed tared filter paper, or a Gooch crucible. 

 The residue is washed with distilled water, dried, and 

 weighed. 



Previous to drying, valuable information may be 

 gained as to the character of the suspended matter by 

 examination under the microscope. 



Colour. — The colour or turbidity of the filtered water 

 should be examined by looking down a 2-foot tube, 

 placed side by side with a similar tube containing 

 distilled water. A tintometer may be used if available. 



The measure of the colour is sometimes a very useful indication 

 of the purity of a water. Yellow or brown tints generally indicate 

 sewage pollution (except in water from peat), or presence of 

 much iron. Green is sometimes formed by organisms containing 

 chlorophyll. 



Taste and Smell. — Smell is observed after gently 

 warming the water in a closed flask on the water-bath 

 to 40° to 50° C. The taste should be observed at 10° 

 to 20° C. and compared with a good tap-water, not 

 distilled water. 



Total Dissolved Solids. 



210. Fifty to 250 c.c. of the filtered water are 

 evaporated to dryness in a weighed nickel or platinum 

 dish on the water-bath. The residue is dried in the 

 steam-oven at 100° C, cooled in a desiccator, and 

 weighed. The volume of water taken depends, of 

 course, on the amount of dissolved solids estimated 

 to be present. The total solids residue should be 

 carefully ignited at a dull red heat If much organic 

 matter is present, blackening will be observed and 

 considerable loss of weight will occur. Too high a 

 temperature must not be employed in estimating this 

 loss, or some of the carbonates will be decomposed 

 and the chlorides volatilised. The loss on ignition 



