72 An Ana 1 1^ sis of Filtered Water — Dodye. 



RIVER WATER NOT FILTERED. 



Oxygen required, 

 1.95 parts per million. 



RIVER WATER FILTERED 



Oxygen required, 

 .11 parts per million. 



Here we see a still greater difference between the ujifiltered 

 and the filtered water than in the other test, the one requiring not 

 much more than one-twentieth of the amount of oxygen required 

 by the other. 



In fact, the filtered water by this test appears to be almost as 

 free from organic matter as the specially prepared distilled water 

 which we use in connection with our water analysis. 



This test, then, confirms the other test. From a chemical 

 stand-point we should be perfectly satisfied with a drinking water 

 giving such results. 



Hence, considering the filtering apparatus in question, we may 

 conclude that it does its work well and runs out a good water. 



With regard to the appearance of the water after filtering, 1 

 will say that in this respect it is above criticism, being perfectly 

 clean and colorless, whereas before filtering it is often decidedly 

 turbid and yellow. In palatable character also, the filtered water is 

 excellent. In both these respects it leaves nothing to be desired. 



The particular kind of filtering apparatus used is of an English 

 make, of George Cheavins' patent. There are various kinds of 

 filters in the market. The filtering and purifying medium used in 

 some of them is the same as in the one described, namely granulat- 

 ed bone charcoal. In others the material is "spongy iron." In 

 others it is "silicated carbon." These filters are all well spoken of, 

 I have not at this date personally experimented with any other 

 than my own. "Spongy iron" is said to be very effective as a 

 means of purifying water from organic substances. It is metallic 

 iron in a spongy state, as reduced from lumps of hematite ore by 

 special furnace processes. Its use has been introduced on a large 

 scale at some places in Europe for purifying the entire water 

 supply of cities. The water supply of Antwerp, taken from a 

 river, is purified by this means. But, on the whole, good bone 

 charcoal is equal to any material thus far used, and on the small 

 scale is perhaps the best material. Professor Wm. R. Nichols, of 

 the Massachusetts Institute of Technology, says that he considers 

 nothing better than well burned bone charcoal. 



Now, in view of what has been shown here in the way of 

 analytical lesults. I can but add my recommendation to the recom- 



