in Analysis of Filtered Water — Dodge. 



71 



were most important in the case, namely the test for (unmoma 

 free and ''albuniinoitr' and the permanganate test. On the same 

 <lay I took a quantity of the unfiltered city water from the pipe and 

 submitted it to the same analysis. Both anal3"ses were conducted 

 with the utmost care and with every precaution to obtain correct 

 results. The results of these analytical determinations areas fol- 

 lows for the ammonia test: 



RIVER WATER NOT FILTERED. 



Free ammonia .030 per million. 

 Album. '" .100 '' 



RIVER WATER FILTERED. 



Free ammonia ,005 per million. 

 Album. '' .015 '' 



On comparing these results, we see that the filtered water 

 shows about one-sixth the amount of both free ammonia and 

 albuminoid ammonia which is shown by the water not filtered. 

 Let me say at this point that the results obtained for the water 

 not filtered are by no means high results. As the members of the 

 Academy have been reminded on previous occasion when results 

 of chemical analysis of the river water have been presented, this 

 water does not show itself decidedly bad through our chemical 

 tests. Moreover, we must be reminded that these chemical tests 

 are not perfectly conclusive as to the real purity or impurity of a 

 v/ater. They do not show all that is in a water; they need to be 

 supplemented by other methods of examination, according to cir- 

 cumstances. But they are very good tests for comparative pur- 

 poses^ such as we are now concerned with. Now if we had sub- 

 mitted to us for chemical examination a sample of water in which 

 we found the free and the albuminoid ammonia as low in amount 

 as we have found them in our filtered water, with 5-1000 parts of 

 free ammonia and 15-1000 parts albuminoid ammonia per million 

 parts of water, we should say — unless other tests gave much higher 

 results — that the water was of a high degree of purity. 



The other test to which the two samples of water were sub- 

 mitted was, as stated, the permanganate or Forschammer test. 

 This is also a test for the organic matter present in water, particu- 

 larly for carbonaceous matter. It consists in determining the 

 amount of pernumganate of potash solution, which is decolorized 

 by a given amount of water, and therefrom, by calculation, the 

 amount ofjoxygen which is required to destroy the organic matter 

 on that amount of water. The result of my determinations for 

 the two samples of water are as follows: 



