212 



Tlie Sanitary Value of the 



ter of a water in a sense to justify the claim of ' absolute ' value for 

 its results, which have been denied to those of all other methods. It 

 is but a method of approximation involving sundry errors, and in part 

 a balance of errors." 



These then are the principal methods and the best at present known for 

 the determination of organic matter in potable water.* It will be seen 

 that no one of them enables us to recognize the real morbific material 

 which water may contain or is able to distinguish with certainty between 

 disease-producing constituents and the less harmful or innocent matter 

 of vegetable origin, or that which has resulted from the conversion of 

 harmful into harmless substances. The English " Society of Public 

 Analysts" have adopted a scheme of analysis which includes both the 

 permanganate and albumenoid-ammonia processes, and this method 

 has been largely followed in this country and adopted by our State 

 Board of Health. I have employed it in quite a large number of cases, 

 and it has frequently happened that waters which had in all proba- 

 bility caused disease, could not be condemned on the evidence furnished 

 by the analysis alone. Mallet would use "all three of the principal 

 processes," since " each gives a certain amount of information which 

 the others do not afford," and adds that " under circumstances admit- 

 ting only of the use of simpler means of investigation, the albumen- 

 oid-ammonia and permanganate processes might be employed to- 

 gether, but in no case should only one of these methods be resorted to, 

 such a course entailing practically the neglect of carbon on the one hand 

 or nitrogen on the other." This opinion is based upon the results 

 of an extended research, and to admit that the determination of car- 

 bon and nitrogen — perfectly harmless elements in themselves — affords 

 us our best indications in judging of the purity or impurity of a water 

 is to acknowledge that our best analytical methods are far from satis- 

 factory. 



What, then, are the questions which a chemical analysis can answer 

 concerning a water viewed from a hygienic standpoint ? It may be 

 answered, first, that all attempts to establish definite standards, so 

 that the points for and against a water can be counted up and a 

 balance struck, have signally failed. For there is no unanimity of 

 opinion as to what degree of importance should be attached to the 

 results obtained, and if there was, such a numerical expression of their 

 relative importance must of necessity be arbitrary and misleading. 

 A committee of the German Public Health Association reported to 



