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SCIENCE. 



[Vol. XXI. No. 536 



SCIENCE: 



Published by N. D. C. HODGES, 874 Broadway, New York. 



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THE VALUE OF A WATER ANALYSIS. 



BY W. P. MASON, EBNSSELAEB POLYTECHNIC INSTITUTE, TKOY, N. Y. 



A GREAT dpal of popular misconception exists upon the subject 

 of the analysis of potable water, and it is commonly supposed 

 that such an examination may be looked upon from practically 

 the same point of view as the analysis of an iron ore. That this 

 belief is founded on fallacy may, however, be readily shown. 

 When an iron ore is submitted for analysis, the chemist deter- 

 mines and reports upon the percentages of iron, phosphorus, sul- 

 phur, etc., found therein ; and at that point his duties usually 

 cease, inasmuch as the ironmaster is ordinarily capable of inter- 

 preting the analysis for himself. Even should the analyst be 

 called upon for an opinion as to the quality of the ore. the well- 

 known properties of the several constituents make such a task an 

 easy one, and, assuming the sample to have been fairly selected, 

 the opinion may be written without any inquiry as to the nature 

 of the local surroundings whence the ore was taken. 



A water analysis, on the other hand, is really not an analysis 

 at all, properly so-called, but is a series of experiments under- 

 taken with a view to assist the judgment in determining the 

 potability of the supply. The methods of conducting these ex- 

 periments are largely influenced by the individual preferences of 

 the analyst, and are far from being uniform or always capable 

 of comparison, thus often introducing elements of confusion 

 where two or more chemists are employed to analyze the same 

 water. Some of the substances reported, "albuminoid am- 

 monia," for instance, do not exist ready formed in the water at 

 all, and are but the imperfect experimental measures of the ob- 

 jectionable organic constituents, which our present lack of knowl- 

 edge prevents our estimating directly. 



Thus the numerical results of a water analysis are not only 

 unintelligible to the general public but are not always capable of 

 interpretation by a chemist, unless he be acquainted with the 

 surroundings of the spot whence the sample was drawn, and be 

 posted as to the analytical methods employed. 



It is very common for water to be sent for analysis, with the 

 request that an opinion be returned as to its suitability for potable 

 uses, while at the same time all information as to its source is 

 not only unfurnished but is intentionally withheld, with a view 

 of rendering the desired report unprejudiced in character. 



Such action is not only a reflection upon the moral quality of 

 the chemist, but it seriously hampers him in his efforts to formu- 

 late an opinion from the analytical results. 



For instance, a large quantity of common salt is a cause for 

 suspicion when found in drinking water, not because of any 

 poisonous property attaching to the salt itself, but because it is 

 usually difficult to explain its presence in quantity except upon 

 the supposition of the infiltration of sewage; yet an amount of 

 salt sufficient to condemn the water from a shallow well in the 



Hudson valley, could be passed as unobjectionable if found in a 

 deep-well water from near Syracuse, N. Y. 



We thus see how important it is for the chemist to be fully 

 acquainted with the history of the water he is to examine, in 

 order that he may compare his results in "chlorine" with the 

 "normal chlorine" of the section whence the sample is taken. 

 A knowledge of the history of the water is no less important in 

 order to interpret the remaining items of a water analysis. Some 

 time since a water was sent from Florida to this laboratory for 

 examination, and was found to contain 1.18 parts "free am- 

 monia" per million. 



Much "free ammonia" commonly points to comtamination 

 from animal sources, and had it not been known that the water 

 in question was derived from the melting of artificial ice made 

 by the ammonia process, the enormous quantity of ammonia 

 found would have condemned it beyond a peradventure. As it 

 was, the water was pronounced pure, the other items of the 

 analysis having been found unobjectionable. 



Analytical results which would condemn a surface-water are 

 unobjectionable for water from an artesian well, for the reason 

 that in the latter case high figures in "free ammonia," "chlor- 

 ine," or ' ' nitrates" are capable of an explanation other than that 

 of sewage infiltration. Even though such water should have, at 

 a previous period, come in contact with objectionable organic 

 waste material, yet the intervening length of time and great 

 distance of underground flow would have furnished abundant 

 opportunity for thorough oxidation and purification. 



" Deep'' samples taken from the same lake, at the same spot 

 and depth, will greatly vary in analytical results if the tempera- 

 ture of the water at the several dates of sampling should be 

 markedly dififerent, owing to the disturbing influence of vertical 

 currents. 



Again, suppose it is desired to determine whether or not the 

 water of a large stream is socontaminated with up-stream sewage 

 as to be unfit for a town supply. An analysis of the water taken 

 from the site of the proposed in-take would very probably be val- 

 ueless, because the enormous dilution to which the admitted 

 sewage would have been subjected would remove from the 

 analytical results everything of an absolute character. Ex- 

 aminations of any real value in such cases should always be of a 

 comparative nature. Samples should be taken above and below 

 the point of contamination and again at the proposed in-take. If 

 the difference between the first and second samples, which is a 

 measure of the pollution, be maintained, or nearly so, at the 

 point of in-take, then the water should be condemned no matter 

 how completely the analytical results fall within the limits of the 

 so-called standards of organic purity. 



Thus it is that a chemist must be in full possession of all the 

 facts concerning the water which he is asked to examine, in or- 

 der that his opinion as to its purity may be based upon the entire 

 breadth of his passed experience, for in no branch of chemical 

 work is experience and good judgment better exercised than in 

 the interpretation of a water analysis. 



As Nichols has well said, " It is a great mistake to suppose 

 that the proper way to consult a chemist is to send a sample of 

 water in a sealed vessel with no hint as to its source. On the 

 contrary, the chemist should know as much aa possible as to the 

 history and source of the water and, if possible, should take the 

 samples himself." 



In the taking of samples for so important a matter as a town 

 supply, the chemist should unquestionably personally superintend 

 their collection; but, for individual outlying waters, printed in- 

 structions have to be frequently depended upon. Those issued 

 from this laboratory are as follows : — 



DIRECTIONS FOR TAKING A WATER SAMPLE. 



Large glass-stopper bottles are best for sampling, but as they 

 are seldom at hand, a two-gallon, new demijohn should be em- 

 ployed, fitted with a new soft cork. Be careful to notice that no 

 packing straw or other foreign substance yet remains in the demi- 

 john, and thoroughly rinse it with the water to be sampled. Do 

 not attempt to scour the interior of the neck by rubbing with 

 either fingers or cloth. After thorough rinsing, fill the vessel to 



