THE SANITARY VALUE OP THE CHEMICAL ANALYSIS 

 OP POTABLE WATEES. 



By Willis G. Tocker, Ph. D. 



For the past six months or more the subject .of our city water sup- 

 ply has received an unusual amount of attention from the citizens of 

 Albany. Very naturally questions concerning the various methods of 

 water analysis and their value have come under discussion, and it is 

 possible, that a brief description of those processes which are employed 

 by chemists to-day and a discussion of their respective merits may 

 be of interest at this time. It may be profitable also to inquire what 

 are the questions which a chemical analysis can positively answer and 

 incidentally to consider the probabilities of disease transmission by 

 water used for drinking and the effect of natural oxidation by aera- 

 tion in purifying those which are polluted by sewage matter. 



The general appearance and physical properties of a water will nat- 

 urally first attract attention when its quality is questioned. An 

 ideally pure water will be clear and colorless, odorless and tasteless, but 

 these qualities, however desirable in themselves, do not necessarily indi- 

 cate freedom from pollution. Waters which have penetrated through 

 the soil are generally bright and clear from the filtration they have 

 undergone, and may have neither odor nor taste and yet be verv dirty 

 waters chemically, while surface waters may show a decided color and 

 even turbidity, may have an earthy, vegetable or peaty odor and taste 

 and yet be quite free from harmful constituents. Pure water does not 

 exist in nature, all dissolved or suspended substances being impurities 

 in water as such, though by no means necessarily harmful. The sensi- 

 ble properties of a water, therefore, unless it be so foul that there is 

 no mistaking its pollution, afford little information as to its quality. 

 Water may percolate through the soil for a mile under a mountain and 

 be as clear as crystal and yet carry typhoid fever from a hamlet on 

 one side to dwellers on the other, as in the celebrated and well authen- 

 ticated case at Lausen, Switzerland. 



The suspended matter contained in potable waters, and naturally 

 most abundant in surface waters, usually consists chiefly of clayey 

 matter, easily removed by filtration on a large or small scale or by mere 

 subsidence. In some cases, however, as in the James river water 

 which supplies Richmond, the suspended matter is so finely divided 



