194 ANNUAL OF SCIENTIFIC DISCOVERY. 



1. All water that has received drainage containing animal and 

 vegetable matter in a state of putrefactive decomposition, and 

 especially excrementitious matter, either is or is liable to be in 

 a state unfit for use as drinking water, and the chemist cannot 

 determine by analysis whether the dangerous state exists or not. 



2. All rivers necessarily receive drainage, and they are gener- 

 ally contaminated with sewage and other decomposing organic 

 matter, which may render the use of such water injurious to 

 health. 



3. Shallow wells situated in large towns are subject to pollution 

 from infiltration, from leakage of sewers, and other similar 

 causes ; and as these waters are stagnant, the organic matter 

 present, if it has not passed, is liable to assume, its most danger- 

 ous conditions. 



4. Spring-water, when favorably situated, is free from sus- 

 picion of its containing organic impurity that could prove injuri- 

 ous to health. 



5. Rain-water, if properly collected and stored, is the best and 

 safest water to use for domestic purposes, and especially for 

 drinking. 



6. In the absence of rain-water or good spring-water, the best 

 and most palatable water should be selected from other sources, 

 choosing that which is most free from organic matter, and which 

 has been least exposed to sewage contamination. In order to 

 guard as far as possible against the influence of living germs, by 

 which it is supposed that disease may be propagated, it is recom- 

 mended on the highest authority that when water to which a sus- 

 picion attaches is used for drinking purposes, it should be pre- 

 viously boiled, the heat of boiling water being destructive to the 

 vitality of such germs. A supply sufficient for the day should be 

 daily submitted to the boiling temperature, and this, after it has 

 cooled, may be rendered more palatable by the addition of a little 

 syrup of lemon, or even a few drops of diluted sulphuric acid. 

 London Journal of Pharmacy. 



Whatever be the nature and quantity of the earthy substances 

 held in suspension in turbid water, it becomes fit to drink in from 

 7 to 15 minutes if to each litre there be added .04 grammes of 

 finely powdered alum, care being taken to agitate the liquid when 

 the alum is introduced (this is about three-fourths of a pound per 

 ton of water) . If potash alum is used, the alum is decomposed into 

 sulphate of potash, which is all dissolved by the water, and sul- 

 phate of alumina, which, by its decomposition, purifies the water. 

 The alumina separates in an insoluble form, and carries down 

 with it, as it precipitates, the matters which render the water 

 troubled, arid the organic matter. The acid attacks the alkaline 

 and earthy carbonates, and transforms them into sulphates. The 

 water becomes slightly richer in bicarbonates and free carbonic 

 acid, whilst all organic matter is destroyed. 7 parts of sulphate 

 of alumina will purify as much water as 10 parts of rock alum or 

 potash alum, and the sulphate of alumina does not introduce any 

 alkaline sulphate into the clarified water. Technologists. 



