PROCEEDINGS OF THE COTTESWOLD CLUB II9 



before said mainly in the form of carbonate, in fact in 

 many waters more than 90 i)er cent, of the entire impurity 

 is carbonate of Hme. The carbonate is of itself quite 

 insoluble in water, but is taken into solution by the aid of 

 free carbonic acid gas and exists in the water as bicarbonate. 

 If the gas be driven off by boiling the water the carbonate 

 of lime is at once thrown out of solution. Carbonic acid 

 gas assumes the same role towards iron, enabling it to 

 enter into solution as an acid carbonate, and most " chaly- 

 beate " waters are such solutions of carbonate of iron. 

 What is known as the hardness of water is due mainly to 

 the impregnation of the water with lime salts, the major 

 portion of the hardness being generally due to carbonate 

 of lime. Magnesia salts produce the same effect in a 

 greater degree. A large proportion of lime in water 

 renders it unsuitable for drinking. It undoubtedly tends 

 to produce dyspepsia, is productive of skin affections, or 

 at least propitious to their production, and has been 

 credited with causing goitre. Sulphate of lime in water 

 is thought to be more harmful than carbonate, and 

 magnesia salts more objectionable in a drinking water 

 than salts of Hme. 



The impurities in water that are of organic origin are 

 no doubt num^erous, but are of unknown composition, and 

 have to be considered in the mass for want of any known 

 means of separating them. They are derived from decay- 

 ing vegetable and animal tissues, or are the more direct 

 products of living creatures. They include organic acids, 

 alkaloidal, gumlike, and other substances that result from 

 the breaking down of cellular tissues and other material, 

 in its passage from very highly complex to simpler forms. 

 In this degradation of organic material the number of 

 compounds formed is probably innumerable, but the 

 minute proportions in which they exist in water prevent 

 their particular and individual examination. Their de- 

 composition when carried to its ultimate end results in 

 H2 



