214 



Mr. Wal die's investigations connected 



[No. 3, 



It may be useful to refer for the purpose of comparison to the 

 composition of some other waters supplied to towns, and I shall take 

 for that purpose one of the most recently published reports on the 

 subject, namely, that by Professor Frankland on the water supply of 

 London during the year from February 1865 to January 1866.* 

 The only points determined connected with the mineral consti- 

 tuents are the total amount of saline matters and the amount 

 of earthy salts as ascertained by the soap test ; this, as is well known, 

 being the application of the familiar fact that hard water curdles 

 soap, to ascertain its purity ; a solution of known strength of soap 

 being added to a measured quantity of the water to be examined 

 from a graduated tube, until the curdling effect of the salts of lime and 

 magnesia which cause the hardness is exhausted, and the water produces 

 a lather on shaking. The quantity of soap required indicates the 

 amount of earthy salts present ; an easy and speedy means of obtaining 

 a sufficiently good estimate of the amount of earthy salts in water. 



By deducting from the total solid matter first the amount of organic 

 matter, the total inorganic is obtained ; and by deducting from this 

 the amount of carbonate of lime, the remainder will indicate, with 

 sufficient approximative accuracy, the amount of alkaline salts. Here 

 are the results of this proceeding — for the waters of 



Five Thames New Kiver Kent and S. 

 Companies and River Essex Co.'s 

 average. Lea. Artes. Wells. 



26.63 26.11 39.03 



1.60 1.30 1.73 



Total solid matters, mean 



Deduct organic and volatile, mean 



Carbonate of Lime 



25.03 

 17.69 



24.81 

 20.65 



37.30 

 25.16 



Alkaline salts 7.34 4.16 12.14 



It will be observed that the alkaline salts are in much larger 

 proportion to the earthy carbonates than in the Hoogly water, this 

 being specially the case in the Artesian well waters. The waters of New 

 Kiver and River Lea come nearest the Hooghly. The amount of solid 

 matter is much greater in the average than that of the Hooghly river 



* Journal of the Chemical Society, June 1866. 



