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experiment. In the first of these two cylinders I i)Ut a pint of 

 ordinary soft water ; in the second cylinder I put the same qnantity 

 of the hard water which we have now prepared. To each cylinder 

 I now add the same volume of a solution of soap and shake vigorously 

 half a minute. A bulky and persistent lather, nearly filling the cylinder, 

 is formed by the soft water, while the hard water shews merely a thin 

 pellicle of scum, the product of the destruction of the soap added. You 

 will observe that it is necessary to add nine or ten times as much soap 

 to the hard water in order to get a lather comparable with that obtained 

 in the first cylinder. Tt is evident that hard water causes a waste of 

 soap, and the amount ot waste is strictly proportional to the amount of 

 lime in the water, since a perfectly definite decomposition takes place 

 between the soap and the lime salt present. Were the lime present as 

 sulphate the destruction of soap would still occur, with this difference 

 that in that case no simple and inexpensive mode of softening the 

 water could be applied, and the water would be what is usually called 

 petmanently hard. The only practicable remedy in such a case is the 

 use of washmg soda, for although such remedies as soluble barium salts 

 are very effective in throwing the sulphates out of solution, yet the 

 poisonous character of barium salts, to say nothing of their cost, makes 

 them unavailable in ordinary circumslances. In the case of water 

 which possesses only temporary hardness, /. e., hardness due to car- 

 bonate of lime, not only may we use washing soda to cure the evil, but 

 two other ])rocesses deserve mention. By boiling the water we drive 

 out of solution the carbonic acid gas, in virtue of which the carbonate 

 of lime is held in solution. On now allowing it to settle, the almost 

 insoluble chalk is deposited, and the soft water may be drawn off. The 

 second and very ingenious plan of softening such water is due to the 

 late Prof. Clarke of Aberdeen, and is usually known as Clarke's pro- 

 cess. It consists in adding slaked lime to the water in proper amount 

 to form chalk with the free carbonic acid, which is therefore withdrawn 

 from solution and precipitated along with the now insoluble lime salt 

 originally present in the water Many large towns and cities in Eng- 

 land and elsewhere now soften their whole supply in this way. The 

 water of the Ottawa River is remarkably soft since the gathering ground 

 is essentially free from limestone rocks. The Upper Ottawa region is 



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