On Water and Air . 
56 
[January, 
produce carbonate of lime or chalk in your presence. [The 
le< 5 turer blew into the lime-water by means of a glass tube.] 
You see a single inhalation is sufficient to produce this chalk 
by the carbonic acid from the lungs. 
Now I am about to approach a very important point, and 
that is a point that practically bears upon the question of 
the solution of minerals in water. This thing which we 
call carbonate of lime exists in two forms. It exists as a 
single carbonate, which takes up a certain amount of car- 
bonic acid ; and it exists as a double carbonate or bi- 
carbonate, which takes up twice as much carbonic acid. I 
say that the carbonate of lime exists in two forms — the 
single carbonate and the bicarbonate ; and what you have 
now to remember is that the single carbonate is almost in- 
soluble in water, and that the bicarbonate is very fairly 
soluble in water. What is the consequence ? The water 
coming from the clouds has always a certain amount of 
carbonic acid dissolved in it. When such water falls upon 
our chalk hills, what occurs ? It soaks into the chalk ; it 
percolates through the chalk ; it dissolves the chalk ; and 
the chalk so dissolved in the rain-water is present as a bi- 
carbonate of lime. If the carbonate were to remain in the 
form of single carbonate, the rain-water could hardly dis- 
solve it at all ; but, as it is converted by the rain-water into 
the condition of bicarbonate, the rain-water dissolves a great 
deal of it. The conversion of the carbonate from the single 
carbonate to the double carbonate renders it very easily 
soluble in water. I have here some water from the neigh- 
bourhood of Canterbury, where there is a well from which 
is pumped a million and a half of gallons every day from 
the body of the chalk. Here is the hard Canterbury water, 
and I pour a quantity of this hard Canterbury water into 
the beaker. Now, I say that the lime there is in the soluble 
form. It is in the form of the double carbonate, or the bi- 
carbonate, which is another expression for the same thing. 
Now I have here some lime-water. This Canterbury water 
is beautifully clear and is pleasant to the taste, but you 
would find it exceedingly difficult to wash in this water. 
In point of fadt, if you operate with soap in this water you 
find it very difficult to get a lather in it. For a certain time 
you cannot possibly get a lather. That water contains, I 
should say, more than 20 grains of carbonate of lime dis- 
solved in every gallon. Where washing operations have to 
be carried on, on a large scale, with this water, an immense 
amount of soap is wasted, not to wash, not to cleanse your 
hands, not to cleanse your linen, but simply, first of all, to 
