Chemical Qualities of Water. 
567 
carbonate of lime, and of the bi-earbonate or soluble carbonate of 
lime. Lime-water is simply a solution of quick-lime, or free Hmo in 
water ; ami when this free lime is added to the hard water containing 
bi-carbonatc of lime, it enters into combination with the carbonic 
acid which previously held the carbonate of lime in solution. The 
original carbonate of lime, now rendered neutral, and that which is 
newly formed will then fall down together. This process has stood 
the test of experience, and answers very well ; its only practical incon- 
venience is, that we have to provide tanks for the deposit which takes 
place in purifying hard water. But there is a process adopted at 
Woolwich for keeping boilers clean, which is very preferable to 
Clarke's purifying process. 
The "Woolwich Boiler-cleaning Process. 
Caustic soda, a material largely manufactured for the use of glass- 
makers, has the effect of rendering water soft and preventing boiler 
incrustation. A small quantity (perhaps a half-pound once a-month 
for a large steam-boiler) suffices for this purpose. Its action very 
much resembles that of the lime in Clarke's purifying process : the 
soda takes up the additional quantity of carbonic acid that keeps the 
carbonate of lime in solution; the neutral carbonate of lime thus 
formed falls down, and the carbonate of soda remains in solution. It 
has this additional advantage over Clarke's process that when the water 
becomes somewhat concentrated by evaporation, the carbonate of. soda 
precipitates the lime from sulphate of lime or gypsum. Having 
strongly recommended this simple material as affording the best 
remedy, I may safely pass by all other inferior processes. 
The Action, of Water ox Leaden Pipes. 
This subject has caused a good deal of unnecessary alarm. Lead, 
in the shape of soluble salts, is a highly injurious substance ; and, as 
it is well known that certain waters act upon and dissolve it, fear is 
frequently entertained that water conveyed by leaden pipes may be 
contaminated with an amount of lead that will act injuriously iqion 
the health of those who use it for drinking purposes. It is, therefore, 
a question of some importance to ascertain what the qualities of water 
are that act upon lead. The records of experience show incontestibly 
that water containing organic matter acts more rapidly upon lead 
than that which is free from such matter. From all the experience 
that is on record this follows incontestibly. In the next place, alkaline 
constituents (and there are some hard waters which contain a good 
deal of carbonate of soda or carbonate of potash) act in a special 
manner on leaden pipes. Hence we possess, in testing the alkalinity 
of water, at once the means of ascertaining whether or not it is likely 
to act upon leaden pipes. Even lime acts strongly upon lead. Salts 
of lime, carbonate and sulphate of lime especially, have, indeed, been 
considered protecting salts ; but I have myself often examined 
waters which are very rich in carbonate and sulphate of lime, 
and yet act very strongly upon lead. It is true that soft waters 
often act upon lead very rapidly ; but perhaps not so much by 
virtue of their softness, as on account of the presence of organic 
