140 
IOWA ACADEMY OF SCIENCE 
plates and even explosion when the fires are again started. As a rule in 
practice the nature and amount of the boiler compound bear little relation to 
the work to be done, the compound of unknown composition being added from 
time to time without much regard to the mineral content of the water or the 
amount of water used. The treatment is likely to be only partial, or the com- 
pound is likely to accumulate and cause trouble. 
The number of boiler compounds on the market is very large and for them 
their venders claim almost miraculous properties, and they sell them at ex- 
orbitant prices. A few days ago there came into my hands a boiler compound 
used in a Grinnell power plant. So far as could be discovered it contained only 
sodium hydroxide, about 18 per cent, and a very little coloring matter that may 
have been due to the action of the strong alkali upon the barrel. It was bought 
by the barrel at eight cents a pound, or about $42.00 a barrel. It was actually 
worth, barrel and freight included, about $5.00. The man who bought this 
compound is one of unusual intelligence and business ability. In fact, the ap- 
peal of the boiler compound to the trade may be likened in many respects to 
that of the patent medicine, and mystery seems to be the controlling factor. 
Now, as a matter of fact there are only a few practically useful chemicals for 
softening water, and they are all perfectly well known as is also their action. 
There is no necessarily efficient nostrum applicable in all cases. Any peculiar, 
secret and patented combination ought to be treated as a fraud, and the 
engineer who applies to a chemist for advice should be plainly told this fact. 
The chief substances in water that make boiler scale are calcium and mag- 
nesium in association usually with carbonic and sulfuric acid ions. The 
scale consists mainly of calcium and magnesium carbonates, hydroxides and 
calcium sulfate. The chief agents of corrosion are free carbonic acid, and other 
acids that may be set free by the hydrolysis of salts at the high temperature of 
the water. The problem is, therefore, to remove calcium and magnesium 
(secondarily aluminium and iron), and carbonic acid ions, to leave the water 
neutral or slightly alkaline, with the introduction of the minimum of soluble 
material. 
First of all one must have an accurate mineral analysis of the water to be 
softened. The volume of the water must be measured and the chemicals must 
be calculated to meet the given case and the amount used weighed. Though 
there is no logical procedure applicable to all waters, effectiveness and cheap- 
ness both considered, it is generally better to use only lime if the calcium and 
magnesium ions do not exceed in equivalence the carbonic acid ion, HCO®; 
otherwise a mixture of lime and soda ash serves the purpose best. The abso- 
lute amounts depend, of course, upon the quantities of substances to be re- 
moved, and their relative amounts must be varied according to the infinitely 
varying proportions of the ions, Ca, Mg, HCO® and SOi. Every water must 
have its own proportions precisely adapted to its mineral content. The chief 
reactions in such water softening are represented by the following equations: 
1. CaCHCOa)^ 4- Ca(OH )2 = 2CaC03 + 2 H 2 O. 
2. Mg(HC03)2 2Ca(OH)2 = 2CaC03 MgCOH)^ 4- HaO. 
3. MgSOi 4- Ca(OH )2 = MgCOH)^ 4- CaSO^. 
4. CaSOi 4- NasCOs = CaCOs 4- CaSO^. 
Equations (1) and (2) show the removal of calcium and magnesium car- 
bonates, or “temporary hardness.” When the water contains sulfates of these 
elements, that is, is “permanently hard,” sodium carbonate is also used, and 
