IOWA ACADEMY OP SCIENCE 
141 
remoYes calcium sulfate already present or formed as in (3) by the reaction 
expressed in (4). 
The chemical scheme that I have outlined is the one that is being used by 
the railroads of Iowa so far as they have taken up the enterprise. The present 
situation is indicated by the following points from the correspondence with the 
chief chemists, or engineers of tests as they are in some cases called. Mr. 
M. H. Wickhorst of the Burlington road writes that they have installed three 
large plants which are giving very satisfactory results. Mr. Geo. D. Prentiss 
of the C., M. & St. P. states that his road has attained excellent results at 
Sioux City and in another plant across the river in South Dakota. Mr. P. O. 
Bunnell states that the Rock Island could scarcely maintain its present schedule 
in some regions without the softening plants, and that their system of soft- 
ening would probably soon be extended to Iowa. 
To the Chicago & North-western railroad, however, is due the credit of the 
widest application of water softening on a large scale. The information at 
hand comes from Mr. Geo. M, Davidson, engineer of tests for many years, 
through correspondence and a paper on the North-western softening system, 
published in the Western Railroad Club. 
This road has in successful operation forty-one softening plants, of which 
twenty-two are in Iowa. With three exceptions these plants have a capacity 
of 240,000 gallons a day. The chemical process has already been essentially 
described. Only a few of the prominent mechanical features and the results 
can be given. 
The apparatus is comparatively simple and is constructed in the shops 
belonging to the road. The essential vessels, excluding the storage tanks for 
the hard and for the softened water are, a small tank to hold the mixture of 
milk of lime and sodium carbonate, the mixing tank provided with stirring 
blades, and two settling tanks. The hard water receives the softening solution 
just before it reaches the measuring apparatus, which consists of a two-com- 
partment tilting box, each compartment holding 100 gallons. The tilting vessel 
operates two pumps whose cylinders supply the softening solution and the 
length of the stroke can be regulated to supply the desired volume. The 
weight of water in the tilting vessel is also the source of power to operate the 
stirring blades and they are reversed with every change of position. Prom 
the mixing vessel the water goes to the settling tanks of which there are two, 
each having a capacity of 77,000 gallons. From them the clear water is pumped 
to the storage tank for use. 
The effectiveness of the process may be illustrated by the results attained 
by three plants, at Council Bluffs, Denison and West Side. The average of the 
incrusting solids of the untreated waters is 644 parts per million, and of the 
treated waters seventy-four parts. About four grains per gallon or seventy 
parts per million of incrusting solids marks the usual efficiency without much 
regard to the character of the water originally. This amount is regarded as 
practically harmless. 
The results of the use of this softened water in railroad engines have been 
very gratifying. The first effect in boilers that have used hard waters is to 
cause leakage owing to the loosening of old scale. If the tubes are then re- 
rolled there is very little farther trouble, and the general results is that boiler 
repair and time lost by engines in the repair shop are reduced to a small frac- 
tion of what they were when untreated water was used. 
