Much expense can be saved in fuel and boiler repairs by a little
preliminary expenditure of money in securing a supply of good water
for the steam boilers of a new establishment. Well water is nearly
always inferior to the running water of streams; water from mines is
especially hurtful, containing, as they do, large quantities of free
sulphuric acid. Wells along the sea shore or on the banks of rivers
affected by the tides, are likely to be saturated with chloride of
magnesium. It is in determining these points that these ready tests of
feed water are most useful.
A thorough and really scientific analysis of feed water is a costly
and tedious process, but _a simple and perhaps sufficiently accurate
test_ may be made as follows: take a large (or tall) clear glass vessel
and fill it with the water to be tested; add a few drops of water of
ammonia, until the water is distinctly alkaline; next add a little
phosphate of soda; the action of this is to change the lime, magnesia,
etc., into phosphates, in which form they are deposited in the bottom
of the glass. The amount of the matter thus collected gives a crude
idea of the relative quality of sediment and scale-making material in
the water.
Water turning _blue litmus paper red_, before boiling, contains an
acid, and if the blue color _can be restored by heating_, the water
contains carbonic acid. Litmus paper is sold by druggists.
If the water has a foul odor, giving a black precipitate with acetate
of lead, it is sulphurous.
An experiment may be tried by dissolving common white or other pure
soap in a glass of water, and then stirring into the glasses of water
to be tested a few teaspoonsful of the solution; the matter which will
be deposited will show the comparative amount of the scale-making
material contained in the feed water.
_In order to ascertain the proportion of soda to the feed water the
following method is recommended_:
1. Add 1/16th part of an ounce of the soda to a gallon of the feed
water _and boil it_. 2. When the sediment thrown down by the boiling
has settled to the bottom of the kettle, pour the clear water off, and
3, add 1/2 drachm of soda. Now, if the water remains clear, the soda,
which was first put in, has removed the lime, but if it becomes muddy,
the second addition of soda is necessary.
In this way a sufficiently accurate estimate of the quantity of soda
required to eliminate the impurities of the feed water can be made and
the due proportion added to the feed water.
By exercising a little judgment, the use of pure chemicals, with
well cleaned vessels, test tubes, etc., the following reagents will
determine the character of the most important elements which injure the
iron surfaces of a steam boiler.
Carbonic acid is indicated by baryta water.
Sulphates are indicated by chloride of barium.
Chlorides are indicated by nitrate of silver.
Lime salts are indicated by oxalate of ammonia.
Organic matter is indicated by chloride of mercury.
The “base” of the better class of the various patented boiler compounds
is tannin (whence tannic acid) and some form of alkali, and if the
compounds were to be deprived of these two elements they would be
absolutely worthless.
Where they contain, as some certainly do, sal-ammoniac, muriatic,
hydrochloric and sulphuric acids, they cannot but act as boiler
destroying agents.
Tannin or tannic acid is the principal ingredient used in preparing
leather. It is found in a great variety of plants—sassafras root has
it in large proportion, the gall nut and the bark of various trees,
especially the oak produce it.
It is the presence of this acid that gives their only value to very
many “compounds,” tan bark, gum catechu (which sometimes contains
one-half part of tannic acid), etc. The acid seems to have but little
effect where large quantities of sulphate of lime are present, but in
waters where carbonate of lime predominates its detersive qualities are
more marked.
The records of the Patent Office show that one boiler compound
_contains 23 per cent. of catechu_, and others, 60, 81, 5,
respectively, by which may be inferred the large quantity of this
agent, which has been sold in combination with other chemicals,
principally soda.