70

THE COLLIERY GUARDIAN

January 12, 1917.

sulphuric acid and decomposable salts of that acid.
The sulphates of iron and aluminum have little effect
on iron while the water is cold, but they are corrosive
if introduced into a boiler as they are decomposed, and
the acid is set free to attack the metal while the iron
and aluminum are precipitated as hydrates. This pre-
cipitation does not take place in water containing much
free acid, but readily occurs in that containing little or
no free acid.

The free sulphuric acid readily attacks iron, and it is
this that necessitates the use of wood-lined or bronze
pumps, and wood pipe. It is known that mine water
will affect cement in.the case of ditches used to carry
mine water, and prevent the contamination of a stream
utilised for boiler supply.

In some cases it becomes desirable to remove from
the water the corrosive substances that it carries, and
which, as has been seen, are free sulphuric acid and
sulphates of iron and aluminum. The free sulphuric
acid can most readily be removed by neutralisation with
an alkali.. The three common commercial alkalies that
are cheap enough to be considered are soda ash (crude
sodium carbonate),, lime, and limestone. Of these,
soda ash acts most rapidly, because it is readily soluble.
The substances formed by its reaction with sulphuric
acid are sodium sulphate and carbon dioxide. Though
cheap, this reagent is too expensive to be used in large
quantities.

Lime Slower than Soda Ash.

Lime acts more slowly than soda ash, because it is
much less soluble, but as it becomes finely divided as
soon- as it is slaked, a large surface is presented, and
its action is sufficiently rapid for use in some cases;
calcium sulphate is formed, by the reaction. Lime is
quite largely used in the treatment of water for' boiler
purposes, and sometimes in the purification of water for
domestic use. When the water is to be used for boiler
feeding, it is necessary, as far as possible, to remove the
calcium sulphate formed by the use of soda ash, which
precipitates the calcium as a carbonate.

The cheapest of the three alkalies mentioned is lime-
stone, but its action is slow unless it is finely pulverised.
It is this substance that is responsible for most of the
natural neutralisation of acid waters. In order that
its action may be effective, it is necessary that the
deposit of iron compounds on the surface of the stone
be removed, Otherwise the underlying limestone will be
so protected from the action of the water that neutrali-
sation will proceed but slowly. It is this fact that
makes it impractical to neutralise a highly polluted
wrater by merely allowing it to flow over limestone;
calcium sulphate is formed, as when lime is employed.

The sulphates of iron and aluminum can be removed
by the-same means that prove effective in the case of
free acid. Ferrous sulphate, iron, and aluminum can
be precipitated as hydrates, or basic sulphates of uncer-
tain composition. The exact form of the precipitate
probably depends principally upon the composition of
the water, the concentration, the amount. of alkali used,
and the temperature.

The neutralisation of water is at present an uncom-
pensated expense, but it is worth while to see what
possibilities exist for obtaining substances of commer-
cial value. It has been shown that the corrosive sub-
stances in the mine water are. principally free sulphuric
acid, and sulphates of iron and aluminum. Sulphuric
acid is one of the most widely used chemicals, and has
so many applications that its market, is stable. The
only practical way to get it out of the water, however,
involves . the, formation . of substances that have little
commercial value, and .from which the sulphuric acid
cannot be recovered economically. ■	-	,	■ '

In the case of the sulphates of iron and aluminum it
is different. When the free acid is neutralised, the iron
and aluminum sulphates are precipitated as basic
sulphates, the composition of which in any particular
case it is impossible to give. It is known that they
contain the metal, OH and S04. By drying and
calcining this precipitate, the sulphuric acid can be
driven off and recovered. Sulphuric acid is so cheap
that this process would not he commercially profitable,
but the value of the acid obtained would partly or wholly
defray the cost of treatment, and might make it possible
to purify water that otherwise could not be treated.

The other substances to be considered are the sul-
phates-: Lof iron and aluminum. Commonly, the
aluminum is much less in amount than the iron, and
while aluminum sulphate has a value, it could not be
separated from the iron' without prohibitive expense.
The iron has two known uses, and it is possible that
others may be developed. In the first place, ferric
hydrate,’ properly prepared, is used to remove H2S from
manufactured gas. The precipitate obtained by
neutralising mine water ought to be useful for this pur-
pose. The substances now most employed for the
process in this country are natural iron oxides made
from certain ores and artificial iron oxides, which are
made by rusting iron borings and turnings. Some
purifier imported from Europe has been made by a
process of precipitation from solution. Many hundreds
of tons are used in this country annually. Good oxide
is worth from 6 to 8 dols. per ton.

Utilising Precipitated Iron.

The other use it seems possible to make of this preci-
pitated iron is that of pigment. Immense quantities
of iron oxides are used as pigments for various purposes.
Some of this is natural and some artificial. Its value
depends- upon its colour and/freedom from impurities.
The highest priced -of all these-oxides is rouge. . This
is used for polishing powder because of its freedom from
foreign substances or hard particles that would cause
scratching.

The precipitate of basic iron sulphates can be calcined
and the -substance, left after driving off the. sulphuric
acid from water will be ferric oxide. Its purity, of
course, will depend upon the method of precipitation,

.which will largely govern the amount of calcium sul-
phate contained in the precipitate.; The colour pro-
duced depends upon the purity and the method of
calcination. There seems to be no reason why it should
not be possible to produce in this way a desirable pig-
ment.

The field of chemistry in the treatment of mine water
has heretofore been studied almost entirely from one
viewpoint, that of prevention of damage to pipes,
pumps, and boilers. It seems probable, .however, that
it will be found worth while to investigate it with the
view of discovering the least expensive methods of
removing the undesirable substances, and of learning
what valuable products can be produced.

TESTING MINE RESCUE APPARATUS.*

By C. E. Pettibone.

The experiments described below were conducted on
the testing of the rescue apparatus (Draeger pattern)
used in the mines of Picklands, Mather and Company,
of Cleveland, Ohio, and it is believed that the principles
of the test can be applied to any type of rescue
apparatus, it being only necessary to develop a few con-
nections, and make other unimportant modifications.

Many articles and much discussion have been devoted
to setting forth the dangers that might arise and have
arisen from leaks in breathing apparatus. Any consider-
ation of the merits of different types of these apparatus
has always brought up the question of negative pressure,
or suction, and of the amount of the apparatus which is
under such pressure.

In order to ascertain whether leaks in the apparatus
are important, the following experiment was tried with
an apparatus not of the -positive pressure design. Several
men were sent into a room filled with formaldehyde
fumes. All the men had good cartridges in their
apparatus, and were told to come out as soon as they
recognised the odour of the formaldehyde vapours. None
of them, however, had any trouble with his apparatus.

A cartridge with a small hole was then inserted in the
apparatus worn by one of the men, but none knew which
man -had the defective cartridge. In a short time the
man with the punctured regenerator was obliged to

Testing Apparatus.

retire. This test was tried several times, and in each
case the man with the defective cartridge was unable
to remain in the formaldehyde fumes.

A similar operation was tried with the Fleuss
apparatus, a hole being cut in the inhalation tube that
connects the breathing bag with the mouthpiece.
Similar results were obtained. There was therefore
convincing evidence that leaks in the apparatus would
prove very serious, if not fatal, when operating in
poisonous gases such as carbon monoxide. It was pro-
bably because of criticism of this character that the
Draeger Company, several years ago, changed its
apparatus to the positive pressure type, in which a
greater portion of the apparatus in use is placed under
positive pressure. The ordinary tests, made with the
litre bag and gauze, show only that the reducing valve
and injector are furnishing the desired quantity of
oxygen and are producing the required positive and
negative pressures necessary to maintain the circulation
of air through the apparatus. Neither of these tests
will indicate leaks. This fact was established by testing
the apparatus with the punctured potash cartridge men-
tioned previously.

The “ smoke house test,” which consists in wearing
the apparatus in smoke or formaldehyde fumes, will not
indicate leaks in parts of the apparatus that are under
positive pressure, and it is questionable whether minor
leaks in those parts that are under negative pressure
would be discovered. Of course, leaks of this latter
type, if not determined in the smoke room, would pro-
bably not be dangerous in the actual use of the apparatus
unless they become larger. But danger lies in the fact
that such minor leaks would, in all probability, become
larger and more serious while the apparatus was being
worn in actual mine rescue work.

It was therefore felt that some more definite method
of determining leaks was desirable. At first different
kinds of rubber plugs were- used, and other provisions
were made by which the open ends of the apparatus
could be blanked off. Then, by admitting oxygen from
the cylinder, the entire apparatus could be put under
pressure. . The apparatus was then immersed in water,

* Coal Age. ■ (From -a paper read before the Mining Section
of the U.S. National Safety Council.)

care being taken to keep the finimeter above the surface.

Many leaks that could not otherwise be determined
were thus made apparent. But there were several
objections to this manner of procedure. First, the pres-
sure put on uhe apparatus was not known; consequently,
it was not determined whether the apparatus was being
overstrained. Second, the constant immersing of the
apparatus^ in water is unquestionably not. beneficial.

The makers supplied three, testing parts by which the
various connections could be blinded, and whereby
proper connection could be made to a pressure gauge;
and a blank was made for the relief valve, so that it
could be used without removing the valve itself. A
water U-tube was arranged, as shown in the illustra-
tion, graduated, for the reading of pressures, in tenths
of ounces. By soldering a pipe in the side of a potash
cartridge near the base, and by other connections, the
circulation could be tapped to determine the pressures
existing under normal operation lat five different points
in the apparatus. The following results are the average
of tests of several apparatus with different'men wearing
them, and with the breathing bag set to release at
+ 2|oz. :—

rpes-fc	Minimum

U-tube attached to During pressure.

Oz.

1	...	Inhalation tube between < Inhalation	...	/

bag and mouthpiece { Exhalation ... 1 to 2|

2	...	Exhalation tube between (Inhalation	...	|

bag and mouthpiece {Exhalation ... 1| to

3	...	Inhalation tube below (Inhalation	...	|

bag	{Exhalation	...	to 2|

’4	...	Exhalation 'pipe below (Inhalation	...	—f

bag	{Exhalation	...	|to2"

5 ... Bottom of potash cart-(Inhalation ...	|

ridge	{Exhalation	...	lito2|

It will be understood-that the pressure as measured
is during inhalation, where it is a negative pressure as
indicated.

Thus the maximum pressures in the apparatus are
2|oz. in back parts and 2^oz. in front parts. When
the bag releases at 2^oz. in front, 2|oz. are recorded
in the back parts. This pressure is about what can be
obtained by inflation with the lungs.

After determining the maximum pressure under which
the apparatus operated, namely, 2|oz., it was decided
to test it with 100 per cent, overload, namely, at 5 oz.

of pressure. It was, however, found impos-
sible to make the apparatus so tight that the

water in the U-tube ' would permanently
remain at 5 oz. This was due unquestion-
ably to infinitesimal' leaks in the fabric and
valves.

Moreover, if the smallest possible pin holo
was made in the potash cartridge, the pres-
sure was relieved, and the water dropped
within half a minute. It was . therefore
decided that the apparatus should be con-
sidered as being in good condition when
under a pressure- of 5 o-z., if the water did
not fall in less time than one minute.

In operation, the. U-tube is filled with
water to a point just below the reservoir, and
the scale is adjusted so that zero on the
scale corresponds to the height of the
water. Care must be taken to make sure
that there are no bubbles of. air in the
column.

The tests are a.s follow :—Test 1 : Con-
nect the entire apparatus as shown in the
figure. Blank off one tube at the top of the
bag with the test plug B. Connect the other
tube to the stop-cock C of the testing set, and
attach this to- the U-tube. Plug up the- release valve
with the plug. Admit oxygen very slowly from the
cylinder until a pressure of 5 oz. is obtained. Shut off
the oxygen. If the apparatus is free from leaks, the
water will remain at this level, or descend very slowly,
taking longer than one minute to descend. If the test
shows leaks in the apparatus, they may be located by
testing portions of the apparatus as follows, but when-
ever a leak is located and corrected the entire apparatus
should be connected up and re-tested.—Test 2 : Test
the flexible tubes by closing one end with the plug B,
and connecting the other to the U-tube by means of C.
—Test 3 : Using tubes tested in test 2, test the bag by
coupling the two front connections by means of the one
flexible tube, and the right hand back connection to the
U-tube by the second flexible tube, the left hand con-
nection being capped. (In tests 2 and 3 inflation can
be obtained from the lungs or. a small pump.)—Test 4 :
Test the entire back of the apparatus by capping the one
flexible pipe, and connecting the other to the U-tube. If
a leak is indicated, it is advisable to remove the potash
cartridge, and insert a cartridge plug consisting of two
bell-shaped cups connected by a pipe fitted with a stop-
cock. While the valves at the top and bottom of the
potash cartridges are shut when the cartridge is removed,
they do not close tight enough for this test.—Test 5 :
Test both circulation pipes in turn, by capping one end
and connecting the other to the U-tube by means of C.
—Test 6 : Used tested circulation pipes, test the bottom
parts by closing the stop-cock in the cartridge plug
described above.—Test 7 : Test the entire back parts
with the stop-cock in the cartridge plug open, using
tested circulation pipes.

When a leak has been localised, it can usually be
found by feeling with a damp finger. If not, the part
may be immersed in water. The foregoing tests of the
apparatus, if made monthly, will maintain it in excel-
lent condition.- In case of actual rescue work, the test-
ing of the entire apparatus, as described, consumes only
a few minutes; and, if desired, the usual pressure test
of the reducing valve and the injectors can be
obtained from the U-tube. Of course, the smoke

house test can be employed in addition to those
just described.