NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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being lighter than air, if there are two storeys begin at the top; and if there are
many rooms in a corridor begin at the farthest from the exit. An assistant may
go in front mixing the acid and water. Great quickness and care are essential
as the gas is so poisonous.
Of course if a tenement is to be disinfected all inhabitants must be cleared
out first. It is essential to have a clear space round the building to be fumigated.
It is recorded in one of the American experiments that persons walking 100
feet from the building could detect the odour of the gas the whole time.
The period of exposure should be two hours at least. It is better not to try
ventilation till 12—24 hours have elapsed. So far as we have seen in our
experiments (with the 1-2-4 formula) in 50 minutes the action of the sulphuric
acid on the potassium cyanide has been completed. So really the ventilation of
the building can be carried out in two hours if the doors and windows can be
opened from the outside. It is at the moment of entering the building after fumi-
gation that danger is most to be guarded against.
After opening the doors and windows from the outside certainly half an
hour should elapse before any one enters the building, and it is safer to
wait three hours. It depends altogether on the character of the building and if
there are many doors and windows which can be opened from the outside. We
have entered a room five minutes after the delivery of the gas has stopped.
There is a very good test suggested to us by Captain Dickinson, the Chemical
Analyst of Bombay. It depends on the formation of prussian blue by the gas if
there is any free in the room. A paste is made up consisting of ferrous sulphate
and caustic potash. A little is put on a rod of glass and the rod introduced into
the room. It is exposed to the air of the room for five minutes. If hydrocyanic
acid gas is present sodium ferrocyanide is formed. A few drops of pure hydro-
chloric acid are then run on the paste and a little water containing a few drops.
of ferric chloride added in a beaker. If there is any hydrocyanic acid gas at all
in the room blue colour is formed—deep blue if much gas ; faint green blue if a
little. If only a yellow colour is present it is quite safe to enter the room. This.
is a most delicate test. It will detect 1/780g r a i n o f h y d r o c y a n i c a c i d i n a v e r y
dilute liquid (Watt's Dictionary of Chemistry). It is much safer to rely on this.
test than on the odour of almonds, as the sense of smell seems to be paralysed
by the diluted gas after the first few whiffs. Even a trace of hydrocyanic acid in
the air leads to headache and nausea. It is so deadly that a whiff of fairly strong
gas kills at once.
It is obvious that the greatest care must be taken during the whole pro-
cedure. No naked lights should be left about a building as hydrocyanic acid gas
is somewhat inflammable.
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The action on animals, insects, plants, food, and fabrics.
Our experiments have been almost entirely on rats and rat fleas, and will be
detailed later. With respect to its action on certain insects, arachnoids and
mammals, Lounsbury states that flies are much more susceptible to the gas than
fleas, and fleas than bed bugs. Argas persicus —the tick of the fowl—is the most
refractory. "The eggs of the bed bug and of the flea (at least of the dog flea,
Pulex serraticeps) are devitalized almost, if not quite as readily as the parent
insects." Rats and mice are also readily killed.
On the subject of the action of the gas on plants a vast amount of literature
is available. Generally speaking the amounts of chemicals recommended above
as sufficient for fumigation do not destroy even delicate plants.
The action on foods and water is of importance. It is agreed that dried
grain is not made poisonous by the action of the gas.* An experiment was
performed by us on that point. Into a fairly air-tight room of 830 cubic feet
capacity the gas evolved from 340 grammes of 98 per cent. potassium cyanide
( equi val ent t o about 1 1/ 2 ozs. t o 100 cubi c f eet ai r space) was i nt r oduced. The
amount of hydrocyanic acid gas was calculated to be about 4.38 cubic feet at 26°C
entigrade. It was allowed to act for 20 minutes. Fleas were found dead after 5
minutes' exposure to the air of the room. The test rod showed a plentiful supply
of hydrocyanic acid gas to be present by the development of prussian blue.
The grains tested were: (1) bajri, (2) wheat , (3) jowari, (4) mula or radish, (5)
rice. Bajri, wheat, and rice were put into kerosine oil tins. A pipe bringing in
gas diluted with air (the mixture was driven in by a fan from the generating
flasks) was led to the bottom of the mass and another pipe was directed on its
surface. Mula and jowari were in small amounts and the gas mixture was
directed on their surface only.
Monkeys, rabbits guinea-pigs, hens, and pigeons were fed on the grains for
twenty-four hours; none became ill.
Chapatis were made of the wheat, jowari, and bajri and given to monkeys
and hens with no ill-results.
On the other hand moist food-stuffs, such as water, milk, butter, and flesh,
are said to absorb the poison. We have not tried experiments on this. Meat and
water exposed to the gas are said by Lounsbury to have proved fatal to dogs.
Therefore, during the fumigation of a building, all such moist food-stuffs ought
to be removed. Dry foodstuffs can be left alone, but had better be thoroughly
aired before use.
Another question is: "Does the gas injuriously affect the germinating
powers of the grain?" This is of importance in view of the amount of grain
stored in native houses to be used later for sowing.
*Repor t of Gover nment Ent omol ogi s t t o Cape of Good Hope, 1901.
8
As all the experience of workers in America and South Africa goes to show
that even delicate plants are not injured by the gas when present in sufficient
concentration to clear them of insects, the answer would be that it is not injurious.
An experiment we did confirmed this. Certain amounts of the above grains
subjected to the gas were planted, and their growth compared with control grains.
which had not been fumigated. No difference in the rate of growth could be
detected. So during a fumigation, stored dry grain can be left in the house
without fear of rendering it poisonous or of destroying its germinating power.
Unlike Sulphur dioxide gas hydrocyanic acid gas has no action on metals
or fabrics.
The action of the gas on bacteria.
About 4.38 cubic feet of diluted gas were introduced into a room of capacity
830 cubic feet and allowed to act for twenty minutes on bacteria. Cultures of
streptococci, Bacillus typhosus, Bacillus coli , and Bacillus pestis on agar slopes
in test tubes with their cotton-wool stoppers removed were put in the room.
After the experiment subcultures on agar showed that the plague was overgrown
with a yellow contaminating organism. The other bacteria had not been killed by
the action of the gas.
This coincides with the experience of the Government Entomologist of the
Cape of Good Hope as noted in the Report for 1901: "Cultures of the plague.
bacillus were found to be unaffected when exposed by substituting a piece of
gauze tied over the top for the plug of cotton-wool ordinarily used for stopping
culture tubes by one hour in 1 to 80 gas—the severest test employed."
Disinfection for plague.
Its harmless effect on the plague bacillus does not condemn hydrocyanic
acid gas as a preventive for the spread of plague. Preventive measures for
this disease fall under two heads :—
(1) Disinfection of clothing of railway and other travellers.
This is.
equivalent to the destruction of plague germ carriers, namely, fleas.
(2) Disinfection of plague houses. This is equivalent to the destruction
of plague rats and of plague fleas.
I .—The use of hydrocyanic acid gas for the disinfection of clothing .
There is no question of its great efficiency, its cheapness, and the rapidity
with which the operation can be carried out—all matters of importance. It has
further the advantage of having no destructive effect on fabrics.
Our experiments were carried out in two ways :—
(a) First method.—Potassium cyanide was mixed with sulphuric acid and
water (1 of sulphuric acid to 19 of water) at first in glass flasks and in later
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experiments in a specially constructed leaden vessel. The mixture was heated
over a Bunsen flame, the whole being placed outside the room to be fumigated,
Tubes conducting the undiluted gas were led directly into the room in some cases ;
in others the tubes were led into a large iron vessel from which the gas was
pumped by a powerful fan into the room through a large delivery pipe. There
was a second opening in the iron vessel through which air was pumped and
mixed with the hydrocyanic acid gas. It was the largely diluted hydrocyanic
acid gas that was introduced. The quantities of hydrocyanic acid gas produced
were calculated as follows : about 82 grammes of pure potassium cyanide taken
as 100 per cent. will produce I cubic foot of hydrocyanic acid gas. We used
for one charge 85 grammes of 98 per cent. potassium cyanide or the equivalent
amount of other strengths of the salt. We were at the time unaware of the
necessity of using sodium chloride free potassium cyanide stated by Wilmon
Newell in his paper and quoted above on page 2.
With the 85 grammes of potassium cyanide we mixed 35 c.c. of strong
commercial sulphuric acid diluted to 700 c.c. with water ( i.e., H2SO4 1i n
2 0
strength).
The room in which these experiments were carried out is comparatively air-
tight. It is of the following dimensions : length 12 feet 6 inches ; breadth 7 feet
8 inches. The roof slopes upward from a wall 5 feet 8 inches to one of 11 feet
8 inches. The cubic capacity is about 830 cubic feet. The walls are of cement.
The floor is of stamped earth. The roof is of corrugated iron made rat-proof
by being firmly fastened to the walls. There is a large window 2 feet 7 inches
by 3 feet 6 inches and opposite it a large door 3 feet 2 inches by 5 feet 6 inches.
The window is capable of being tightly closed by shutters. Through the shutters
the delivery pipe was led into the room. The door, which leads into another
room, was closed and any cracks or obvious holes sealed over, so that a com-
paratively air-tight chamber was produced.
In the different experiments varying amounts of gas from 2 to 4.38 cubic feet
were introduced into the room for different periods of time.
The results giving details of amounts of gas used, the time of exposure, and
the effect on fleas in different situations are given in Experiments I to VI.
Rats were introduced into the room simply to discover what amount of gas
would be necessary to kill them. They require more gas and a longer exposure
than fleas. But the effect of the gas on them is of no importance for this investi-
gation—namely, disinfection of clothing.
Two points were aimed at : (a) to obtain a sufficient penetration of clothes,
and (b) to conclude the whole operations in a short period of time, so that no
great delay to the persons waiting for the clothes would occur.
Both objects were attained. Bundles of clothes wrapped fairly tightly up
were thoroughly penetrated by the gas. A consideration of the tables will show
this. For example, in Experiment I the gas penetrated through four bags,
—three of coarse blanket and one of cotton, killing 10 fleas out of 11 placed
centrally. It penetrated through three bags, two of blanket and one of cotton
killing all the fleas placed centrally. The gas was led direct from flasks outside
the room without the use of a fan. About two cubic feet of gas were introduced
into the above described room of 830 cubic feet capacity and the time of exposure
was 51 minutes.
Experiment II shows the same condition of affairs as Experiment I, but
a shorter exposure of 30 minutes with not so successful a result.
The most successful experiment is No. III. About 4.38 cubic feet of gas
were pumped into the room by a fan for 20 minutes and then the delivery of gas
was stopped. The gas was distributed by nine small tubes throughout the
room. The fleas in all parts of the room were killed, even though the tubes con-
taining them were wrapped up in several layers of thick sheeting and blanket.
But in series 3 where they were surrounded by a durree, blanket, and coat very
tightly rolled, eight fleas remained alive out of nine. Fleas put in cages with bran
and sand at the bottom were all killed in this experiment, showing that there
is a certain penetration of the gas into these substances,—an important point in
the disinfection of houses, as the fleas bury themselves in dust, grain, etc.
If clothes are left loosely in boxes, can we say the gas will penetrate suffi-
ciently to kill? If so, it would obviate the necessity of hanging out the clothes
for disinfection.
Experiments IV and V were tried to determine this point. If pipes were
led with great care into the boxes, fleas were killed. But it will be noted that
failure occurred in some instances, where, perhaps, owing to the tube being
kinked, some obstruction to the entrance of the gas occurred. It is much
safer to hang up the clothes on pegs or scatter them loosely about the room.
In Experiment IV it is noted that the room was entered in 30 minutes from
the commencement of the operations. The disinfection of the clothes was very
thorough, so that it is possible by pumping gas into a room to kill fleas in clothes
and deliver clothes back to their owners in thirty minutes. The use of the test
rod mentioned on page 6 enables one to enter the room with safety.
(b) Second method.— The fan and pipes are, however, a complicated and
expensive means of distributing the gas. Accordingly the method of producing
the gas, as detailed on pages 5 and 6, was tried.
A flea-tight and very air-tight godown—one of those used in the Plague
Commission's experiments—was taken. Its cubic capacity is about 346 cubic
feet. Into a small china vessel 4 ozs. of water were put, 2 ozs. of commercial
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strong sulphuric acid were added evolving heat, and then I oz. of potassium
cyanide was finally put in and the door closed. The gas was left in contact with
the clothes for forty minutes and then the door was opened. The room was
entered fifteen minutes later. The fleas left in different parts of the room were
a l l k i l l e d , —t h e , ' g a s e v e n p e n e t r a t i n g t h r o u g h f o u r b a g s , t h r e e o f b l a n k e t a n d o n e
of cotton, killing all the fleas placed centrally. Fleas were put in various situa-
tions in a box full of clothes ; some escaped. For details see Experiment X.
So again it was shown that it is necessary to take the clothes out of a box and
hang them up. The strength of gas used was less than one-third that suggested
by fumigators elsewhere (1 oz. to 100 cubic feet) ; yet it was completely success-
ful. The action of the sulphuric acid on the potassium cyanide is not com-
pleted for forty minutes probably, as when the door was opened in the above
experiment fumes were still being evolved from the generating pot. After sixty
minutes the evolution of gas is completed. Accordingly some means must be
thought of to cut off the supply of gas, say after fifteen minutes, to allow
one to enter the rooms safely and give the clothes back quickly to their owners.
That the fleas are killed in five minutes was shown in one of our experiments.
In five minutes after the commencement of the evolution of gas a tube containing
fleas was withdrawn ; they were all dead.
In another experiment larvæ of rat fleas loose on sand were subjected to the
same strength of gas, I oz. potassium cyanide to 346 cubic feet for an hour.
They were all killed. Controls were all living at the time of examination.
Eggs and cocoons of the rat flea were subjected to a stronger gas, 1 oz. to
100 cubic feet. The eggs were all killed. Larvæ hatched out of control eggs
not subjected to the gas but otherwise under the same conditions.
All the cocoons, however, were not killed by the gas.
But the important point is to kill infected fleas. Infected fleas have not
been shown to transmit plague bacilli to their eggs.
I I . — T h e D i s i n f e c t i o n o f P l a g u e H o u s e s — t h a t i s t o s a y , t h e d e s t r u c t i o n
of rats and fleas in these houses.
A room was chosen which presents the characters of most native huts in
Bombay,—that is to say, not at all air-tight. Its length is I2 feet 6 inches ;
breadth 15 feet 7 inches ; height at one end 5 feet 6 inches ; at the other end
I I
feet 4 inches. The cubic capacity is 1,640 cubic feet. The floor is of
stamped earth and the roof of country tiles. Below the edge of the roof and the
smaller end wall a small space communicates with the outside. There is also
very free ventilation between the edges of the tiles. There are two large
windows which can be well closed with shutters and two doors, one of which com-
municates with the outside and one with the small room described on page 9.
C2
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In the following experiments as many of the large ventilating holes as could
be filled up were closed with tightly packed paper and the room was made as
air-tight as most native huts can be made.
In the floor of the room four types of rat burrows were present, each
consisted of a small wooden box to contain rats and fleas and one or two passages
leading from it to the floor of the room. The boxes measured 21 by 10¾ by
12 inches. They are fitted with hinged lids and are sunk in the ground. Inside
each box is a rack to hold test-tubes containing fleas. The cage for the rat
can be placed inside the box. The channels consist of a series of short sections
of earthenware pipes sunk in the ground. Each section is made up of concave
country roofing tiles placed together to form a somewhat tapering pipe, the
narrow end of one section fitting into the broad end of the other. The narrow
end of the lowest of these sections projects slightly into the box. These
"burrows" measured from 5½ to 12 feet.
There are four types of burrows :—
Type A.—A blind burrow with a single opening.
Type B.—A blind burrow with a single opening inside the room. The
box for the cage was outside the room for facility of obser-
vation.
Type C.—Two burrows with S-shaped curves on the horizontal, leading to
the box containing the cage.
Type D.—Same as type C, but with the curves vertical.
Over the tiles 4 to 6 inches of earth were placed and, after the fleas and rats
had been placed inside, the lids of the boxes were carefully sealed down with moist
clay.
These burrows and observation chambers were originally devised by Captain
Gloster, I.M.S., for his experiments with the Clayton gas apparatus.
The results of experiments in this room are detailed in Experiments VII to
Ix.
Experiment VII shows the results when the gas was generated outside the
room and introduced by tubes without pumping. Some tubes were also led a
little distance into the burrows and the mouth of the burrows closed up. The gas
is lighter than air and better results were obtained at the upper layer of the room
than on the floor. Neither rats nor fleas in the burrows were affected by the
gas. At the level of the floor many fleas in cages with sand at the bottom
managed to escape by burrowing into the sand, while those in bran were killed.
In Experiment VIII the gas was introduced by larger calibre tubes and
pumped in by a fan ; four of the tubes were led into the burrows and the mouth
of the opening closed up with mud round the pipe. This was a most successful
experiment. Fleas in all situations,—in the room, in cages with sand and bran at
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the bottom, and in test-tubes in the burrows,—were killed. Six out of eight rats
on the floor or 4 feet above floor level were killed and seven rats at higher level
were all killed. The rats in burrows A and C were killed. There was some
obstruction in burrow D preventing all the gas entering. Burrow B was the
observation burrow and was opened during the experiment when the rat was
found to be sick. The whole experiment was completed in forty minutes with
an introduction of about 438 cubic feet of the gas equivalent to 340 grammes of
98 per cent. potassium cyanide about ¾ oz. to the 100 cubic feet space.
Experiment IX.—Rats loose in the burrows were also killed.
Attempts were made to dispense with the complicated apparatus of fans
and tubes by generating the gas inside the room, as described on pages 5 and 6.
They are detailed in Experiments XI and XII. At higher levels of the room
rats and fleas were killed, but rather unsatisfatory results were obtained at floor
levels, and the experiment was an absolute failure in the burrows, both rats and
fleas escaping.
Therefore, with artificially constructed burrows and the use of an apparatus
with a fan to pump in the gas small rooms can be disinfected thoroughly in, say
one hour.
Whether natural burrows can be penetrated by the gas remains to be
proved. As the gas is so poisonous, special permission must be obtained before
experiments can be carried out. As far as we can see at present with small
isolated huts when the inhabitants are all cleared out there would be no danger.
The inhabitants could return with perfect safety in two hours after ventilation
was begun, but to make it absolutely sure, say twelve hours.
When houses are placed close together, as in a Punjab village, the whole
would require to be evacuated simultaneously for two reasons :-
(1) As rat burrows run from one house to another the gas produced in one
house might find ingress into others causing great danger to the
inmates. The faint almond odour of the gas and the taste at the back
of the throat is only appreciated for the first few moments. The gas
then paralyses the sensory nerves and though dangerous quantities
may be present they would not be appreciated.
(2) For a successful experiment such contiguous houses should be done
simultaneously in order that no rats may escape.
With tenements in cities like Bombay evacuation of the whole tenement
would be necessary for the same reasons. Further, a clear space round is a
necessity, as even when only 4 ozs. of potassium cyanide were used in a small
godown the odour of the gas was perceived twenty feet away when the door was
first opened. See also on this point what is noted above on page 6. For these
reasons the wholesale use of the gas is impossible. It ought first to be tried