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46
The gas is not immediately and directly poisonous in the tissues of any organism,
its action being chemical reduction, irrespirability and direct irritation to mucous
surfaces, which all require time for the development of lethal effect.
Hydrocyanic acid gas, on the other hand, is swiftly lethal to organisms by
almost immediate production of vitiating compounds with the protoplasmic
radicles constituting the animal and vegetable cell or living unit. The gas is rapidly
fatal to bugs, beetles, fleas, lice and mosquitoes and to some extent their progeny
in any stage of development, to rodents—and to man.
It is readily and rapidly produced by the addition of potassium or sodium
cyanide to sulphuric acid in proportions per unit capacity which give a lethal
percentage of gas in the atmosphere.
It is practically non-destructive to tissues themselves, but only to their capacity
for liveliness, does not attack metals, does not dull paint work, and does not discharge
colours of fabrics, as does sulphur dioxide.
It does kill the unskilful or careless operator and any person who for any reason,
or for want of it, is not responsive to danger notices, flags or warnings of whatever
nature.
Your Medical Officer is, therefore, at once attracted to and repelled from the
use of a gas of such lethal qualities, both in spite of and because of the practical
results attained in various ports abroad and at home, where it is used as a fumigant
on ships.
The one great objection is the danger to man. The question of costs of the
process to shipping is so intimately connected with the question of time (thus
money) saved to be balanced against intrinsic cost, that I have no data for computation
; it is one for the shipping companies to decide.
Your Medical Officer was approached by a firm which proposed to use the
Hydrocyanic Gas fumigation in the Port of London with full precaution against
danger to life of man.
One or two scientific and practical questions were discussed, such as proof of
clearance of the gas from the ship, its riddance from absorbtive insulating material
and " pockets " before the ship which has been under fumigation is handed over
to the crew.
The main point of discussion was that of the certificate of efficiency issued by
the Authority. I assured the representative of the proposers that, provided the
well-known or the prescribed unit lethal quantities and methods were utilised,
the Port Sanitary Authority would not hesitate to give a certificate in accordance
with the facts of the fumigation, and affirming its efficiency as and when supervised
by an officer of the Authority.
DATA FOR FUMIGATION BY HCN.
l-gall. of water=10-lbs.
1 ,, ,, =2 Winchester Quarts.
S.G. H..SO+ =1-8 l-pint=2-3-lbs. or 36'8-ozs.
£-oz. NaCN for 100-c. ft.
1-lb. NaCN for 3,200-c. ft.
American requirements.
For convenient handling, quantities are used in pounds of NaCN, Winchester Quarts of Acid,
Gallons of water.
KCN _65_ , oo
NaCN 48
add £ for KCN.
Proportions by Weight.
NaCN -f H2S0,=NaHS04 + HCN
49 : 96 are therefore proportion of NaCN to Acid, 1 : 2 by weight.
Excess of acid is advisable for completion of the reaction.
Theoretical Quantities.
For 1,000 c. ft.
NaCN 5-ozs.
H„S04 10-ozs. avoirdupois.
Water 10-ozs. (Water by vol. is less than \ weight of acid).