PART III.—POISONOUS GASES : CARBON MONOXIDE- 
CHLORINE—HYDRIC SULPHIDE. 
I.—Carbon Monoxide. 
§ 43. Carbon monoxide, CO, is a colourless, odourless gas of 0-96709 
sp. gravity. A litre weighs 1-25133 grm. It .is practically insoluble 
in water. It unites with many metals, forming gaseous or volatile 
compounds ; e.g., nickel carbon oxide, Ni(C0 4 ), is a fluid volatilising 
at 40°. These compounds have, so far as is known, the same effects 
as CO. 
Whenever carbon is burned with an insufficient supply of air, CO 
in a certain quantity is produced. It is always present in ordinary 
domestic products of combustion, and must be exhaled from the 
various chimneys of a large city in considerable volumes. A “ smoky ” 
chimney or a defective flue will therefore introduce carbon monoxide 
into living-rooms. The vapour from burning coke or burning char¬ 
coal is rich in carbon monoxide. It is always a constituent of coal 
gas ; in England the carbon monoxide in coal gas amounts to about 
8 per cent. Poisoning by coal gas is practically poisoning by carbon 
monoxide. Carbon monoxide is also the chief poisonous constituent 
in water gas. 
Carbon monoxide poisoning occurs far more frequently in France 
and Germany than in England ; in those countries the vapour evolved 
from burning charcoal is a favourite method of suicide, on account of 
the supposed painlessness of the death. It has also occasionally been 
used as an instrument of murder. In this country carbon monoxide 
poisoning mainly takes place accidentally as the effect of breathing coal 
gas ; possibly it is the secret and undetected cause of ill-health where 
chimneys “ smoke ” ; and it may have something to do with the sore 
throats and debility so often noticed when persons breathe for long 
periods air contaminated by small leakages of coal gas. 
The large gas-burners (geysers) emit in burning under certain con¬ 
ditions much carbon monoxide. It has been proved by Grehant 1 that 
1 Compt. Rend. Soc. de Biol., ix. 779-780. 
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