82 POISONS : TIIEIR EFFECTS AND DETECTION. [§ 50. 
A more reliable method to detect small quantities of carbon monoxide 
is, however, as proposed by Hempel, to absorb it in the lungs of a living 
animal. 
A mouse is placed between two funnels joined together at their 
mouths by a band of thin rubber ; one of the ends of the double funnel 
is connected with an aspirator, and the air thus sucked through, say for 
half an hour or more ; the mouse is then killed by drowning, and a 
control mouse, which has not been exposed to a CO atmosphere, is also 
drowned ; the bodies of both mice are cut in two in the region of the 
heart, and the blood collected. Each sample of blood is diluted in the 
same proportion and spectroscopically examined in the manner detailed 
at p. 66. The limit of the test lies at about 0-03 per cent, when large 
volumes of the gas are used. 
A more delicate reaction, and one which may be used for the estima¬ 
tion of CO, is that of Nicloux and Gautier. The gas to be examined is 
freed from unsaturated hydrocarbon by shaking with fuming sulphuric 
acid, and from carbon dioxide by passing over soda-lime ; it is then 
passed over iodine pentoxide heated by means of an oil-bath to a 
temperature of from 150°-200°. The iodine pentoxide is decomposed in 
accordance with the equation I 2 0 5 +5C0=I 2 +bC0 2 , the liberated iodine 
is caught in 10 per cent, potassium iodide, and may be determined by 
N 
sodium thiosulphate. Thorpe, 1 using this method, has obtained 
good results with as little as *0025 per cent, of carbon monoxide. 
II.—Chlorine. 
§ 50. Chlorine is a yellow-green gas, which may, by cold and pressure, 
be condensed into a liquid. Its specific gravity is, as compared with 
hydrogen, 35-37 ; as compared with air, 2-45 ; a litre under standard 
conditions weighs 3-167 grms. It is soluble in water. 
The usual method of preparation is the addition of hydrochloric acid 
to bleaching powder, which latter substance is hypochlorite of lime 
mixed with calcic chloride and, it may be, a little caustic lime. Another 
method is to treat manganese dioxide with hydrochloric acid or to act 
on manganese dioxide and common salt with sulphuric acid. 
Accidents are liable to occur with chlorine gas from its extensive use 
as a disinfectant and also in its manufacture. In the “ Weldon ” process 
of manufacturing bleaching powder, a thick layer of lime is placed on 
the floor of special chambers ; chlorine gas is passed into these chambers 
for about four days ; then the gas is turned off ; the unabsorbed gas is 
drawn off by an exhaust or absorbed by a lime distributor, and the doors 
1 lxxxiii. 318, 1903. 
