ON THE PURIFICATION - OF CHLOROFORM. 329 
purified, is quite identical in all its properties. Its smell, 
density, boiling-point, and action in the system, are in both 
cases exactly the same. That from alcohol is no doubt 
more easily purified than the other, but it also contains cer- 
tain volatile oily impurities, which must be removed before 
it can be safely used. The peculiar oils which adhere to 
both kinds of chloroform are not identical, or at least, not all 
identical, but they are of analogous constitution and proper- 
ties. 
3. Soubeiran and Mialhe have examined these oils. They 
contain chlorine, have a disagreeable smell, and when in- 
spired or smelt "cause distressing headache and sickness. In 
the case of wood-spirit, some of its own impurities distil over 
unchanged, and are also found in the chloroform. 
4. It is well known that many persons, after the use of 
chloroform, have suffered from headache, nausea, and even 
vomiting, as I have more than once seen. Headache and 
nausea I have myself often experienced, when I have tried 
different specimens of chloroform, without taking so much, 
as to produce the full effect. 
5. Perfectly pure chloroform does not, so far as I have 
seen or experienced, produce these disagreeable effects. It- 
is therefore highly probable that when they occur, as they 
do with some individuals, from the use of chloroform of more 
than the average goodness of quality, they depend on the; 
presence of a trace of these poisonous oils. 
6. All good manufacturers of chloroform purify it by the 
action of oil of vitriol, which destroys the oils, while at the 
same time a part of the acid is reduced to sulphurous acid. 
The chloroform, to remove this, is then distilled with lime 
or carbonate of baryta, and is tolerably pure if the process 
be well conducted. 
7. But it is not quite pure, and contains a trace, more or 
less distinct, of the oils. I have found this to be the case 
with all the best chloroform made here up to 1849; and I 
have several times seen headache and sickness from the use 
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