CHLOROFORM. 
155 
§§ l8l, 182.] 
Chloroform is sometimes impure from faulty manufacture or decom¬ 
position. The impurities to be sought are alcohol, methylated chloro¬ 
form, 1 dichloride of ethylene (C 2 H 4 C1 2 ), chloride of ethyl (C 2 H 5 C1), 
aldehyde, chlorine, hydrochloric, hypochlorous, and traces of sulphuric 
acid : there have also been found chlorinated oils. One of the best tests 
for contamination by alcohol, wood spirit, or ether is that known as 
Roussin’s ; dinitrosulphide of iron 2 is added to chloroform. If it contain 
any of these impurities, it acquires a dark colour ; but if pure, remains 
bright and colourless. 3 
The chief B.P. tests for purity are as follows :— 
It should not give any colour with 1 c.c. of solution of cadmium 
iodide and 2 drops of starch mucilage (absence of free chlorine), and yield 
not more than a slight opalescence with 4 drops of solution of silver nitrate. 
After shaking sulphuric acid with twice its volume of chloroform for 
five minutes and setting aside for fifteen minutes, both the acid and the 
chloroform should be nearly colourless ; also 2 c.c. of the sulphuric acid 
diluted with 5 c.c. of water should be colourless and have a pleasant 
odour. When this acid liquid is further diluted with 10 c.c. of water 
and stirred with a glass rod, it should still be transparent and colourless, 
giving with 4 drops of solution of silver nitrate only a slightly diminished 
transparency. Water shaken with half its volume of chloroform that 
has been treated as above with sulphuric acid, also should yield no more 
than a slightly diminished transparency with solution of silver nitrate. 
§ 181. The ordinary method of manufacturing chloroform is by 
distilling alcohol with chlorinated lime ; but another mode is now much 
in use—viz. the decomposition of chloral hydrate. By distilling it 
with a weak alkali, this process yields such a pure chloroform that, for 
medicinal purposes, it should supersede every other. 
1. AS A LIQUID. 
§ 182. Local Action of Chloroform.— When applied to the skin or 
mucous membranes in such a way that the fluid cannot evaporate—as, 
for example, by means of a cloth steeped in chloroform laid on the bare 
skin, and covered over with some impervious material—there is a 
1 Methylated chloroform is that which is prepared from methylated spirit. It 
is liable to more impurities than that made from pure alcohol, but, of course, its 
composition is the same, and it is now manufactured from this source almost 
chemically pure. 
2 Made by slowly adding ferric sulphate to a boiling solution of amnionic sulphide 
and potassic nitrite, as long as the precipitate continues to redissolve, and then filtering 
the solution. 
3 An attempt has been made by Besnou to estimate the amount of alcohol by 
the specific gravity. He found that a chloroform of 1-4945 gravity, mixed with 5 
per cent, of alcohol, gave a specific gravity of 1-4772 ; 10 per cent., 1-4602 ; 20 per 
cent., 1-4262 ; and 25 per cent., 1-4090. It would, therefore, seem that every per 
cent, of alcohol added lowers the gravity by -0034. 
