60 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



form is drawn off into a clean, dry flask and dried by adding anhydrous 

 calcium chloride, either by shaking for 5-10 minutes or allowing to 

 stand from 12-24 hours, until it is clear. The chloroform is filtered 

 into a clean, dry distilling flask and distilled. 



The mechanism of the reaction by which the chloroform is formed 

 is probably : 



1. The oxidation of the alcohol to aldehyde (p. 80), 



CH 8 . CH a OH + O = CH, . CHO + H 2 O. 



2. The chlorinatiori of the aldehyde to chloral, 



CH, . CHO + 3 C1 2 = CC1 3 . CHO + 3 HC1. 



3. The decomposition of the chloral to chloroform and calcium 

 formate by the calcium hydroxide (p. 87), 



2CC1 3 . CHO + Ca(OH) 2 = 2CHC1 3 + (HCOO) 2 Ca. 



Purification of Commercial Chloroform. 



Chloroform prepared from alcohol, methylated spirit (methylated 

 chloroform) or acetone may contain chlorine, hypochlorous acid or 

 hydrochloric acid, aldehyde, etc. 



The specimen is shaken several times with water, the chloroform 

 is separated, dried with (i) calcium chloride, (2) phosphorus pentoxide 

 and distilled. 



The last traces of alcohol may also be removed by adding slices of 

 metallic sodium, allowing to stand for 12-24 hours and then distilling. 



Properties. 



Chloroform is a volatile colourless liquid with a distinct and sharp 

 odour and sweetish taste. It boils at 61 and has a sp. gr. of I '483-1 '487. 



Its vapour does not burn, but when mixed with alcohol the com- 

 bined vapours burn with a smoky flame edged with green. 



It is soluble in about 200 volumes of cold water (-44 gm. in 

 100 c.c.) to which it gives a sweet taste. 



It mixes in all proportions with absolute alcohol, ether, benzene, 

 petroleum ether. It is slightly soluble in dilute alcohol and readily 

 dissolves fats, resins, india-rubber, camphor, iodine, bromine. 



Many specimens of commercial chloroform undergo change on 

 keeping, especially in the light, and are liable to contain chlorine, 

 hypochloro'us acid or hydrochloric acid. This decomposition is hin- 

 dered by the addition of I per cent, of alcohol. The bottle should 

 be kept in the dark. I c.c. of chloroform on evaporation should leave 

 no residue and if allowed to evaporate on clean filter paper should leave 

 no disagreeable odour. 



Chloroform is decomposed by boiling with aqueous alkali, more 

 rapidly in alcoholic solution, into alkali formate and chloride : 

 CHC1 8 + 4 NaOH = HCOONa + sNaCl + 2H a O. 



