42 



KNOWLEDGE. 



February, 1913. 



with chlorine gas to convert it into dichlorides, 

 thus : — 



CH 3 CH 2 CH 2 CH 2 C1 + CI,. = CH.sCHClCH 2 CH 2 Cl+ HC1 



Butyl Chloride. 



Chlorine 

 Gas. 



Butylene Dichloride. 



Hydro- 

 chloric Acid. 



Bichlorides of the formulae CH 3 CH 2 CHC1.CH 2 C1 

 and CH 2 C1.CH 2 CH 2 CH 2 C1. are simultaneously 

 formed. 



If chlorine acts unrestrainedly upon the butyl 

 chloride other products in addition to dichlorides are 

 produced. A special apparatus had to be invented 

 so as to remove the dichloride as rapidly as it is 

 formed. The apparatus of Mr. Charles A. Pirn (see 

 Figure 40) is shown in Figure 43. The butyl 

 chloride is boiled in the flask until the chlorinating 

 chamber is full of vapour and liquid drops from the 

 end of the reflux condenser, while a stream of dry 

 chlorine is passed in rapidly, care being taken, how- 

 ever, that the butyl chloride remains in excess. 

 During the whole operation the apparatus must 

 stand in a good light, and on dull days ultra-violet 

 light from a mercury lamp is used to facilitate 

 chlorination. As fast as the higher-boiling di- 

 chloride is produced it drops back into the boiling 

 flask, and as this is provided with an efficient 

 fractionating column, only the lower-boiling butyl 

 chloride can pass into the chlorinating column ; the 

 dichlorides are thus removed by gravity from the 

 sphere of the action of the chlorine and thus escape 

 further chlorination. The liquid in the flask is 

 finally fractionated and the dichlorides isolated in a 

 pure condition. 



These dichlorides are next passed over hot soda 

 lime contained in a tube heated to 470°C as shown 

 in Figure 42; the soda lime abstracts hydrochloric 

 acid from the dichlorides and produces butadiene 

 thus : — 



Hot Soda-lime. 



CH 3 CHC1CH 2 CH 2 C1 - — — > CH 2 = CH-CH=CH 2 



Butylene Dichloride. iliLl Butadiene. 



The issuing butadiene is a gas, but on cooling it 

 condenses to a colourless liquid, and so is easily 

 separated by passing the vapour coming from the 

 hot soda-lime through a vessel immersed in a freez- 

 ing mixture. A similar method is used for making 

 isoprene from amyl alcohol — as we will see 

 presently. 



Professor Perkin also proposes to produce buta- 

 diene from aldehyde, CH 3 CHO, which is produced 

 from alcohol merely by oxidising it — the alcohol 

 being obtained from the starch of cereals or potatoes 

 by ordinary fermentation with yeast. The aldehyde 

 is treated with a dilute solution of potassium car- 

 bonate (washing soda, soda ash) wherebv aldol, 

 CH 8 CH(OH)CH 2 CHO, is formed. This "is then 

 reduced with nascent hydrogen and yields butylene 

 glycol, CH 8 CH(0H)CH 2 CH 2 C1., which is then 

 converted into 1:3 dichlorobutane, CH 3 CHC1.CH 2 

 CH 2 CL, which yields butadiene when passed over 

 hot soda lime as above described. Alcohol at present 

 costs about threepence per pound. 



The butadiene, no matter by which of these pro- 

 cesses it is produced, is then converted into butadiene 



rubber by warming with sodium in the manner pre- 

 viously described. 



The formation of butadiene rubber is thus repre- 

 sented by Prof. Harries, of Kiel : — 



CH 2 =CH-CH=CH 2 

 CH 2 =CH-CH = CH 2 " 



Butadiene. 



Sodium. 



/CH 2 -CH = CH-CHa 



->(' i ) 



r \CH 2 -CH = CH-CH/x 



Butadiene Rubber. 



A yellowish mass is thus obtained, which is washed 

 with alcohol or heated with steam to drive off any 

 unchanged hydrocarbon. It can be vulcanised to 

 produce an excellent rubber. 



It will be noticed that in the two processes above 

 described the raw materials are : maize or potatoes — 

 the starch of which at present costs less than one 

 penny a pound ; common salt (to produce the chlorine 

 and sodium) ; and lime. The total cost of the raw 

 materials does not exceed twopence per pound. In 

 fact, Mr. Strange calculates that synthetic rubber 

 could be produced at fourpence to sixpence per 

 pound. I understand that quite recently Professor 

 Fernbach has further developed the bacteria, so that 

 they will ferment wood in the form of cellulose — 

 instead of maize or potatoes — and produce a fair yield 

 of acetone and fusel oil. This advance, however, 

 has still to be utilised commercially — so that it 

 remains an interesting laboratory experiment. 



Instead of starting with butyl alcohol, which is the 

 main constituent of wine fusel oils, but which can 

 now be obtained in almost unlimited quantities by 

 the fermentative processes introduced by Professor 

 Fernbach, we can start with isoamyl alcohol, which 

 is the main constituent of the fusel oils obtained in 

 spirit manufacture from cereals or potatoes. 



/soamyl alcohol has the constitution (CH 3 ) 2 CH 

 CH 2 CH 2 OH. It is first converted into the chloride 

 (CH 3 ) 2 CHCH. 2 CH 2 C1. by dry hydrochloric acid gas, 

 and the monochloride thus produced is then con- 

 verted into a dichloride by treating with chlorine gas 

 in a Pirn's apparatus as previously described under 

 butyl alcohol. Three dichlorides are thus pro- 

 duced, namely: isopropylethyltrimethvlenedichloride, 

 (CH 3 ) 2 CHCHC1.CH 2 C1. (B.P. 142) ; gem-dimethyl- 

 trimethylene dichloride, (CH 3 )CC1.CH 2 CH 2 C1. (B.P. 

 152-155) and /3-methyltetramethvlene dichloride, 

 CH 2 C1.CH (CH 3 ) CH 2 CH 2 C1. (B.P.170-172). These 

 dichlorides when passed over hot soda-lime produce 

 isoprene, the soda-lime extracting the elements of 

 hydrochloric acid, thus : — ■ 





CH 3 



CH;, 



>C-CH 2 -CH 2 C1. 



Hot Soda. 

 Lime. 



CH;, 



-> 



CH 



// 



C-CH = CH 2 



CI. 



Butylene Dichloride. Isoprene. 



The isoprene is then converted quantitatively into 

 rubber by metallic sodium. 



However, as amyl alcohol fusel oils are to-day 

 quoted at one hundred and forty pounds a ton, and 

 have a host of other useful applications, it is 

 doubtful whether such a process would survive com- 

 petition with the butyl fusel oil process which can 



