SOME AUSTRALIAN ESSENTIAL OILS. 
be accomplished in two ways; the one, by careful fractional distillation, 
and the other, by what is known as the bisulphite method. For myselt, 
I prefer the fractional distillation process, and I have tried both. What 
little terpene the oil contains may be withdrawn at a temperature below 
110°C. at a pressure of 14 M.M., or below 117°C. at 20 M.M. When 
the terpene ceases to drop, and it should never be distilled at a greater 
speed than 60 drops per minute, the temperature may be raised, and 
the distillate directed into another receiver. Distillation is continued 
until the citral ceases to come over at 112°C. at 12 M.M. It is usual 
with writers on the subject to recommend the distillation of the citral 
with steam, after the terpenes have first been removed from the oil by 
fractionation, but I have found the product not so satisfactory, some 
of the resinoids being assisted over with the steam. 
T have found a fractionating column with four bulbs the most satas- 
factory, and if pieces of pumicestone are placed in the distilling flask 
there will be no “bumping.” The bisulphite method depends on the 
property of the aldehyde citral to combine with a hot 30 per cent. 
solution of bisulphite of soda; the other constituents of the oil remain- 
ing uncombined. These latter must be carefully remoyed by filtration 
and washed out with benzene, the application of an aspirator or vacuum 
pump being necessary to remove the last trace of benzene. The solid or 
concrete mass is now placed in a warm solution of carbonate of soda; 
this causes disunion of the citral and bisulphite, the former floating on 
the solution, from which it may be easily separated. The next step is the 
condensation of the citral to a ketone; this is accomplished by dissolving 
the citral in an equal volume of acetone, and adding thereto a solution 
of hydrate of barium; this mixture must be frequently agitated during 
seven days to complete the condensation. After a short repose, the 
solution of barium is removed, and the product of the reaction dissolved 
in ether, and separated; on the ether being evaporated the residue is 
fractionally distilled under reduced pressure of 12 M.M., and the 
fraction distilling at a temperature of 138°C. to 150°C. is collected, 
any unattacked citral and unchanged acetone being removed by a cur- 
rent of steam. The remaining ketone must now be carefully purified 
by fractional distillation in vacuo under a pressure of 12 M.M.; the 
liquid that distils off at a temperature of 142°C. to 145°C. is reserved. 
This liquid is called “ pseudo-ionone,” and has the formula CLedsl, fOr 
now has to be converted to ionone by being heated for about seven hours 
in an oil bath, with water, sulphuric acid, and glycerol in suitable pro- 
portions, a reflux condenser to prevent loss by evaporation being 
affixed. The product of this reaction must now be separated with ether, 
the latter evaporated, and the residue fractionated in vacuo. The frac- 
tion distilling under a pressure of 12 M.M. at a temperature of 125°C. 
to 135°C. is collected If all the foregoing conditions are properly 
carried out ionone will be produced. 
Citral can be converted to other commodities beside ionone; it is 
largely. used by distillers of inferior oil of lemon to ‘raise the citral 
content of their product. The terpenes that are a by-product in the 
manufacture of terpeneless oil of lemon are again used for the manu- 
facture of fictitious oil of lemon, citral being added to supply the 
deficiency. ; 
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