> ae aie 4 
" SciENTIFIC AND OTHER ‘NOTES ON ESSENTIAL OILS. 59 
as certained as was necessary ‘to Hobtuin a maximum of cymene sulphonic acid in the 
_ upper layer. The quantity of water required was one-fifth of the total volume of 
‘the mixture. Generally, it will not pay to recover the free sulphuric acid from the 
lower layer. 
The neutralization of the sulphonation products is effected by means of finely divided 
limestone or lime. In the former case, the evolution of carbon dioxide causes foaming. 
EThe calcium sulphate is removed by a filter-press, the filter-cake being worthless. 
Simultaneous neutralization of the sulphonation products and formation of sodium 
_ cymene sulphonate from the calcium salt may be effected by addition of sodium 
carbonate solution, the calcium sulphate and carbonate can then be removed by a 
' single filtration. With these processes a minimum of water must be employed, for the 
_ teason of Saving time in evaporating the solution of sodium cymene: ‘sulphonate. This 
: solution is difficult to evaporate to dryness at atmospheric Ee which may be — 
4 perfected by applying a vacuum or a film dryer. § - | 
When fusing the sodium cymene sulphonate the problem was to determine a) the 
best fusion reagent, b) the proper fusion temperature, c) the most suitable type of fusion 
kettle, d) the time required for completion of the reactions, and e) the minimum amount 
4 of fusion reagent for obtaining the maximum yield. : 
The fusion apparatus used by Hixson and Mc. Kee was a cylindrical steel vessel 
beh in. in diameter and 5 in. deep, the thickness being */16 in. The cover was a Steel 
plate with openings for the stirrer sHaft and the thermometer. Heating was effected 
_ by placing the vessel in a bath containing a eutectic mixture of sodium and potassium’ 
“nitrates, since by heating with a Fletcher burner it was not possible to control the 
_ temperatures closely enough. Commercial caustic soda was used with satisfactory 
success as fusing reagent. The best yields were obtained with fusion temperatures of 
:: from 360 to 370°. It is necessary to. operate with the vessel covered, as otherwise © 
_carvacrol escapes and the fusion mass oxidizes and thickens. The experiments were 
Started with 150 g. dry sodium cymene sulphonate and 450 g. caustic soda; the latter — 
was fused first and the sodium cymene sulphonate added slowly. ‘Addition of water 
enables to keep the fusion temperature lower, but offers no advantages. Fusions carried 
out at 360° yielded 48.33, 49.91, and 49.14 g. carvacrol, i.¢., 50.14, 52.31, and 51 60 per cent. 
At 370°, the yield’ was 50.65 per. cent. Beyord ores; thie yield decreases. About 18 
to 20 per cent. of the sodium cymene sulphonate are transformed into cymene, which 
when working on factory scale might be profitable to recover. During the fusion process 
two reactions take place: — a) formation ‘of sodium carvacrolate and sodium sulphite, 
_b)of cymene and sodium sulphate. In addition, other reactions pass off, as is evident 
from the formation of hydrogen, methane, and tarry products. 
| The best yield was obtained with fusion periods of from 4 to 6 hours. In these 
experiments a large excess of soda was used. Nevertheless, much less soda, even only 
the theoretical quantity, yielded equally favourable results. : 
_ It is also possible to fuse calcium cymene sulphonate with caustic alkali, thus 
“saving one filtration and the sodium carbonate ‘for the making of the sodium salt, but 
‘this would rcsult in requiring more caustic necessary for the fusion, and in difficulties 
arising from the insolubility of the calcium sulphite formed. In ae process, also 
_cymene is formed. 
__ Neutralization was effected by dissolving the fusions in 2 liters of water and adding 
an excess of dilute sulphuric acid (40° Bé) until sulphur dioxide was evolved. The acid 
must be added to the solution by leading it through a tube to the bottom of the vessel, 
: otherwise an excess of the acid on the surface reacted with the sodium sulphite in 
