PREPARATION OF ESSENTIAL OILS, 77 
sence of the salt augmented the proportion of essential oil. 
But is the same the case in the treatment of aromatic vege- 
tables ? 
I poured upon 2500 grammes of cassia, thirteen litres of 
boiling water; after forty-eight hours I distilled over until the 
water was no longer milky. Three litres of water were thus 
separated, from which I obtained by decanting, after three 
days of repose, five grammes of essential oil, and which re- 
tained in solution 5.3 more grammes. I ascertained this 
by agitating a part of the water with pure ether, and evapo- 
rating spontaneously the etherial solution. This water of 
cassia was poured back again into the cucurbit and again dis- 
tilled. Three pounds of milky water were obtained; a third 
distillation afforded no more. By abstracting the volatile oil 
contained in the distilled water that served for cohobation, I 
obtained by this second distillation 2.25 grammes. 
I then made a parallel trial with the same quantities of 
cassia and water, at the same time adding 4500 grammes of 
salt, and I obtained three litres of the milky product, which 
furnished six grammes of oil, and 5.3 grammes remained in 
solution; in all 11,3 grammes. 
In the second distillation the water ceased to pass clear 
after half a litre. The oil collected in this part of the opera- 
tion weighed two grammes. A third distillation afforded 
no more. 
If we compare results, we shall find that, with water alone, 
the first distillation afforded 10.3 grammes of oil; that with 
salt water, 11.3 grammes; that the whole of the essence 
required six litres with the water alone; that the same 
quantity was obtained with four litres of salt water. In this 
case there is certainly an advantage; it is, however, of little con- 
sequence; it does not compensate for the expense which the 
employment of the salt occasions, and no advantage results if, 
in place of saturating the water with chloride of sodium, only 
one-tenth of its weight is added, as directed by the formularies. 
It is remarkable that, in the extraction of volatile oils by 
distillation, it is always necessary to drive over a considerable 
