21,1 Perkins: Drugs for the Treatment of Leprosy 9 
centimeters, each portion being distilled before the next one is 
added. When properly adjusted the still delivers at the rate 
of 4 liters an hour. After about 50 liters have been distilled 
the still head is taken off and the accumulated pitch cleaned 
out from the body of the still. Solvents are not very effective, 
so the pitch is liquefied by heat and removed by mechanical 
means. 
The distilled esters contain volatile impurities which were 
found to be irritating. They are therefore placed in a stoneware 
carboy and agitated vigorously by a current of steam for two 
hours. Sometimes we wash the esters again with alkali at this 
point, but as the free fatty acid is seldom more than 1 per 
cent this step is generally omitted. In either case the product 
is freed from the accompanying water in a separatory funnel, 
and then filtered. The clear, almost colorless, filtered esters 
are next placed in small bottles, loosely corked, and heated to 
150° C. Each cork is then pushed down and paraffined. In 
this form the ester is ready for use. 
The ethyl ester is used not only in the pure form but also 
mixed with 2 per cent iodine, which is the standard preparation 
used by McDonald and Dean. The iodine is added to the dry 
ester, in which it gradually dissolves, combining chemically. 
We recover alcohol from the first washings mentioned above 
_by neutralizing with lime, and fractionating through an iron 
pipe 240 by 15 centimeters (8 feet by 6 inches) filled with 
broken glass. The alkaline wash water is collected in a barrel 
and acidified to break the emulsion. A mixture of ester and 
fatty acid rises to the top, and is skimmed off for reésterification 
along with another batch of oil. About 5 per cent requires 
reésterification in this manner. 
The theoretical yield of ethyl ester is 1.05 kilograms per kilo- 
gram of chaulmoogra oil. A small amount of the oil remains 
as glyceride, which, along with unknown impurities and decom- 
position products from the ethyl ester, account for the accumula- 
tion of tar in the still. The amount of glyceride is low, and the 
decomposition of ethyl ester is also very small if a good vacuum 
is maintained. Under average working conditions 50 kilograms 
of oil have been found to give 2 kilograms of residue in the 
still. Together with the usual mechanical losses in handling, 
this cuts down our working yield to 90 or 95 kilograms of 
finished ester per 100 kilograms of chaulmoogra oil. 
