10 BULLETIN 372, U. S. DEPARTMENT OF AGRICULTURE. 
The apparatus should be set up with the flask supported over a 
good flame which can be easily regulated, such as that from a large 
oil burner or from a gas or gasoline burner. The condenser is sup- 
ported in a vertical position and the bottom side tube connected with 
a supply of cold water. The column is filled to within 1 or 2 inches 
of the side tube with glass beads one-half inch in diameter or with 
small unpainted baked clay or glass marbles. The hole in the top 
of the column is fitted with a tight cork, through the center of which 
a tube is placed just large enough to admit a common chemical ther- 
mometer graduated in centigrade degrees, with the scale reading from 
100 to 300. This thermometer should be placed through the cork so 
that the bulb is just opposite the side tube. The flask is then filled 
a little more than half full of the horsemint oil and the joint between 
the flask and the column made tight with a leather gasket and clamp, 
or it may be secured by the use of a ground-joint brass union, one 
half of which is brazed to the neck of the flask and the other half to 
the column. This does away with the use of the gasket, which must 
be frequently renewed. 
An apparatus of the size described will take 15 pounds of oil at a 
charge and in a day work up 75 to 100 pounds of oil. The cost of 
construction would be about $50. 
YIELD PER ACRE. 
During the past five years areas up to 1 acre in extent have been 
grown on various soils and as far as possible under actual commer- 
cial conditions. The results thus far secured show that an average 
of 20 pounds of oil per acre from first-year plantings may be regarded 
as a fair crop, although the test areas have sometimes shown a greater 
quantity. In succeeding years the yield should be at least 30 pounds 
of oil per acre, and under good conditions 40 pounds may be expected. 
Assuming the average phenol content of the oil to be 70 per cent, a 
figure which is somewhat below the average found for five years, and 
using the process of manufacture previously described, there may be 
expected for the first year a yield of 12.86 pounds of pure thymol per 
acre and for the succeeding years, 19.29 pounds per acre. Taking 
$2 per pound as the average price of thymol for a period of years, 
there would be a gross return per acre the first year of $25.72 and for 
each succeeding year, $38.58. In addition to this there should doubt- 
less be added a small amount for the value of the residues, which at 
the present time has not been determined. 
COMMERCIAL PROSPECTS. 
For many years the commercial source of thymol has been chiefly 
the oil of Carum ajowan derived from ajowan seed, which is grown 
in the region of northern India and shipped to northern Europe, where 
