Oils and Fats- 



286 



YIELD PER ACRE. 



Up to the third year after the plants are laid down the yield increases. In 

 the third year a eitronella plantation is at its zenith of production, giving as 

 much as 18,032 lb. of grass per acre for the year. This was the average yield 

 of a 12-acre plot. The return of oil from above plot was 13,644 ozs. of oil. This 

 is equivalent to a yield of 71 lb. 3 ozs. oil per acre per year. After the third 

 year there is a decline in the yield of oil even when the quantity of grass 

 obtained is comparatively high. The yield ot oil begins to fall steadily after 

 the third year, and I know of a plantation, which is in about its 18th year, 

 which, in spite of its good appearance due to good attention, gives only an 

 average of about 26 lb, of oil per acre per year. There is also a difference in the 

 yield of the different crops of the year, the crops during the South-west monsoon 

 giving a better return. 



DISTILLATION. 



The distillation is done one day after the grass is cut and exposed to 

 the drying influence of the sun. In packing the vats or stills with the grass 

 too much pressure shoiud not be resorted to. In a factory there are generally 

 two stills and an interchangeable alembic. The advantage of having two stills 

 is obvious, for while the contents of one are still being steamed, the other can 

 be packed with grass and got ready to be steamed as soon as the alembic has 

 been shifted on to the same. The steaming is done by means of an ordinary 

 regulation steam boiler provided with safety valve. 



As a high pressure of steam is not necessary it has been found conve- 

 nient to make use of old boilers i*emoved from factories where they have been 

 used driving engines. In some cases, when plantations have been located at 

 places far removed from the main roads, boilers made by the native boiler 

 smith have been successfully employed. In our every-day experience we have 

 found tubular boilers to be anything but a success, while on the contrary. 

 Cornish or Lancashire have given very good results, a decided advantage with 

 the latter mentioned kinds of boilers being they can be easily repaired when 

 occasion arises. 



The steam enters the still at the bottom and, after traA^ersing the grass, 

 carries with it the essential oil and finds its way into the condensing pipes 

 suspended in a tank of cold water. Often the water in the cooling tank gets 

 so heated that the oil and water are not properly separated entailing consider- 

 able loss in the percentage yield of oil. The steam should flow in at a constant 

 pressure, for any variation in the issue and pressure of steam lessens the yield of 

 oil. The cooling pipes are in the majority of instances made of copper, and 

 till 1889, when I introduced lead piping, were without exception made of copper. 

 Lead piping, besides lessening the cost of distillation plant, ensures better 

 cooling, whilst in addition it does not tend to colour the oil, which is the case 

 when copper piping is used. 



The cooling of the oil-laden steam is very unsatisfactorily done by the 

 majority of the distillers. As a result of this a certain proportion of the oil 

 is resinified. The adoption of a 60-ft. coil, as suggested by Mr. Wright, would 

 be a decided improvement over the present state of affairs obtainable in most 

 distillation plants. Still more satisfactory results may be obtained if the water 

 used in cooling the distillate be made to travel in a direction opposite to the 

 direction of the oil-laden steam in the coil. This is not at present attempted in 

 a ny factory that I know of. I am inclined to believe that a factory fitted 

 with the most recent and up-to-date distillation plant would amply repay the 

 additional expense incurred thereby and greater returns could be ensured. Yet by 

 the majority of the eitronella oil distillers this is held to be a negligible quantity. 



