Oil of Andromeda Leschenaultii.
(Extract from letter from J. Broughton, Esq., Government Quinologist, to the Secretary to Government Revenue Department, Fort St. George, dated Ootacamund, 9th January, 1871.)
. . . Early in 1867 Mr. M'Ivor requested me to examine an essential oil which he had obtained from a very common hill plant, the Andromeda Leschenaultii. I did so, and was enabled to identify the oil as methyl-salicylic acid, and almost identical with the Canadian oil of wintergreen.
Oil of wintergreen is an object of some slight commerce, being used in perfumery, and occasionally in medicine as an antispasmodic. The oil from this Indian source contains less of the peculiar hydrocarbon oil, which forms a natural and considerable admixture with the Canadian oil, and therefore is superior in quality to the latter. The commercial demand for the oil is not, however, considerable enough to make its occurrence in India of much direct importance.
It occurred to me in 1869 that methyl-salicylic acid would, however, under suitable treatment, furnish carbolic acid according to a decomposition described by Gerhardt. After a few experiments I was successful in preparing considerable, quantities of pure carbolic acid.
The method of manufacture is as follows:
The oil is heated with a dilute solution of a caustic alkali, by which means it is saponified and dissolved, methylic alcohol of great purity being liberated. The solution of the oil is then decomposed by any mineral acid, when beautiful crystals of salicylic acid are formed. These are gathered, squeezed, and dried. They are then mixed with common quick-lime, or sand, and distilled in an iron retort; carbolic acid of great purity, and crystallizing with the greatest readiness, passes into the receiver.
This acid is equal to the purest kind obtained from coal tar, and employed in medicine. I exhibited a specimen of it at the Neilgherry Exhibition in 1869. It, of course, possesses all the qualities which have rendered this substance almost indispensable in modern medical and surgical practice.
I had hoped, from the inexhaustible abundance with which the plant grows on the Neilgherries, that the carbolic acid from this source could be prepared at less cost than that imported. I have not yet had an opportunity of working on a large scale with an itinerant still, as would be necessary for its cheapest production; but from some calculations I have lately made, I am led to think it can scarcely be prepared for less than the price of that procured from coal-tar. The purest kinds from the latter source cost four shillings a pound; I estimate the cost of that from this indigenous source at from rupees 2.8 to rupees 3.8 (5 to 7 shillings) per pound in this country.
The carbolic acid from the same source has certain advantages over the coal-tar acid, consequent upon its extreme purity. It is less deliquescent, and cannot possibly be open to the suspicion of contamination with certain other products of coal-tar which possess injurious qualities. This occasional suspicion, indeed, has led to the introduction of the costly thymol in France, as a substitute, in delicate cases, for carbolic acid.
In conclusion, I am led to the belief that it would not be advisable to prepare carbolic acid from this singular source, when the comparative cost shows that the gain must be very small or non-existent. But it appears to me well worthy of record that, should circumstances render the supply of the English product difficult or uncertain, as in the case of war, or the English price increase, a practically inexhaustible source exists in this country from which this indispensable substance, in its purest state, can be obtained at a slight enhancement of the present price.—Pharm. Journ., Lond., Oct. 7, 1871.