July i, 1884.] 



THE TROPICAL AGRICULTURIST, 



47 



made at the base of the tree ou the skle facing the east, ami 

 this is retouched every three or four months. The cutting 

 is commenced in April and continued until the end of Sep- 

 tember, during which time it should reach a height of about 

 half a metre. Care, however, is taken early in the season, 

 about the beginning of March, to define the extent of the 

 incision by removing the external surface of the bark from 

 the part of the tree which is to be denuded. The following 

 year the incision is continued upwards, and afterwards, for 

 five consecutive years, until a height of two and a half or 

 three metres is reached. A similar operation is then com- 

 menced ou the side of the tree exposed towards the south, 

 and by the time this has had its turn a return can be made 

 to the first incision, which has become cicatrized. When 

 the operation is well conducted a tree can be thus bled 

 dining more than two hundred consecutive years (pendant 

 plus di deux cents amiees consScutives.) 



Two methods are in use to collect the exudation. 'The 

 older one, which is the most simple, consists in making a 

 small trench at the base of the tree, in which the runnings 

 from the tree collect. While the incision is near the ground 

 the collection is effected fairly well ; but after two or three 

 years, when the incision has attained a considerable length, 

 the exudation reaches the ground with difficulty. Under the 

 influence of wind and sun the greater part of the essential 

 oil is volatilized or resiuified, and the collection becomes 

 insignificant. The second method called "Hughes's method," 

 after its inventor, partially avoids these inconveniences, and 

 besides, has the advantage of yielding a "gemme" much 

 more free from soil and vegetable debris. It consists in 

 affixing to the tree, by means of a nail, a small pot, which 

 is placed every year under the fresh cut. The turpentine 

 thu6 caught, having to run a less distance to reach the 

 recipient, is always richer in essential oil than that obtained 

 according to the older method. 



The collection of the " gemme " is made every two or three 

 weeks. The pots are first emptied into a vessel of forty or 

 fifty litres capacity, from which the contents are transferred 

 to a large trench in the ground capable of holding four or 

 five hundred litres, from which the casks are filled when 

 required for sale. In October the resin that has solidified 

 on the tree is gathered. This can be added to the other 

 portion for the purpose of distillation, but usually it is kept 

 separately, and sent into commerce under the name of 

 " galipot " or " barasse." 



The " gemme " is the primary material for the manufact- 

 ure of oil of turpentine ; it is a mixture, or rather a solution 

 of colophony in the oil. Under the influence of heat the oil 

 is volatilized and the colophony is left as a residue. The in- 

 dustrial distillation of the "gemme" is carried on in small 

 factories usually situated in the midst of the forest. The sea- 

 son commences in the month of May aud terminates in 

 October. 



1 Hi the arrival of the "gemme" at the factory it is de- 

 canted into two large wooden vats capable of containing one 

 hundred barrels of 340 litres each. By means of a kind of 

 saucepan fastened to the end of a long wooden staff the 

 material is dipped from these vats and introduced into two 

 large copper boilers, known as preparatory boilers, of six to 

 eight barrels capacity. In these boilers the "gemme'' is 

 heated during a whole day over alow fire. The water collects 

 at the bottom, whilst foreign substances, such as chips of 

 wood, twigs, etc., rise to the surface, from whence they are 

 skimmed off and put to drain in straw filters arranged above 

 the second boiler. In the evening the fire is allowed to go. 

 down aud the boiler is kit to itself. In the morning the 

 " gemme," freed in this way from the water that it held in 

 suspension and which frequently amounts to 12 or 1"> per 

 cent, as well as earthy and ligneous matters, is introduced 

 into a copper receiver of a fixed capacity of 300 litres. 

 At the bottom of this pan there is a pipe, fitted with a 

 tap, the other end of which opens at about eight inches 

 from the bottom of the still in which the distillation has 

 to be effected. The still is of copper aud furnished with 

 a worm that dips into a wooden receiver full of water. 

 Three hundred litres of "gemme" are run iu and heated 

 strongly. The oil commences to distil over and at the end 

 of fifteen or twenty minutes about eighty or a hundred 

 litres of hot water are run into the still through a tap 

 fixed in the upper part of it. This addition of watei has 

 for its object to facilitate the volatilization of the rem 

 of the essential oil. The distillate is received in a vessel 



made of sheet-iron and fitted at its upper part with a 

 capacious pipe, by which the essential oil, being lighter 

 than water, passes oil into the casks set for its collection. 

 When the liquid issuing from the worm no longer con- 

 tains much essential oil, the supply of water is stopped ; 

 the distillation is then continued for a few minutes more 

 aud the operation is finished. The yield of essential oil 

 various with the season and is about 15 to 18 per cent of 

 the weight of the " gemme." The exit pipe at the bottom 

 of the still is then opened and the " brai," or resinous 

 residue, is run iuto a sheet-iron tank, after having been 

 made to pass over a copper plate pierced with holes, so 

 as to eliminate various impurities that it may contain. The 

 apparatus is then ready for a fresh operatiou, which is com- 

 menced without allowing it to get cold. Iu this way eight 

 or ten distillations are effected daily. 



After the " brai " has been allowed to cool for some time it 

 is run into wooden casks, where it solidifies. That which is 

 derived from "gemme " collected by Hughes's method is sent 

 into commerce under the name of "yellow colophony," and 

 that obtained from "gemme" collected by the old method 

 is sold under the name of " brai clair." The resins of in- 

 ferior quality, or"brais uoirs," are obtained by the same 

 method, but are the product of the distillation of the less pure 

 portion of the " gemme " which collects towards the bottom 

 of the preparatory boilers. 



Sometimes the " brai," instead of being run directly into 

 casks, is used for the manufacture of resin. In this case, 

 upon issuing from the boiler of the still, it is run into a 

 special vat, and whilst it is still liquid about 15 to 20 per 

 cent of hot water is added, in quantities of 20 to 30 litres at 

 a time. The mixture is stirred energetically with staves 

 until the whole mass has become opaque and thoroughly 

 homogeneous; then it is run through a trough in sand into 

 cyliudrico-conical moulds also in sand, where it solidifies. 

 The resin thus obtained is of a pale yellow shade, and un- 

 der the name of " yellow resin " or " r.esine de boutique" is 

 used in the making of resin candles. 



The straw filters, upon which have been deposited all 

 the impurities collected upon the surface of the preparatory 

 boilers, are used for the preparation of a further quantity 

 of "gemme" of inferior quality. They are introduced to- 

 gether with the detritus remaining upon them into a kiln, 

 resembling a lime-kiln, known as a "four a pegle." The 

 fire being lighted and a portion of the material burnt, deter- 

 mines the liquefaction of .the "gemme," which runs off 

 through an orifice situated in the lower part of the kiln 

 iuto a receiver containing water. This "gemme," submitted 

 to distillation, yields about 10 per cent of its weight of 

 essential oil. 



Manufacture of Resin Oils. 

 This industry dates back half a century, and at the 

 present time has attained a considerable development. In 

 1832, M. Dives, whilst distilling "gemme" for the extraction 

 of oil of turpentine, made the observation accidentally that 

 in continuing the operation beyond the poiut when only 

 colophony was left in the still this was decomposed, giving 

 use ti>an oil. He therefore replaced the copper alembics 

 by cast iron retorts, and the mode of distillation which he 

 adopted is the same as is employed at the present time. 



Eighteen hundred kilograms of "brai" are introduced 

 into a huge hemispherical cast iron boiler, heated over arches, 

 together with li or 2 per cent of lime, added with the object 

 of rendering the oils more fluid. The boiler is covered 

 with a copper dome, which is luted with clay; this is iu 

 enmmunication with a worm, also in copper, disposed in a 

 vat full of coldwater. Pine wood is employed as fuel in heating 

 the boilers. The operatiou is commenced at three o'clock 

 in the morning, the fire being urged strongly at the com- 

 mencement, and in two or three hours the distillation begins; 

 the fire is then moderated and maintained so until seven 

 in the evening. The distilled products are received in a 

 small sheet iron vessel, having in its upper part a tube 

 by which they can be passed iuto the casks. At the com- 

 mencement of the operation water passes over, which is 

 run ell through a tap placed in the lower part of the re- 

 ceiver. Afterwards about 25 kilograms of a light fraction 

 are collected, aud then nine or ten barrels of oil, each con- 

 taining 100 kilograms. At the end of the operation 

 the bottom of tin- boiler is brought tu a dull red heat. 

 There remains then only a solid carbonaceous residue, which, 

 has to be removed by mtansof a pick after each distillation 



