Scientific and other notes on essential oils. 79 



and water vapour does not condense and flow back so long as when a dome, made 

 of stone, is employed which of course remains cool much longer. 



Harkort had the opportunity of closely investigating such a plant with Russian 

 furnaces, combined with the production of tar, which enables him to give particulars 

 concerning the method of working, yield, §c. 



It was a case of a plant consisting of three furnaces: a smaller one of 4.20 m. 

 height and diameter, with 4 ring-shaped fire-conduits, and of 2 larger ones of 5.60 m. 

 height and diameter, with the zigzagging arrangement mentioned above. The furnaces 

 are in such a position that their fire-places are protected by a covered shed. The 

 chimneys have the same height as the furnaces themselves and are built up, close to 

 the fire-place, on the stout side of the lower part of the furnace. The outside dimensions 

 of the chimneys are about 40X80 cm. They contain 2 flues, corresponding to the 

 division of the fire left and right. The furnace is charged with root-stocks by means 

 of an aperture on the floor and another one in the dome. The small furnace, having 

 a calculated available space of about 39 cbm., is charged with 32 cbm. of root-stocks 

 which produce about 700 kg. of pine oil during one heating period of the furnace, 

 lasting 15 to 16 days. The dimensions of the large furnace are about 90 cbm. It is 

 charged with 72 cbm. producing about 14 kg. of oil. When one connecting conduit 

 is used the time of charring amounts to about 20 days, when 2 are employed, about 

 16 days. The heating material which is not placed on a grate consists of wood or 

 bark, and first of all the fire is actively fanned. After 3 or 4 days the first traces of 

 oil appear at the end of the cooling pipe in an almost colourless, transparent state. 

 Day by day it becomes yellower in colour, whereby the fire is reduced and finally is 

 only allowed to glow. The termination of the process is announced by the appearance 

 of a very dark oil which is collected separately, whereas the distillation-products of 

 all the previous days are united. The dark oil can be made clear by standing for a 

 long time. After the fire is extinguished the draught in the chimney is closed by 

 means of two dampers with the object of recharging the furnace in as warm a state 

 as possible. If the furnace is allowed to get quite cold, the yield of the oil is said 

 to diminish considerably. The consumption of firewood amounts to about 40 cbm. 

 = 22500 kg. for one charge of the large furnace. Even 2 days after the fire has gone 

 out oil still continues to pass over, after which the apertures in the head are closed 

 with stoppers. 



Doubtless the successful development of the furnace system proves that one has 

 tried to improve it, and the method of distillation employed can by no means be 

 described as primitive and medieval. From the technical point of view the construction 

 of the furnace is at least on a level of many of our own ceramic plants working with 

 periodically heated furnaces. 



Harkort asserts the following concerning the dissemination of such plants in the 

 occupied districts: — 



In the Government of Grodno, 22 are to be found, of which 9 exist in the forest 

 of Bialovitch. In the Government of Wilna 7, in that of Minsk 3, and in that of Cour- 

 land 4. Only part of them have been re-started, several having been completely 

 destroyed. On the whole 36 plants with about 90 furnaces and an average production 

 each of 120000 kg. (12000?) of pine oil a year or with a total yearly production of 

 1100000 kg. are in existence. If one calculates the price of one kg. of pine oil at 

 3 marks (decidedly a war-price, the price in times of peace only amounting to about 

 40 pf.), the sum total would be about 3300000 marks. Doubtless this production could 

 be considerably raised by means of an extensive and systematic increase of the plants. 



