39 



in close contact with the combustion furnace the whole length of the tube is kept at a temperature 

 above the boiling point of tuiijentine oil; in this way a complete distillation is insurert. 



All the moisture is retained by c, while the CO2 is absorbed in the potash bulb d. The gain 

 in weight of c represents the moisture originally present in the sample of wood + the water pro- 

 duced in the combustion of the hydrocarbons. The gain in weight of <1 represents the amount of 

 COi derived from the combustion of the volatile products. 



The tube a is now transferred to an ordinary Loxhlet's extraction apparatus and exhausted 

 witli ether. The latter is distilled off. th(>. residue dried for about 2 hours at 100° C. and weighed. 

 This represents the amtiunt of rosin iu the sample of wood taken. 



As has been previously mentioned, the volatile oil of the oleoresin is not pure australene 

 CioHip = (C5H8)2. It probably contains some other hydrocarbons, either of the same formula or 

 belonging to the class of polyterpenes {G^Ha)!!- It is clear that whichever they be, their jtercent- 

 age composition is alike iu all; they all have = 88.2.3 per cent, H= 11.77 per cent. Therefore, 

 so far as th« combustion of the volatile terpenes is concerned, they can all be represented by the 

 equation 



0,0 H,6 + UO2 = IOGO2 + 8H2O 



130 440 144 



In other words, 440 parts of GO2 are derived from 136 parts of volatile terpenes. 



440 : 1.3G = 1:X; X = 0.3091 



i. e., 1 pait of OO2 obtained in the combustion i-epresents 0.300 parts of volatile hydrocarbons. 

 For every 440 parts of CO2 produced there are 144 parts of H2O formed. 



440:144 = 1:X; X = 0.3272. 



i. e., simultaneously with 1 part of CO2 tliere is produced 0.327 parts of HjO. 



Let the weiglit of the sample taken = ((' 

 Let the weight of CO2 obtained^ TT' 

 Let the weight of H2O obtained = W" 

 Then — JT' x 0.309 = T, the amount of volatile hydrocarbons. 



W X 0.327 = if', the amount of H.iO corresponding to the volatile hydrocarbons. 

 tV" X — H'^H, the amount of moisture in the vrood. 

 T = per cent of T; H = per cent of moisture. 



w 7f 



Thus the moisture, the volatile hydrocarbons, and rosin are obtained directly from the same 

 sample. Where many estimations are to be made it is of course unnecessary to cool down the 

 combustion tube between successive combustions. 



The temperature of distillation. — Some experiments were made to determine at what tempera- 

 ture it is safe to conduct the distillation. Although pure turpentine boils at 156-160° C, yet 

 in open air it can be volatilized at a much lower temperature, even on the water-bath, without any 

 difficulty. Especially is this the case when the vapors are removed as soon as formed by a stream 

 of air, but it must be remembered that the volatilization of the essential oil directly from the wood 

 might be considerably hindered by the large amount of rosin. 



A sample of wood distilled by tlie method outlined above gave the following results at diiier- 

 ent temperatures : 



Another sample gave: 



T = 

 HjO = 



Per cent, l Per cent. 

 4.00 ■ 3.98 

 8.79 



