338 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



or any accumulation of condensed vapors. In about fifteen minutes all the moisture appears at 

 the forward end of the combustion tube. The clamp is no\v opened and a stream of air at the 

 rate of somewhat over oue liter an hour is passed through the whole apparatus, while the tem- 

 perature of the air bath is raised to 155 to 160 C., and kept, at that point for about forty-h've 

 minutes. Toward the end of the operation the temperature is raised to 105 to 170 C. for ten 

 minutes. Then the light under the air bath is turned off and air aspirated for twenty to tweuty- 

 fivc minutes longer. As the air bath is in close contact with the combustion furnace, the whole 

 length of the tube is kept at a temperature above the boiling point of turpentine oil. In this 

 way a complete distillation is insured. 



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

 weight in < represents the moisture originally present in the sample of wood plus the water 

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

 of CO.;, derived from the combustion of the volatile products. 



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

 witli ether. The latter is distilled off, the residue dried for about two hours at 100 C., and 

 weighed. This represents the amount of rosin in the sample of wood taken. 



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

 C u ,Hn; = (C 5 H||);. It probably contains some other hydrocarbons, either of the same formula or 

 belonging to the class of polyterpenes^CjHu),,. It is clear that whichever they be 1 heir percentage 

 composition is alike in all; they all haveC = 88.23 per cent, H = 11.77 per cent. Therefore, so 

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

 equation: 



C 10 H I6 + 140 = 10 C0 2 ,= 8 H,O 



136 



440 



144 



In other words, 440 parts of CO 2 are derived from 130 parts of volatile terpenes. 



440 :136 = 1 :X ; X = 0.3091 , 



i. e., 1 part of CO 2 obtained in the combustion represents 0.30!) parts of the volatile hydrocarbons. 

 For every 440 parts of CO;j produced there are 144 parts of H 2 O formed. 



440:144 = 1:X; X = 0.3271*, 



i. e., simultaneously with 1 part of CO 2 there is produced 0.327 parts of 1I 2 O. 

 Let the weight of the sample taken = W, 

 Let the weight of CO 2 obtained = W, 

 Let the weight of H 2 O obtained = W", 

 Then W x 0..".09 = T, the amount of volatile hydrocarbons. 



W x 0.327 = H', the amount of H 2 O corresponding to the volatile hydrocarbons. 

 W" x H', = H the amount of moisture in the wood. 



T FT 



^y =per cent of T; 117= per cent of moisture. 



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 156-100 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 the method outlined above gave the following results at 

 different temperatures: 



