Journal of Agricidliirc. [8 April, 1908. 



To return to the retorts ; after the load is run in, the doors closed and 

 luted up with clay to prevent escape of gases, firing is commenced, gently 

 at the start, and harder towards the end, to get the right percentage of 

 charcoal, which amounts to about 2| tons per charge. The process occu- 

 pies about twenty-two hours for dry, and up to thirty-six for green wood. 

 The charcoal is practically pure carbon, the percentage of ash being about 

 .5. From the retort the gases resulting from the distillation are sucked 

 out by a fan or blower, there being a pressure to overcome in the tar separa- 

 tor. The gases go through a trough which has a system of water-pipes 

 to keep the temperature down to about 150 deg. C. The tars separate at 

 this temperature, and are collected in a copper separator, from the lower 

 portion of which the tar flows continuously. The more volatile gases con- 

 taining pyroligneous acid (the acetic acid group), wood naphtha or methyl 

 alcohol, acetine, and a host of minor compounds of little value, are passed 

 through a condenser, and the condensed liquid run into vats. These con- 

 tain partitions for separating the wood oils distilled over, the heavier sink- 

 ing to the bottom, and the lighter floating on top of the aqueous solution 

 of wood naphtha and pyroligneous compounds. They are drawn off and 

 run to the tar distillery, a cast iron kettle holding some 360 gallons of tar. 

 The tar distillation secures some more acetic acid still remaining in it, and 

 yields various oils such as creosote, well known as a meat and timber pre- 

 servative. The volatile gases remaining unliquefied in the condenser are 

 passed through scrubbing columns filled with coke and dripping water to 

 extract any remaining wood spirit. After this, the gases are still of use 

 to burn for heating purposes. When everything is working well, these 

 gases are almost sufficient to supply all the heat required for the retorts, 

 very little other fuel being needed. The water solution of wood spirit, 

 &c., is run from its vat into neutralizing vessels. These are fitted with 

 circular stirrers. Lime is put in until the free acetic and other acids are 

 neutralized, and form lime acetates. From the neutralizing vessels the 

 liquor is run into a sump where the heavier impurities in the lime, clay, 

 sand, &c., are allowed to settle. It is then pumped through a filter press 

 and raised to a de-alcoholizing or rectifying column, where, owing to its 

 low boiling point 55 deg. C, the methyl alcohol is separated. The metlivl 

 alcohol product is kept at between 80 and 90 per cent, strength. The solu- 

 tion of acetate of lime is concentrated almost to saturation, using the waste 

 steam from engine. It is then dried bv blowers and rotary driers, produc- 

 ing grey acetate of lime in a dry state. From this either commercial or 

 glacial acetic acid is produced by heating in a cast iron vessel with strong 

 sulphuric acid. 



This covers the present scope of the operations, but additions are con- 

 templated to separate acetone for local use or for export. Acetone is a 

 powerful solvent, and forms a most important constituent in some of the 

 more recent high explosives used in warfare. From acetone, chloroform 

 and iodoform are also derived. There is also a possibility of further by- 

 products such as creosote compounds for wood, &c. The products of i 

 ton of dry wood are : — 



90 lbs. acetate of lime equal to 25 lbs. glacial acid worth is. lb. 

 25 lbs. methyl alcohol at 6d. lb. 

 70 lbs. Stockholm tar at |d. lb. 

 5 cwt. charcoal at is. 6d. cwt. 

 equivalent to over ^2 per ton in value. 



