62 BULLETIN 983, U. S. DEPARTMENT OF AGRICULTURE. 



off. The commercial values of the beer-still slops that contain the 

 unfermented pentoses, and of the solid residue from the diffusion 

 battery are being investigated. Recent investigations point to the 

 use of the latter as a stock food. The potential value of both of 

 these by-products is very great, and their investigation is exceedingly 

 interesting both as a chemical and as a commercial question. 



ANALYSIS OF RESULTS. 



In a review and summary of the results obtained from the experi- 

 ments described in this paper, the following points seem to be estab- 

 lished for coniferous woods: 



1. The temperature and pressure of cooking should not exceed 7.5 

 atmospheres (112 to 115 pounds per square inch). 



2. This temperature and pressure should be reached as soon as 

 technically possible, and the boiler capacity of the plant should be 

 such that this may be accomplished in 15 or 20 minutes. 



3. The digester contents should be cooked at the above pressure 

 and temperature for 15 or 20 minutes. This requires only enough 

 steam for radiation. 



4. The ratio of water to dry wood should be about 125 parts of 

 water to 100 parts of dry wood. 



5. The ratio of sulphuric acid (100 per cent) to dry wood should 

 be from 1.8 to 2.5 parts of acid to 100 parts of dry wood. 



6. Under the above conditions a yield of 25 gallons of 190-proof 

 alcohol per dry ton has been obtained, allowance being made for a 

 distillation loss of 2.5 per cent, but no allowance being made for any 

 manufacturing losses. 



7. After the cooking, the digester should be blown off as quickly 

 as possible. If the plant is operating on longleaf pine or a similar 

 resinous wood, about 1 gallon of crude turpentine can be recovered 

 per cord. If the plant is operating on other coniferous species, the 

 amount of turpentine in the blow-off will not pay for recovery; and 

 the same thing is true of the volatile acid in all coniferous species. 

 Usually the digester may be blown off directly into the air. 



8. Under the above conditions a complete cycle for each digester 

 would be about as follows: 



Minutes. 



Loading 5 to 5 



Heating 15 to 20 



Cooking 15 to 20 



Blowing-off 5 to 8 



Discharging 5 to 7 



Total 45 to 60 



9. Broad-leaved woods produce only about one-half as much fer- 

 mentable sugars and alcohol as do coniferous woods, although the 



