DENATURED ALCOHOL 251 



A large cylindrical vessel, of a capacity somewhat over 1,600 gal- 

 lons, lined with lead which is not attacked by dilute sulphuric acid, 

 is mounted in such a way that it may be revolved to agitate the con- 

 tents. It is strongly built to resist considerable pressures. Such an 

 instrument, whether large or small, intended for carrying out re- 

 actions under the combined influence of heat and pressure, is called 

 an autoclave. 



In Simonsen's process the autoclave is charged with 100 kilo- 

 grams (220 lbs.) of sawdust and between 300 and 500 kilograms of 

 dilute sulphuric acid (0.5 per cent. acid). Steam is blown in through 

 openings in the axles until the whole has reached a temperature of 

 100° Centigrade (212° Fahr.), when the autoclave is closed. Then 

 it is heated to about 175° Centigrade, the pressure in the interior 

 simultaneously rising to about 135 lbs. per square inch. These con- 

 ditions are maintained for about half an hour, while the contents 

 are thoroughly stirred by rotation. The autoclave is then opened 

 and the liquid is filtered off from the solid residue. A portion of the 

 cellulose, under the influence of the acid, the heat and the pressure, 

 has been converted to glucose, fermentable sugars, which are soluble 

 and so are contained in the liquid, the filtrate. The solid residue is 

 made up into briquettes for fuel. The acid in the filtrate is almost 

 neutralized with lime (it is desirable to leave it feebly acid), and this 

 necessitates another filtration, for the neutralization results in the 

 formation of a solid precipitate of calcium sulphate which must 

 be removed. Yeast, and a small amount of nutrient material for the 

 yeast, are then added, and the whole is maintained at a temperature 

 of 25° Centigrade for from three to five days. At the end of this 

 time the fermentation is complete. The first distillation yields a 

 15 per cent, alcohol and a second distillation brings the concentration 

 of the alcohol up to about 75 per cent. 



Pine and fir wood give about the same quantities of alcohol, birch is 

 better for the purpose. In a general way hard woods appear to give 

 better results than soft woods. Seven liters of absolute alcohol from 

 100 kilograms of sawdust containing 20 per cent, of moisture must 

 be considered a satisfactory yield. 



Simonsen estimates that he can make 100 liters of absolute alcohol 

 for 5.86 Marks, that is, at a cost of about 5% cents a gallon. If 

 this estimate were strictly correct, the process could compete with 

 those based on the direct fermentation of agricultural produce; if 

 it were strictly correct, it is reasonable to suppose that there would be 

 more factories making alcohol from wood than there are. 



Classen's process is similar to Simonsen's, but the chemistry of it 

 appears to be more economical. Classen runs sulphur dioxide gas 

 (which can be easily and cheaply obtained in any of the numerous 



