110 FOREST UTILIZATION 



§ XXXVIII. MANUFACTURE OF OXALIC ACID FROM WOOD. 



A. Principle. 



Any wood heated to about 400° F. in the presence of caustic sub- 

 stances yields, among many other products of disintegration, a 

 goodly percentage of oxalic acid. 



B. Raw material. 



Any wood finely ground or pulverized, and especially sawdust and 

 mill refuse, is well adapted to the process — oak as well as beecS, 

 pine, chestnut etc. Cottonwood is said to be rather poor as a 

 raw material. 



C. Process. 



A mixture of caustic soda, caustic potash and sawdust is heated, 

 under continuous stirring, in open -pans (yi foot deep and 6 feet 

 square) by superheated steam or air. The temperature is grad- 

 ually raised to 480° (not over) F., remaining at that figure for 

 about lYz hours. The melted mass, consisting of oxalate of 

 sodium and of carbonate of potassium, is thrown into \yater and 

 allowed to cool, when the oxalate forms a dough of minute crys- 

 tals. This dough is freed from water by centrifugal power, then 

 treated with lime and thereafter with sulphuric acid, with the 

 result that gypsum is precipitated from a solution of 'oxalic acid. 



D. Output. 



One hundred parts of wood yield up to 80 parts of oxalic acid. 

 The quantity of output depends oil proper mixture of caustic soda 

 and potash, and on proper regulation of the temperature. 



§ XXXIX. THE MAPLE SUGAR INDUSTRY. 



In the sap of all broad leafed species considerable quantities of s.ifgar 

 are found. This quality is commercially important, however, only in the 

 case of hard maple, [n igoo there were produced 51,000,000 pounds of 

 maple sugar and about 3,000,000 gallons of maple syrup. 



New York, Vermont and' New Hampshire lead this industry. Seven- 

 teen percent of all granulated sugar made in the United States is obtained 

 from the maple tree. 



Vermont protects its maple sugar industry from counterfeits by State 

 inspection and official stamp. 

 A. Tapping the trees. 



I. Time. End of January and February is best. 



Cold nights and hot days necessary for best results. 

 11. A hole is made, with an auger, Y^ inch to Y^ inch in 

 diameter, slightly slanting towards the entrance, to a 

 depth of 2 inches. to 8 inches, at a point 2 to 3 feet above 

 ground. Holes on north side of tree said to be most 

 productive. Holes 10 feet above ground do not yield 

 any sap. * 



III. A wooden or galvanized iron spout (3 to 8 inches long 



with a hook at the end to suspend the bucket) is in- 

 serted into the hole. 



IV. Buckets are emptied at least daily, as the sap ferments 



