QUALITATIVE AND QUANTITATIVE ANALYSIS 71 



outlet tube connected with condenser. One hundred cubic 

 centimeters of 12 per cent hydrochloric acid (specific gravity 

 1.06) is added from separatory funnel, and 30 cubic centimeters 

 distilled over in 10 minutes, the distillate passing through small 

 filter paper into receiver. As soon as 30 cubic centimeters of the 

 distillate are collected, 30 cubic centimeters more HCl is added to 

 flask and distillation continued. This is repeated until 270 cubic 

 centimeters of distillate are collected. Forty cubic centimeters of 

 filtered phloroglucide solution (11 grams of phloroglucinol 

 dissolved in 300 cubic centimeters of 12 per cent hydrochloric 

 acid) are added to the distillate and made up to 400 cubic centi- 

 meters with hydrochloric acid. After standing 16 hours, the 

 precipitate is filtered off using a weighed Gooch crucible with 

 thick asbestos mat. Wash with 150 cubic centimeters of water, 

 dry at 100 to 105°C. for 4 hours, and weigh. If a is the weight 

 of the precipitate, the pentosan content is, when less than 0.03 

 gram 



(a - 0.0052) X 0.8949. 



When the precipitate weighs 0.03 to 0.3 gram, the pentosan 

 content is 



(a - 0.0052) X 0.8866. 



4. Starches. — Starches are soluble in hot water and are readily 

 hydrolized by dilute acids and by diastatic enzymes giving the 

 reducing sugars maltose and glucose. 



A definite amount of material (4 to 5 grams), previously 

 extracted with ether and alcohol, is treated with 50 cubic centi- 

 meters of water, in a double boiler and brought to the boiling 

 point; it is kept at that point for 15 minutes, until all the starch 

 has gelatinized. The mixture is then cooled to 50°C. and treated 

 with 10 cubic centimeters of malt extract. The temperature 

 (50°C.) is maintained for 30 to 60 minutes. The mixture is 

 again heated, cooled to 50°C., again treated with 10 cubic centi- 

 meters of the malt extract, and incubated for 30 to 60 minutes, 

 until no blue color is given with iodine solution. The mixture is 

 made up to 250 cubic centimeters and filtered through paper; 

 200 cubic centimeters of the filtrate is treated with 20 cubic 

 centimeters of hydrochloric acid solution (specific gravity 

 1.125) and heated, under a reflux condenser, for 2 hours. 



