FOODS AND FEEDING STUFFS. 55 



Filter the amorphous black precipitate into a tared gooch crucible through 

 an asbestos felt, wash carefully with 150 cc of water In such a way that the 

 water is not entirely removed from the crucible until the very last, then dry 

 for four hours at the temperature of boiling water, cool and weigh, in a weigh- 

 ing bottle, the increase in weight being reckoned as phloroglucid. To calculate 

 the furfural, pentose, or pentosan from the phloroglucid, use the following 

 formulas given by Krober : 



(a) For weight of phloroglucid "a" under 0.03 grams. 



Furfural = (a+0.0052) X 0.5170. 

 Pentoses = ( a -f 0.0052 ) X 1.0170. 

 Pentosans = ( a + 0.0052 ) X 0.8949. 



(b) For weight of phloroglucid " a " over 0.300 gram. 



Furfural = (a+0.0052) X 0.5180. 

 Pentoses = ( a + 0.0052 ) x 1 .0026. 

 Pentosans = (a-|-0.0052) X0.8824. 



For weight of phloroglucid "a" from 0.03 to 0.300 grams use Krober's table 

 or the following formulas : & 



Furfural = (a +0.0052 ) X 0.5185. 

 Pentoses = ( a +0.0052 ) X 1.0075. 

 Pentosans = (a+0.0052) X0.8866. 



10. Galactan. Provisional. 



Extract a convenient quantity of the substance, representing from 2.5 to 3 

 grams of the dry material, on a hardened filter with five successive portions of 

 10 cc of ether, place the extracted residue in a beaker about 5.5 cm in diameter 

 and 7 cm deep, together with 60 cc of nitric acid of 1.15 specific gravity, 

 and evaporate the solution to exactly one-third its volume in a water bath at a 

 temperature of 94 to 96 C. After standing twenty-four hours, add 10 cc of 

 water to the precipitate, and allow it to stand another twenty-four hours. The 

 niucic acid has in the meantime crystallized, but it is mixed with considerable 

 material only partially oxidized by the nitric acid. Filter the solution there- 

 fore through filter paper, wash with 30 cc of water to remove as much of the 

 nitric acid as possible, and replace the filter and contents in the beaker. Add 

 30 cc of ammonium carbonate solution, consisting of 1 part ammonium carbo- 

 nate, 19 parts water, and 1 part strong ammonium hydroxid, and heat the 

 mixture on a water bath, at 80 C., for fifteen minutes, with constant stirring. 

 The ammonium carbonate takes up the mucic acid, forming the soluble mucate 

 of ammonia. Then wash the filter paper and contents several times with hot 

 water by decautation, passing tha washings through a filter paper, to which 

 finally transfer the material and thoroughly wash. Evaporate the filtrate to 

 dryness over a water bath, avoiding unnecessary heating which causes decom- 

 position, add 5 cc of nitric acid of 1.15 specific gravity, thoroughly stir the 

 mixture and allow to stand for thirty minutes. The nitric acid decomposes the 

 ammonium mucate, precipitating the mucic acid; collect this on a tared filter 

 or gooch, wash with from 10 to 15 cc of water, then with GO cc of alcohol, and 

 a number of times with ether, dry at the temperature of boiling water for 



.T. Landw., 1900, 48: 379. See p. 226 of this bulletin. 



6 These factors were calculated from Krober's tables by C. A. Browne. 



