70 LABORATORY MANUAL OF MICROBIOLOGY 



To test the strength of the reagent, 5 cubic centimeters are 

 placed in a crucible of constant weight, near a dish of H2SO4 

 under a bell jar. As soon as all the ammonia is absorbed, the 

 Cu(0H)2 is dried and heated to constant weight and weighed as 

 CuO. 



Cellulose Determination.^ — Cellulose is added to the soil either in 

 the form of finely cut or well ground filter paper. After the soil 

 is properly mixed, a 20-gram sample is obtained from moist, or 

 preferably air-dried, soil. The sample is placed in a 250-cubic 

 centimeter sampling bottle, 100 cubic centimeters of Schweit- 

 zer's reagent is added; the bottle is then stoppered with a 

 rubber stopper and shaken for an hour in a shaking machine. 

 After settling, somewhat more than 50 cubic centimeters of the 

 liquid is filtered through a Gooch crucible by the use of suction. 

 Fifty cubic centimeters of the filtrate are then precipitated with 

 200 cubic centimeters of 80 per cent alcohol and the precipitate 

 is filtered through a Gooch crucible and washed as follows: (1) 

 dilute 1 per cent HCl, (2) warm distilled water, (3) dilute 2 per 

 cent KOH to get rid of humic acids — washing with KOH is 

 continued until all brown color disappears, (4) warm distilled 

 water, (5) dilute 1 per cent HCl to get rid of free alkali, (6) warm 

 distilled water until free from chlorides, (7) alcohol — after 

 cooling the crucible, (8) ether. 



Dry to constant weight at 110°C., weigh, burn off and weigh 

 again. The difference between the two weights gives the 

 quantity of cellulose for 10 grams of the sample. 



2. Celluloses in Plant Tissues. — Treat fresh or decomposed 

 material with 2 per cent solution of hydrochloric acid for 5 hours 

 under reflux condenser. Filter, and wash residue. Take aliquot 

 portion of residue and treat with 10 volumes of 80 per cent solu- 

 tion of H2SO4, then proceed as outlined on page 77. Calculate 

 cellulose content in original material. 



3. Pentosans. — The determination of pentosans is based upon 

 their transformation into furfural when boiled with 12 per cent 

 hydrochloric acid : 2 grams of material are placed in a 500-cubic 

 centimeter flask provided with a separatory funnel and an 



1 Charpentier, C. a. G. Thesis, Helsingfors, 1921; Waksman, S. A., and 

 O. Heukelekian, Soil Sci., 17: 275-292, 1924; Barthel, Chr., Abder- 

 halden's Handbuch, p. 754, 1927. 



