June IS, 1920 Effect of Manure-Sulphur Composts on Greensand 243 



acidity, sulphate, and potassium at the start, were then taken, after 

 which each compost was inoculated with the sulphofying organisms, 

 and the aluminum and ferrous sulphates were added in solution to 

 composts 6 and 13.* 



The period of composting was 23 weeks. Once each week the amount 

 of water lost by evaporation was added, and the composts were removed 

 from the pots and mixed, in order to provide thorough aeration. 



The composts were kept in the greenhouse throughout the entire 

 period and were covered at all times with a double thickness of white 

 muslin to protect them from direct sunlight. The temperature of the 

 greenhouse ranged from 50° to 100° F. 



For the water extraction a 75-gm. sample was weighed from each com- 

 post, air dried, and 50 gm. of the air-dry material were shaken every half 

 hour for 8 hours with 500 cc, of distilled water in a i -liter Pyrex flask. 

 After standing over night, the contents of the flasks were again shaken 

 and filtered rapidly through folded No. 3 Whatman filter papers. The 

 first 100 cc. of filtrate were poured back. The filtrates obtained were 

 absolutely clear and free from sediment. 



The acidity was determined by boiling aUquots of the water extract to 

 expel carbon dioxid, cooling, and titrating with Njio sodium hydroxid, 

 in terms of which the results are stated. Phenolpthalein was the indi- 

 cator used. Titration was continued until all soluble iron, aluminum, and 

 silica were precipitated and the clear solution retained the pink color for 

 one minute. 



Sulphur was determined by acidifying aliquots of the water extract 

 with 2 cc. of concentrated hydrochloric acid and precipitating at the 

 boiling point with barium chlorid. The results are expressed as sulphur 

 trioxid (SO3). 



The potassium determinations were made gravimetrically by the 

 platinic chlorid method from aliquots of the water extract, first elimi- 

 nating the soluble organic matter, silicates, iron, aluminum, and phos- 

 phorus by evaporation with sulphuric acid, ignition, and subsequent 

 precipitation. The determination for composts i and 8 throughout and 

 the first three determinations for the other composts not containing 

 manure were made colorimetrically because of the small amounts of 

 potassium present. 



Moisture determinations were made by heating separate 5-gm. por- 

 tions of the air-dry compost for 15 hours at 105° C. All results reported 

 in this paper are calculated to the moisture-free basis. No duplicate 

 determinations were made, the idea being that one series of compost 

 treatments would act as a control for the other in regard to the general 

 trend of the reaction and that any serious error in analysis would 



■ Cultures containing sulphofying organisms were supplied by Dr. J. G. Lipman and Prof. A. W. Blair, 

 of the New Jersey Experiment Station. 



