178 MASS. EXPERIMENT STATION BULLETIN 155. 



phosphate is not greater than 1 to 8 or 10. Cyanamid should 

 not be used in the same mixture with ammonium sulfate, as 

 free ammonia will be liberated from the latter salt. It should 

 prove a valuable source of quick-acting nitrogen for most crops, 

 but is not recommended as a top dressing for grass. It will not 

 be found injurious when applied unmixed at the rate of 200 

 pounds per acre as a source of part of the nitrogen for tobacco. 



Sewage Tankage {No. 8). — Sewage tankage, as the name 

 indicates, is a product recovered from sewage by means of the 

 precipitation method. In the sample here reported the grease 

 was extracted from the dried material, which was then ground 

 to a good mechanical condition. The sample analyzed carried 

 about 78 per cent, of organic matter. Products of this char- 

 acter vary greatly in composition, as two samples examined at 

 this laboratory in 1912 showed only .32 per cent, nitrogen, the 

 phosphoric acid running 6.67 per cent, and the potash .78 per 

 cent. Such a product would be valued commercially at about 

 $5.50 per ton. 



It has not been found commercially profitable to extract the 

 fat from sewage tankage. The unextracted material has a very 

 slow action in the soil, and practical experience does not en- 

 courage its use.^ 



No. 9. Picker Dirt from Cotton Mill, Average of Three Analyses. 



No. 10. Cocoa-shell Dust. 



No. 11. Shoddy Dirt from Woolen Mill. 



Analysis. 



I See Monthly Bulletin, State Board of Health, Vol. 8, No. 12, December, 1913. 



