456 APPENDIX. 



1003. (KO, SOs + Cr 2 O 3 , 3S0 3 ) + 3KO = 4(KO ; 

 SO 3 )+Cr 2 O 3 . 



1025. 



MODE OF ESTIMATING THE VALUE OP GUANO, &C. In 



estimating the money value of guano for agricultural pur- 

 poses, ammonia may be set down at 16 cents per pound, 

 potash at 4 cents, and phosphoric acid at 1 to 2 cents. As 

 far as the latter exists in a soluble form, its value is doubled. 

 Other substances are of so little comparative value that they 

 need not be taken into the account. These valuations are 

 based, not alone on their relative value as fertilizers, but on 

 the cost of the different substances when obtained from other 

 sources. They are somewhat arbitrary, but may serve as a 

 means of approximate estimation of the value of guano and 

 other fertilizers. 



As an average of the composition of thirteen samples of 

 Peruvian guano, Prof. Way obtained the following results : 

 ammonia, 17*41 pgr cent.; phosphoric acid, 11-13; potash, 

 3*50. This would seem to be considerably above the or- 

 dinary average. The pecuniary value of such an article, 

 according to the above valuation, would be $63.00 per ton, 

 of which 855.60 would lie in the ammonia. No distinc- 

 tion is made in the potential and actual ammonia of guano, 

 because the conversion of the former into actual ammonia, 

 takes place so rapidly in the soil. But the potential ammo- 

 nia of most nitrogenous substances, as of clippings of hides 

 and other similar refuse, is to be estimated at least 25 per 

 cent, lower, in view of their comparatively slow conversion. 



In all analyses of concentrated fertilizers excepting guano, 

 in which the first distinction may be neglected, the amount 

 of actual and potential ammonia, of soluble and insoluble 

 phosphoric acid, and of potassa, should be separately stated. 



