DIRECTIONS 5 



The organic nitrogen in superphosphates, special manures and 

 mixed fertilizers of a high grade is usually valued at the highest 

 figures laid down in the trade values of fertilizing ingredients in 

 raw materials ; namely, eighteen and one-half cents per pound, it 

 being assumed that the organic nitrogen is derived from the best 

 sources; viz., animal matter, as meat, blood, bones or other equally 

 good forms, and not from leather, shoddy, hair or any low priced, 

 inferior form of vegetable matter, unless the contrary is evident. 

 In such materials the insoluble phosphoric acid is not given any 

 value or only a mere trifle per pound. These values change as 

 the markets vary. 



The scheme of valuation prepared by the Massachusetts station 

 does not include phosphoric acid in basic slags. By many experi- 

 menters the value of the acid in this combination, tetracalcium 

 phosphate, is fully equal to that in superphosphates soluble in 

 water and ammonium citrate. It would perhaps be safe to assign 

 that value to all the phosphoric acid in basic slags soluble in a 

 five per cent, citric acid solution. 



Untreated fine-ground phosphates, especially of the soft variety 

 so abundant in many parts of Florida, have also a high manurial 

 value when applied to soils of an acid nature or rich in humus. 

 On other soils of a sandy nature, or rich in calcium carbonate, 

 such a fertilizer would have little value. The analyst in giving an 

 opinion respecting the commercial value of a fertilizer must be 

 guided not only by the source of the material, its fineness or 

 state of decomposition, and its general physical qualities, but also 

 by the nature of the crop which it is to nourish and the kind of 

 soil to which it is to be applied. 



GENERAL PRINCIPLES OF SAMPLING 



6. Directions. It is impracticable to give definite directions for 

 getting samples of fertilizers which will be applicable to all kinds 

 of material and in all circumstances. If the chemist himself have 

 charge of the sampling it will probably be sufficient to say that it 

 should accurately represent the total mass of material at hand. 

 Generally the samples which are brought to the chemist have been 

 procured without his advice or direction, and he is simply called 

 upon to make an analysis of them as they are presented. 



