EXPEEIMENT STATION. 25 



The sample was very fine, all of it passing through a sieve 

 having -^ inch meshes. Prolonged treatment with ammonium 

 citrate dissolved only 4-|- per cent, of the phosphoric acid. 



The phosphoric acid is therefore mostly "insoluble" but mate- 

 rial as finely pulverized as this " Ground Phosphate Rock " might 

 be often used to advantage where phosphates are deficient, espe- 

 cially on soils with abundant humus or decaying vegetable matter, 

 as in case of reclaimed swamps, and where green-crops are plowed 

 in, or on moist grass lauds. At the price quoted it would also 

 make a cheap and excellent superphosphate by treatment with oil 

 of vitriol. 



It was finally, learned that this ground phosphate was not in 

 the market, but was from a sample in the hands of an importer. 



783. Phoenix Guano. Sold by W. C. Staples & Son, West- 

 , port. Sampled and sent by W. L. Coley, Westport. 



Analysis. 



" Reverted " phosphoric acid, 16.52 



Insoluble phosphoric acid, 6.52 



Cost per ton, - $40.00 



Estimated value per ton, 33.65 



Phoenix Guano from McKean's Island, like the Baker and Jarvis 

 Islands, Cura9ao, Orchilla and other guanos from rainy regions, 

 has lost by atmospheric agency all or all but a trace of the 

 nitrogen and potash which it originally contained. The phos- 

 phoric acid in them is much more readily soluble than in the 

 rock phosphates, and on that account they are more active as fer- 

 tilizers when applied to the land without previous treatment with 

 oil of vitriol. Sample 783 was from a small stock remaining in 

 possession of the dealer. The importations of Phoenix Guano are 

 understood to have ceased some years ago. 



Plain (Non-Nitrogenous) Superphosphates. 



Four articles of this class have been examined within the year. 

 The analyses and valuations of three of them will be found on 

 page 26. 



These are superphosphates in the true sense of the terra, for 

 essentially all the phosphate of lime which they contain is soluble 

 in water. In such cases it is of little importance to the purchaser 

 3 



