322 EXPEKIMENT STATION RECORD. 



Duplicate results secured in the determination of available lime by 

 the 10 per cent ammonium chlorid method were tolerably concordant 

 for each worker, but there were wide differences between analysts. 



A paper by B. L. Hartwell and J. W. Kellogg, presented by H. J. 

 Wheeler, discussed The Effect upon the Residue after Extracting the 

 Soluble Phosphoric Acid of Postponing the Treatment with Ammo- 

 nium Citrate. The differences between the amount of reverted phos- 

 phoric acid as determined at once and after standing- 15 weeks were in 

 nearly all cases within the limit of error liable to occur under the 

 conditions of the work. The results indicated that "no large error 

 will arise if, for the sake of greater convenience, the dried residues 

 from the extraction with water are kept a number of weeks before 

 the reverted phosphoric acid is removed by the ammonium citrate." 

 The relative value of open-hearth and ordinary basic slag, and of 

 raw and roasted redondite, was briefly discussed by several members. 



A paper on the Estimation of Small Quantities of Phosphoric Acid 

 by the Volumetric Method was read by F. P. Veitch. The deduction 

 from the results presented was that "accurate results can be obtained 

 on such small quantities of phosphoric acid as exist in drainage waters 

 and water extracts of soils, neither evaporation nor filtration appear- 

 ing to affect the results seriously." 



Recommendations. — The referee for the coming j^ear was instructed 

 to continue the stud}' of methods of determining total and available 

 phosphoric acid in slag, and also to study the solubility of phosphoric 

 acid in the same samples of slag reduced to different degrees of fine- 

 ness. It was also recommended that the referee plan field and pot 

 experiments with cultivated plants, looking toward the determination 

 of the relative value of the total phosphoric acid of slag, Redonda, 

 and precipitated phosphates of different degrees of fineness, in com- 

 parison with that of the phosphoric acid in acid phosphate and other 

 common phosphatic materials, and invite cooperation in this under- 

 taking on as many soil types and by as many workers as possible. 



NITROGEN. 



The report of the referee, C. H. Jones, read by F. C. Weber, was 

 devoted mainly to a comparison of the neutral and alkaline permanga- 

 nate methods for determining the availability of nitrogen in fertilizers. 

 The reports received from 15 chemists were on the whole very 

 satisfactory. The results by the neutral permanganate method agreed 

 closely and indicated that, if directions are followed in the digestion 

 with permanganate solution, uniformity may be obtained among differ- 

 ent analysts. The chief trouble found in operating the alkaline method 

 seemed to be from excessive frothing during distillation and an uncer- 

 tainty as to when to stop. Serious frothing may be avoided, according 



