346 



SCIENCE. 



[N. S. Vol. XIX. No. 478. 



The method is described at length (loc. cit., 

 pp. 97-98) and since the author of the circular 

 quotes freely from the paper he is presumably 

 familiar with its contents, and his statements 

 are inexplicable. The absurdity of the state- 

 ments is also apparent from the fact that 

 the dilute acid digestion is reported to yield 

 one to six parts per million of P^Oj in the 

 Eothamsted soils, the lower figure being ob- 

 tained for four out of the seven soils, and 

 supposing the entire solution to be used for 

 the phosphate determination, there would be 

 only from 0.00016 gm. to 0.00096 gm. of phos- 

 phoric acid (P.Oj) available for weighing. 



It would not be proper, and it is not per- 

 mitted me, to discuss here the methods or re- 

 sults given in the Journal article as the au- 

 thor is a colleague in this department. It 

 seems worth while, however, to call attention 

 here to the work upon which the method used 

 by the Bureau of Soils rests. 



This method is the one described by 

 Schreiner* and in the appendix of Bulletin 

 No. 22. It appears to have been first suggested 

 by Lepierre,t was worked out further by JoUes 

 and Neurath,:}: Woodman and Cayvan§ and 

 others. Its value for solutions containing dis- 

 solved silica as well as phosphates, a condition 

 existing in aqueous extracts of soils, was crit- 

 ically tested in the laboratory of the Bureau 

 of Soils by Veitch]| and Seidell,** and at the 

 University of Wisconsin by Schreiner. ft 



The results of these investigators showed 

 the method to be of a very high order of ac- 

 curacy as well as delicacy. The figures in 

 the published papers of Veitch and Schreiner 

 speak for themselves, and it seems entirely 

 unnecessary to add additional ones here, al- 

 though a large number of results obtained by 

 the method on solutions of known concentra- 

 tions are in our possession, and show remark- 

 ably good agreements between the results ob- 

 tained and the known concentrations. The 



*Jour. Am. Chem. Soc, 25, 1056, 1903. 



t Bull. Soc. Chem., 15, 1213. 



t Monatsh. Chem., 19, 5. 



%Jour. Am. Chem. Soc, 23, 96. 



II Jour. Am. Chem. Soc., 23, 169, 1903. 



** Results unpublished. . 



■\\ Loc. cit. 



concentrations of phosphoric acid, stated as 

 POj, involved in these Eothamsted soils was 

 found to be 10.5 to 19.6 parts per million of 

 air-dry soil or within the limits of 2 to 4.5 

 parts per million of solution actually ex- 

 amined. Veitch has given results for solu- 

 tions containing from 1 to 10 parts per mil- 

 lion and Schreiner from 1.35 to 42.8 parts per 

 million of solution, which leave absolutely no 

 doubt as to the validity of the method for the 

 concentrations involved in the examination of 

 these Rothamsted soils, or the other soils 

 cited in the bulletin. 



The papers cited are all contained in readily 

 accessible journals and they have never been 

 disputed or controverted. It seems wiser, 

 therefore, to confine attention to data already 

 published than to add further figures from our 

 own experience, which would merely accumu- 

 late evidence, all in the same direction. It is 

 worth while to note, in this connection, that 

 while Dr. Sehreiner's investigation was done 

 for and at the instance of the Bureau of Soils, 

 it was actually carried on in the laboratory of 

 the University of Wisconsin in entire igno- 

 rance of the work being done by Veitch and 

 Seidell, and before he was acquainted with 

 any member of the laboratory force in Wash- 

 ington or with the work upon which they were 



The statement in the ' Added Note ' ' that it 

 has long been common chemical knowledge 

 that water dissolves but the merest trace of 

 phosphorus from soils ' is, to say the least, 

 misleading, and in this connection entirely 

 unjustifiable. It must be assumed that the 

 author is familiar with the classic paper of 

 Dyer* in which he proposes the use of his now 

 famous method for digesting soils in a solution 

 of citric acid. In the early pages of this 

 paper Dyer cites some results he obtained by 

 digesting a soil in water. 250 grams of soil 

 in 1,000 c.c. of water gave six parts phos- 

 phoric acid per million of dry soil. The soil 

 and solution were in contact for two days be- 

 fore the examination, but no further phos- 

 phoric acid was obtained when the solution had 

 acted on the soil for 28 days, so that it is fair 

 to assume that the solution of the phosphoric 



* Jour. Chem. Soc, 65, 115, 1894. 



