ELISHA MITCHELL SCIENTIFIC SOCIETY. 6/ 



use of the water wash is found to be open to the very serious objec* 

 tioD that it carries particles of the residue through the filter "as 

 soon as the saline matters are extracted." The writer found this 

 difficulty quite grievous, in fact in some cases (e. g., in case of bone 

 ash, finely ground phosphates or "fioats," and similar finely divided 

 substances), this difficulty rendered analysis by the method well 

 nigh impossible. The result is seen, furthermore, in almost all 

 analyses of ordinary fertilizers by the dark ring on top the filtrate 

 after the water wash has been applied. Others experienced the 

 same practical difficulty. Prof. S. W. Johnson, of the Connecticut 

 Experiment Station, met with it, and suggested that *' probably the 

 use of any indifferent saline solution, e. g., sodium chloride or sodium 

 sulphate, as a wash liquid, would prevent this practical difficulty." 

 A solution of the best sample of NaoSO^ in the laboratory at the 

 time gave me an acid reaction with litmus, due, doubtless, to impu- 

 rities, and "was abandoned. A solution of ordinary commercial 

 NaCl (table salt) was then made, which was found to react neutral 

 with either blue or red litmus. 



I then determined to test the action of the NaCl solution, if any, 

 on insoluble phosphate (CaaPoO^), by a few practical experiments. 

 Want of time and pressure of other work made the investigation 

 much less thorough than I would have desired, and the experiments 

 far too few to have any very great weight. Yet I deem the results sig- 

 nificant. 



The solution of salt used was made by dissolving 200 grammes of 

 commercial table salt in a litre of water, making a solution of about 

 1.11 spec. grav. (The solution upon test failed to reveal a trace of 

 P3O5). The solution, as made, was stronger, I should judge, than was 

 necessary, but was purposely so made in order to give it a fair trial. 

 Also subsequently in the experiments the washing was prolonged so 

 as to give the NaCl every opportunity to act. 

 The samples selected were : 

 I. Orchilla Guano. 

 II. Ammoniated Fertilizer. 

 III. Acid Phosphate (from South Carolina Rock). 

 In the case of the orchilla one gramme was acted on by 100 c. c. 

 ammonium citrate solution (sp. grav. 1.09 and neutral) on account 

 of the large amount of so-called '* reverted " phosphoric acid it con- 

 tains. In each of the other two cases two grammes were acted on 

 by 100 c. c. citrate solution as in ordinary practice. 



When the water wash was applied it carried through a small 

 amount of the residue in each case as usual, but it happened fortu- 



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