8 EXPERIMENT STATION EECOED. 



nections it is probably possible to operate j doz. filters with one pump. In any 

 event, at least 1 doz. solutions can be filtered in One day by this apparatus." 



"After each filtration the tube should be washed out. A test-tube brush was 

 found to be serviceable in removing the clay from the inner walls of the filter 

 tube." 



The results obtained show that the modified clay filter method yields higher 

 results than either the Hilgard, Mooers-Hampton, or the Cameron-Breazeale 

 method, and lower results than the Rather and oflicial methods. The latter 

 2 methods, however, could not be relied upon as far as Hawaiian soils are 

 concerned. The Rather method in most instances did not bring about a coagula- 

 tion of the clay. On the other hand, although the results obtained with the 

 Mooers-Hampton, Hilgard, and Cameron-Breazeale methods at times furnished 

 concordant results, on the whole they were found to be in disagreement. 



It was furthermore noted that as much as 4 gm. of ammonium cai'bonate per 

 100 cc. of soil extract was necessary to effect a complete coagulation of the clay 

 with the Rather^ Rather modified, and the modified clay filter methods. In 

 some instances, however, a partial precipitation of humus also took place with 

 the Rather methods. Organic matter was precipitated with all the methods. 

 The fundamental reason for the differences in coagulability of the clays seems 

 to lie in the fact that the clays under examination were different in composition. 

 The uncoagulated suspensions were always found to contain relatively more 

 iron and correspondingly less aluminum. The iron and aluminum in such solu- 

 tions were found to be present in about the proportions necessary for the for- 

 mation of a double silicate. 



The detection of nitrates with diphenylamin, H. Cakon (Arm. Chim. 

 Analyt., 16 {1911), No. 6, pp. 211-215; ahs. in Chem. Zentbl., 1911, II, No. 6, p. 

 890). — The diphenylamin reaction for nitrates was found to depend upon the 

 concentration of the diphenylamin and sulphuric acid and the temperature. 

 The reaction w'as more pronounced if the diphenylamin was present in small 

 quantities and concentrated sulphuric acid was used in the test. 



The test is best conducted by adding tp 1 volume of the solution containing 

 the nitrate 2A volumes of a 0.002 per cent diphenylamin solution in concen- 

 trated sulphuric acid. The presence of hydrochloric acid or chlorids will not 

 affect the reaction if concentrated sulphuric acid is used. If, however, diluted 

 reagents are employed the presence of a drop of hydrochloric acid will render 

 the reaction more sensitive. Glycerin, acetone, carbohydrates, salicylic acid, 

 phenol, etc., destroy the intensity of the reaction more or less, particularly if the 

 reagent employed has been prepared with concentrated sulphuric acid. When 

 these substances are present the reagent must be prepared with hydrochloric 

 acid. 



The determination of nitrogen in commercial ammoniates, P. Rudnick 

 ET AL. (Jour. Indus, and Engin. Chem., S (1911), No. 10, p. 7S3). — This is the 

 second report of the committee on nitrogen, which was appointed by the division 

 of fertilizer chemists of the American Chemical Society. It contains the reports 

 of 15 analysts who determined the nitrate nitrogen according to the modified 

 Gunning-Kjeldahl method and the moisture, using 2 gm. samples of fertilizer. 



A wide range in the results on both moisture and nitrogen was reported, 

 and no definite conclusions could be drawn. Local conditions of manipulation 

 and reagents were deemed probably responsible for as much variation as any 

 other factor. A further study of the subject with a view to the establishment 

 of a standard sample is recommended. 



An apparatus for preparing ammonium citrate solution, G. Vecchi (Staz. 

 Sper. Agr. Ital., J,/f (1911), No. 1, pp. 56, 57, fig. 1). — A simple apparatus, which 



