Mabch 2, 1906.] 



SCIENCE. 



325 



determined. The graphical representation 

 of the results indicates that the soils are 

 approaching a saturated condition for phos- 

 phate, as is shown by the fact that each 

 curve is evidently approaching a horizontal 

 asymptote. It has been found that these 

 absorption phenomena are quite accurately 

 described by the differential equation 



which, is of the same form as the equation 

 for a reaction velocity of the first order 

 and other analogous processes. Integx-at- 

 ing we get 



log (A — y) — log A = — Kv, 

 where K is a constant, A the maximum 

 amount of phosphate the soil can take up 

 under the conditions of the experiment, 

 and y the amount it has taken up when 

 the volume v of the phosphate solution has 

 passed through the soil. A may, therefore, 

 be defined as the specific absorptive capac- 

 ity of the soil for phosphate. This ab- 

 sorptive capacity for phosphate varies 

 greatly in different soils, being most pro- 

 nounced in the clays and loams as a rule 

 and less so in the sandy soils. The solu- 

 bility of the phosphate originally present 

 in the soils was also determined by percolat- 

 ing water through the untreated soils in 

 the above-mentioned apparatus. It was 

 found that the concentration of the sepa- 

 rate fractions of percolate was practically 

 a constant for each of the soils studied. 

 If this concentration is reduced through 

 any cause, such as the absorption by plants 

 or influx of rain water, the original con- 

 centration will be again restored by more 

 of the phosphate of the soil entering into 

 solution. If, on the other hand, the solu- 

 tion is somewhat stronger than the natural 

 concentration for that soil through any 

 cause whatever, such as the application of 

 a soluble phosphate, the concentration is 

 reduced by absorption to the original 

 strength. This is sti'ikingly shown by the 



absorption results with the first few hun- 

 dred cubic centimeters of phosphate solu- 

 tion. This constancy in the strength of 

 the soil solution, so far as phosphate is 

 concerned, is further shown by the removal 

 by water of the absorbed phosphate, which 

 has been similarly investigated. It was 

 found that the concentration of the sepa- 

 rate percolates decreases rapidly until the 

 concentration is reduced approximately to 

 that of the original soil solution. This 

 concentration of phosphate is then main- 

 tained with much persistence, although 

 only a fractional amount of the absorbed 

 phosphate has been removed, thus indicat- 

 ing that while the absorbed phosphate is 

 apparently rendered insoluble, it is, never- 

 theless, slowly but constantly going into the 

 soil moisture and is, therefore, available to 

 plants. 



Citric Acid: F. L. Kortright. 



A discussion of various unsuccessful at- 

 tempts to make anhydrous citric acid ac- 

 cording to the method of Buchner and 

 Witter, was followed by a description of 

 two methods used in getting the equi- 

 librium relations between citric acid and 

 water. The cryohydric point of the mono- 

 hydrate and water, the transition point of 

 the monohydrate to the anhydrous acid,, 

 and the transition point of one form of 

 anhydrous acid to another, have been deter- 

 mined. The work is to be continued. 



The Action of Metals on Complex Cyanides 

 in Aqueous Solution: G. McP. Smith. 

 (By title.) 



Electrolysis and Endosmosis in the Study 

 of Bock Decomposition : A. S. Cushman. 

 (By title.) 



AGRICULTURAL AND SANITARY CHEMISTRY. 



H. W. Wiley, chairman. 



Filtration and Purification of the Missis- 

 sippi River Water at Neiv Orleans: J. L. 

 Porter. (By title.) 



