120 



the constitutional formulas usual in organic chemistry. Nevertheless 

 they present problems of great interest from the standpoint of chemistry 

 and vegetable physiology because of the phenomena of hydration and 

 dehydration, molecular condensation, and of transformation of colloidal 

 substances which they manifest. 



After devoting some time to the study of nitrogenous humus com- 

 pounds which occur in the soil and are complex and of uncertain origin, 

 it seemed advisable to the authors to devote their attention to those 

 formed artificially in accordance with well-defined princi[)les, and con- 

 taining only carbon, hydrogen, and oxygen. For this purpose they 

 used the product of the action of hydrochloric acid on cane sugar, which 

 is known as ulmin and ulmic acid, and which in their view should be 

 regarded as a condensed anhydride or a mixture of several anhydrides 

 derived from certain acids which result from the metamorphosis of 

 sugar. Treated with alkaline solutions, this anhydride swells up in the 

 manner of colloid substances and forms salts of different degrees of 

 basicity, some of which are soluble and some insoluble. The insoluble 

 basic potassium salts are of special interest. These have escaped the 

 attention of previous observers, having been mistaken for other sub- 

 stances. Such is their insolubility that the anhydrate formed from 

 sugar, just referred to, is able to remove nearly the whole of the potash 

 or soda from a solution in water by forming the insolnlde basic salts. It 

 is also able to decompose small quantities of i)otassium chloride setting 

 hydrochloric acid free. Its behavior with sodium, barium, calcium, and 

 also with ammonium is similar to that with potassium. The authors 

 devoted their special attention to the insoluble potassium salt, because 

 of its especial interest in explaining the absorptive powers of humic 

 compounds. The salt resists the solvent action of water to a very 

 marked degree. Even when boiled with 120 limes its weight of water 

 for an hour it was but slightly decomposed, and was but little acted upon 

 by carbonic acid in the cold. From a solution of potash in 120 times 

 its weight of water, the anhydride takes the amount required to form 

 the insoluble salt just described, and by this means nearly all the 

 potash can be removed from even a very dilute solution. Other salts 

 of potassium, sodium, barium and ammonium were studie«l. Ammonia 

 forms with the anhydride amido acid salts. 



These researches throw a new ligiit on the function of humus com- 

 pounds in the soil, by indicating that they combine with both ammonia 

 and the mineral alkalis. i)rotoct them from the leaching action of the 

 water which circulates through the soil, and hold them in reserve for 

 the use of the plants. In other words, the absorptive power of the 

 soil which has been currently attributed to hydrous silicates, is shared 

 also by the humus compounds. — fW. O. A.] 



Gain or loss of nitrogen by soils, A. Pagnonl {Ann. Agron., XVI 

 (ISDO), V,,p. 2.j0).— To test the gain or loss of nitrogen in a soil with and 

 without crops growing ui)on it, trials were made with soil in glazed 



