119 



bell pflass. At the end of tlio oxporimeiit determinations were made of 

 (1) the aininonia absorbed by tlie dilute sulphuric acid ; (2) the ammonia 

 taken np by the water of condensation and expelled by distilliiifj with 

 maj;nesia; (.J) the or^'anic nitro^'en reniaininj^: after treatment with 

 maj^Miesia. Other experiments were made in the same way, except 

 lliat sundry non-nitrof^enous organic matters, such as mannite, starch, 

 and humus derived from sugar, were adde<l to the soil, but without 

 essential ditterence in result. While the soils were kept moist, a not 

 inconsiderable amount of ammonia and a still larger (juantity of organic 

 nitrogen compounds were given off. The total nitrogen volatilized in 

 these forms and collected in the acid and water was 2 mg. from 1 kg. 

 of soil in 2.^ months. During the time that the soil was not moistened, 

 only minute (piantities were exhale<l. In these cases also the propor- 

 tion of organic nitrogen was several times larger than that in the form 

 of ammonia. 



The most interesting result was that the nitrogen given off under 

 these conditions by argillaceous sand in the form of volatile organic 

 compounds, was invariably larger in amount than that given off as 

 ammonia. In the previous experiments referred to, cultivated soil 

 twenty times richer in nitrogen than theargillac^eoussand of these experi- 

 ments like wise gave oil" two kinds of compounds, but the ammoniacal 

 nitrogen exceeded the organic in amount. This was the case both with 

 soil destitute of vegetation and with plants of a higher order. The 

 author iiders that these i)henomena are always brought about by the 

 influence of microbes or of plants of a low order, which are contained 

 in all soils and which manulacturo the small quantities of volatile 

 organic nitrogenous comi)ounds observed. These latter he speaks of 

 as a kind of vegetable ptomaines. — | \V. (). A.] 



Researches on humus substances, Berthelot and Andr^ {Compt. 

 rend., 112 (LSOl), ;>. DID). — Our cultivated soils are formed by the union 

 of various minerals with brown organic compounds. The latter, clas- 

 sified as humus, j^lay an important nMo in the fertility of soil and in 

 the nutrition of the plant, but their function has been established by 

 practical observers rather than defined and analyzed by scientific 

 research, and still remains one of the great unsolved problems of 

 agriculture. 



Not only do these compounds or the products of their transformation 

 play an essential nMe in the nutrition of plants and especially in the 

 circulation of nitrogenous i)ro(lucts, but they also contribute to the 

 power of the soil to hold in reserve certain mineral compounds despite 

 the dissolving action of water, a faculty which is also possessed by basic 

 silicates and is inaptly designated as absorptive power. Great as is 

 the agricultural interest attaching to these humus comp(mnds, chem- 

 ists appear to have been repelled from their study by their instability, 

 their insolubility, ami their non crystalline n'ature. It is hardly 

 possible in the present state of our knowledge to represent them by 



