1917] SOILS FERTILIZERS. 815 



action of heat upon the protozoa is very similar to the action of the volatile 

 disinfectants. . . . 



" Regarding the action of toluene upon the bacteria, there is indicated, in the 

 formation of the sulphid, the probability that certain oxidizing organisms in 

 the wet soils are, by the treatment, either destroyed or overwhelmed in numbers 

 by the surviving reducing bacteria. In dry soil this does not occur. Conditions 

 which cause the apparent destruction of the sulphur-oxidizing bacteria also 

 cause the destruction of the ciliates." 



In the second paper, experiments with garden soil are reported, from the 

 results of which it is concluded that " the formation of toxins in the soil free 

 from vegetation occurs most rapidly when the temperature is near 28° C. and 

 the moisture content is one-fourth of the water-holding capacity. The soil ex- 

 tract is, as a rule, either nutritive or toxic according to the volume of water, 

 relative to the soil, used in preparing the extract. It is most nutritive when 

 the ratio of soil to water is 1 : 0.5, and most toxic when it is 1 : 1. 



"A previous drying or chloroforming of the soil generally causes the extract 

 to be much more nutritive than when the raw soil is used. The addition of 

 small quantities of dextrose to soil brings about a more rapid production of 

 toxin, while aeration of the treated soil accelerates the formation and decay 

 of the toxin." 



Experiments are reported in the third paper in which it was found that 

 chloroform acts as a stimulant in soil extracts. It is considered justifiable 

 to conclude that chloroform will act in the same manner in soil moisture. " Its 

 persistence in the soil after treatment, combined with its action in soil extracts, 

 argues in favor of the stimulation theory that the great increase in the bac- 

 terial numbers, following treatment of a soil with chloroform, is due in part to 

 the stimulation of the bacteria by small doses of the disinfectant retained by 

 the soil." 



The organic matter of the soil. — II, A study of carbon and nitrogen in 

 seventeen successive extracts; with some observations on the nature of the 

 black pigment of the soil, R. A. Gortnee (Soil Sci., 2 {1916), No. 6, pp. 539- 

 548, fig. 1). — Supplementing a pi'evious paper of this series (E. S. R., 36, 

 p. 512), an account is given of a further study of the hydrochloric acid and 

 sodium hydroxid extracts of a silt loam soil. Examinations of these extracts 

 as well as of the residual soil at different stages of the extraction confirmed 

 the author's previous conclusion that 4 per cent sodium hydroxid solution does 

 not dissolve the black soil pigment. This pigment was found to be soluble in 

 very dilute sodium hydroxid solutions, but precipitates from solution on the 

 addition of sodium hydroxid in sufficient amount to make a 4 per cent solution. 



" The soil pigment is also precipitated from solution by salts of the heavy 

 metals and by acidification, is not dialyzable, and forms a stable water-soluble 

 compound with ammonia when an ammoniacal solution is evaporated to dryness. 

 Two attempts were made to prepare the soil pigment in pure form, but the re- 

 sulting products contained such a high content of ash (37.47 per cent and 51.17 

 per cent, respectively) as probably to render the ultimate analysis unreliable. 

 The analysis of the product with the least ash content gave carbon 61.3 per 

 cent ; hydrogen 4.3 per cent ; nitrogen 2.8 per cent ; oxygen 31.6 per cent ; all 

 calculated to an ash-free basis. The first six extractions with NaOH removed 

 relatively more nitrogen than carbon from the soil, but the remaining three 

 NaOH extractions as well as the six pigment solutions contained relatively 

 more carbon than nitrogen. The final soil residue had a carbon-nitrogen ratio 

 very much higher than that of the original soil." 



References to the more important literature on the subject are given. 



