900 
Arrangemeut and course of the experiment. 
If a mixture of sulfur and chalk is introduced into a saltpetre 
solution with addition of some garden soil or canal mud, there will 
soon evolve at room temperature or at 25° to 30° C., a current 
of gas consisting of free nitrogen and carbonic acid. Thereby the 
saltpetre is denitrified, the sulfur is oxidised to sulfurie acid, found 
back as gypsum and potassiumsulfate, after the formula 
6 KNO, + 55 + 2 CaCO, = 3 K,SO, + 2 CaSO, + 2 CO, + 3N, 
whereby per gram of decomposed nitrate about 1 cal. is produced. 
When after some days the process has become intense, the mud 
with the gas rises to the surface, and if the experiment is carried 
out in a flask, the contents can flow out with the gas as a slimy 
mass. This is bacterial slime, which keeps the sediment together. 
If using distilled water with 10 °/, chalk, 10 °/, sulfur, 2 °/, potassium- 
saltpetre, 0.02 °/, bipotassium phosphate, 0.02 °/, magnesium chloride, 
and infecting with a small floecule from the said denitrification, we 
see after some days at 25° to 30° C. the very same phenomena 
as when using soil, only less intense; so the presence of soil is not 
necessary, but it clearly acts favourably. If the soil or mud is before- 
hand left a few days under a dilute saltpetre solution, so that all 
the organic substances fit for denitrification are removed, the soil 
remains quite as good for the sulfur-chalk experiment, hence the 
organic matter cannot be the cause of the favourable action on the 
process. It seems to result from the presence in the soil of colloidal 
silicic acid and aluminium silicate, which are to be considered as 
catalyzers that hasten the decomposition. So, in a thiosulfate denitri- 
fication the reaction goes on much swifter in presence of chalk and 
bolus (aluminium silicate) than with chalk only. 
The saltpetre solution can be used in the most different concen- 
trations. Even in 10°/, solutions in tapwater made to a pap with 
sulfur and chalk, | saw at room temperature a spontaneous, intense 
gas production, with slime formation. The gas was nitrogen and 
carbonic acid; nitrogen oxydul seemed quite absent. The slime is 
bacterial slime, for the greater part consisting of different varieties 
of Bactertum stutzeri and B. denitrificans. It is so voluminous that 
its formation can only be explained by admitting that the said bacteria 
themselves produce this slime from the carbonic acid by chemo- 
synthesis. With distilled water the result of the experiment is the same. 
In a closed bottle and with distilled water the process goes on as with 
accession of air, which proves convincingly, that presence of organic 
substance is not required for the development of the rich bacterial 
