218 Scientific Intelligence. 
very anys the salifiable base eames sai 4 Caton by the 
dec “ic on of the tart 
gradual tion takes | 
place speedily only when an excess of “Saliffable base, such as cal 
cium carbonate, is cola 6. Nitrification ag occur in solutions 
in which calcium salts are appar ently abse y ae: Few of 
orapnie carbon (as tartrate) to nitrogen ati as NH,Cl) equal 
:10 by weight suffices for the purposes of nitrification, and 
pod dee say less would be suffic me 8. Solutions containing 
as muc 640 milligrams NH,Cl per liter can be completely 
nitrified, though the limit of concentration up to which nitrifica- 
n a 
active work of the ferment. Whether this is due to the necessity 
of Cag A the germ to p roduce the effect or to the existence 
of th a passive senation, us an yet settled. 14. Increase 
in the cone Sedcniin n of the ammoniacal solution lengthens the 
riod of iecatauen, 15. sien of temperature within certain 
imits greatly reduces the —_ of the period of incubation, It 
being shorter at 30° than at 20°. 16, The period of actual nitri- 
fication, which succeeds the period of incubation, increases wi 
the concentration of the ammoniacal solution, and if the tempera- 
ture its length varies nearly as the degree of concentra- 
tion. Strong solutions require rather less time in proportion to 
their strength than weak ones. 17. The period of actual nitrifica- 
tion diminishes greatly in length by rise in temperature ; thoug' 
it is not yet proved to be shorter at 30° than at 20°. 18. Fro 
16 and 17, it follows that the average rate of oxidation increases 
up to a certain point with rise of temperature and is also somewhat 
increased with increasing concentration of the solution. 19. The 
rate ot oxidation is not uniform throughout, the process of nitrifi- 
eation beginning slowly, then scsouning in rapidity and after 
reaching a the nti ation i 8 again toward the close. 20. The 
