66 
IOWA ACADEMY OF SCIENCES. 
and potash. With reference to available nitrogen its adapta- 
bility cannot be pronounced upon without further research. 
The acknowledgements of the writer are due to Mr. O. H. 
Pagelsen and Mr. D. B. Bisbee, for their assistance in the above 
recorded work. 
NITROGEN COMPOUNDS OP THE SOIL. 
BY D. B. BISBEE. 
(Abstract.) 
In examining for ammonia a soil-extract, prepared by digest- 
ing soil for three days in dilute HCl, the author noticed that 
Bchloesing’s method (distilling the extract with excess of MgO) 
gave a continuous separation of ammonia, amounting in this 
case to .0024 per cent. Another portion of the extract was 
filtered after the addition of MgO and before boiling. In it the 
separation of ammonia ceased after boiling a comparatively 
short time, and the total separated was .0017 per cent. The 
evident inference is that “part of the amides in Schloesing’s 
extract can be precipitated by magnesia; and, by the second 
method ‘results are obtained which are much nearer the truth 
in respect to the ammonia of the soil than by the original 
Schloesing’s method.’” 
Kjeldahl’s process for determining the total nitrogen in a 
soil-extract consists in boiling the extract with H^SO^ and 
salicylic acid till colorless, adding HgO and KMnO^, and distill- 
ing with NaOH. The same results were obtained by reducing 
the nitrates, preferably with a zinc-copper couple, and distilling 
with a strong excess of alkaline permanganate. 
Prom experiments with citric acid it was found that “a 
one per cent solution of citric acid dissolves a part of the 
nitrogen of the soil as amides and none as ammonia. If ammo- 
nia is in the soil citric acid either does not dissolve it or else 
converts it into amide-like bodies. These amides dissolved in 
citric acid are volatile at least in part. The volatile part is 
converted into ammonia by long boiling with dilute HCl, or by 
boiling a short time with alkaline permanganate. ” 
