13 
in this phase of the work were the same as those employed in the 
studies reported in the preceding pages. 
NITROGEN DISSOLVED IN THE PRELIMINARY 1 PER CENT 
HYDROCHLORIC ACID EXTRACTION. 
Calcium and magnesium are generally combined to some extent 
with the humus bodies in such a way as to render the organic matter 
less soluble in dilute alkalis. In order to break up such combina- 
tions the soils are treated with 1 per cent hydrochloric acid until no 
further amounts of calcium and magnesium are dissolved. It is 
customary in humus determinations, then, to dissolve the humus 
bodies in 4 per cent ammonia solution. In brief investigations l 
carried on in this laboratory it was observed that the dilute hydro- 
chloric acid extracts obtained in the preliminary treatment contained 
considerable organic matter. In one instance the solution was 
darkly colored and found to contain a notable amount of organic 
matter. Usually such solutions are discarded. It has been shown, 
however, that considerable amounts of nitrogen are dissolved from 
certain soils 2 in this preliminary acid extraction. In the work here 
reported the soils were first extracted with 1 per cent hydrochloric 
acid, then filtered and washed to neutrality. The solutions thus 
obtained should contain the ammonia originally present. The solu- 
tions were evaporated to a small volume and the nitrogen in them 
was determined by the Kjeldahl method, with the following results: 
Nitrogen of soils soluble in cold 1 per cent hydrochloric acid. 
Soil No. 
Per cent 
of soil. 
Per cent 
of total 
nitrogen. 
Soil No. 
Per cent 
of soil. 
Per cent 
of total 
nitrogen. 
379 
0.019 
.041 
.012 
.004 
.004 
3.21 
5.33 
3.39 
3.28 
1.82 
345 
0.007 
.029 
.009 
.012 
3.21 
428 
347 
2.34 
447 
[ 405... 
4.61 
292 
' 406... 
2.63 
343 
By comparing these data with those given in the first table it will 
be seen that in every instance the soils contained only about one-half 
as much ammonia nitrogen as was dissolved by 1 per cent hydrochloric 
acid, while in a number of instances still greater amounts of nitrogen 
were dissolved. Some organic nitrogen, therefore, was thus dis- 
solved, although the amounts were small. 
In preparing the humus solutions for studies on the nitrogen 
bodies a 3 per cent solution of sodium hydrate was employed. With 
Hawaiian soils sodium hydrate solution has a special advantage of 
i Hawaii Sta. Press Bui. 33. 
2 Rimbach, Jour. Amer. Chem. Soc., 22 (1900), p. 695. 
