7'22 
Journal of Agricultural Research voi.xxvu.no. ro 
A qualitative test was made, using much smaller samples than those 
used in the preceding experiments, in order to determine whether a 
negative qualitative test might have resulted even from plants containing 
a considerable amount of hydrocyanic acid, because too small a sample 
had been employed. As 15 or 20 gm. is about the smallest sample 
that can be conveniently ground through the food chopper, these small 
samples of 2 or 3 gm. each were crushed in an agate mortar with a 
pestle. The plants tested were grown on Merrimac Loamy Sand, with 
nitrate added, and were dark green in color. They were from 20 to 28 
cm. in height, and about 1 gm. in weight each. Two plants were used 
for each sample. In the analysis of all four samples, a satisfactory blue 
color resulted, about equal to that from 0.2 mgm. of potassium cyanid. 
It thus seems probable that working with very small plants, provided the 
sample is representative and thoroughly crushed or ground and adequately 
autolyzed, the failure of even a small sample (5 gm.) to give good quali¬ 
tative test should be looked upon as indicating a probable lack of nitrate 
in the soil. 
Although it has been generally recognized that the content of hydro¬ 
cyanic acid is much greater in the leaves of sorghum than in the stems, it 
was not deemed safe to rely on analyses of the leaves only, but in the case 
of larger plants, the leaves and stems were analyzed separately and the 
hydrocyanic acid in the whole plant computed from these separate 
analyses. In the case of young small plants, it is difficult to separate leaf 
and stem; hence in those cases the whole plant was analyzed as one 
sample. 
A few of these separate analyses of leaf and stem are reported in Table V 
to show that there is no characteristic difference in distribution of the 
hydrocyanic acid between fertilized and unfertilized plants, at least at 
the ages taken. The amount increases with the amount of nitrate sup¬ 
plied, and the percentage is usually several times as great in the leaves 
as in the stem. 
If the plant is employed as an indicator, it may be found that analysis 
of the leaves only will give as correct an indication of the readily available 
nitrogen in the soil as analysis of the whole plant. 
Table V .—Distribution of hydrocyanic acid between leaf and stem of the same plant 
Sample 
number. 
Age of 
plant. 
Soil. 
Nitrate 
added per 
jar. 
Hydrocyanic acid content. 
Leaves. 
Stem. 
Whole 
plant. 
107 
108 
109 
no 
in 
127 
129 
134 
Days, 
69 
71 
71* 
92 
92 
88 
88 
Coloma sand. 
Merrimac loamy sand.... 
.do. 
do . . 
Gm. 
O- 75 
None. 
o- 75 
None. 
1. 00 
i- 50 
1. 25 
Per cent. 
O. 1510 
None. 
. mi 
. 0040 
. 1150 
. 0610 
. 0180 
. 2697 
1 
Per cent. 
O. 0221 
None. 
. 0062 
Trace. 
. 0088 
. 0100 
Trace. 
.0519 
Per cent. 
0. 0627 
None. 
.0369 
.do. 
Thurston loam subsoil.... 
.do. 
Coloma sand. 
.0417 
. 0340 
. 0080 
. 1360 
