SOME EFFECTS OF SODIUM AESENITE 9 
Arsenious acid and the sodium arsenites were further compared 
in water cultures, using seedling barberries. The results of one 
of these series are shown in Table 2. 
Table 2. — Effect of arsenic applied to small barberry seedlings in water cultures 
Concentration of arsenic 
Arsenious 
acid, H3ASO3 
Na 2 HAs0 3 
Na3AsOs 
+NaOH 
25 parts per million.. 
50 parts per million.. 
100 parts per million. 
200 parts per million. 
Injured. 
Dead... 
do.. 
do.. 
Healthy. 
Injured. 
Dead.... 
do... 
Healthy. 
Do. 
Injured. 
Dead. 
Here, again, it is evident that arsenious acid is more toxic than 
sodium arsenite and that the addition of more sodium to the solution 
reduces the toxicity. The solutions were prepared by first dissolv- 
ing a given quantity of CP white arsenic in water to form the arseni- 
ous acid. Sufficient sodium-hydroxide solution was then added to 
portions of this arsenious acid to give the theoretical formulae stated, 
after which the solutions were boiled. In this way it was certain 
that exactly equal quantities of arsenic were present in each of the 
three series. 
It is interesting to note that much more dilute solutions caused the 
death of the plants in water cultures than in soil. This may be the 
result either of a physical absorption of the chemicals by the soil 
particles or of the formation of insoluble arsenic compounds caused 
by the presence of iron or other substances. It is conceivable also 
that, when iron or other chemicals which would have a tendency to 
form insoluble arsenic compounds are present in quantity, more 
alkali in the solution might reduce this action somewhat and allow 
the poison to act in the plant and in this way justify the use of 
solutions stronger in alkali than the 8-pound material chosen. 
In another experiment seeds of various farm crops were sown in 
a dark silt-loam soil which contained 0.04 per cent of arsenic. This 
soil was obtained on November 17, 1923, from around the base of a 
large barberry bush that was treated on September 20, 1922, with 
sodium-arsenite solution. Undoubtedly the 0.04 per cent of arsenic 
remaining in this soil at the time it was collected was not all in the 
form of sodium arsenite, but no attempt was made to determine its 
chemical form. All the seeds used — oats, wheat, rye, barley, corn, 
pea, winter vetch, rape, and buckwheat — germinated well, and the 
plants grew to a height of 2 to 3 inches without noticeable injury. 
About that time some of the cereals assumed an unnaturally deep 
blue color and cases of tipburn developed. There also was a notice- 
able slackening in the rate of growth in all the plants in the arsenic 
soil, while the controls in arsenic-free soil continued to develop 
normally. Some of the plants were then dug and the root develop- 
ment compared. In the soil containing arsenic very few roots had 
developed, particularly in the oats, where the roots w T ere only a few 
millimeters long (PI. I, fig. 2). With pea, vetch, and corn the roots 
had grown about 1 centimeter but were brown and dying, and 
many short lateral roots had started (PL I, fig. 1, and PI. II). The 
barley, wheat, and rye appeared to have been injured least by the 
15691°— 25 2 
