Apr. 28.1923 T oxicity and A niagonism of A Ikali Salts in Soil 325 
as the soil and sodium carbonate as the common salt in all the mixtures. 
In each trial three different substances were added, so that the effects 
of 15 materials in conjunction with sodium carbonate have been studied. 
The triangular arrangement of the experiment was adhered to, but 
the number of individual treatments was reduced from 66 to 15, as shown 
in figure 7. In addition there were included in each triangular arrange¬ 
ment five control treatments in which each of the four individual mate¬ 
rials and also distilled water were added to the soil alone. The whole experi¬ 
ment was done in duplicate. The same sodium carbonate treatment was 
present in five of these triangular groupings in which the concentrations 
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of the other added substances, when they were toxic in themselves, were 
made to range as nearly as possible from stimulating amounts to decid¬ 
edly toxic quantities. Four concentrations of sodium carbonate ranging 
from 1,000 to 7,500 parts per million made up a trial, which thus con¬ 
sisted of 20 units containing 40 tumblers each. 
In figures 8 to 13 the results of six trials are presented graphically on 
the basis of the dry weight per plant. The straight dotted line across 
all the charts gives the yield secured from the untreated soil, as derived 
from 40 tumblers. The heavy unbroken line shows the yield from the 
soil treated with sodium carbonate alone and is the average of 10 tumblers. 
It will be noticed that every concentration of sodium carbonate is rep¬ 
resented in the figure by three charts containing six curves in each. On 
