Apr. s8, X933 
Toxicity and A ntagonism of A Ikali Salts in Soil 
327 
SULPHURIC ACID, POTASSIUM SULPHATE, AND SODIUM SULPHATE 
The concentrations used in this trial (fig. 8) are as follows: 
Parts per million at concentration— 
Z 
2 
3 
4 
5 
H2S04.... 
2, 000 
4, 000 
6, 000 
8,000 
10,000 
K2S04 . 
I, 000 
3, 000 
5,000 
8, 000 
10,000 
Na2S04. 
I, 000 
3,000 
5, 000 
8, 000 
10,000 
Na2C03. 
I, 000 
2, 000 
4, 000 
6, 000 
Fig. 7.—Diagram showing the arrangement of the tumblers in the final experiments. A uniform cOTcen- 
tration of sodium carbonate was present in all the tumblers and the treatment was added as indicated 
by the shading. The maxium concentrations used are given in the text. 
When added to the untreated soil, the potassium sulphate is only 
slightly toxic at 8,000 and 10,000 parts per million; the sodium sulphate 
is very detrimental to plant growth at 8,000 parts per million, and the 
acid is not harmful at all at 10,000 parts per million. This is indicated 
by the left section of figure 8, which also shows that the presence of 
sodium carbonate in the soil lowers the positions of these curves in pro¬ 
portion to its amount. The divergence of these pairs of curves due to 
