UTAH ACADEMY OF SCIENCES 99 
These tables show little difference in the tests for 
sodium chloride and sodium sulfate but sufficient differ- 
ence in the sodium carbonate to make this salt show 
more or less toxic than sodium chloride according to how 
it is determined. None of the regular tests consistently 
show over half of the sodium carbonate added to the soil. 
The exact explanation of this is still a matter for research. 
The deviations are not noticeably different for any of 
the methods showing that most of the deviation is in the 
crop growth and not in the analysis. This would indi- 
cate that in field work it makes little difference what 
method is used to determine the salts in the soil so long 
as the data on the relative crop growth or toxicity have 
been worked out by a similar method. 
Summarizing briefly, these experiments show that: 
1. Different methods of determining the alkali con- 
tent of soils give widely different results, especially with 
‘sodium carbonate or “black alkali.” 
2. There are great differences in the toxic Seppe 
of alkali as found by different investigators. 
3. The methods tried out in detail are about 
equally satisfactory in themselves. 
4. In field studies it is necessary to use figures for 
the toxic limits which were determined by the same 
method of testing as employed in the work. 
5. Tables have been prepared showing the toxicity 
of three alkali salts as determined by four different 
methods. 
