646 
Journal of Agricultural Research voi. xxvti, No. 9 
the sum of these basic constituents makes up about one-third of the 
weight of the total solids. Where only the calcium and magnesium 
have been determined by analysis, the percentage statement of the 
results indicates approximately at least whether the water is to be 
classed as “hard” or “soft” with reference to the balance between the 
two classes of bases. 
If the sum of the calcium and magnesium is about 15 per cent of the 
total solids, it may be assumed that the calcium-sodium ratio is not 
far from 50-50. 
For a discussion of the significance of the calcium-sodium ratio in 
irrigation waters see Scofield and Headley ( 16 ). 
An example of a report on the quality of certain underground waters 
is shown in Table XIII, In this table the figures in the column headed 
“total solids” give the percentage of these to the original solution. 
The other figures in the table report the constituents that were identi¬ 
fied in terms of percentage of the total solids. With this form of report 
it is less difficult to compare different waters as to the proportion of 
their important dissolved constituents even though the total quantities 
of these constituents are very different. It is obvious that the propor¬ 
tion of calcium and magnesium to the sodium must be low in samples 
1, 4, 5, and 7. Sample 3 is high in bicarbonate though low in total 
solids. Samples 1 and 2 are high in chlorids, while samples 4 to 7 are 
high in sulphates. 
Table XIII .—Composition of certain underground waters in which the total solids are 
stated as percentage of the solution and the important groups of constituents are stated 
in terms of percentage of the total solids 
Sample No. 
1 
2 
3 
4 
5 
6 
7 
Total 
solids. 
O. 161 
. 145 
•053 
•357 
.914 
• 540 
. 586 
Ca+Mg. 
9.8 
16. I 
23. 2 
7- 1 
7- 7 
17. 6 
7-9 
Constituents as percentage of total solids. 
CO3+ 
HCO? 
7.8 
6. 1 
22. 1 
3-91 
2.8 
5- 1 
3- 7 
Cl. 
39-8 
34-8 
21. 5 
8.7 
i- 5 
3 -o 
1. 4 
SO4. 
13 - 1 
17.4 
23.8 
53*8 
64. 5 
sO. O 
58. 4 
NOs. 
i -3 
Total 
acids. 
60. 7 
59- <> 
67. 4 
66.4 
6<:. 2 
58. 1 
63.» 
The method of reporting the constituents as percentages of the total 
dissolved solids or total salts does not permit close or'accurate comparisons 
between different waters because these constituents have different 
molecular or combining weights. For example, 12 parts per million of 
magnesium has the same combining value as 20 parts per million 'of 
calcium. In the same way with the acids, 48 parts per million of sulphate 
has the same combining value as 35.5 parts per million of chlorin or 30 
parts of carbonate. These differences in molecular or combining weight 
make it impossible to express the true character of solutions by the 
percentage method of statement. This method is simple and convenient, 
but at best it permits only approximate comparisons. Where it is 
desired to make more accurate comparisons between different waters it 
is advisable to use a method which takes into account these differences 
