344 
Journal of Agricultural Research 
Vol. XXXI, No. 4 
penetration where part of the water was applied later. The chemical 
tests emphasized this difference. Where all of the water was applied 
in the chemical solution, the test for mercury was often very faint 
in samples from near the point of maximum penetration. The 
strength of the test was apt to be variable, not only between different 
tubes but within a tube. When part of the water was withheld and 
applied after the application of the chemical solution, stronger and 
more uniform tests were obtained at points nearing the maximum 
depth of penetration, and the tests from different parts of the same 
tube were more nearly uniform. 
What proportion of the water could be applied as such is not 
known. In our experiments three proportions were tried: 1 + 1, or 
equal parts of solution and water; 1 + 3, or one part solution to three 
parts of water; and 1 + 7, or one part solution to seven parts of water. 
As shown by Tables VII and IX, no one of these proportions is 
superior to the others in every case. In practically every case all 
three were equal to or superior to the 1 + 0 applications in the depth 
of penetration obtained. In applying solutions and water to the 
tubes the liquid was simply poured from the graduate. In some 
cases, especially where the amount of solution was small, it is quite 
possible most of the solution was applied to one side of the tube and 
that the water was poured on the other side of the tube. This 
would tend to reduce the amount of chemical forced down the tube 
by the water. So far as the writers are aware, the limiting factors 
in reducing the amount of water used in making up the solution 
would be the amount necessary to put the chemicals into solution 
readily and the amount of solution necessary to insure even distribu¬ 
tion over the soil surface. 
Penetration of Strong Solutions of HgCb+NaCl when Immediately 
Followed by an Application of Water and when Followed Later 
by an Application of Water 
As previously shown, the depth of penetration of mercury in 
HgCl 2 + NaCl solutions is about the same whether all the water 
is used in making up the solution or part of it is withheld and applied 
immediately after the application or the chemical solution, but the 
latter method gives a more even distribution of the mercury in the 
soil. This latter method offers another advantage in that no special 
apparatus is required in applying water while special apparatus and 
special care are required and therefore additional expenses incurred, 
in using mercuric chloride, on account of its corrosive action. Some¬ 
times rain might supply at least a part of the water. Whether the 
water is applied with a hose or falls as rain it is important to know 
whether this water application must follow the chemical solution 
immediately or whether the water may be applied at some later and 
perhaps more convenient time. That final penetration of the 
mercury is not adversely affected by delaying the application of the 
water is indicated by the results given m Table XI, summarizing 
the penetration data from four sets of tubes. In every case the 
maximum penetration was the same for treatments differing only 
in the amount of time elapsing between the application of the first 
and second parts of the treatment. While these experunents gave 
favorable penetration with delayed applications, it is conceivable that a 
soil might react so rapidly with the bichloride of mercury that the delay 
would result in a serious reduction in the strength of the solution. 
