Aug. 15, 1925 
Soil Disinfection for Potato Wart 
337 
234 gallons per square foot). Six glass tubes were used for each of 
the four sets and the soil columns were from 9 to 1034 inches deep. 
Strong positive tests for formaldehyde or for bichloride of mercury 
were obtained in the percolate of all tubes. Percolation of the 
formaldehyde solution was more rapid than that of the mercuric 
chloride solution. In Manor loam the formalin solution percolated 
in 29 to 35 minutes, averaging 32 minutes, while mercuric chloride 
percolated in 38 to 54 minutes, averaging 49 minutes. In potting 
soil the formalin solution percolated in 4 to 27 minutes, averaging 
8 minutes, while mercuric chloride percolated in 12 to 14 minutes, 
averaging 13 minutes. 
Manor loam soil containing 8.2 per cent of moisture, and potting 
soil containing 6.8 per cent of moisture were used in two paralell 
sets of tubes treated with 2 per cent mercuric chloride and with 2 
per cent mercuric chloride plus 10 per cent sodium chloride at the 
rate of 2 gallons per square foot. Three hours after the tubes were 
treated the percolate from the 12 potting-soil tubes gave positive 
tests for mercury. In three days the Manor loam tubes were tested 
and positive tests secured in the bottom inch in each case. There 
was no percolate from the Manor loam tubes. The height of the 
soil columns varied from 934 to 1034 inches at the time of testing. 
Penetration of Meectjkic Chloride 
STANDARD APPLICATION OF MERCURIC CHLORIDE 
The foregoing experiments showed that mercuric chloride with its 
simple and rapid H 2 S test might be successfully used in penetration 
studies. The strength of solution was modified on the basis of fur¬ 
ther experiments, some of which are recorded below. One gallon of 
34 per cent HgCl 2 + 234 per cent NaCl solution, or its equivalent, 
per square foot was adopted as the standard application. In a com¬ 
parative test of applications of 1 gallon of 34 per cent mercuric chloride 
+ 2J4 per cent sodium chloride versus 34 per cent mercuric chloride 
+ 134 per cent sodium chloride, tubes tested at the end of two days 
and others at the end of three days showed 9 to 10 inches penetra¬ 
tion for the stronger solution, and. 8 to 9 inches penetration for the 
weaker solution. The soil in these tubes contained 15.1 per cent 
moisture. That mercuric chloride alone in solution does not give 
satisfactory penetration at similar strengths and applications is in¬ 
dicated by a test on soil containing 11.9 per cent of moisture. One 
gallon of 1 per cent mercuric chloride solution showed 6 to 7 inches 
penetration in one day and the same in two days, and 34 per cent 
solution showed 4 + inches penetration in one day and 5 to 6 inches 
in two days. 
The above test3 were on Manor loam. Later Leonardtown silt 
loam containing 6.23 per cent moisture was treated with 2 quarts of 
1 per cent HgCl 2 + 2 quarts of water. At the end of 2 days 5 tubes 
showed 7 inches penetration, in 8 days 4+ inches, and in 11 days 5 to 
6 inches. This would seem to indicate the gradual removal of the 
bichloride of mercury after penetration. 
Reducing the proportion of salt from five times to twice the amount 
of mercuric chloride reduced penetration (Table VI). Applying the 
solution in two parts did not give as good results as applying the 
chemicals in half the water and applying the other half subsequently. 
