76 
Journal of Agricultural Research 
Vol. XXXI, No. 1 
Table III .—Interfacial tension between paraffin oil and miscellaneous substances 
in solution 
Material 
Con¬ 
centra¬ 
tion 
Inter¬ 
facial 
ten¬ 
sion 
Per 
Dynes 
cent 
per cm . 
Water___ 
24.4 
Sodium palmate_ 
0.1 
11.0 
Do_ 
.01 
19.7 
Do_ 
.001 
22.1 
Sodium stearate_ 
.1 
8.2 
Do_ 
.01 
19.2 
Do_ 
.001 
22.1 
Sodium oleate... __ _ 
.1 
3.8 
Do_ 
.01 
17.1 
Do_ 
.001 
20.8 
Potassium oleate _-_ 
.1 
5.5 
Do_ 
.01 
18.1 
Do_ 
.001 
21.4 
Soap, Castile._ 
.1 
6.1 
Do_ 
.01 
16.6 
Soap, Ivory_ ... . . . _. 
.1 
10.2 
Do_ 
.01 
18.6 
Soap, linseed oil_ 
.1 
7.1 
Do_ _ _ 
.01 
12.6 
Mineral oil emulsion No. 1 _ 
4.0 
2.5 
Do_ 
2.0 
6.0 
Do_ 
1.0 
10.1 
Do_ 
.1 
18.1 
Mineral oil emulsion No. 2 _ 
4.0 
7.5 
Do_ .. . .. 
2.0 
10.6 
Do__ 
. 1 
18.1 
Casein (in saturated lime water).. 
1.0 
8.5 
Do_ 
.1 
8.6 
Do_ 
.01 
11.5 
Casein (in 1 per cent Ca(HO) 2 
suspension)_ 
1.0 
6.7 
Do_ 
. 1 
8.1 
Do,._ _ 
.01 
11.2 
Casein (in 0.05 per cent NaHCO) 3- 
1.0 
8.3 
Material 
Con¬ 
centra¬ 
tion 
Inter¬ 
facial 
ten¬ 
sion 
Per 
Dynes 
Casein (in 0.05 per cent NaHC O3) . 
cent 
0.1 
per cm. 
9.2 
Do_ 
. 01 
11. 5 
Milk, skim (on dry basis) _ 
1.0 
9.4 
Do_ 
.1 
10.1 
Do_ 
.01 
11.9 
Gelatin (purified)_ 
1.0 
10.8 
Do_ 
. 1 
14.6 
Do _ - _ 
.01 
17.4 
Glue (commercial)_ _. 
1.0 
12.2 
Do_ 
.1 
15.3 
Do_ 
.01 
17.5 
Saponin (bark extracted with 
water)_ _ 
1.0 
5.0 
Do _ 
. 1 
5.4 
Do_ 
.03 
9.3 
Tannin._ __ _ _ 
1.0 
10.1 
Do _ 
.1 
18.0 
Do_ 
.01 
19.3 
Gum arabic _ 
1.0 
15.4 
Do.. _ . -_ 
.1 
18.6 
Do_ 
.01 
20.2 
Creosote (meta).- 
. 1 
20.2 
Creosote (beechwood).. .. _ 
. 1 
20.8 
Cresol__ __ 
. 1 
17.1 
Resorcin_ 
. 1 
21.0 
Gualiacol_ _ _ . 
.1 
20.8 
Pyrogallol_ 
.1 
21.1 
Phlorglucine_ 
. 1 
20.2 
Evgenol... ... . __ 
.1 
19.0 
Oil of cloves_ 
.1 
16.5 
Oil of Eucalyptus_ _ . _ 
.1 
16.0 
Oil of cedar- 
.1 
14.4 
Oil of cedar in 10 per cent alcohol-_ 
.1 
19.9 
Oil of pears (amyl acetate)_ 
.1 
21.3 
Correlating the results in Table III with the actual spreading prop¬ 
erties of the different substances as observed in Table II, it is to be 
noted that the, interfacial tension values, where oil is substituted 
as the solid, are not proportional to the spreading properties of the 
various materials. If conditions favorable to spreading are expressed 
in equation form, then: 
A t >B t +A t B t 
in which A t is the surface tension of the solid, or surface to be covered; 
B t , the surface tension of the liquid or spreader solution; and A t B tj 
the interfacial tension between the liquid and solid. By substitut¬ 
ing the values given in Tables I and III one finds that negative 
results are obtained for most of the substances tested. This indi¬ 
cates that there is not complete wetting or spreading of the different 
substances on the oil used. As an example, the surface tension of 
the oil (A t ) was 30.4 dynes-cm.; the surface tension of a 1.0 per cent 
solution of sodium palmitate ( B t ) was found to be 31.2 dynes-cm.; 
the tension at the solute-oil interface ( A t B t ) was 11.4 dynes-cm. 
Substituting these values in the inequality one obtains —12.2. 
Although good spreading was observed on the solid or surface tested 
in Table II, the negative value, -12.2, indicates the opposite on 
the oil as a solid. Other oils, both mineral and vegetable, were also 
used, but similar results were obtained. The oils used, therefore, 
can not be substituted for waxy or other surfaces of the plant to 
