I
4
It is evident that none of the substances except Pesterine Emulsion approach Emulsion
A in cheapness of effective solution and it remains only to be seen whether this can be made
and used in a practical manner.
To emulsify refined oil is very easy and emulsions described as being made by churning up
oil and strong soap solution are stated by Lefroy to be in common use against insect pests ;
whether what I have termed saturated soap emulsions have been employed I do not know.
What I have called a non-saturated emulsion requires so much soap that the cost of this item is
very considerable. In the saturated emulsion the cost of soap is an almost negligible quantity.
If equal quantities of oil and soap solution are shaken up a milky fluid at once forms. On
standing this separates into two layers an upper white stratum of emulsified oil and a lower
stratum of clear soap solution. In other words it may be termed a :non-saturated emulsion
since there is still soap solution left presumably capable of emulsifying more oil. If saturation
is attempted by adding in the first place to the soap solution much in excess of its own volume
of oil emulsification either does not take place or takes place with great difficulty and imperfectly.
But if oil be added from time to time in small quantities a soap solution if well shaken is I
capable of converting as much as twenty times its volume of oil into an emulsion being a thick
cream or even semi-solid which shows no tendency to separate into layers. The addition of a
trace more oil beyond a certain amount has the effect of destroying the emulsion, the point at
which over saturation point is reached varying with the soap used, the strength of solution and
the method of agitation employed.
Cost being an important point and soap compared with the original oil being an expensive
addition to the cost, the effect of a number of soaps in making emulsions was tried. The soaps
experimented with were—
(1) Sunlight and Beeches bar soap, both English soaps of good quality containing a
considerable proportion of real soap and capable of emulsifying large quantities of oil before
over saturation point was reached. Of the two sunlight was the more effective and after a
number of trials has been chosen for routine production Emulsion A ;
(2) Golden bar soap, a cheap soap commonly used by dhobies and natives generally. This
soap contains an extraordinary large amount of water and a corresponding small amount of
actual soap, a whole bar being about equivalent to one cake of sunlight or a sixth of a bar of
Beeches bar soap. Used for emulsification it produces an emulsion of the consistence of clotted
cream or even under certain conditions of stiff butter. The reason for this was at first not under-
stood but was found to depend upon the presence of a large amount of free alkali in the soap, the
addition of free alkali to sunlight soap or Beeches bar soap producing the same type of emulsion;
(3) True native soap or so called "Chunam Soap." This is a soft soap containing much
water and even more alkali than the golden bar soap. From its alkaline character it produces
solid emulsion.
Turning from the making of emulsion in small amount to the production of large quantities
it was found impossible to obtain with commensurable labour so great saturation. Since it was
desired if possible to turn out the emulsions by unaided cooly labour at a small cost experiments
in the laboratory where replaced by the formation of emulsion in bulk under different condi-
tions. The different soaps were found to behave in the following manner when quantities of
from 3 to 4 gallons were made at a time by beating up with a cocoanut spoon.
By the addition of a proportion of sunlight or Beeches bar to yellow bar or country soap
the saturation point was raised sunlight and golden bar giving the better results than sunlight
and native chunam soap. But none of the combinations of alkaline soap with sunlight gave
so good "jelly" emulsions as sunlight and alkali, the alkali used being ordinary washing soda
in the proportion of ¼ lb. to ½ gallon of soap solution containing three cakes of sunlight soap.
The emulsion produced in this way which is a solid somewhat resembling in consistency crude
oil emulsion has been called Emulsion B.
TABLE C.
Soap dissolved in half gallon water.
Number of gallons of oil
at which over saturation
occurs.
Nature of emulsion.
as. A. p.
4 cakes sunlight cost
...
...
0 5 0
1 bar Beeches bar soap cost
...
0 7 0
2 bars golden bar soap cost
...
0 4 0
1 viss native chunam soap cost
...
0 4 0
2 bars golden bar soap, 1 cake
sunlight cost
...
...
...
0 5 6
1 viss native chunam soap, 1 cake
sunlight cost
...
...
...
0 5 6
3 cakes sunlight, 4 lb. washing
soda cost
...
...
...
0 4 6
4 or more
3
2
2
3 or more
2 ½
3 or more
Creamy—Emulsion A.
Creamy.
Solid emulsion.
Solid emulsion.
Solid emulsion.
Solid emulsion—Has tendency to be
curdy and not to mix with water.
Solid emulsion—Emulsion B.