902 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[May 11,1872. 
water, tlie gum-resins somewhat similarly treated, 
and the yolk simply diluted with water, will then 
all assume the physical characteristics of milk. 
A perfect artificial emulsion is physically identical 
with the natural,—that is, as far as the extinction of 
the oil is concerned,—and this peculiarity is, in 
fact, the distinctive feature of an emulsion. 
The preparation of a correct emulsion has been 
rightly judged as one of the most difficult tasks of 
the dispenser,—so much so, that a successful issue 
of the operation was attributed more to the dexterous 
skill of the manipulator than to the application of 
any particular method. However, as a successful 
result is not always assured, even in the aptest 
hands, it scarcely admits of a doubt that most of the 
manipulations now in use for the production of 
emulsions are utter failures—failures so far as to 
preclude the probability of an invariably definite 
result, not to say but that chance would frequently 
likewise lead to the same. The desideratum, there¬ 
fore, consists in a process which, under certain ne¬ 
cessary conditions, will always yield a perfect emul¬ 
sion. To arrive at this, it is, firstly, required to 
examine the methods at present in use, and, secondly, 
necessary to inquire into the conditions most favour¬ 
able for the production of an emulsion, and the 
principles upon which its formation rests. The fol¬ 
lowing processes are such as came under the writer’s 
observation:— 
Firstly, the most inefficient of all methods was 
one strongly suggested in the Druggists' Circular a 
number of years ago, which consisted in shaking 
the oil, gum and water in a bottle until the emulsion 
was formed; it did produce a sort of mixture, but 
not what pharmaceutists usually accept as an emul¬ 
sion. The shaking process is admirable for effecting 
solutions, but not so effective as the mortar and 
pestle for mechanical combinations. 
The second process required that sugar, gum and 
oil be all rubbed together in a mortar, and then 
water be gradually added in small portions, with 
constant trituration. By chance a good emulsion 
would occasionally result in this manner, but mostly 
a large proportion of water would be absorbed, and 
the mixture still be too thick to pour. After a short 
time the peculiarly slimy mixture would suddenly 
resolve itself into a curdy or granular-appearing 
liquid having considerable fluidity. The same phe¬ 
nomenon occurs if a moderately increased quantity 
of water is added at once to the slimy combination, 
and then slowly stirred. After this relapse, the mix¬ 
ture could occasionally be doctored into a passable 
combination, by introducing more gum and tritura¬ 
ting violently. But, in either case, most of the oil 
would rapidly separate on standing. It was sup¬ 
posed in this instance that the sugar greatty aided 
the process, but in the writer’s experience sugar is 
really detrimental to the formation of emulsions. 
This process, among all the rest, is the most fatal, as 
in case of failure the loss of both time and material 
is incurred. The operation is more successful, how¬ 
ever, if the sugar be added to the mixed oil and 
gum in the condition of syrup, and then followed by 
water. 
By a third process, devised by Overbeck, given in 
a note to the U.S. Dispensatory, and also recom¬ 
mended by Mohr in his ‘ Pharmaceutical Technics,’ 
a definite quantity of oil, gum and water, in propor¬ 
tions adjusted according to the nature of the oil that 
is employed, is all rubbed up at once in a mortar, 
and, when the proper union has taken place, more 
water is gradually added. This method is quite 
good, and yields very few failures where the oil does 
not exceed 2 fluid ounces, but with 4 fluid ounces of 
oil in one quantity the process becomes precarious. 
A fourth method is given in the U.S. Dispensa¬ 
tory. According to it the gum is first mixed with 
water, in the same proportion as it exists in the offi¬ 
cinal mucilage of the Pharmacopoeia, the oil then 
added, mixed and diluted with the prescribed amount 
of water. In this case the oil is usually added in 
a thin but continuous stream with rapid stirring. 
This process is nearly as good as the preceding one, 
but often the emulsion is not as j>erfect as it should 
be. 
These operations have mostly reference to the 
fixed oils and balsams, and are not equally applic¬ 
able to the volatile oils, which, as a class, are much 
more difficult to emulsify. Experience demonstrates 
that the thicker and more viscid the oil the easier it 
is emulsified. The volatile oils, owing to their great 
mobility, are the most difficult to overcome. Castor 
oil and oil of turpentine are typical of these opposite 
extremes. 
Thus it becomes evident from the disconnection 
and dissimilarity of these methods, that the true 
principle upon which the process of emulsification 
depends, has been either entirely unknown or com¬ 
pletely disregarded. A perfect emulsion is charac¬ 
terized by its dazzling whiteness, its uniformity, and 
the property which admits of its dilution to even an 
extraordinary extent without destroying it appear¬ 
ance or identity. The incipient or complete emul¬ 
sion, in its most concentrated form, from the moment 
of its generation, is unmistakably distinguished by 
its whiteness, and the peculiar tenacity which causes 
the pestle, when moved through it, to give the cha¬ 
racteristic crackling sound of the emulsion; when 
these indications evince themselves the success of 
the operation is assured. 
Now, the writer observed that by following Over¬ 
beck’s method, and using a broad mortar, if the tri¬ 
turation be confined to a narrow space for a moment 
until perfect emulsification had taken place, even in a 
small portion of the material, and then gradually 
bringing the rest of it within this centre, a perfect 
emulsion was invariably attained. Applying this 
manner of manipulation in the process of the U.S. 
Dispensatory, that is, instead of pouring the oil 
upon the mucilage in a continuous stream, adding 
only a small portion at first; this, with the large 
proportion of mucilage, never fails to emulsify. The 
remainder of the oil is then added in small quanti¬ 
ties at a time, and each perfectly emulsified before 
introducing the next. Finally, the perfect emulsion 
is diluted to the required measure. The writer now 
further observed that when the proportion of oil was 
great, in comparison to the mucilage, a time would 
arrive during the addition of the oil when this ceased 
to merge with the emulsion; in no instance, how¬ 
ever, was the previously-formed emulsion ever dis¬ 
integrated or deranged. Therefore, it was assumed 
that the inaction originated in a deficiency of water, 
consequently this addition was made, and complete 
emulsification again and immediately resulted. The 
addition of oil was then continued, occasionally add¬ 
ing water, until the original volume of mucilage had 
lost its comparative individuality in the overwhelm¬ 
ing proportion of the oil, and still the process of 
emulsification progressed. The emulsion, during 
