ON THE RANCIDITY OF FATS. 
251 
of humidity would be impossible, except by tedious and expensive methods. 
Still a partial drying is better than none, and the experience of housewives is 
unanimous on the point as regards the melting of lard, which they say will not 
keep unless it has been made to boil. Albumen has been sought to be remoA r ed 
by agitation with sulphuric acid of 40° Beaume, washing with water and subse¬ 
quently drying. The process was employed some years ago in preparing rape 
oil for burning in lighthouses, and was found to hinder its oxidation. I have 
not been able to imagine an easy process for freeing oils, etc., of this dangerous 
ingredient, and have therefore made no experiments in that direction. M. 
Pelouze made many attempts to insulate the body, but failed. Nevertheless 
he was able from its effects to identify it as one of the albuminous series. 
I shall be able to show, further on, that its activity may be effectually neutra¬ 
lized by a simple method. The entire exclusion of air is of course prac¬ 
tically impossible. 
The length of time required for the development of these changes makes 
experimenting very tedious, and renders one unable to do so much in a given 
time as one could wish. I have therefore confined myself within very nar¬ 
row limits, relating to practical remedies only, and to Lard as the base of ex¬ 
periment. 
Shortly after the use of benzoinated lard had been recommended for the 
preparation of zinc ointment, which it is well known to preserve against ranci- 
iication, I applied with success the same idea to other ointments of similar 
composition, viz. those containing metallic oxides, whose presence had been 
found to act unfavourably on the keeping qualities of the fats with which they 
were associated. These were calamine cerate and oxide of mercury oint¬ 
ment. I have found that M. Deschamps, in 1843, recommended the same 
proceeding in making oxide of mercury ointment, and also the ointments of 
iodide of potassium and acetate of lead. For ointment of tutty and blue 
ointment, where a little extra colour would not be objectionable, he directs 
the use of “ graisse populinee,” the keeping qualities of which are really ex¬ 
traordinary. M. Deschamps states that whilst the “graisse benzinec ” will keep 
good for one year, the “graisse populinee ” will keep good for an unlimited 
time. He suggests its use for greasing machinery even. I intended to make 
some of this preparation, but could not get the poplar buds. The French 
perfumers, in preparing the base of their pomades, adopt a process somewhat 
similar, viz. digestion with benzoin after a preliminary washing, and boiling 
with solution of salt and alum. Their method yields a stable fat, but it is 
too troublesome to be frequently performed, and succeeds best on the large 
scale,—consequently is not well adapted for the pharmaceutist. 
For experiment on the nature of the preservative power exercised on fats 
by bodies like benzoin, the oxide of mercury ointment was evidently well 
adapted, as the progress of rancification is marked by alteration ot colour— 
the oxide being reduced pari jpassu with the oxidation of the fat. 
It was my impression that the essential oil had more to do in the matter 
than any other constituent of the gum, though it had been asserted that ben¬ 
zoic acid answered equally well. But the acid of commerce contains an abun¬ 
dance of the odorous principle. 
To test the truth of the surmise, and at the same time ascertain what degree 
of effect, if any, was produced by various essential oils, I prepared, on Dec. 
5th, 1861, a quantity of red precipitate ointment, using ordinary lard and wax 
in the prescribed proportions, and a smaller quantity using benzoinated lard. 
To small portions of the former I added essential oils, in the proportion of 4 
drops to the ounce. The oils I used were fennel, almond, bergamotte, cassia, 
turpentine, lavender, neroli, lemon, rose, rosemary, caraway, nutmeg, savine, 
inmento, cumin, clove, and sassafras. I also tried creasote, balsam of Peru, 
