416 
PREPARATION OF SOAP FOR SOAP LINIMENT. 
dissolved by digestion with heat, the liniment gelatinizes on a reduction of tem¬ 
perature. From this it follows that good soap liniment should consist of a solu¬ 
tion of oleate of soda, as free as possible from the alkaline margarate or stearate. 
Hence Castile soap, which is prepared from olive oil, is the only commercial 
soap adapted to the purpose, the other soaps being made from solid fats, and 
containing a much smaller proportion of the oleate. Mr. Squire mentions in 
his book an experiment indicating that white Castile soap is soluble to the 
extent of 80 per cent, in cold rectified spirit. This is the soap described in the 
Pharmacopoeia, and I have no doubt that if the process there given for preparing 
the liniment be carefully followed, it yields a sufficiently satisfactory result. 
Nevertheless, if a soap could be obtained containing a still larger proportion of 
the soluble constituent, it would doubtless be preferred. For some time past I 
have prepared such a soap for myself by a very ready method, and have found 
it to possess considerable advantages. 
To produce a soap as rich as possible in oleate of soda, an oil should be selected 
containing the largest proportion of olein and the smallest quantity of solidifiable 
constituents. Almond oil is therefore better suited for the purpose than olive 
oil, and it is from this material that I obtain my product. 
The saponification of oil as commonly performed is a protracted and somewhat 
tedious process to conduct on the small scale. For this reason, probably, chemists 
are not in the habit of preparing their own soap. But if, instead of boiling the 
oil and alkali together until they unite, the oil be first treated in the cold with 
^th of its weight of strong sulphuric acid and allowed to remain for twenty-four 
hours, it is rendered so soluble in liq. sodsethat its conversion into soap becomes 
a matter of the utmost facility. Adopting this plan, I have found the process 
to be one of the easiest of pharmaceutical operations. The acid mixes freely 
with theioil, forming a blackish-coloured fluid. On the addition of the soda 
this colour entirely disappears, and the soap obtained is quite white. The fol¬ 
lowing is the method of procedure I have found to be the most convenient:— 
Almond oil.1^ pound 
Sulphuric acid.1 ounce (weight) 
Liq. sodse.10 pints. 
Add the acid to the oil, stirring the mixture. Allow this to remain for 
twenty-four hours. Then pour it into the liq. sodse contained in a clean iron 
vessel, and apply heat. Very shortly after it boils, the liquid becomes per¬ 
fectly bright and transparent; the fire is then removed, and the whole allowed 
to become perfectly cold. The soap is then found as a coherent cake floating on 
the top of the liquor. It is laid on a calico filter, and left to drain for several 
hours ; or, if it is desired to obtain it perfectly free from all traces of caustic 
alkali, it may be redissolved in 10 pints of boiling water, and a strong solution 
of 5 oz. of common salt added. As the mixture cools, the soap rises to the 
surface ; and when quite cold, again forms a firm layer, resting on the aqueous 
liquid. No loss of weight is thus incurred. The soap is placed on calico to 
drain, after which it may be submitted to moderate pressure, or melted in a 
tared dish, and reduced to a uniform weight of 2 \ pounds. When thoroughly 
cold, it forms a firm white soap, which may be cut into pieces, and kept for use 
in a covered pot. 
In the preparation of linimentum saponis, this soap is macerated in the spirit 
in the cold. It very quickly dissolves, especially if the mixture be agitated. 
From 4 to 5 per cent, of the weight of the soap remains insoluble, as a flocculent 
deposit. After this is filtered out, a pale liniment is obtained, which may be 
kept at 32° F. for any length of time without thickening or depositing. The 
Pharmacopoeia does not direct the soap to be dried before use. Fresh soap 
