(Intermittent Displacement Employed.)
By ROBERT F. FAIRTHORNE, PH.G.
A question that has often presented itself to my mind is whether there is any necessity for the use of alcohol in making the compound syrup of sarsaparilla of the U. S. Pharmacopoeia, and, after reflection and experiment, I have found that there is none. This conclusion has been arrived at from the following reasons:
- That in the officinal syrup there is little or no alcohol;
- That by the process now used only such principles as are soluble in water are retained, the remainder being separated by filtration previous to the addition of the sugar;
- That by intermittent displacement with cold water as much of the medicinal virtues of sarsaparilla can be obtained and retained in solution as when diluted alcohol is employed in the quantity ordered by the Pharmacopoeia, with subsequent evaporation.
The directions given are to macerate 24 troyounces of sarsaparilla in moderately fine powder and other ingredients in 3 pints of diluted alcohol for 4 days, and to gradually displace with diluted alcohol until 6 pints of tincture have passed. This liquid is then evaporated to 3 pints, when one pint of water is added and the sugar necessary to make the officinal syrup.
When the tincture is reduced to 3 pints there will be left in solution such substances only as are soluble in water, with a trace of such as dissolve in extremely dilute mixtures of alcohol with water, on account of the very small amount of spirit retained after evaporation. When, therefore, another pint of water is added we may reasonably suppose that even the small amount which might possibly be retained in the liquid, will be almost entirely precipitated, so that practically it would contain no substances that are not soluble in water alone after nitration.
Now, by the method adopted by the Pharmacopoeia the tincture is deprived of its alcohol by the heat of a water bath, which requires an exposure of several hours' duration, during which time it is not only possible, but very probable, that a part of the sarsaparillin, and certainly of the essential oil, is volatilized. This being the case, I believe that if cold water only is employed for the extraction of the medicinal virtues of the root that a syrup can be made by means of it that will be equal in every respect to that as now made with diluted alcohol. What, therefore, is the advantage of its employment? Some druggists may, perhaps, be inclined to think that the use of spirit ensures greater permanence to the finished preparation, on account of some of the inert constituents of sarsaparilla being insoluble in alcohol but dissolving in water, such as albumen, pectin and gum; although these substances are not soluble in strong spirit, yet they will dissolve to a certain extent in equal parts of water and alcohol, and will therefore be present in the tincture which is used in preparing the officinal syrup. This being the case, I do not see what advantage there is in using diluted alcohol. In order, therefore, to test this practically I have prepared the syrup in the following manner:
Having taken 24 troyounces of sarsaparilla in moderately fine powder and the other solid ingredients called for in the Pharmacopoeia, with the exception of sugar, for making about a gallon of syrup, I put them loosely into a percolator which had previously been closed by means of a cork. Cold water was then poured on and sufficient was added to saturate the ingredients. After standing 24 hours in a cool place the cork was removed, the articles firmly pressed and packed in the displacer, and enough water allowed to pass through so as to produce a pint of liquid. After an interval of a day another pint of fluid was produced in the same way. Then, after setting aside for 24 hours, more water was passed through so as to obtain another pint. These 3 pints were mixed together and kept in a cool place. Percolation was then continued until half a gallon of liquid was obtained, which was evaporated to a pint by means of a water bath. When this is accomplished, the liquid is mixed with the reserved 3 pints, and, the sugar having been added, it is dissolved by the aid of heat, which should reach 162°F., so as to coagulate any albumen present, strained and the essential oils are added.
The syrup thus made will be found equally strong in taste as that prepared by the process generally employed, and by dispensing with the use of alcohol great saving in expense will be effected. In appearance it is, if anything, superior, being clearer and quite as dark in color.
By intermittent displacement is meant the treatment of materials as described in the process just mentioned, namely, by alternately displacing a portion of the fluid (after maceration) and allowing an interval of time to supervene before continuing to do so. By this means, in ordinary practice, a thorough exhaustion of the active or medicinal ingredients of the plants can be effected even when the drug is not quite as finely powdered as would be necessary when continued percolation is used. It combines the advantages of both maceration and displacement, and I can confidently recommend its utility.
The American Journal of Pharmacy, Vol. 53, 1881, was edited by John M. Maisch.