This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
"Repercolation, or, as it has been called by Professor Diehl, fractional percolation, is a process recommended by Dr. Squibb, in 1866, and was more recently somewhat modified with the view of obtaining more uniform results, the object being preparation of fluid extracts without the use of heat. The process may be briefly described as follows: 32 parts of powder are divided into four equal portions, one of which is moistened, packed, macerated, and then slowly displaced until exhausted. The percolate is collected in fractions, the first 6 parts being reserved, and the next fraction used for moistening the second portion of 8 parts of the powder, which is afterwards macerated and displaced with the remaining fractions, the weakest being used last. Of this portion 8 parts of percolate are reserved. The third and fourth portions of 8 parts each of the powder are percolated in the same manner as the second portion, and, finally, the 4 reserved percolates are mixed to obtain 30 parts of fluid extract. The weaker percolates from the fourth portion are preserved for a subsequent operation, when from each portion of 8 parts of powder 8 parts of percolate are reserved". - N. D.
On the subject of repercolation we found in the National Bottlers' Gazette the following practical directions:
"The cost involved in repercolation is practically no more than that entailed by simple percolation, which usually involves more loss of menstruum and less permanency of product. Repercolation only necessitates the keeping on hand of a certain volume of reserve percolate for use in the next batch of the same drug. It accomplishes its object without any heat whatever. Ordinary percolation involves the reduction of the second or dilute percolate to a soft extract by the aid of more or less heat (sometimes so low that the recovery of the alcohol by distillation on a small scale is inadmissible), and the solution of this soft extract in the first percolate, with enough addition of the menstruum to make the proper volume. The process of repercolation may be started and carried on in a practical way as follows: Supposing ginger is the subject, and troy ounces and United States measure is to be used -
Ginger, in very fine powder . . . . 16 tr. oz. Alcohol...a suff. quant.
Moisten the ginger with 4 fluid ounces of alcohol, let stand awhile, well covered (a maceration of more or less duration, according to the nature of the drug, in all cases is preferred); then pack firmly in a percolator, and pour one quart of alcohol on top. When liquid begins to drop, close the orifice of the percolator and allow to macerate (well covered) for a few hours [it is not necessary, and sometimes even injurious, to macerate long, as the dense percolate which began to collect at the bottom will gradually diffuse upwards, thus causing a less rapid exhaustion of the powder]. Then allow the percolation to proceed until 12 fluid ounces of percolate have been slowly obtained. This is used as fluid extract.
"The percolation is then continued, and more alcohol, if necessary, is poured on top until one quart more of percolate is obtained. It is of advantage to receive this in two or three separate portions, marked re -spectively 1, 2, and 1, 2 and 3. These several portions are put away, well corked, and used in the next operation. As No. 1 is to be used first for moistening the next batch, this portion had better be 4 fluid ounces, being the 4 ounces passing through the percolator immediately after the 12 fluid ounces collected as fluid extract. The other portions may be, say: No. 2, 12 fluid ounces; No. 3, 16 fluid ounces. Of course, the 12 fluid ounces thus obtained in the first batch do not fully represent the 16 fluid ounces of drug; yet it is generally conceded that they contain, here as well as in most other drugs, practically all the useful constituents of the drug. In the next operation, the product will approximate already much closer to a standard fluid extract, and in the succeeding operations this will be obtained practically without any difficulty. If the constituents of the 16 ounces of drug were known exactly, and how much of each the first 12 fluid ounces collected did not contain, and which are, therefore, carried over into the second percolate, it would be an easy matter to make all ready the first batch of fluid extract perfect. All that would be required would be to weigh out the constituents obtained in any manner, to dissolve them so as to make 4 fluid ounces, and to add them to the 12 fluid ounces previously obtained. Yet even if this were possible, it is a question whether the fluid extract thus obtained would be permanent, as an artificial solution prepared in the manner described is very much different in behavior from a natural extract, which would probably make a much more permanent and better blended mixture. As it is, the first fluid extract obtained is deficient by just so much of the constituents as are still contained in the drug. But these constituents are carried into the next lot of 16 troy ounces, when the second batch of fluid extract is to be prepared, and thereby add to the constituents of the latter just about as much extra matter as is finally left in it at the end of the percolation.
Ginger in very fine powder . . . . 16 tr. oz.
Reserve Percolate 1...4 fl. oz.
2 (and 3) (on hand).
Alcohol ..'. a suit, quant.
"Moisten the ginger with reserve percolate 1, and proceed as in first lot. When packed, pour on top reserve percolate 2, or, if this has been collected in two lots, pour on 2, and when this has just disappeared from the surface, pour on 3. Collect the first 14 fluid ounces of percolate, and use this as fluid extract. Continue the percolation, using finally alcohol as menstruum, until the same amounts of reserves are collected as in the first lot.
"Proceed as in the preceding, but collect fully 16 fl. oz. of percolate, or fluid extract this time, and continue to do so afterwards".
The National Dispensatory says: "A series of percolators may be conveniently arranged on a retort stand, and the rapidity of percolation regulated, as suggested by Dr. Squibb, by connecting the lower aperture of the percolator with a thin rubber tube, the end of which is raised high enough to prevent the liquid from escaping during maceration, and afterwards lowered, so that the percolation may proceed in drops, the position of the rubber tube being changed to ensure uniformity and regularity; the last portions of the liquid as withdrawn from the percolator, either by removing the rubber tube or by straightening it by sufficiently elevating the percolator. A uniform supply of menstruum may be provided for in various ways, the most simple of which is to invert a bottle containing the requisite quantity of liquid over the orifice of the percolator. The mouth of the bottle should be immediately above the disc covering the powder, and, if necessary, may be lengthened by a piece of rubber tubing".